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Welding fume plume dispersion Geoffrey Reginald Slater University of Wollongong
Slater, Geoffrey R, Welding fume plume dispersion, PhD thesis, School of Mechanical, Material and Mechatronic Engineering, University of Wollongong, 2004. http://ro.uow.edu.au/theses/384 This paper is posted at Research Online. http://ro.uow.edu.au/theses/384
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WELDING FUME PLUME DISPERSION
A thesis submitted in fulfilment of the requirements for the award of the degree
DOCTOR OF PHILOSOPHY from
UNIVERSITY OF WOLLONGONG
by
GEOFFREY REGINALD SLATER
SCHOOL OF MECHANICAL, MATERIALS AND MECHATRONICS
2004
Abstract The main concern with welding processes has in the past, generally, concentrated on productivity and quality. However, the occupational health of the welder has become a major focal area in the last decade, and the working environment of the welder is becoming a more important area of investigation. One particular area of interest is the amount of fume present in the operator’s breathing zone. With the potentially hazardous material present in the breathing environment of the welder, an effective method of controlling this airborne contaminant must be adopted to limit exposure levels to within occupational health and safety limits and to ensure the well being of the worker. This investigation examines the distribution of fume and breathing zone concentration within a controlled space using the gas metal arc welding (GMAW) process. The controlled working environment provided the basis for quantifying breathing zone exposure concentrations, and the ability to predict operator exposure. The initial evaluation focused on determining the breathing zone concentration and the welding fume plume dispersal within a confined enclosure. Within a sealed environment GMA welding was performed for approximate 100% duty cycle with two types (copper and non-copper coated) of ER-70S filler wire. The breathing zone and background enclosure concentrations were measured. The purpose of this initial investigation was to evaluate the breathing zone concentration within a confined environment, and to determine a fundamental concentration for direct evaluation of control procedures. The inclusion of the non-copper (low-fuming) coated electrode was to validate the measurements obtained during the study. The low-fuming electrode provided the expected reduction in exposure concentrations in comparison with the copper coated wire, however the concentrations measured over a 15 minute welding cycle were substantial higher than Occupational Health and Safety (OHS) exposure limits. To aid the evaluation of fume control effectiveness, various ventilation strategies were incorporated into the controlled environment. Utilising various modes of general and local extraction enabled an evaluation of the measured breathing zone concentration to be compared with the non-ventilated situation, as well as indicating their relationship with the occupational i
exposure limits for welding fume. This enabled the breathing zone exposure concentration to be effectively reduced to meet the OHS exposure limits. Although all techniques significantly reduced the exposure concentration, in direct comparison with the confined ‘fundamental’ concentrations, only an appropriately installed local extraction technique provided the required reduction. As well as the breathing zone evaluation, a model to predict the initial dispersion of GMAW fume was developed, aiding in better determining welding fume plume flow behaviour characteristics. This analysis, in addition with classical plume theories, enabled a model of the fume plume characteristics to be developed.
ii
University of Wollongong Thesis Declaration This is to certify that I, Geoffrey Slater, being a candidate for the degree of Doctor of Philosophy, am fully aware of the University of Wollongong’s rules and procedures relating to the preparation, submission, retention and use of higher degree theses, and its policy on intellectual property. I acknowledge that the University requires the thesis to be retained in the Library, and that within copyright privileges of the author, it should be accessible for consultation and copying at the discretion of the Library officer in charge and in accordance with the Copyright Act (1968). I authorise the University of Wollongong to publish an abstract of this thesis. I declare that the work reported in this thesis is my own, except where explicitly specified and referenced. I further declare that this thesis has not been submitted for a degree at any other university or institution. Signed: Dated:
iii
Acknowledgments I would like to thank Professor John Norrish and Associate Professor Paul Cooper for all their guidance, knowledge and assistance during the course of this study. I am also indebted to the invaluable assistance and expertise of Mr Joe Abbott for construction and maintenance of the experimental equipment. In addition, I would also like to thank Dr Gary Hunt for his invaluable insight and assistance. To Associate Professor Naj Aziz, thank you for allowing me the use of the monitoring equipment. Thanks also to Mr Martin Morillas, Mr Ian Laird and Mr Stuart Rodd for their assistance with experimental equipment. In addition, I would like to thank Shao Wei Huang for his input during these investigations. I would also like to show my appreciation for the members of the Welding Institute of Australia (WTIA), especially Mr Alistair Forbes, for all the information they have provided. I would like to dedicate this work to the memories of James Davidson, Reginald Slater, Robyn Slater Carr, Ron Thomas, Markus Proemper and Jeffery Gao Jinn whom I had the greatest pleasure of knowing. They graced this place all too briefly with their brilliance. Thank you to my fellow work colleagues, in particular Brad Glass, Ben Lake, Shams Huque and Apichart Chaengbamrung, who have shared in the trials and tribulations, as well as the ‘magnificent’ working headquarters. Also, I would like to show my appreciation to Dr Brett Lemass, Associate Professor Peter Wypych, and Dr Ajit Godbole for their assistance during my studies. To my wonderful parents, I am forever indebted for all their time, money and energy ‘wasted’ on me. Most importantly, I wish to convey immeasurable gratitude to my girlfriend, Gabrielle Gutjahr. Her guidance enabled me to learn, achieve success and enjoy this wonderful experience. Gaby, I am grateful for your patience, perseverance and loyalty. Thank you. iv
CONTENTS Abstract
……………………………………………………………
i
Declaration
……………………………………………………………
iii
Acknowledgments
……………………………………………………………
iv
Contents
……………………………………………………………
v
Nomenclature
……………………………………………………………
xi
List of Figures
……………………………………………………………
xv
List of Tables
…………………………………………………………… xxvii
1
Introduction
2
Literature Review 2.1
Introduction to Welding 2.1.1
Introduction
5
2.1.2
Gas Metal Arc Welding Process
6
2.1.3
Equipment
7
2.1.3.1 Power Supply
8
2.1.3.2 Electrode Feed Unit
8
Principles of GMAW
8
2.1.4.1 Arc Principles
10
Electrode
12
2.1.5.1 Solid Wire
13
2.1.5.2 Tubular or Flux-Cored Wires
14
2.1.6
Shielding Gas
14
2.1.7
Metal Transfer in GMAW
16
2.1.7.1 Free Flight Metal Transfer
17
2.1.7.2 Short Circuit Transfer
18
2.1.4 2.1.5
2.2
1
Welding Fume 2.2.1
Origin Of Welding Fume
19
2.2.2
Fume Particle Size
20 v
2.2.3
Hazards of Welding Fume And Gases
2.2.4
Contribution of Welding Consumable to the Fume Composition 23
2.2.5
Measuring Fume Formation Rates
24
2.2.6
Measurement of Welding Fume Concentration
26
2.2.7
Factors that Influence Fume Formation Levels
28
2.2.7.1.1
Electrode Influence
28
2.2.7.1.2
Electrode Composition
29
2.2.7.1.3
Electrode Coating/Core
30
2.2.7.1.4
Electrode Diameter
33
2.2.7.1.5
Electrode Droplet Size
34
2.2.7.1.6
Arc Length
36
2.2.7.1.7
Electrode Manufacture
37
2.2.7.2.1
Welding Conditions
37
2.2.7.2.2
Type of Current and its Polarity
41
2.2.7.3
Metal Transfer Mode
43
2.2.7.4
The Effect of Spatter
44
2.2.7.5
Power Sources
45
2.2.7.6.1
Shielding Gas Effects
46
2.2.7.6.2
Shielding Gas Consumption Rate
47
2.2.7.7
Base Metal (Compositions and Coatings)
48
2.2.7.8
Welding Speed
48
2.2.7.9
Welding Geometry and Orientation
50
2.2.8
2.2.9 2.3
22
Gases – OZONE
53
2.2.8.1 Welding Effects on Ultraviolet Radiation Production
54
2.2.8.2 Shielding Gas Influence on Ozone Production
55
2.2.8.3 Welding Process Influences on Ozone Production
57
Welding Fume Summary
58
Plumes and Air Movement
60
2.3.1
Laminar and Turbulent Flow
62
2.3.2
Buoyancy or Reduced Gravity
63
2.3.3
Boussinesq Approximation
63
vi
2.3.4
Plume Flow Characteristics
64
2.3.5
Buoyancy Flux
65
2.3.6
Forced Plumes and Jets
67
2.3.7
Shielding Gas Effects
71
2.3.8
Governing Equations of Motion
72
2.3.8.1 Entrainment
72
2.3.8.2 Velocity and Temperature Profiles
74
2.3.8.3 Relationship Between the Gaussian and Top-Hat Profiles 2.3.9
2.4
Maximum Plume Rise Height
76 77
2.3.10 Turbulent Sources of Convection in Confined Spaces
79
2.3.11 Virtual Origin Modelling
83
2.3.11.1
Measurement Technique
84
2.3.11.2
Conical Correction
85
2.3.11.3
Jet-Length Based Correction
86
Ventilation of Contaminants 2.4.1
Introduction
87
2.4.2
Air Distribution - Displacement and Dilution
88
2.4.3
Natural Ventilation
89
2.4.4
Exchange Flow Through a Single Vertical Opening
89
2.4.5
Doorway Flow
90
2.4.6
Mechanical Ventilation Systems
92
2.4.7
Work Place Ventilation Conditions of Contaminant Release
92
2.4.8
Contaminant Removal Effectiveness
93
2.4.9
General Ventilation
94
2.4.10 Local Extraction Ventilation
95
2.4.10.1
Fan Blowers
96
2.4.10.2
Cross Drafts
97
2.4.10.3
Fixed Welding Extraction Tables
99
2.4.10.4
Moveable Exhaust Hoods
102
2.4.10.5
‘On-Torch’ Fume Extraction System
105
vii
2.5
3
2.4.11
Appropriate Selection of Ventilation Method
107
2.4.12
Effective Fume Control With Ventilation
109
Summary
110
Experimental Equipment and Methodology 3.1
Introduction
112
3.2
Welding Fume Apparatus
113
3.2.1
Selection of Equipment
114
3.2.2
Workbench
115
3.3
3.4
3.2.3 Calibration of the Welding Fume Bench
117
3.2.4
Welding
117
3.2.5
Welding Set-Up Calibration/Testing
118
Concentration Measurements 3.3.1
Particulate Measurement
119
3.3.2
Breathing Zone Concentration Measurements
121
3.3.3
Background Concentration Measurements
123
Temperature Measurement 3.4.1
Temperature Measurement
124
3.4.2
Calibration of Thermocouple System
125
3.5
Confined Space
126
3.6
Ventilation of the Confined Space 3.6.1
General Extraction using a Mechanical Ventilation System
128
3.6.2
Extraction Volumetric Flow Calibration
128
3.6.3
General Extraction using Natural Ventilation
130
3.6.4
Local Extraction
131
3.6.5
Cross Flow Ventilation Set Up
132
3.7
Visualisation of the Welding Fume Plume
135
3.8
Observations of Shielding Gas Effects on Welding Fume Dispersion
139
3.9
Fountain Experimental Apparatus and Methodology
139
3.10
Summary
142
viii
4
Experimental Results 4.1
Confined Space Investigation Results 4.1.1
Background
143
4.1.2
Set Up For Initial Fume Measurements
144
4.1.3
Breathing Zone Concentrations for ER-70S-6 Wire
145
4.1.4
Results of the Enclosure Concentrations Within The Confined Space
4.2
4.3
148
4.1.5
Breathing Zone Concentrations for Non-Copper Coated Wire
150
4.1.6
Summary of Confined Environment Results
151
Ventilated Enclosure Results
152
4.2.1.1 General Mechanical Ventilation
153
4.2.1.2 Variation in Extractions Rates for General Ventilation
156
4.2.2
General Natural Ventilation
159
4.2.3
Cross Flow (Laminar Flow) Ventilation
161
4.2.4
Local Extraction Ventilation
163
Thermal Investigations of Controlled Space 4.3.1
Thermal Monitoring Of The Controlled Space
4.3.2
Temperature Measurements for Confines Space Investigations 168
4.3.3
Determination of the Virtual Source of the Welding Fume Plume
168
174
4.3.4 Temperature Measurements of the Mechanical Ventilation Systems for Ventilation Investigations
176
4.3.5 Temperature Measurements of the Doorway Extraction for Ventilation Investigations 4.4
5
178
Shielding Gas 4.4.1
Shielding Gas Experimental Results
179
4.4.2
Salt Water Simulations
180
4.4.3
Determination of the Correction Factor (y)
185
Modelling Fume Plume Dispersion Within A Working Environment 5.1
Welding Source Conditions
188 ix
5.1.1
Simulation of Welding Plume Flow Within a Confined
Environment 5.1.2
189 Estimation of Fume Released into an Enclosure
5.2.1
Concentration Estimation within a Confined Space
196
5.2.2
Additional Ventilation Control of a Confined Environment
198
5.2.3
Buoyancy Driven System With Enclosure Ventilated By A Side Opening
199
5.2.4
Buoyancy Driven System With Enclosure Ventilated By A Doorway
201
5.3
Shielding Gas Effects
202
5.3.1
206
5.4
6
Practical Application
Summary
207
Discussions 6.1
Discussion of Results
6.2
Recommendations 6.2.1
208
Recommendations for Controlling Breathing Zone Concentrations
6.2.2
7
192
Recommendations For Further Work
Conclusions
220 223
225
Appendix A
Technical Drawings and Calibrations
Appendix B
Concentration Results
Appendix C
Temperature Results
Appendix D
Shielding Gas Calculations
Appendix E
Welding Parameter Measurements
x
Nomenclature
† † † † † † † †
† †
Symbol A Ad Ao Acrit A0 A(z) A1, A2,. An a at ab ACH B B0 Bl b bG C Cbz Ce Ci Co C0 C˙ ˙ ˙ C1, C2 ... C˙ N C C (t) c cc cd ce cp c1 c2 c(t) D D¢ d dmm d1 d2 E Fr FFR FGR G¢ g g¢
Description Area of enclosure Cross sectional area of duct Cross sectional area of opening Critical vent area for exchange flow Area of source Effective area of plume at height z (Eqn 5.11) Area of multiple openings (1, 2, … n openings) Cross-sectional area of electrode wire Area of top opening Area of bottom opening Air changes per hour Buoyancy flux Buoyancy flux at source Total buoyancy of upper layer formed initially Radius of plume (horizontal scale length) Radius of the plume (gaussian profile) (§2.3.8.3) Constant Breathing zone concentration Exhaust concentration Average concentration within space Concentration entering space Initial concentration within space Measured concentration of fume Samples of measured fume concentration Mean concentration (Eqn 3.2) Instantaneous spatially averaged concentration † Constant Contraction coefficient Discharge coefficient = 0.6 (Eqn 2.57) Effective discharge coefficient Coefficient of specific heat Constant (Eqn 2.11) Constant (Eqn 2.20) Non-dimension equation (Eqn 5.21) Depth (General) Constant = 1256 for pure iron (Eqn 2.2) Height of vent opening Droplet diameter Height above the neutral plan of an opening Height below the neutral plan of an opening Constant = 0.7884 for liquid iron (Eqn 2.2) Froude number Fume formation rate Fume generation rate (§2.2 Eqn 2.5) Local reduced gravity Acceleration due to gravity Reduced gravity, or buoyancy
† †
xi
units m2 m2 m2 m2 m2 m2 mm2 m2 m2 1/hr m4/s3 m4/s3 m4/s2 m m mg/m3 mg/m3 mg/m3 mg/m3 mg/m3 mg/m3 mg/m3 mg/m3 mg/m3
m m mm m m mg/m3 Defined m/s2 m/s2 m/s2
†
† †
†
†
†
g¢H g¢0 H h hT I Ip K k k1 k2 L Le Lj Lm Lo l M ( z) M0 MR m m0 m1 m2 m˙ FFR m˙ VGR N No Ns N˙ N 2 ( z) OEL P p p0 Q Q0 QInterface QPlume QVent Qtot Q˙ Q( z) qT q0 q1 q2 q¢ Re
Reduced gravity at a distance H above source Reduced gravity of the source Height of enclosure Interface height above floor Terminal height of plume † Welding current Inertia of plume at ceiling Coefficient of extraction (Eqn 2.64) Coefficient of a vertical door opening (Eqn 2.59) Coefficient of a vertical window opening (Eqn 2.59) Removal reaction rate constant (Eqn 2.61) Characteristic length scale Length of extraction opening Plume jet length Length above source Length of opening Electrical stick-out extension Momentum flux of the plume at height z Initial momentum flux Melting rate of electrode wire Collected mass †Initial mass flux Mass flux Mass flux Fum formation rate (Eqn 2.4) Vapour generation rate (Eqn 2.3) Number of samples Number of openings in ceiling Number of sources on floor Rate of contaminant generation within space Stratification parameter, or Brunt-Väisäla frequency Occupational exposure levels Pressure Static pressure † Stagnation pressure Volumetric flow rate Initial volume flow rate Volumetric flow rate of boundary interface Volumetric flow rate of plume Ventilation volumetric flow rate of through opening Total volumetric flow rate Rate at which air enters or leaves ventilated space Volumetric flow rate of the plume at height z Total heat input Initial heat flux Convective heat from arc and weld pool †Heat effects from shielding gas Convective heat from workpiece and spatter Reynolds Number (see Eqn 3.43 and 3.44) xii
m/s2 m/s2 m m m Amperes m4/s2 m2/s hr-1 m m m m m mm m4/s m4/s
mm3/s or kg/s
mg kg/s kg/s kg/s g/hr g/hr
mg/min 1/s2 Pa Pa Pa m3/s m3/s m3/s m3/s m3/s m3/s m3/s m3/s kW kW kW kW kW
†
†
†
† † † †
R Rsp R0 r S S˙ T TVL
Equivalent radius of the enclosure Radial spread of plume Plume radius at source Radial co-ordinate from the plume axis Welding plume stratification parameter (see Eqn 2.43) Sample rate Temperature Threshold value limit
TWA
Time weighted average
Tavg Tint T• t U U ref u edge
Average temperature of inside and outside conditions Temperature of interface Temperature of ambient or surrounding fluid Time Horizontal velocity Mean external wind speed at some reference point † Entrainment velocity
V V Vx v(z) W Wo w w wG w0 X x y ye z zI zM zcrit zf zi zv z0 § a aG a¢ b b¢ bTh d d•
Voltage †Fluid Velocity Minimum capture velocity †Velocity of the plume Wire feed rate Width of opening Mean vertical plume velocity Vertical velocity at the plume axes Vertical velocity of plume (gaussian profile) (§2.3.8.3) Velocity at the source † Contaminant capture distance Coordinate on x-axis Coordinate on y-axis † Effective head Coordinate on z-axis, height of plume above source Impingement height Maximum welding plume height Critical height based on jet length Final length of critical height Initial length of critical height Distance between source height and virtual source Height of interface above datum Section Entrainment constant (refer §2.3.8.1) Gaussian entrainment constant (refer §2.3.8.1) Constant (refer Eqn 2.1) Constant Constant (refer Eqn 2.1) Volumetric thermal expansion coefficient Non-dimensional buoyancy (Eqn 5.18) Non-dimensional buoyancy of ambient (Eqn 5.20) xiii
m m m m L/min C (K) mg/m3 or ppm mg/m3 or ppm o C (K) o C (K) o C (K) Defined m/s m/s m/s o
Volts m/s m/s m/s m/s m m/s m/s m/s m/s m m m m m m m m m m m m
† † †
† †
ebzc fe f0 g l1 l2 m n q r rref r• r•0 r0 t x0 y z 0 (t ) DC p Dp Dr DT DTD DTd "
Contaminant Removal Effectiveness Effective nozzle diameter Actual nozzle diameter Vent aspect ratio = D/Wo Constant (Eqn 2.29) Constant (Eqn 2.30) Kinematic Viscosity Dynamic Viscosity Spreading angle of the plume Density Reference density of fluid Density of ambient or surrounding fluid Density of ambient fluid at source level Density of plume source Non-dimensional time Non-dimensional height of interface = h0/H Radial spread constant Non-dimensional height as function of t (Eqn 5.18) Mean wind pressure coefficient Pressure difference across opening Density difference of inside and outside enclosure fluids Temperature difference † Temperature difference across interface Superheated temperature of droplet Volume of enclosure
xiv
m m
Pa.s m2/s o
kg/m3 kg/m3 kg/m3 kg/m3 kg/m3
Pa kg/m3 o C (K) o C (K) o C (K) m3
List of Figures Figure 2.1
Welding is one of the most popular methods for joining materials together
Figure 2.2
Diagram of Gas Metal Arc Welding or GMAW process
Figure 2.3
Typical equipment used for GMAW (MIG/MAG)
Figure 2.4
Metal transferred from the filler metal to the base plate constitutes the
process of welding Figure 2.5
A depiction of the arc region. It is noted that the electrode fall zones are small in comparison with the arc column
Figure 2.6
Arc efficiency depends largely on the energy losses experienced by GMAW
Figure 2.7
Temperature distribution of a welding arc for GTAW
Figure 2.8
Simple schematic of the electrodes purpose in GMAW, showing the current flow through the circuit for DCEP
Figure 2.9
Illustrates the effect that addition of active gases has on weld quality and spatter generation
Figure 2.10
Classifications of Metal Transfer in GMAW …
Figure 2.11
Fume generation due to GMAW is illustrated by this schematic of the
fundamental elements involved in fume generation Figure 2.12
Particle sizes of different airborne contaminate sources
Figure 2.13
Illustration of the mean particle size of welding fume for GMAW
Figure 2.14
The distribution of the aerodynamic particle diameter corresponding to
the operator’s breathing zone in CO2 welding Figure 2.15
A diagram of the standard fume emissions box (or Swedish Fume Box) used to evaluate total fume generation of a welding process
Figure 2.16
Welder’s breathing zone is defined as a distance (r = 300-500 mm) from the workers nose
Figure 2.17
Factors that influence the formation of welding fume
Figure 2.18
Breathing zone concentrations of respirable and total fumes
Figure 2.19
The spatter generation and fume emission rates for copper and non-
copper coated electrodes Figure 2.20
The effect of wire diameter on the FFR of GMAW with Ar + 5% O2
shielding gas xv
Figure 2.21
Deposition rates of electrodes alter the formation rate of fumes. The
higher deposition rates of the electrode generate higher FFR Figure 2.22
Measured droplet sizes of 1.2 mm mild steel electrode compared to the welding feed rate in GMAW
Figure 2.23
Droplet diameter effects on the fume formation rate
Figure 2.24
An increase in arc length produces an increase in fume generation rates for selected covered electrodes
Figure 2.25 Fume box experimental result for seven different manufacturers of electrodes Figure 2.26
The effects of welding current and voltage on the formation of fume of GMAW with different shielding gas compositions
Figure 2.27
The effects of the welding parameters on fume formation rates
Figure 2.28
The effects of welding voltage on fume generation rates
Figure 2.29
The variation in fume generation rates as a relationship to welding
current and arc voltage Figure 2.30
The effects of welding power on fume generation rates
Figure 2.31
Wire feed speed is proportional to the welding current. The overall effect of WFR on the FFR is similar to that of current
Figure 2.32
The effects of electrode polarity on FFR from various electrodes for
MMAW Figure 2.33
Fume formation rates for GMAW for (a) DCEP and (b) DCEN of solid wire electrode
Figure 2.34
The addition of CO2 to the shielding gas generates an increase in fume
production for greater than 4-5% CO2 Figure 2.35
The relationship between welding speed and FFR
Figure 2.36
The effect of voltage and welding speed of FFR
Figure 2.37 A three-dimensional graph highlighting fume formation rates as functions of arc current, welding voltage and weld speed Figure 2.38
The effect welding position has on the FFR
Figure 2.39
Relationship between inclination of the electrode and the FFR
Figure 2.40
Welding fume exposure for various positions of the operator
Figure 2.41
Ultraviolet (UV) radiation splits O2 molecule into two atoms of oxygen, which react with another O2 molecule to form ozone O3
xvi
Figure 2.42
Mean stable ozone concentration in the welder's breathing zone during
the pulsed MIG welding of mild steel Figure 2.43
Breathing zone concentrations for fume and ozone during GMAW of a
steel plate Figure 2.44
The volcanic eruption of Mt St Helens, 1980, sent a plume of smoke and ash into the atmosphere
Figure 2.45
2-D depiction of Schmidt’s observation of the vertical motion of a
plume, and an image of a turbulent plume flow from a nozzle Figure 2.46
Variation of the ratio of initial heat flux of the welding plume to total
power input (q0 q 0 q T ) with melting rate Figure 2.47
Illustration of the effect the Froude number has on the flow characteristic of the fluid
Figure 2.48
† † Schematic depiction of flow characteristic exhibited by a) Positively
buoyant jet, and b) Turbulent fountain. The buoyancy of the turbulent fountain opposes the initial motion of the fluid Figure 2.49
Images of a turbulent fountain with respect to time
Figure 2.50
A jet of fluid strikes a plane at some angle, and spreads out over the
impinged surface. This is the effect of the shielding gas used in GMAW Figure 2.51
Two-dimensional schematic illustrating ambient fluid entrainment into a plume. The eddy currents on the edge of the plume draw in ambient fluid
Figure 2.52
Flow profiles of a plume, a) The Gaussian profile and b) Top-Hat profile are used to describe the velocity and temperature profiles relative to height from origin
Figure 2.53 Schematic demonstration of plume rise behaviour within a stably stratified environment Figure 2.54
A schematic of the formation and development of welding fume plume in a stably stratified environment
Figure 2.55
A diagram of a filling box with a source plume at the bottom. The left
side shows the density profile of the enclosure, while the right hand side illustrates the fluid motion Figure 2.56
Interface height of the contaminated as a function of time
Figure 2.57
The interface descends through the enclosure with time
Figure 2.58
A Graphic representation of the density profile d as a function of height x for various times t xvii
Figure 2.59
Virtual origin at a distance zv below the actual origin
Figure 2.60 Virtual origin can be predicted using empirical measurements and extrapolation
† The conical technique for determining the virtual origin of a plume. The
Figure 2.61
actual origin lies at z=0, while the virtual origin lies beneath at a distance zv Figure 2.62
Common airflow patterns
Figure 2.63
Schematic of natural convection across a vertical opening
Figure 2.64
A classic gravity current flow interface through a doorway
Figure 2.65
A typical system used for heating, ventilating and air conditioning for a conditioned space
Figure 2.66
General layout of a ventilated working environment with general supply and exhaust systems, local wall-mounted extraction hoods and air supplied from the ambient
Figure 2.67
Direction of the cross draft is vital for effective fume control. Previous
studies indicate that the flow direction of the cross draft should be perpendicular to the welder’s face Figure 2.68
Simulation of welding fume plume dispersion under the influence of a
horizontal cross draft of 0.1 m/s Figure 2.69
Breathing zone concentration levels as a function of cross-draft velocity at angle of 90o to welder’s face
Figure 2.70
Breathing zone concentration levels as a function of cross-draft velocity at 0o and 180o to the welder’s face
Figure 2.71
Local extraction units demonstrating the removal of contaminants from
the source (Crossdraft Table) Figure 2.72
Downdraft extraction units demonstrating the removal of contaminants
from the source a) typical downdraft extraction bench b) a typical design for a downdraft table Figure 2.73 Combining cross-flow and extraction (Push-pull Ventilation) is particular effective at capturing contaminants Figure 2.74
Movable exhaust nozzles should be located within close proximity to
source of pollutant Figure 2.75
To maximise the extraction effectiveness of the ventilation method, the
extraction nozzle should be positioned centrally with respect to the weld length xviii
Figure 2.76
Velocity profiles for a circular opening
Figure 2.77
On-torch extraction unit fitted to a GMAW gun
Figure 2.78 Effect of work area size on the mean welding fume exposure concentration Figure 3.1
Illustration of the design criteria used to incorporate a length of pipe to deliver the required weld bead length and weld period for concentration sampling
Figure 3.2
Photographs of the welding bench designed to allow pipe rotation as well as axially translation
Figure 3.3
Control Units for traversing bed system and rotation control. The bench can traverse in both directions, but the pipe rotation was restricted to only one direction
Figure 3.4
a) The PanaStar Inverter welding supply, and b) a rotating earth clamp proved invaluable to ensuring stable arc conditions for the fume trials
Figure 3.5
Welding wire used during the experimental investigation
Figure 3.6
Computer system used to monitor welding conditions and the thermal conditions
Figure 3.7
A sample of the recorded welding parameters during experimental investigations. The irregular current indicates that the weld characteristics follow a mixed trend
Figure 3.8
Personal sampling equipment used to monitor fume concentrations
Figure 3.9 Exploded view of the cassette filter holder highlighting the location of the filter paper, and the functionality of the components Figure 3.10
The location of the breathing zone sampling point, with respect to the
arc. The cassette holder was situated 30 mm from the nose and 20 mm off the right cheek of the mannequin Figure 3.11
Photograph of the balance used during these investigations
Figure 3.12 Real time display of the thermocouples’ readings provides easy temperature monitoring during investigations Figure 3.13
Photograph of the contained environment used for the breathing zone
investigations Figure 3.14
Schematic layout of the welding enclosure, highlighting the locations of the position of the arc, the sampling point on the mannequin, and general enclosure dimensions xix
Figure 3.15 Schematic depiction of the extraction points on the ceiling of the enclosure Figure 3.16
An illustration of a portable extraction unit similar to the system used in these investigations
Figure 3.17 Photographs demonstrates the ventilation area provided by the enclosure’s doorway from an external and internal viewpoint Figure 3.18
Location of the local extraction nozzle was close to the source of the
welding contaminants Figure 3.19
Photographs of the purpose designed duct system to generate a cross-
flow within the welding enclosure Figure 3.20
Schematic depiction of the ductwork utilised to generate the cross-flow air regime within the controlled enclosure, while the photograph displays the power inverter used to control to fan power for the cross-flow experiments
Figure 3.21
(a) Photograph of hot wire anemometer used to measure air velocities.
Images include the (b) anemometer/thermometer probe and (c) LCD display of unit Figure 3.22
Locations used to measure the airflow velocity within the environment
Figure 3.23
Photographs simulating the release and dispersion of a welding fume
plume within the confined enclosure Figure 3.24
Photographs highlighting the effect of various cross draft velocities on
the dispersion of the plume Figure 3.25 The simulated doorway flow, with the buoyant fluid exiting the enclosure in a channel. The contaminated ‘buoyant’ fluid exits the enclosure through the upper section of the door, while clean ambient fluid enters through the lower section. The interface between the two flow regimes is highlight (in left photograph) Figure 3.26
Schematic of the salt water modelling apparatus set up
Figure 3.27 Photographs of equipment used in salt-water modelling of GMAW shielding gas Figure 3.28
Shadowgraph image, taken from DigImage analysis, demonstrating the
elements of the impinging turbulent fountain Figure 4.1
Scatter of breathing zone concentration results for the confined space welding trials xx
Figure 4.2
Normal distribution of breathing zone exposure concentration for ER70S-6, 1.2 mm copper coated electrode
Figure 4.3
Weld beads were approximately 2 mm between each bead, and a thickness of 6 mm
Figure 4.4
Background concentrations within the welding enclosure. These
measurements were taken in the background area of the welding space, at a distance of 1.6 metres and height of 0.45 metres from the arc Figure 4.5
Distribution of concentrations from background enclosure concentrations
Figure 4.6
Photograph illustrating the continuity of the filter paper before and after collecting fume within the confined environment
Figure 4.7
Breathing zone concentration results using the non-copper coated ER70S-6 electrode
Figure 4.8
Distribution of breathing zone concentrations from ER70S-6, 1.2 mm non-copper coated electrode
Figure 4.9
Comparison between breathing zone concentrations for copper and noncopper coated electrodes, as well as the background concentration for both wires
Figure 4.10
Breathing zone concentration results for each sample taken using general ventilation via extraction point 1 (Far corner, on the ceiling of enclosure). (Extraction rate is 0.7 m3/min)
Figure 4.11
Distribution of the breathing zone concentration results for the general
ventilation via extraction port in the far corner of the enclosure. (Extraction rate is 0.7 m3/min) Figure 4.12
Breathing zone exposure concentrations due to the relocating the ceiling extraction point. The extraction port was above the source of contaminate and the operator’s breathing zone (Extraction rate 0.7 m3/min)
Figure 4.13
Breathing zone exposure concentration distribution due to the general
ventilation at position 2 (On enclosure ceiling, above source and breathing zone) Figure 4.14
Breathing zone concentration results due to variations in extraction rate. The general ventilation was provides by an extraction port, in the far corner of the enclosure
xxi
Figure 4.15
Breathing zone concentration distribution due to the general ventilation
of the confined space. Ventilation point was in the far the corner of the enclosure, with an extraction rate of 0.5 m3/s (2.7 ACH) Figure 4.16
Breathing zone concentration distribution due to the general ventilation
of the confined space. Ventilation point was in the far the corner of the enclosure, with an extraction rate of 0.3 m3/s (1.6 ACH) Figure 4.17
Distribution of measured breathing zone concentrations, due to the effect of various extraction rates of general ventilation
Figure 4.18
Breathing zone concentration results using natural ventilation (doorway
flow) to control welder exposure. Figure 4.19 Distribution of breathing zone concentration generated by using a doorway (natural ventilation) to reduce welding fume levels Figure 4.20
Schematic of cross-flow air movement, with airflow passed across the
welder’s breathing zone and above the workpiece Figure 4.21
Breathing zone concentration results for both flow directions, using a
crossdraft directed across the welder’s frontal region Figure 4.22
Distribution of breathing zone concentration generated by using a crossflow to reduce welding fume levels
Figure 4.23 Increasing the crossdraft velocity, across the face of the operator, produced a reduction in the total breathing zone exposure to contaminants produced by the welding process Figure 4.24 Schematic depiction of local extraction orientation, with respect to operator and source. The extraction nozzle position is relative to the welder, with the lower edge of the duct positioned horizontally from the arc Figure 4.25
Breathing zone concentration results due to varying the distance between the extraction nozzle and the contaminant source (located at 50o or adjacent to the operator). The extraction rate is maintained at 0.32 m3/min
Figure 4.26
Breathing zone concentration distribution due to varying the extraction
nozzle to source distance Figure 4.27 Breathing zone concentrations for varying the orientation of the extraction nozzle with respect to the operator, but 100 mm separation between the source of the contaminant and the extraction nozzle. As above, the extraction rate is 0.32 m3/min
xxii
Figure 4.28 Exposure concentration percentages for a local extraction nozzle positioned a distance of 100 mm at an angle of 50o (adjacent to) and 180o (directly opposite) to the operator Figure 4.29
Repositioning the extraction nozzle closer to the arc source produced a
reduction to the measured breathing zone concentration. These results highlight the exposure ranges, and mean breathing zone concentrations measured, for various positions of the extraction nozzle. The nozzle was next to the welder during these investigations Figure 4.30
Repositioning the extraction nozzle closer to the arc source produces an increase in capture velocity, effectively reducing the measured breathing zone concentration. These results highlight the mean breathing zone concentrations measured, quantified against various capture velocities
Figure 4.31
Measuring the thermal distribution within the enclosure, thermocouples
were positioned 100 mm apart, resembled in the diagram above. Figure 4.32
Average temperatures for all experiments between the initial and final
states of the confined welding space. Figure 4.33
Example of the temperature rise during the arcing period, within the
enclosure for the ER70S-6 copper coated electrode wire. All heights are in relation to the position of the arc. Figure 4.34
Example of the temperature rise during the arcing period, within the
enclosure for the ER70S-6 non-copper coated electrode wire. All heights are in relation to the position of the arc. Figure 4.35
Graphical relationship of the interface position with respect to time for
the copper coated ER-70S electrode. The interface position was determined by monitoring temperature differences of 0.1, 0.2 and 0.5oC Figure 4.36
Representation of the temperature step profile over the 15-minute arcing period. This representation of the temperature step can be utilised to visualise thermal levels over the arcing period
Figure 4.37
Graphical relationship of the interface position with respect to time for
various experiments using the copper coated ER-70S-6 electrode with an interface step DT = 0.5 oC Figure 4.38
Graphical relationship of the interface position with respect to time for
various experiments using the non-copper coated ER-70S-6 electrode, with an interface step DT = 0.5 oC xxiii
Figure 4.39
Plot highlighting interface height relationship against theoretical and
actual time period to obtain the ideal virtual origin for a welding source with copper coated ER-70S-6 electrode wire (0.5 oC temperature step). Figure 4.40
Plot highlighting interface height relationship against theoretical and
actual time period to obtain the ideal virtual origin for a welding source with non-copper coated ER-70S electrode wire (0.5 oC temperature step). Figure 4.41
Temperature measurements for the general ventilation of the enclosure
through an opening away from the arc. The extraction rate utilised during monitoring was 0.7 m3/s Figure 4.42
Temperature measurements for the general ventilation of the enclosure
through an opening above arc and breathing zone regions. The extraction rate utilised during monitoring was 0.7 m3/s Figure 4.43
Plot of the temperature measurements for the natural ventilation of the enclosure via flow through the doorway
Figure 4.44
Photographs of the fumes generated by FCAW a) without shielding gas, and b) with shielding gas
Figure 4.45
Images of the radial spread of an impinged fountain on an acrylic sheet
Figure 4.46
Radial spread of fluid as a function of the nozzle-to-surface distance,
over four experimental runs ( L j = 0.128 m) Figure 4.47 Radial spread of fluid as a function of the nozzle-to-surface distance, over four experimental runs ( L j = 0.07 m) † Figure 4.48 Radial spread of fluid as a function of the nozzle-to-surface distance, over four experimental runs ( L j = 0.063 m) † Figure 4.49 Radial spread of fluid as a function of the nozzle-to-surface distance, over two experimental runs ( L j = 0.034 m) † Figure 4.50 Corrective factor used in Equation 4.2 was determined from plotting a dimensionless comparison between the measured mean radial spread of the † fluid against its theoretical prediction. The gradient of the slope
(
)
y = (Rsp L j ) 1- (H L j ) represents this correction factor Figure 5.1
†
Graphic representation of buoyancy, volumetric flux and momentum flux as a function of plume height
xxiv
Figure 5.2
The height of the contaminant interface as a function of time (for a continuous source input). The time period begins when the interface layer has developed
Figure 5.3
The density profile of the enclosure as a function of time, at various heights with both non-dimensional and dimensional parameters
Figure 5.4
a) Estimated temperature difference of the welding enclosure over the 900-second arcing cycle, b) Estimated concentration of the welding enclosure over the 900-second arcing cycle
Figure 5.5
Estimate enclosure concentrations due to increasing an extraction flow rate
Figure 5.6
The steady extraction of contaminants through an ceiling opening, with a continuous source, produces a displacement flow with the interface stationary with time (when the extraction rate is equal to volumetric flow rate of the contaminant at z0)
Figure 5.7
Relationship between contaminant interface height and the extraction volumetric flow
Figure 5.8
Enclosure with a point source of buoyancy and a vertical opening at a height h above floor illustrating flow with the critical vent area, Acrit, required to ensure buoyant layer remains above opening
Figure 5.9
Plot of the critical vent area required to restrict the buoyant,
contaminated layer above the mid-height of the enclosure opening with vent aspect ratio, g, taking values of 0.1, 0.5, 1, 2 and 10 Figure 5.10
Enclosure with a point source of buoyancy and a vertical doorway
opening, with height H Figure 5.11
Diagrammatic evaluation of how the shielding gas flow redistributes the fume plume generated by the GMAW process. This is known as an impinging fountain
Figure 5.12 Parameters of a welding nozzle that are relevant to modelling the dispersion of the ejected fluid. These critical parameters are used to generate a simulation with a salt-water model Figure 5.13 The non-dimensional radial dispersion of the impinging fountain,
Rsp L j , as a relationship between non-dimensional height from the workpiece, H L j , and the jet length constant, y = 1.5
†
xxv
†
†
Figure 6.1
The increase in extraction rates provides reductions for both the modelled space concentrations and measured breathing zone concentrations
Figure 6.2
The effective capture velocities used during the local ventilation of welding fume from GMAW. These results highlight the need of an appropriate capture velocity, to provide adequate operator conditions
Figure 6.3
The descent of the contaminated interface for the actual welding scenario exhibits a similar trend to the theoretical model (dashed line). The intense initial conditions of the welding fume plume, and the unrestrictive environment below the arc have a drastic effect on plume and interface dispersion
Figure 6.4
Experimental and theoretical non-dimensional radial spread as a function of non-dimensional height. The corrective theoretical model provides a good approximate of the radial dispersion
Figure 6.5
Utilising a radial jet of shielding gas (issued from the end of the torch nozzle) may aid in controlling breathing zone concentration exposure by displacing the contaminant away from the source
Figure 7.1
The overall breathing zone concentrations, generated by these
investigations into breathing zone exposure
xxvi
List of Tables Table 2.1
Summarisation of the various welding and allied processes
Table 2.2
Energy gains and losses experienced during GMAW
Table 2.3
Comparison of shielding gases and atmospheric air
Table 2.4
Effects of shielding gases have on different type of materials
Table 2.5
Classification of metal transfer modes
Table 2.6
Contaminants encountered during GMAW
Table 2.7
A brief view of some of the effects attributed to bi-products of welding fume
Table 2.8
Fume Analysis for MIG consumables
Table 2.9
FFR and Composition of GMAW of aluminium alloys
Table 2.10
FFR and specific emission of elements for different binder contents in E7018 electrode coating
Table 2.11
Results of copper influence on the fumes produced by E70S-3 electrodes in GMAW
Table 2.12
These are for GMAW using Power Source D, Electrode 1.2 mm ER70S3, Ar 15% CO2 Shielding Gas at a wire feed speed of 212 mm/s
Table 2.13
Spatter contributes a small percentage (0
Environment Condition Stable Stratification
N2(z)=0 N2(z)50% occupied zone Mixing Ventilation Extract Air Conditions >50% 2.4.3 Natural Ventilation Natural ventilation can be defined as the exchange of fluid between an interior and exterior environments via an opening such as a door, window, etc. The fluid flow produced is driven by a natural pressure difference between the two spaces. This pressure difference is produced by the action of wind movement or by a temperature difference between the environments. The natural movement of air between the environments allows an exchange of air to occur. That means, the contaminated air within the internal space is removed, and clean, ‘fresh’ air is added. An approximation of the volumetric flow (Q) through the openings is given by the formula Ê 2Dp ˆ1 2 Q = Aoc d Á ˜ Ë r ¯
2.57
Where the pressure difference is ∆p, r is the air density, Ao is the area of the opening and c d is the discharge coefficient of the opening. This expression is viable only for † appropriate sized openings. Larger orifices and very small openings have a more complex relationship between flow characteristics and applied pressure. † 2.4.4 Exchange Flow Through A Single Vertical Opening Consideration here is focussed on a confined space with a single opening positioned in one of the vertical walls. This opening is rectangular with a depth (D), width (W o) and area (Ao). For an enclosure with no other ventilation openings, the net volumetric flow 89
Chapter 2
through the opening will be zero. The hydrostatic pressure either side of the opening varies with height, and there will be a neutral plane where the internal and external hydrostatic pressures will be equal as shown in Figure 2.63. The buoyancy difference, g¢, across the opening is taken to be that at the neutral plane. If the flow is assumed to
be Boussinesq then symmetry considerations dictate that the neutral plane is at the halfheight of the opening, providing the opening is some distance from the ceiling or floor † as discussed by Dalziel & Lane-Serff (1991).
z D1
neutral plane
D D2
Figure 2.63 Schematic of natural convection across a vertical opening Thus, D1 + D2 = D and for an ideal flow through the vertical opening with an imposed buoyancy difference of g'!=!g(Dr/r), Bernoulli’s equation gives velocity, V, at any height, z, above the bottom of the opening as: 12
V = [2 g¢z]
2.58
The volumetric flow of inflow or discharge, Qvent , is therefore †
D 2
Qvent
=
12
Ú kW [2g¢z] o
0
dz
†
k 12 = W o D[ g¢D] 3 12 = k1 Ao [ g¢D]
2.59
Shaw & Whyte (1974) state that the coefficient for a vertical door opening is k = 0.65, while Linden et al (1990) † give the constant k1 = 0.25 for a window. 2.4.5 Doorway Flow The flow of air through a doorway generates a thermal exchange (or gravity current) similar to the flow through a vertical opening. This form of ventilation has been a source of investigation by many including Davies and Linden (1992), Shaw and Whyte 90
Chapter 2
(1974), etc. Davies and Linden state “the incoming air flows through the doorway and then takes the form of a gravity current flowing along the floor or the ceiling depending on whether the external air is cooler or warmer than that in the corridor.” As previously identified, the interface height of a vertical opening is located at the midpoint of the opening height. However, Davies (1993) noted that experimental work by Dalziel and Lane-Serff (1991) confirmed that the interface between the counterflowing fluids is located at 0.625 the doorways height, with the lighter fluids reservoir much greater in depth than the doorway itself. This is depicted in Figure 2.64 below.
r Dr+r D 0.625D Figure 2.64 A classic gravity current flow interface through a doorway. Another difference between window and door exchange flows is that the inflowing fluid in a doorway is dominated by the ambient external conditions. The flow through a window is similar to the Baines and Turner (1969) filling box model stated in §2.3.10. The inflowing fluid is mixed with the interface, so that the lower layer is generally lighter fluid than the external environment. Thus the doorway will produce a displacement type of ventilation, where the fresh air is introduced at a lower level, while the internal contaminants will be forced out through exchange with the ambient external environment. This type of natural ventilation is predominately utilised in small to medium sized fabrication workshops, employing a large door opening to provide a clean airway for contaminants to be controlled, or used in combination with a general extraction fan on the ceilings. The ease of having the two running in parallel make them an ideal for controlling the general occupational conditions of a low level concentration environment, however the breathing zone exposure levels of the welder/s still need to be considered.
91
Chapter 2
2.4.6 Mechanical Ventilation Systems Air supplied to and/or extracted from an environment generates a pressure difference between the internal and external conditions via a mechanical device. This is referred to as mechanical ventilation and generally utilises a blower or extraction fan to introduce and remove air respectively (as demonstrated in Figure 2.65). Air will enter a building where it meets the least resistance, either by a supply provided by the fan system, or through external openings, windows, etc. The function of an extraction fan is to capture the contaminated air (either close to the source or in the general environment) and remove it from any inhabited space. In addition to the air supplied to the environment, thermal additives can be utilised, whether it is a cool draft supplied to a system, or heating elements added to provide buoyancy to internal conditions. All these factors combine to generate a clean and comfortable working environment. 2.4.7 Work Place Ventilation Conditions of Contaminant Release A steady release of welding contaminate within a controlled, confined environment will disperse throughout the space. Cooper and Alley (2002) estimated the space concentration level, within a simple box environment, determined from the equations: Ci =
N˙ + Co , Q˙
2.60
"dCi ˙ 2.61a = QCo + N˙ - Q˙ Ci - k 2Ci" , dt Ï Ê Q˙ Ê Q˙ N˙ ˆ¸ N˙ ˆ 2.61b Ci = ÌC0 - t Á Co + ˜˝{exp†[- t t ]} + t Á Co + ˜ . " ¯˛ "¯ Ë" Ë" Ó † Where Ci is the average concentration of a contaminant within the space (mg/m3), k2 is the removal reaction rate constant (hr-1), N˙ is the rate of contaminant generation within † the space (mg/min), Q˙ is the ventilation rate (mg/min), " is the volume of the † † -1 3 enclosure (m ), t = (Q˙ V + k 2 ) , C0 is the initial concentration of the space and Co is † 3 the concentration of a contaminant † of concern entering the space (both in†mg/m ).
† † 2.60 can be used to determine the Equation concentration level Ci or the necessary
†
extraction rate to control the space concentration. For a confined welding scenario, N˙ is equal to the fume formation rate (FFR), while the extraction rate, Q˙ , is zero. The † instantaneous spatially averaged concentration C ( t ) of the welding fume within a confined space (assuming complete mixing) is related to FFR through the formula † 92 †
†
Chapter 2
2.62
Please see print copy for Figure 2.65
Figure 2.65 A typical system used for heating, ventilating and air conditioning for a conditioned space [McQuiston and Parker, 1994]. Carter (1998) measured the effect of two emission rates released into a small environment, over the same working timeframe. The results found highlighted that the higher input of contaminant into the confined working area produced higher exposure concentrations (Table 2.23). The size of the enclosure was 3 metre square environment, using barriers as walls, and 2 metres in height. Table 2.23 Effect of fume emission on exposure in a small working environment, with a duty cycle was 25% [Carter, 1998].
Please see print copy
2.4.8 Contaminant Removal Effectiveness The ventilation efficiency, or contaminant removal effectiveness, is defined as the ratio between the contaminant concentrations in the exhaust air in comparison with the concentration at a point within an occupied space. This is calculated via the equation;
ebzc = Ce Cbz
2.63
Where e cbz is the contaminant removal, Ce is the concentration of the exhaust air, and
†
Cbz is the breathing zone concentration. †
†
93
†
Chapter 2
2.4.9
General Ventilation
General ventilation can be defined as the ventilation generated by the movement of air within a contained space (building or room). General ventilation of a workspace has traditionally involved the removal of air by ceiling or wall mounted extraction units or using natural air movements from external winds, drafts and thermal conventions (Figure 2.66). This method of ventilation may be useful in controlling occupational comfort levels and minor emissions within the general welding environment, providing the space is relatively large and unconfined, or if welding is performed intermittently within the workspace. When non-toxic contaminants are involved, the extracted air may be recirculated back into the working environment, in conjunction with the addition of ambient clean air.
Please see print copy for Figure 2.66
Figure 2.66 General layout of a ventilated working environment with general supply and exhaust systems, local wall-mounted extraction hoods and air supplied from the ambient [Zhivov, 1993]. Disadvantages associated with this form of ventilation include the high air quantity required to provide sufficient dilution to contaminant, as well as the lack of assurance that the welding fume concentration is adequately controlled to meet exposure limits within the working environment. Another problem can arise from working barriers or openings, which can disrupt the general flow of air through the workspace, and obstruct effective fume control. Rigorous control over all sources of air movement is needed to maximise the ventilation efficiency. Thus, general ventilation systems are not usually a 94
Chapter 2
satisfactory method of effectively controlling welding contaminants within the operator’s breathing region. Table 2.24 Effects of ventilation on the background and breathing zone concentrations for welding fume in a shipyard [Department of Employment and Productivity, 1970].
Please see print copy
In the nineteen-seventies, the British Department of Employment and Productivity report (1970) into ventilation techniques on welding fume within a shipyard observed that natural ventilation produced no substantial effect on the breathing zone, and background concentration levels (Table 2.24 above). The addition of a forced general ventilation system produced a significant reduction in the background concentration level, as well as a reduction of approximately 50% for the breathing zone samples. However, the average breathing zone sample still exceeded the exposure limit by a factor of 2. This study indicated that the general ventilation strategies used was inadequate for effective control of the breathing zone concentration, however the forced (mechanical) system was quite suitable for general environment control. 2.4.10 Local Extraction Ventilation Some welding processes, such as GMAW, are believed to necessitate the use of local ventilation to adequately control fume pollution, even during operation in a nonrestrictive environment [Alpaugh, Phillippo and Pulsifer, 1968]. Local extraction ventilation (LEV) is generally considered the most effective method of controlling airborne particles within a workplace. In a welding environment where workers are within close proximity to a source of high contaminant emissions, general ventilation techniques are not effective at fume control. The object of local extraction is to control and contain these emissions close to the source, before they can disperse into the 95
Chapter 2
working area. Local exhaust systems usually consist of a hood, ducting system, some form of air cleaning device (filters, etc), and a fan. There are two operational modes for localised control of fumes: =
A fan blower is used to create a cross draft in the arc area to project the fumes away from the welder, and disperse them into the ambient environment
=
Utilising an extraction unit. The fume is extracted through a hood opening locating within close proximity to the contaminant source. The contaminant then travels through a duct system to either a small extraction unit, which has a filter system build-in or to a main area where the contaminant is diluted with fresh air, and dispersed to the atmosphere.
Both of these methods are effective means of controlling welding fume, but efficiency is dependent on the position of the extraction inlet in comparison to the contaminant source. No local ventilation is 100 % effective in capturing welding fumes, as there will be circumstances where arcing period or awkward workpiece positioning will affect contaminant control. For a given volumetric flow, an extraction system needs to be located within close proximity to the arc, while a blower can be at a distance to produce the same velocity flow across the arc. The required airflow velocity across the arc in order to control welder’s breathing zone from exposure to fume concentrations is 0.5 m/s [WTIA, 1999]. This airflow is quite effective at reducing operator’s exposure to acceptable levels. The contaminant needs to be captured and removed to provide sufficient exposure reduction. The particulate fume and gases generated by a welding process have a relatively low capture velocity due to the small particle sizes. According to the ASHRAE ventilation manual, the capture velocity recommended to control a welding fume release into a moderately still environment is 0.5-1 m/s [ASHRAE, 1989]. 2.4.10.1 Fan Blowers The use of a blower fan to deflect the path of the rising fume plume from the welder’s breathing zone is an effective method of exposure control. However, exposure control is highly dependent on the direction of the flow with respect to the welder. The greatest control comes from the airflow directed across the front of the welder (Figure 2.67). 96
Chapter 2
Flow from behind or in front of the welder can obstruct the efficiency of the flow, and can actually generate higher concentrations within the operator’s breathing zone due to airflow stagnation. Operator’s movement can also obstruct the airflow of the cross draft.
Please see print copy
Figure 2.67 Direction of the cross draft is vital for effective fume control. Previous studies indicate that the flow direction of the cross draft should be perpendicular to the welder’s face [WTIA, 1999]. 2.4.10.2 Cross Drafts The deflection and capture of welding fume from the operator’s breathing environment is highly dependent on draft aspects with regards to the welder’s position. That is, the exposure of the welder to hazardous fumes depends on the position of the airflow relative to his breathing region. If the flow is directed towards the welder’s front, higher exposure levels are expected than if the flow comes from behind, although wakes generated around the body can entrain the fume plume towards the welder. This can be attributed to a stagnation point in front of the welder. This is illustrated by the studies carried out by the A W S (Figure 2.70), where an increase in breathing zone concentrations are observed for certain air velocities directed towards the breathing zone either from in front or behind the operator. The most effective method of utilising cross-draft ventilation is for the air to directly flow across the welder’s front, from left to right (Figure 2.69). It should be noted that the welder’s movement have an effect on the distribution of plume, but as long as there is limited movement by the welder the cross draft should not be significantly effected. Using this cross-draft air movement to reduce concentration levels is an effective method of reducing gaseous pollutants generated by GMAW. Tinkler (1980) evaluated the breathing zone reduction of ozone from GMAW of aluminium. Horizontal airflow
97
Chapter 2
parallel, but opposing the welding direction reduced allowable ozone levels for velocities of 0.7 m/s and higher.
Please see print copy
Figure 2.68 Simulation of welding fume plume dispersion under the influence of a horizontal cross draft of 0.1 m/s [Gray and Sutherland, 1996].
Please see print copy for Figure 2.69
Figure 2.69 Breathing zone concentration levels as a function of cross-draft velocity at angle of 90o to welder’s face (Cv0 = 37 mg/m3), [AWS, 1979]
98
Chapter 2
Please see print copy for Figure 2.70
Figure 2.70 Breathing zone concentration levels as a function of cross-draft velocity at 0o and 180o to the welder’s face (Cv0 = 37 mg/m3), [AWS, 1979]. Figure 2.68 illustrates a simulation of the effects a horizontal airflow has on the dispersal of a welding plume. Gray and Sutherland (1996) further noted that with the absence of the human disturbance, “the dispersion could be well described by a vertical gaussian model” Naturally, implementation of this strategy should be done carefully, so that the displaced contaminated air does not come within close proximity of other occupants. The major disadvantages associated with this ventilation strategy include the restrictive nature of airflow in regard to welding orientation as well as disruptions to the airflow by interference of the welder i.e. operator movement. There are several main methods of close proximity local extraction. These include: =
Fixed Extraction Units;
=
Moveable Extraction Units (e.g. moveable hoods, portable extraction systems);
=
‘On-torch’ fume Extraction System.
2.4.10.3 Fixed Extraction Units Products that are small or have minor welder mobility can be performed at a workstation that incorporates a fixed extraction unit. Using the fixed unit (known as a welding booth), the fume is extracted through an opening on the bench. There are 99
Chapter 2
several variations of this technique of fume extraction. These are crossdraft and downdraft tables. 2.4.10.3.1 Crossdraft Table A crossdraft table is a welding bench that encompasses grilles, vertically slots, or circular exhaust hoods through which fume is extracted, as seen in Figure 2.71. The table may be enclosed at the sides and top forming an open-front box. Welding is performed directly opposite the opening. The minimum extracted volume flux can be calculated by the formula, Q = KLoW oVx
2.64
where Q is the extraction volume, W o and L o are the width and length of the opening respectively, Vx is the minimum † capture velocity, and K is the coefficient of extraction (2.4 with baffles and 2.8 without baffles). For GMAW and GTAW processes, extraction velocities are between 0.5-1 m/s, as greater extraction velocities may impair the shielding gas flow and produce poor weld quality [Jenkins, 1986]. Control over extraction velocities is critical in obtaining the balance between adequate fume control and a high quality product.
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Figure 2.71 Local extraction units demonstrating the removal of contaminants from the source (Crossdraft Table) a) ACGIH welding bench design [ACGIH, 1978], and b) crossdraft table design [Tinkler, 1983].
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2.4.10.3.2 Downdraft Table A downdraft table uses a grill top (instead of a table top) to support the workpiece, and serve as the hood face, extracting the fume from below (Figure 2.72). The welded item is positioned to allow the surface from which the contaminant is released to be vertical not horizontal. The work is also in a position so that the source is no higher than 1/4 of the shortest distance of the hood face. Minimal capture velocity at the grill face is greater than the capture velocity of the crossdraft table (generally 0.8 to 1.5 m/s). This method is extremely costly, requires higher airflow rates than cross draft tables and could lead to unsatisfactory results.
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Figure 2.72 Downdraft extraction units demonstrating the removal of contaminants from the source a) typical downdraft extraction bench b) a typical design for a downdraft table [Tinkler, 1983]. 2.4.10.3.3 Push-pull Ventilation The supply of air across the area of contamination is useful in assisting the control of the pollutant from the breathing zone. The addition of an exhaust system to this system would collect and remove the contaminant forced towards the exhaust hood by the supplied air. This is referred to as a push-pull ventilation system. The combination of these two ventilation processes increases the effectiveness of the capturing the release of the welding contaminant.
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Figure 2.73 Combining cross-flow and extraction (Push-pull Ventilation) is particular effective at capturing contaminants [Koken Ltd, 2003]. 2.4.10.4 Moveable Exhaust Hoods Movable exhaust hoods are attached to flexible ducting, which can be positioned in required location for welder. This can be seen in Figure 2.74 below. These devices offer the welder a high degree of mobility and flexibility to suit most requirements. If mobility is limited, the flexible ducting can be manipulated and appropriately positioned enabling the hood to give adequate ventilation. This type of ventilation can be achieved from a central extraction unit with ducting around a plant, or via a portable system. This method can extract the fume and using a filtration system either recycle the air back into the working environment or vent contaminated air outdoors. A small portable unit will dispense the recycled air back into the working environment within close proximity of the extraction site. Since some of these devices recycle the filtered air, control of gas pollutants such as ozone, and nitrogen dioxide becomes an important issue. For this, special filter cartridges are required, and this may still not provide adequate control and protection from pollutant gases. Both high velocity, low volume flow (small ducts) or low velocity, high volume flow designs can be utilised to control most fume conditions. The low volume flow ventilation requires the nozzle to be position close to the source for them to be effective.
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The extraction nozzle should be positioned so that the capture velocity produced by the removal meets the recommended quantity. To effectively produce this recommended parameter, the nozzle needs to be located within close proximity to the source of the contaminant. Figures 2.74 and 2.75 indicate how a duct should be located as to maximise the capture of the contaminant during a GMAW operation.
Flanged Hood
X – Distance (m) from source of contaminant to extraction nozzle Figure 2.74 Movable exhaust nozzles should be located within close proximity to source of pollutant
Figure 2.75 To maximise the extraction effectiveness of the ventilation method, the extraction nozzle should be positioned centrally with respect to the weld length. With most GMAW operations, the position of the arc, torch and fume origin will change to produce the weld bead. The disadvantage with a local extraction nozzle is that the distance between nozzle and workpiece is fixed in one orientation. If the path of the weld bead deviates beyond the effective limits of the nozzle, then the contaminant control is reduced. This may result in operator’s exposure concentrations to exceed the allowable OHS exposure limit. 103
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There are various hood (nozzle) designs, all of which produce different extraction (air intake) flow contours. These are displayed in Table 2.25, which also indicates the different intake volumetric flow for different nozzle configurations. The data presented in this table can be used to assess of a particular nozzle’s effectiveness (if extraction flow rate is known), or calculate the required airflow to produced required capture velocities ( Vx ). Table 2.25 Design data for extraction nozzles [WTIA, 1997]
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† The velocity profile around a nozzle differs for a slot and circular openings, as well as
flanged and non-flanged openings. Figure 2.76 demonstrates the velocity streamlines and contours for a circular nozzle with both a flanged and non-flanged opening. It is clear that the flanged nozzle face has better extraction characteristics than a standard circular opening.
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Figure 2.76 Velocity profiles for a circular opening. [Tinkler, 1983] 2.4.10.5 ‘On-Torch’ Fume Extraction System These use a low volume extraction unit fixed on the end of the GMA welding gun (Figure 2.77), can be used to remove the fume from close range. It has the advantage of being situated right in the origin of the fume generation. However, the addition of the small extraction nozzle adds extra weight and bulk to the welding gun, which can cause greater operator fatigue, as well as producing an obstruction to the workpiece. Another disadvantage of having a gun mounted extraction unit is the possible disruption of the shielding gas. Extraction of the shielding gas adversely affects the quality of the weld produced, so a greater flow rate may be required to compensate. A study by Head and Silk (1979) on GMAW of mild steel noted that a gun held in a vertical position produces the highest capture efficiency, while increased inclination decreases capture efficiency (as shown in Table 2.26). As with all local extraction systems, considerations have to be made about the extraction rate required to remove contaminants, yet not disturb the welding process and the flow of the shielding gas. For a contaminant released at relatively low velocity into a moderately stable environment, a capture velocity of 0.5 m/s is required for the control of fume from welding, as stated previously. A general expression for extraction flow has not been established due to variations in nozzle designs. Generally, gun extraction can be an effective method of fume control for GMAW of mild steel, however fume levels from stainless steel may not be adequately controlled to avoid the risk of 105
Chapter 2
breathing zone contamination with regards to chromium exposure. A disadvantage of the gun extraction is the production of ozone, since the fume is removed from the arc, UV radiation can penetrate further from the arc generating more ozone.
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Figure 2.77 On-torch extraction unit fitted to a GMAW gun. [Health and Safety Executive, 1990] Table 2.26 Influence of Shielding Gas on Fume Control From Extraction Gun [Head and Silk, 1979]
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The use of local ventilation systems significantly reduces the number of air changes required of a general ventilated environment, and under restricted or confined spaces may be the only method of effectively controlling excessive exposure. 106
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An investigation by Metcalf and Davies (1975) reported that, within a confined environment, a free nozzle local extraction technique was not as effective as a torch mounted extraction nozzle due to the movement of the arc location. To maintain control effectiveness with the free extraction nozzle, the operator was required to constantly reposition the extraction nozzle to keep close proximity to the arc. 2.4.11 Appropriate Selection of Ventilation Method From the critical analysis of previous investigations, welding requires some form of ventilation to provide protection to the operator against excessive exposure to welding fume. It was identified from almost all of the literature available, that the general exposure concentration for a welding process will exceed the permitted occupational exposure standard, set forth by each country. The selection of an appropriate ventilation strategy to adequately control occupational concentration levels is highly dependant on several main parameters. These include the: =
Size of the occupational environment;
=
Work duration, ventilation area;
=
Occupational positioning to contaminant source; and
=
Contaminant concentration.
A restrictive environment has a greater probability of accumulating higher contaminant concentrations compared to a larger, more open environment where pollutant dispersion and dilution can occur. A confined environment will therefore require a ventilation strategy to prevent the concentration level from exceeding the recommended levels. The smaller the environment, the more rapidly the exposure level will exceed limits. However, an environment that is open (not constrained by either wall or ceiling boundaries) requires only general air movement to maintain acceptable concentration levels. The WTIA (1997) has derived some standard guidelines for appropriate usage of ventilation systems, for welding uncoated carbon and low alloy steels, and is noted in Table 2.27. Carter (1998) investigated the exposure concentration in three different work area sizes (Small, medium and large). For similar work cycles and fume emission rates, Carter
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demonstrated that the decrease in working environment increases the occupational exposure (Figure 2.78). Table 2.27 Excerpt from guide of welding ventilation requirements for uncoated carbon and low alloy steels [WTIA, 1997]
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Figure 2.78 Effect of work area size on the mean welding fume exposure concentration [Carter. 1998]. The average fume emission rates for the two electrodes were 6.1 mg/s and 9.5 mg/s for the 2.5 mm and 4 mm electrodes, respectively. A small work cycle of low-level contamination, within an environment, may be controlled with the use of a small portable extraction unit or general ventilation via a combination of natural and mechanical systems. Heavy manufacturing industries with high welding fume concentration levels will greatly benefit from a purposed built extraction system to effectively control fume generation. Materials of greater concern (such as Barium, Beryllium, Cadmium and Chromium) require a more stringent ventilation strategy. The guidelines demonstrate that confined environments require greater ventilation control to effectively reduce contaminants within the occupational domain. It was also noted that for an open or limited working space, mechanical or local ventilation techniques are unlikely to be required for small
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welding periods (less than 24 minutes of a standard 8 hour working day). This is provided that the process is used intermittently (not more than 5 minutes every hour). The WTIA (1999) has released simple guidelines concerning the general features of different ventilation methods, Table 2.28, as well as the ANSI/AWS F3.1 document derived by the AWS which outlines the correct procedures to design and implement an effective ventilation system. 2.4.12 Effective Fume Control With Ventilation An investigation exploring the effects of confined space ventilation was performed by Ojima, Shibata and Iwasaki (2000). This study noted the efficiency of ventilating an enclosure while by welding with CO2 shielding gas, for a period of 30 minutes. The investigation was performed over a 30 minute welding cycle, with a 6 minute arcing period (ARC ON), followed by a 24 minute period of no welding activity (ARC OFF). The enclosure was ventilated via a horizontal duct positioned 0.85 metres above the welding bench. By increasing the air changes per minute (ACM) by 68% (0.4 – 0.67 ACM), the fume concentrations measured within the breathing zone were reduced by approximately 5% during arc time, and approximately 1% for the total cycle period. Ozone in the breathing zone is reduced by factor of approximately 3 during arcing period, and overall period. These results are included in Table 2.29. Table 2.29 Efficiency of duct ventilation in reducing welding fume concentration [Ojima, Shibata, Iwasaki, 2000]
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These results indicated that an increase in ventilation rate produced an initial increase in the measured fume concentrations. A further increase in the extraction rate generated a 109
Chapter 2
decrease in measured concentration. However, the continual increase in the extraction rate resulted in a reduction in measured ozone concentration. As with all ventilation methods, the chemical composition of the welding fume generated must be considered to establish an adequate extraction system to aid operator’s exposure levels. Welding of stainless steel produces relatively high concentrations of hexavalent (VI) chromium, which has an exposure limit lower (0.05 mg/m3) than normal welding fume (iron oxide of 5 mg/m3). 2.5 Summary This literature review has identified the need for controlling the fume contaminants generated by GMAW, or any welding process. This control is critical to preserving the health of the welder. Welders are exposed to excessive quantities of harmful contaminants that can be reduced via several engineered parameters including process automation, welding parameter control, and ventilation methods. In spite of all the information reviewed in this chapter, there is very little quantitative data to describe the effect that welding fumes have on breathing zone exposure. However, there have been some European investigations into the health effects associated with industrial welding. The limited literature demonstrates the lack of investigations that have been previously undertaken into breathing zone exposure concentrations. So by manipulating the ventilation modes within a controlled enclosure, it is hoped that this study will illustrate how varying these modes will have on controlling the concentration levels within the operator’s breathing zone. Jin (1994) described the temperature distribution of a welding fume plume in an unrestrained environment, but there has only been limited research into plume dispersion. By using classical plume theories, this research hopes to clearly model the welding fume plume produced, and indicate how the ventilation modes influence the flow of this plume in an enclosed environment, and with respect to the breathing zone. As with a buoyant plume from a localised source of heat, the fume plume will rise to a height of neutral buoyancy within a steady stratified environment. A terminal height arises from the vertical momentum reducing to zero, with the plume returning to the 110
Chapter 2
neutral height and spreading sideways. The occurrence of plume motion stagnation within a large working environment could prevent effective contaminant control via ceiling mounted extraction units and a possible accumulation of fume concentration within office working areas. Initial plume parameters such as temperature or heat flow, radius, and the initial velocity have been characteristically difficult to determine, due to a lack of understanding of the welding process and extreme local fluctuations close to the source. Heat input from the arc is dissipated in three ways, convection, conduction and radiation with either the workpiece or ambient. The actual mechanism by which heat is dissipated is not fully understood. The orientation of the operator in relation to the workpiece can vary the workers exposure levels, although no obvious prediction has been made about the breathing zone concentrations (Tinkler and Ditschun, 1984). A head positioned directly above arc source is more likely to be exposed to higher levels than welding vertically with the head to the side. This is also related to the parameters influencing fume formation. An understanding of the generation of welding fumes, and how these fume levels are influenced by the process itself, should enable the improved control. As described in §2.4.7, the greater the emitted contaminant into a space, the higher the space concentration will be. The increased concentration will affect the quality of air to which the operator is exposed during welding. This relationship between the space concentration and emission, however, does not describe the actual breathing zone concentration exposed to a welder during operation. Therefore, correlation between FFR and the breathing zone exposure would be invaluable, but this depends on a thorough understanding of the fume dispersion. Due to the lack of information on operator exposure concentrations, this study aims to explore this and develop a stronger understanding of how to provide effective control a welding fume plume within a controlled environment. In addition to the experimental investigations, estimating the flow characteristics of the welding fume plume aid in determining an effective ventilation system capable of controlling breathing zone concentrations for the workplace.
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Chapter 3
Chapter 3 EXPERIMENTAL EQUIPMENT AND METHODOLOGY Scope This chapter discusses the design and implementation of apparatus used for the welding and ventilation experiments performed within a test cell. The main criteria for the welding rig design, was that sufficient fume levels were required to conduct the breathing zone measurement examination documented in Chapter 4. Implementation of various ventilation strategies enables the control of breathing zone exposure levels to be recorded for later comparison. This chapter also highlights the measurement techniques used to monitor and control the parameters used within these trials. The initial sections of the chapter outline the process behind the design, construction and implementation of the welding fume apparatus. Section 3.4 and 3.5 detail the techniques of calibrating and monitoring particulate fume dispersion together with temperature measurement using thermocouples. Section 3.6, examines the controlled environment used to conduct these fume exposure trials, while Section 3.7 defines the ventilation techniques used in this assessment. 3.1 Introduction The experimental studies into welding fume plume behaviour present several challenges. Firstly, the primary focus of this study entailed the measurement of the breathing zone concentration produced by GMAW of mild steel within a controlled environment. The use of the confined environment aided in generating an understanding of how the welding contaminant was affected by the confined situation. The confined space also enabled greater control of internal air movement, as well as providing high concentrations of welding fume for monitoring purposes. Secondly, varying the method of ventilation enables the possibility of developing a greater understanding of how different ventilation techniques reduce pollutants and the requirements needed to control occupational exposure to meet prescribed limits. The rig was also designed to facilitate the visualisation of the fume plume dispersion within the confined environment. Using a mild steel pipe with a diameter of 220 mm, thickness of 6 mm, and length of around 725 mm (± 75 mm), continuous circumferential weld periods of 15 minutes could be maintained to establish an initial concentration measurement for the conditions stated below. Also, these initial studies allow a period of adjustment, to gain an understanding of what is required during the experimental procedures. 112
Chapter 3 The motivation behind these studies was to determine whether a welder’s breathing zone was exposed to unacceptable levels of welding fume and how effectively exposure levels can be controlled or reduced. The current understanding of breathing zone concentration levels is limited. The way in which fume is dispersed into the welding space, and what effect various ventilation methods have on controlling operator exposure were the immediate interests in this study. Previous studies have quantified the total fume emissions (fume formation rates) from various welding processes, however investigations into actual breathing zone concentrations to which the welder is exposed have had limited attention. Intuitively, the greater the volume of airborne contaminant within a working environment, the higher the occupational exposure risk becomes, but this is no indication of actual operator exposure. Some British studies during the 1970s (by the Department of Employment and Productivity) found that the introduction of ventilation does reduce the concentration levels of fume within the breathing zone, but there are no clear guidelines to indicate how effective control is achieved. Present practice is to remove as much fume from close proximity to the source as possible, before it can reach the breathing zone. This is achieved by utilising a local extraction system to remove contaminant. This method is believed to be the most effective in reducing operator exposure, but there has been no definitive evaluation of how effective these modes of ventilation are at controlling exposure levels. Local extraction has come under scrutiny in recent years since the removal of fume close to the source increases ozone levels, since the absence of fume reduces the attenuation of UV radiation. Trials carried out by the Welding Technology Institute of Australia [WTIA, 1999], noted that for GMAW of steel plate, fume and ozone levels within the breathing zone were considerably higher than the Australian Exposure Standard of 5 mg/m3. These results found the levels of fume were as much as 18 times higher than the prescribed limits, while ozone levels exceeded the national standard by a factor of 10. The results for the trials were previously shown in Figure 2.43. Based on the lack of the current literature, a greater need of understanding is required on welding plume behaviour to aid in controlling the exposure levels of the fumes generated by this process. 3.2
Welding Fume Apparatus
Standard breathing zone tests are taken over a daily (8 hour) period. This delivers a Time Weighted Average value, indicating how much fume the welder has been exposed to during the working day. This daily period generated a problem for several reasons. The first issue was the length of time required for welding. This poses a problem, as the amount of fume concentration 113
Chapter 3 varies with the amount of welding activity carried out. For example, if there is a low production day, the worker will naturally be exposed to lower levels of contaminants than on a day with heavy productivity. The lack of continuity in this measuring technique of breathing zone concentrations can produce a false complacency or concern in regards to occupational fume exposure of the worker. Thus, the simplest and most consistent method would be to monitor a continuous welding breathing zone concentration during a defined period of time. Utilising a 15-minute welding period, the collection of a steady sample of contaminant from within the welder’s breathing zone can be achieved. It should be noted that welders are not normally exposed to such lengthy, continuous doses, as the arc is not maintained for such long periods of time. It is however a useful exposure period, as the fume plume generated settles into a steady flow. Initial fume plume conditions can produce varied concentration levels, so a larger period was required to generate a steady fume production. 3.2.1 Selection of Equipment To obtain the required weld lengths, both temporally and spatially, there were two possibilities considered. Firstly, in order to generate reliable concentration levels, a continuous weld bead was required, as well as a suitable time frame. As noted above, a 15 fifteen minute arcing period was selected. In order to generate a continuous, stable arc for the entire weld period, an automated welding system was deemed the most appropriate method. To generate the weld bead for the time scale required a large weld surface. The options for generating the require weld length were a flat plate or rotating pipe system. These were considered the two most viable options, with the rotating pipe system selected as the best course of action. This selection was based on the rotating system providing extensive weld surface, without excessive lengths of material, and the capability of providing a static arc position. Utilising a static arc position provided an appropriate source, as variation in the distance between source and sampling point will effect the total measured concentration. A motorised system was needed to rotate the pipe as well as to traverse the pipe axially. A welding bench system was designed to incorporate the axial motion, whilst providing the additional rotation. A simple illustration of this system is highlighted below in Figure 3.1, while Figure 3.2 presents several photographs of this rig.
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Rotation of the pipe provides the material length require to generate weld bead for 15 minute timeframe.
The rotation table is position upon a traversing bed, allowing axially directed movement
Figure 3.1 Illustration of the design criteria used to incorporate a length of pipe to deliver the required weld bead length and weld period for concentration sampling. The welding torch was held vertically above the pipe on an arm attached to the base of the traversing bench, maintaining a static arc point will reference to the ground. Constraining the arc point means that the plume origin does not have to be continuous tracked as it moves around work piece. As stated above, this helps the monitoring of concentration levels, as well as aiding in a visual understanding of the plume movement through the workspace.
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Figure 3.2 Photographs of the welding bench designed to allow pipe rotation as well as axially translation. 3.2.2
Workbench
A simple design was used, and the materials were selected to provide strength, flexibility and adequate rotation speeds. The frame of the rotator had to be capable of supporting the weight of the pipe, shafts, bearings and the motor. Square steel tubing was chosen for the frame due to its strength, low weight and cost. The workbench housed the two rotating shafts, attached via 115
Chapter 3 bearings at either end of the frame. Rotation of the pipe was achieved by a DC motor, attached to one of the shafts via a pulley. This motor provided enough torque to rotate the pipe with the desired low rotation speeds. The bearing selection had to cater for the weight and low thrust forces presented by the rotation of the pipe. A dc motor speed controller was attached to allow the motor speed to be adjusted to adequate pipe rotation speeds. The rotating workbench was fixed onto a pre-existing traversing bench, with a separate adjustable motor speed, so that the user could control of both rotational and traverse speeds. The workbench was designed to allow a continuous weld to be made up to 15 minutes. With this in mind, the base dimensions of the pipe were selected to give a good quality weld, without requiring a large length. A pipe with a diameter of 200 mm and length of 700 mm were chosen as adequate sizes to provide enough weld length to obtain the required 15-minute weld times. To provide an ideal “clean” contact, the surface oxidation was removed by machining or sand blasting. Detail drawings of the rig are shown in Appendix A.1. A transformer and control unit (Figure 3.3) were used to reduce the 240 Volt power supply to the required 12-15 volts, as well as allowing rotation speed modulation.
TRAVERSING BED CONTROL UNIT
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ROTATION SPEED CONTROLLER
Figure 3.3 Control Units for traversing bed system and rotation control. The bench can traverse in both directions, but the pipe rotation was restricted to only one direction. 116
Chapter 3 3.2.3
Calibration of the Welding Fume Bench
With a pipe on the test rig, a set distance was marked out and the period of time it takes the bench to travel the defined distance was recorded. This method was repeated several times, over a range of different settings to give an average bench traversing speed. The calibration of the welding bench travel speed indicated a linear relationship between the bench speed and controller. The pipe rotation speed was calibrated by measuring the period for one rotation. Errors associated with these calibration procedures are human errors such as visual errors, termination of stopwatch, etc. The varying differences between the pipes length (the mass of the pipes) does not impede travel speed. Calibration results are shown in Appendix A.2. 3.2.4
Welding
The power supply used for the fume experiments was a Panasonic Panastar HF-500 Inverter Controlled welder (Figure 3.4 below). The simple operation of the power supply made it ideal for the controlled welding parameters required for the experiments. Throughout the welding fume investigations, the welding conditions were not altered. The only modifications to the welding parameters were with regard to welding wire. Both a copper coated and non-copper coated (or low fuming) solid wires were used to generate a comparison of fume exposure generated within the breathing zone. Figure 3.5 illustrates the different visual characteristics between the copper and non-copper coated electrode wires. The quality assessments of the weld bead during the investigations were based on visual inspection of the weld as well as the monitoring of the welding parameters (voltage and current). A simple ‘rotating earth’ was used to provide a stable work return connection and eliminate arc interference and cable ‘wind-up’. This system is shown in Figure 3.4b. A simple screw clamp system was used to provide contact between the pipe and the earth clamp. Table 3.1 displays the welding parameters used for these studies. Table 3.1 Welding parameters utilised during the breathing zone investigations Electrode Wires Main Electrode Wire - Hyundai AWS A5.18/ASME SFA5.18 ER70S-6 SM-70 Solid Wire - Copper coated, 1.2 mm (0.045”) Hyundai AWS A5.18/ASME SFA5.18 ER70S-6 SM-70 Solid Wire – Non-Copper coated, 1.2 mm (0.045”) Cigweld AWS ER70S, Autocraft LW1, Copper coated, 0.9 mm, Welding Conditions Voltage: 25 Volts; Current: 200 Amps Shielding Gas Type BOC Argon 50 (Universal), 82% Ar + 13.25% CO2 + 2.75% O2 Shielding Gas Flow-rate 15 L/min = 0.0025 m3/s 117
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Figure 3.4 a) The PanaStar Inverter welding supply, and b) a rotating earth clamp proved invaluable to ensuring stable arc conditions for the fume trials.
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Figure 3.5 Welding wire used during the experimental investigation. The wire of the left was the copper coated ER70S-6 was the primary electrode wire used, while the non-copper coated ER70S-6 (right) was used for low fuming measurements. 3.2.5
Welding Set-Up Calibration/Testing
The welding conditions chosen for these experiments were chosen to deliver a good quality, steady weld bead during the total run, and to generate sufficient fume levels. To achieve this, the welding parameters were manipulated until a good quality weld bead was generated. This was then monitored using the ARCWATCH data-logging program (Figure 3.6 and 3.7), to ensure the uniformity of the parameters. A mixed metal transfer characteristic was selected to generate 118
Chapter 3 large, measurable fume generation rates (refer to Figure 2.26 for demonstration). This transient mode generated the desired weld characteristics of fairly low spatter ejection, good quality weld bead and good fume production.
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Figure 3.6 Computer system used to monitor welding conditions and the thermal conditions (discussed in §3.5). Parameters recorded include welding voltage, current and wire feed speed.
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Samples
Figure 3.7 A sample of the recorded welding parameters during experimental investigations. The irregular current indicates that the weld characteristics follow a mixed trend. The sample rate was 100 Hz, and measurements were recorded for a period of 8 minutes 40 seconds (58% of the total arc cycle). 3.3.1 Particulate Measurement For an accurate measurement of particulate fume in the breathing zone, there were two techniques available, a gravimetric system and laser particle counter. The laser particle counter 119
Chapter 3 calculates the particle concentration of the sampled air, while the gravimetric system collects a sample of the air concentration. The gravimetric measuring system was chosen due to its ease of operation, and ease of movement, i.e. can easily be moved to different locations. Another decisive factor was based on specified standard procedures for sampling particulate welding fume, as published by the American Welding Society ANSI/AWS F1.1 (1985) and Australian Standard AS 3853.1-1991. Using a lightweight personal measuring pump (DuPont Model P2500A Air Sampler as seen in Figure 3.8) a small amount of air was drawn into the sampling cassette, which holds the filter (Figure 3.9) at a constant volume. The air ‘inhaled’ by the pump was passed through a small filter (MILLIPORE Type AA 0.8 mm and Pall-Gelman Laboratory DM 800 Metricel“ Membrane Filter 0.8 mm, 25 mm diameter). This lightweight, air-sampling device was capable of drawing between 1.5-2.5 litres per minute (+-5%), for particulate collection over a general working day.
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Figure 3.8 Personal sampling equipment used to monitor fume concentrations. The (c) DuPont personal sampling pump extracted air through which breathing zone and background exposure concentrations were taken, while b) demonstrates the size of the filter cassette holder, and (a) the components of the cassette holder. 120
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Collection cap that collects larger particles deflected off the filter paper
Filter Paper
Extraction point to pump Sampler Inlet Nozzle
Brass plates that hold filter paper in place
Airflow
Figure 3.9 Exploded view of the cassette filter holder highlighting the location of the filter paper, and the functionality of the components. There are sampling mannequins available, that replicate the respiratory system of an operator, but these were deemed unnecessary and too costly for the current work. Instead, the sampling cassette was positioned on the facial area a normal mannequin, adjacent to the right cheek, to approximate the breathing position of a welder. Positioning the sampler behind the helmet allowed the protective characteristic of the helmet to be included, providing a more realistic sampling exposure concentration. The position of the sampling point is x = 200 mm, y = 450 mm, and z = 180 mm, with respect to the arc. 3.3.2
Breathing Zone Concentration Measurements
The Australian Standard AS 3853.1-1991 recommends the position of sampling cassette be taken at cheek level, within 50 mm of the nose, and 25 mm from the cheek when a helmet is worn, or within 225mm for a hand shielded welder or non-welder. The sampling position during these trials was 40 mm from the nose. This position was selected to satisfy the standard’s recommendation, as well as accommodating the helmet. Figure 3.10 illustrates the position of the sampling point used on the mannequin. A Mettler H51AR balance was used to weigh the collected particulate matter to the nearest 0.01 mg (Figure 3.11). The Australian Standards for welding fume measurement recommend a minimal sample weight of 0.05 mg. By converting the results using the following equation, the total fume collected from the measured volume of air may be calculated. This is expressed as an airborne concentration (in mg/m3) by the expression,
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1000m 1000m . C˙ = = S˙t 28.5
3.1
Where C˙ is the concentration of fume (mg/m3), m the mass of particulate collected (mg), S˙ is the sample rate of pump†(L/min), and t is the sample time scale (minutes). For these experimental investigations, the sample rate of pump was 1.9 L/min, and the sample period was † † 15 minutes. The measured concentration results were expressed in terms of mean concentration, standard deviation and coefficient of variation.
Mean: C =
C˙1 + C˙ 2 + ...+ C˙ N , N
3.2
N
 (C˙ - C )
2
i
Standard Variation: SD = †
i=1
,
N -1 SD Coefficient of variation: CoV = 100 . C
3.3 3.4
† †
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(Sampling) Point
Figure 3.10 The location of the breathing zone sampling point, with respect to the arc. The cassette holder was situated 30 mm from the nose and 20 mm off the right cheek of the mannequin.
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Chapter 3 Calibration of the balance was achieved by measuring a known weight (of 20 grams) before and after concentration measurements were performed. The balance provided the required resolution of 0.01 mg, and was reliable at giving positive results, that is, the known mass variations for before and after measurements altered, at worst, by 0.02 mg.
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Figure 3.11 Photograph of the balance used during these investigations. The Mettler H51AR balance provided the required resolution of 0.01 mg, as stipulated in AS 3853.1-1991. 3.3.3
Background Enclosure Concentration Measurements
Background enclosure concentration measurements were taken in much the same way as breathing zone measurements, but at a distance of two metres or more from the arc region. The position of the sampler intake was at a height of 0.45 metres above the arc, to simulate the average ‘nose height’ of a human, and the air intake was directed downwards. There are no specific guideless regarding the distance required to measure the background concentration of a welding environment, however, a distance greater than 2 metres is recommended. Due to the restrictive nature of the experimental enclosure, the background concentrations were taken at a distance of 1.6 metres (the furthest horizontal distance away from the arc) and 0.45 metres above the arc height.
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Chapter 3 3.4.1
Temperature measurement
The measurement of the ambient temperature distribution in the cell was achieved by the use of thermocouples. Type T, or copper verses copper-nickel (constantan), thermocouples were used for temperature measurement within the confined environment, with a wire diameter of 1.2 mm and sheathed in a PVC coating. The type of the thermocouple was chosen due to its simplicity and range. The use of OMEGA® data acquisition system, in conjunction with a type T thermocouple wire, provided good resolution and accuracy for the expected temperature gain of these welding experiments (between 10oC and 50oC). The Omega® data acquisition manual noted that resolution of the data using this thermocouple type is indicated below in Table 3.2. The thermocouples were enclosed in a PVC pipe to avoid any thermal gains (or noise interference) from the radiation generated by the welding arc. Table 3.2 Excerpt from Omega® Manual describing the thermocouple accuracy using the Omega® data acquisition system [OMEGA®, 1999] Thermocouple Temperature Range (oC) Resolution (oC) Accuracy (oC) Type T
-210 to –120 -120 to -25 -25 to 200 200 to 400
0.03 – 0.1 0.02 – 0.03 0.01 – 0.02 0.01
±3 ± 0.9 ± 0.7 ± 0.5
An Omega® WB-DynaRes 16 channel data acquisition system was used to record all temperature readings. The thermocouple inputs run through a DataShuttle DS-16-8-TC, an input board with 8 input channels, as well as an aluminium isothermal block that allows improved accuracy of the readings by “attenuating differences at the cold junction connector”. This provides a more stable and reliable data output. The critical sampling rate for this experiment was 128 hertz. The Omega® data acquisition software (Quicklog™) and WB-DynaRes were designed to synthesise the ice-point reference. With this, the software converts voltage measurement to display temperature. As noted above, the WB-DynaRes logging card provided a resolution of 0.01-0.02 K ± 0.7 K. The data scan rate was adjustable from 45/55 reading per second (for a low noise resolution) up to 1400 reading per second. This was dependent on the data length chosen. When the data length was 16 bits, the maximum data scan rate was 200 samples per second, while the shortest data length, 12 bits, has a scan rate of 900 Hertz. A relationship between the resolution, scan rate and data length is shown below in Table 3.3 taken from the Omega® DataShuttle user manual, while the real-time display window is demonstrated in Figure 3.12.
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Chapter 3 Table 3.3 Data length, resolution and scan rate for the DataShuttle-16 [OMEGA®, 1999] DATE LENGTH (bits)
Low Noise Mode 16 bits + digital filter
16 bits
15 bits
14 bits
13 bits
12 bits
10 bits
Resolution (%) Scan Rate (Hz)
0.0015 45/55
0.0015 200
0.003 330
0.006 500
0.012 700
0.024 900
0.1 1400
Please see print copy
Figure 3.12 Real time display of the thermocouples’ readings provided easy temperature monitoring during investigations 3.4.2
Calibration of thermocouple system
The standard calibration method used for thermocouple measurements involves using “an oil bath, consisting of a air cooled condenser unit, heating element, a small pump and a thermoregulator” [Tian, 1997]. For this study, a constant temperature water bath was used to calibration the thermocouple. This consisted of fluid (water) circulated around a ’bath’ with a small heating element. The small heating element, located at the bottom of the bath, controlled the temperature via a potentiometer allowing voltage variation. A glass thermometer was placed within the fluid, at some distance away from the bath surface, to provide a temperature scale (within 0.5o C) for comparison with the thermocouple. Starting at an initial water temperature of 20o Celsius, and by varying the temperature in 5o increments, for 40o, a comparison was established between the thermocouple and fluid temperature. The thermocouples tip was dipped into the fluid, and left for approximately 10 minutes, to allow for the water temperature to stabilise. These results are reported in Table 3.4.
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Chapter 3 Table 3.4 Summary of measured water-bath temperatures, recorded via a glass thermometer (bath temperature) and the thermocouple system. Run Number Bath Temperature (oC) Thermocouple Temperature (oC) 1 2 3 4 5 6 7 8 9 3.5
20 25 30 35 40 45 50 55 60
19.98 25.02 30.03 35.05 40.09 45.12 50.10 55.12 60.15
Confined Space
According to the Australian Standards AS/NZS – 2865:2001 – an enclosure or partially enclosed space that is at atmospheric pressure during occupancy, and is not intended or designed primarily as a place of work a) Is liable at any time to; i)
Have an atmosphere which contains potentially harmful levels of contaminant, ii) An oxygen deficiency or excess, or b) Could restrict means of entry or exit. The use of a confined environment to investigate the welding fume breathing zone exposure concentration provided an ideal environment to study the dispersion of the released pollutant. Control of the ambient conditions, by restricting any unnecessary air movement, also provided the perfect situation to investigate the appropriate methods to controlling/reducing operator exposure. The room also incorporated the relation between the height and length of the space (§2.12), as noted by Baines and Turner (1969). This was to ensure that the plume generated by the welding operation would produce a stratified environment within the sealed space, rather than a turbulent internal condition. A suitably small shed was chosen and constructed to house the welding operation and the mannequin (Figure 3.13). The enclosure also allowed various ventilation techniques to be evaluated. All other welding components were located outside the space. The dimensions of the enclosure were 2.3 x 2.3 metre square base with a height of 2.1 metres. The controlled space was sealed using an expanding polyurethane product in the roof corrugations and gaps, to provide an airtight environment. The air tightness was tested using a smoke generator. Smoke was injected 126
Chapter 3 into the enclosure and assessment was determined visually. The location of the welding arc is x = 1035 mm, y = 950 mm, z = 900 mm and is highlighted in Figure 3.14.
Please see print copy for Figure 3.13
Figure 3.13 Photograph of the contained environment used for the breathing zone investigations. The shielding gas bottle (shown here in front on enclosure) was fastened around the side for safety purposes. It was determined that the enclosure would experience heat loss between the ambient external surroundings and the interior, as the plume convection and radiant heat from the arc zone transfer to the outer surface. In addition to this heat loss, a small portion of heat will be reflected due to the surface quality of the enclosure. Due to the fire hazards involved with insulating the inner surface (from ejected spatter), it was left unaltered.
Welding Bench
y 1035 mm x
Elevated View
2300 mm
Arc 775 mm
Arc
900 mm
Mannequin
1490 mm
950 mm
1400 mm
2100 mm
Sampling Position
800 mm
1050 mm
z 2300 mm Plan View
x
Figure 3.14 Schematic layout of the welding enclosure, highlighting the locations of the position of the arc, the sampling point on the mannequin, and general enclosure dimensions. 127
Chapter 3 3.6 Ventilation Of The Confined Space 3.6.1 General Extraction Using A Mechanical Ventilation System The first step of ventilating the enclosure was to utilise a portable extraction unit with an inlet positioned on top of the enclosure, to provide an extraction point away from the source and out of the enclosure. It should be noted that for this initial condition, the point of extraction was behind the welder. The opening or extraction area for the general ventilation strategies was 0.042 m2. Extraction was achieved via a portable extraction unit (WIA Single Head Fume Extractor CA93293), with an extraction volumetric flow rate of 0.708 m3/s. The extraction unit was located outside the controlled space, so that recirculation of the exhausted air did not affect fume plume dispersion, as well as preventing any concentration addition from the exhaust. Figure 3.16 presents a diagrammatical example of the extraction unit utilised in these trials. 3.6.2 Extraction volumetric flow calibration Calibrating the volumetric flow of the extraction unit was an easy process of simply measuring the differential pressure between the static and total pressure of the air flowing through the ducting. This was achieved by using a pitot tube or a stagnation pressure probe. This comprised two concentric tubes with openings that allowed the measurement of total and static pressure. _ Ceiling Openings f = 230 mm
Extraction Position 1
Arc Welding Bench
_
Arc
2300 mm
Mannequin 2105 mm 1490 mm 1265 mm
1150 mm
Sampling Position
1575 mm
2100 mm
_ _ _ _ __ _ _ _
2075 mm 1045 mm
Extraction Position 2
2300 mm Plan View
Elevated View
Figure 3.15 Schematic depiction of the extraction points on the ceiling of the enclosure. The red circles highlight the position of the ventilation openings on the ceiling of the enclosure.
128
Chapter 3 From this, the velocity of the air movement, and volumetric flow were calculated using:
V=
2( p0 - p) , r
3.5
Q = VAd Where p0 and p are stagnation and static pressures, respectively, r is the density of the air, and Ad is the cross sectional area of the † ducting. The tube was pointed in the opposite direction to the air motion, or into the airflow. The results are highlighted below in Table 3.5. Table 3.5 Evaluation of the extraction volumetric flow rate of ventilation strategies utilised during investigations Method of Extraction Pressure Difference Extraction Volumetric Flow Ventilation Duct Diameter Measured Rate ( p0 - p) (Pa) (mm) (m3/min) General Extraction 200 0.083 0.702 Local Extraction
100
452
12.9 †
Figure 3.16 An illustration of a portable extraction unit similar to the system used in these investigations
129
Chapter 3 During these investigations the extraction rate of the general ventilation scenario was varied, via a power inverter, to allow an analysis into the relationship between extraction rate and the measured breathing zone concentration. The evaluation of the inverter input is detailed in Table 3.6 below. Table 3.6 Evaluation of the extraction volumetric flow rate of ventilation strategies utilised during investigations Extraction Rate Inverter Reading Pressure Difference Actual Extraction Rate (m3/min)
(Hz)
(Pa)
(m3/min)
0.3 0.5 0.7
18 26 50
0.016 0.042 0.083
0.3 0.5 0.7
3.6.3 General Extraction Using Natural Ventilation Natural ventilation of the enclosure was carried out via the doorway of the enclosure. Leaving the door open generates a vertical channel of clean airflow into the space, while the contaminated air was forced out. This technique was described in the literature review chapter (§2.4.5). The doorway’s dimension was 715 mm in width and 2010 mm in height, generating an area of 1.44 m2, occupying approximately 30% of the front wall area. The doorway of the enclosure is illustrated below in Figure 3.17.
Please see print copy
Please see print copy
Figure 3.17 Photographs demonstrates the ventilation area provided by the enclosure’s doorway from an external and internal viewpoint.
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Chapter 3 3.6.4 Local Extraction The actual position of a local extraction system was a critical parameter that determined the effectiveness of the extraction. The ideal position of the extraction nozzle was determined simply by using the capture velocity of the contaminant and the parameters of the extraction system. Of course, the design of the extraction hood, whether it is flanged or unflanged, the opening shape, etc. all have a significant effect of the velocity profiles around the hood, and ultimately the efficiency of extraction (as described in §2.4.10.4). The position of the nozzle was calculated from the expression,
X=
(Q Vx ) - Ao
3.6
10
where X is the location of the extraction nozzle away from the source (m), Q is the volumetric flow rate of the extraction unit, † Vx is the capture velocity of welding fume (as designated by the ASHRAE manual [1989]), and Ao is the extraction nozzle area (m2). For these experiments, Vx was chosen as 2 m/s, Q = 0.319 m3/s, A = p(0.05)2 m2 generating an extraction position of 100 † mm from the arc. The extraction method used in the trials was that of a free round duct design. The selection of a free round duct provided an extraction process with the least efficient method of controlling welding fumes generated. This enabled an estimate to be established for the breathing zone
Mannequin
LEV 1
LEV Nozzle
1200 mm
2100 mm
Sampling Position
Arc
2300 mm
reduction with low control efficiency
LEV 2
Arc
Location of LEV nozzle with varying radius
Welding Bench
2300 mm Elevated View
Plan View
Figure 3.18 Location of the local extraction nozzle was close to the source of the welding contaminants.
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†
Chapter 3 3.6.5 Cross Flow Ventilation Set Up The design and construction of a ventilation system to provide a uniform airflow across the face of the welder requires several considerations. Firstly, to generate the required 0.5 m/s of crossflow air, a simple estimate of the required volumetric flow was determined to evaluate the size of the fan. The 0.5 m/s air velocity was chosen as the initial air cross-flow velocity based on results of the critical literature analysis. This was found simply by multiplying the vertical crosssectional area of the enclosure and the required air velocity. For the enclosure used, the cross sectional area (A) was 4.83 m2 (2.1 m x 2.3 m) resulting in a volumetric flow rate of 2.4 m3/s, to produce the desired minimal airflow across the breathing zone. This airflow was achieved by utilising a large fan to extract the 2400 litres per second required, through a duct system exhausted to the ambient. _ A Fantech APP0634/14/ axial fan with a diameter of 630 mm, 4 pole and a three-phase, 4 Kilowatt motor was used to produce to desired extraction rate (Figure 3.19). The original 14blade system had several damaged blades, which generated severe vibrations during operation of the fan. To eradicate this undesired fan vibration, the damaged blades were removed. To produce an efficient extraction system, the remaining intact blades were positioned in every second location. This 7-blade, 25o angle of attack system provided a balanced system, as well as conforming to the manufacturers performance data. To allow this volume of airflow to move, a small ducting system was designed and incorporated with the fan into the enclosure. This extraction system ran around the outside of the enclosure, exhausting to the atmosphere. The ducting system consisted of two 90o elbow, smooth radius bends featuring a singular splitter vane to aid in flow motion. A square duct size of 500 mm x 500 mm was chosen to produce a duct velocity in the vicinity of 10 m/s, as recommended by the ASHRAE design manual for air movement. The details are included in Appendix A.3. To decrease the overall output of the fan, an inverter motor control unit was used, enabling the fan speed to be continuously adjusted to produce the desired air speed (the results are presented in Table 3.7). Within the enclosure, two fabric (shade cloth) barriers (one with a of 90% and one 70% reflectivity) were erected to unify the volumetric flow within the occupational environment by providing a perforated surface that diffuses the large volumetric inflow (Figure 3.20). These aided in generating greater uniformity of the airflow velocity across the welding arc and breathing zone sampler. Measurements of the velocity within the enclosure were taken using an 132
Chapter 3 AIRFLOW TA5 hot wire anemometer with an accuracy of 0.01 m/s (Figure 3.21). Verification of the airflow pattern, within the enclosure, was achieved through two methods. Firstly, via a visual assessment using a smoke generator, as well as measuring air velocities at various positions throughout the enclosure (constructing an air velocity field). This enabled the general flow of the air to be validated. Due to the small wind velocities involved, the assessment combination used was deemed appropriate.
Please see print copy
Please see print copy
Please see print copy
Figure 3.19 Photographs of the purpose designed duct system to generate a cross-flow within the welding enclosure. Table 3.7 Table demonstrating the measured cross-flow velocities, as well as the inverter frequency utilised to produce specified airflow. Desired Air Speed Measured Air Speed Inverter Output (Hz) 0.5 0.6 0.7
0.52 0.61 0.72
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20 22 25
Chapter 3
Fabric Barrier (90%)
AXIAL FAN
Please see print copy
NOT TO SCALE
Fabric Barrier (70%) Figure 3.20 Schematic depiction of the ductwork utilised to generate the cross-flow air regime within the controlled enclosure, while the photograph displays the power inverter used to control to fan power for the cross-flow experiments.
Please see print copy for Figure 3.21
Please see print copy for Figure 3.21
Please see print copy for Figure 3.21
Figure 3.21 (a) Photograph of hot wire anemometer used to measure air velocities. Images include the (b) anemometer/thermometer probe and (c) LCD display of unit. Display shows air velocities to 2 decimal places. Measurement of the air velocity field was performed using a hot wire anemometer. A threedimensional system was used to evaluate the airflow pattern of the crossdraft. Using five planes in the x-y plane, air velocity measurements were averaged over 20 samples for each point. To ensure the measuring points were perfectly vertical, a piece of string, with a small weight 134
Chapter 3 attached to the bottom, was fastened to the ceiling of the enclosure. The length of string, which hung freely, had distance markings to provide accurate measure points. The layout out of the airflow sampling points is illustrated below in Figure 3.22, while the mean velocity measurements are displayed in Table 3.8. 500
535
1
535
2
730
A
B
C
D
E
3 20
4
5
6
7
8
9
500
250
150 150
250 1000
20 Figure 3.22 Locations used to measure the airflow velocity within the environment. All dimensions are taken from the arc (All dimensions in millimetres, drawing not to scale). Table 3.8 Velocity profiles for evaluation of cross-flow air behaviour. Measurements were for an air velocity of 0.5 m/s across the breathing zone of the operator and arc region. A B C D E 1 0.49 0.5 0.51 0.5 0.49 2 0.49 0.5 0.52 0.51 0.5 3 0.5 0.45 0.51 0.51 0.51 4 0.5 0.51 0.51 0.51 0.49 5 0.51 0.51 0.52 0.51 0.5 6 0.49 0.46 0.51 0.5 0.51 7 0.48 0.5 0.53 0.51 0.5 8 0.51 0.52 0.53 0.52 0.51 9 0.51 0.47 0.52 0.51 0.51 3.7 Visualisation of the Welding Fume Plume There are many techniques available to visualise fluid motion. Techniques such as seeding the flow with an indicator, lighting techniques (such as Tyndell and Schlieren) etc all assist in visualising fluid motion. Visualisation of the welding fume plume during these investigations was extremely difficult, due to the intense light from the arc and the reflective nature of the enclosure. Several techniques were used to aid the visualisation process, however, these were deemed unsuccessful. If an effort to visualise the behaviour of the plume, a fog machine was used in place of the arc source. Smoke was released into the confined space to simulate welding plume behaviour. The 135
Chapter 3 smoke was directed to the arc region through small plastic tubing attached to the output nozzle of the smoke generator. Upon release, the smoke travels through the tubing into the confined space, were it rose and dispersed. It should be noted that the source of a welding plume is highly buoyant in nature, as stated previously, where the smoke machine produces a buoyant flow for small periods of time. The main purpose of utilising the smoke generator was to visualise the behaviour of welding fume dispersion within occupied environment. The smoke became a model of the welding fume scenario. Although the smoke is ejected at a high temperature (approximately 200oC), it quickly cools, and within 20 seconds of dispersion will descend to the ground. To generate the plume like images seen in Figures 3.23, the smoke was continuously pumped into the space, using the continual input momentum to generate a ‘buoyancy’ effect. In addition to simulating the dispersion of the welding plume, within the enclosure, the smoke visualisation was used to assess the quality of the ventilation methods. The most critical ventilation method to assess was the cross-flow strategy. To verify the uniform characteristics of the crossdraft, the air was seeding with smoke and observed. The flow exhibited a uniform flow for the low cross-flow velocities. Visualising the plume dispersion for this ventilation strategy demonstrated how an increase in crossdraft velocity (extraction rate) deflected the plume from its vertical path (demonstrated in Figure 3.23). Figure 3.24 illustrates the deflected path of the plume due to the various crossdraft velocities. The dispersion of the smoke plume into the confined environment demonstrated the filling box effect, with the plume travelling to the ceiling, where it spread and formed an interface. However, as stated previously, the smoke cloud was not buoyant, so it quickly descended and dissipated. Another ventilation strategy investigated was that of natural ventilation. Using the doorway of the enclosure, the outflow of fluid was observed and photographed. The images display the channel of fluid (Figure 3.25).
136
Chapter 3
Please see print copy for Figure 3.23
Figure 3.23 Photographs simulating the release and dispersion of a welding fume plume within the confined enclosure. Images are taken over intervals of 5-second period.
137
Chapter 3
Please see print copy for Figure 3.24
Figure 3.24 Photographs highlighting the effect of various cross draft velocities on the dispersion of the plume. Images (from left to right) depict cross draft velocities of 0.5, 0.6, and 0.7 m/s.
Please see print copy for Figure 3.25
Please see print copy for Figure 3.25
Figure 3.25 The simulated doorway flow, with the buoyant fluid exiting the enclosure in a channel. The contaminated ‘buoyant’ fluid exits the enclosure through the upper section of the door, while clean ambient fluid enters through the lower section. The interface between the two flow regimes is highlight (in left photograph).
138
Chapter 3 3.8
Observations of Shielding Gas Effects on Welding Fume Dispersion
A major area of interest with the dispersal of welding fume lies with the source boundary conditions. With GMAW, the shielding gas impinging on the workpiece, used to aid the weld, affects the initial behaviour of the plume. To investigate this initial plume dispersion, a fluxcored welding operation was performed (with and without the addition of the shielding gas) in an attempt to visualise the shielding gas influence. Flux cored wire generates more visible fume and assists in the visualisation. The initial plume position was photographed using a digital camera. To avoid the intense light from the arc, a rectangular pipe was positioned in front of the arc to obstruct the arc light. Some of the photographs of this assessment are reproduced in §4.3.1. The constituents of this simple initial plume appraisal are illustrated below in Figure 3.26. 3.9
Fountain Experimental Apparatus and Methodology
These experiments were performed in an acrylic tank of internal dimensions 1180 mm long, 470 wide and 490 mm deep. The flow was observed using the shadowgraph method for visualisation. Modelling the negatively buoyant fountain was achieved using a salt-water solution, coloured with blue food dye (for the jet) injected into a tank of ‘fresh’ water (representing an ambient environment). The source fluid was stored in a large tank on the floor, and was pumped to the header tank situated 3 metres off the ground, through a small bilge pump with a flow rate of 360 gallons/hr. The flow rate was produced from this gravitational head and adjusted via a valve, enabling finer control of the flow. The source nozzle was fixed by a light aluminium bar, and ejected upwards into the tank. A stage light was used to pass a beam of light through the tank and onto a translucent screen, highlighting the behaviour of the fluid in the model. By using dense fluid as the turbulent jet, the model must be inverted to portray a similar behaviour to the heat generated welding plume. The source of the fountain was injected vertically upwards towards a horizontal acrylic sheet. Threaded rods were used to enable the nozzle-to-acrylic distance to be modified with ease and accuracy. The drawings for this design can be found in Appendix A.4. This rig was designed to use pre-existing equipment, as utilised by several previous researchers at the University of Wollongong. A schematic showing the layout is shown in Figure 3.26 and details of the equipment can be found in Figure 3.27. The first experimental investigations involved varying the distance between the acrylic sheet and the nozzle. Using the jet length Lj as the maximum possible displacement from the surface, the 139
Chapter 3 height was reduced in approximately 20 mm ± 10 mm increments to observe how the height of the jet nozzle affects the radial spread, for a fluid striking perpendicular to a flat surface. These experiments were repeated several times at each height, allowing an average of the observed radial spread to be recorded. The initial upward flow of the fountain was jet-like in nature, before impinging on the acrylic surface. Header Tank
Fresh Water Supply
Filter Rotameter
Impingement Rig
Pump
Video Camera
Storage Tank Light Source
Fresh Water Tank
Drainage System Transparent Transparent Paper Paper and and Reference Grid Grid
Valve Direction of Flow Figure 3.26 Schematic of the salt water modelling apparatus set up. Secondly, variation of the salt solution concentration was undertaken to investigate the influence of buoyancy on the radial spread. An increase in buoyancy should result in a reduction in the radial spread. This is due to a decrease in L j , and an increase in the buoyancy-induced momentum. Alternately, the increase in the initial volumetric flow rate causes an increase in the initial momentum flux. This leads to an increase in thermal length of the system, and provides † greater motivation for the fluid to spread over the impinged surface. The nozzle has an effective diameter ( D0 ) of 10 mm. If the nozzle diameter remains constant, Equation 5.42d illustrates that, there are only three variable parameters that influence the radial spread. These three influential parameters are the distance between the nozzle and plate ( zI ), the † initial volumetric flow rate ( Q0 ) and initial buoyancy ( g¢0 ). Experimentally, these parameters represent the nozzle-to-surface height, the concentration of the salt solution and flow rate of the injected fluid. Only the ambient conditions and nozzle dimensions remain constant. Great care † † was used to guarantee that the impingement surface was horizontal, and perpendicular to the 140
†
Chapter 3 input fluid. A spirit level was used to check the orientation of the test equipment. A small grid was placed in front of the tank, to use as a reference scale for later observations. Header Tank
Please see print copy for Figure 3.27
Figure 3.27 Photographs of equipment used in salt-water modelling of GMAW shielding gas. A small bilge pump was used to supply the header tank. The salt experiment were video recorded using a Panasonic Super VHS camera, and utilising the CFD program, DigImage, the radial spread was determined. A sample of the image analysis provided by DigImage is illustrated below (Figure 3.28). Surface of Impingement Rsp - Radial Spread Height of Nozzle - H
Please see print copy for Figure 3.28 from impingement surface
Nozzle
Figure 3.28 Shadowgraph image, taken from DigImage analysis, demonstrating the elements of the impinging turbulent fountain. 141
Chapter 3 To simulate the welding nozzle source with these salt-water experiments, the parameters of the welding nozzle were scaled according with the actual welding torch nozzle, used in the experiments (refer to Appendix B). 3.10 Summary Analytical techniques for measuring the particulate contaminant from the GMAW process are well documented, and readily available. The major point of interest and ambiguity for field measurements of breathing zone concentration levels was the positioning of the sampler. The standard hygienist’s practice is to position the sampler on the lapel, while the welding community recommend the sampling position be located behind the welder’s mask, which was believed to provide a form of fume protection. The difference between an in helmet sensor and a lapel worn probe yields vastly different concentration samples. This discrepancy has been resolved in the United States where all welding fume breathing zone measurements are to be taken from behind the welding mask. These investigations adhered to the internal helmet mounted sensor, since it was believed to simulate the ‘actual’ effective breathing zone more accurately. The test rig was constructed for the specific purpose of collecting fume samples, allowing the determination of the overall exposure concentration produced by GMAW fume. By maintaining the welding parameters such as a voltage and current, as well as a shielding gas flow, it is possible to observe the overall effect that various ventilation modes have on reducing the breathing zone concentrations measured. The dimensions of the space were 2.3 m wide by 2.3 m deep by 2.1 m in height. However, the effective height of the enclosure is only above the source of the contaminant (1.15 metres). The breathing zone was located 0.45 metres vertically above, and 0.27 metres horizontally from the arc source (with 0.52 metres of the source). It should be noted that there was an approximate 10-second time difference between the total arc period and the total sampling time or approximately 0.01-0.02% of the total time there was no welding activity. This was due to the manual starting and stopping facility of the sampling device. It is argued that this time discrepancy does not significant affect the results gathered by the personal sampler, but if left for a sufficient period of time, it can effect the total fume concentration collected. This was one of the main concerns associated with the conventional eight-hour working/sampling period, as noted previously.
142
NOTE: All photographic images have been removed from this chapter to reduce the file size. Please see the print copy of this thesis for these images.
Chapter 4
Chapter 4 EXPERIMENTAL RESULTS Scope This chapter presents the fume measurements recorded during the breathing zone experimental study. These initial trials were carried out within a controlled environment with no ventilation. Section 4.1 examines the scenario of the non-ventilated, confined environment used to obtain a benchmark exposure concentration quantity so as to obtain a reference concentration to aid in the determination of control effectiveness for the later ventilated experiments, and secondly, to explore the contaminant levels within a confined space. Section 4.2 presents the results from the introduction of the ventilation strategies to the confined enclosure. Here the various strategies implemented are explored and are briefly discussed. The thermal examination of the enclosure is presented in Section 4.3, while Section 4.4 introduces an experimental method used to simulate the flow of shielding gas from a GMAW nozzle. 4.1.1
Background
When a potentially hazardous operation is performed within a restricted environment, the risk of the occupant being exposed to excessive levels of pollutants becomes significant. It has already been established that GMAW produces a contaminant, which if inhaled poses a threat, if not immediate then long term, to the health of the welder. It is generally considered that a more restrictive working environment increases the probability of pollutant levels exceeding exposure standards. The restrictive nature of the working environment can limit contaminant dispersion, generating an undesired accumulation of any hazardous pollutants produced within the enclosure. Typical confined spaces used for welding operations include boilers, pressure vessels, tanks, small compartments (in ships), pipes, etc. When welding within an enclosure, the buoyant fume plume ascends towards the ceiling, where it forms a hot layer. This contaminated layer will slowly fill the enclosure with contaminant, generating a hostile working environment. Breathing zone contamination can occur by direct contact with the contaminated emissions, or by
143
Chapter 4
secondary exposure from the background environment, generated by the dispersion of the contaminants. A study into the condition of the operator’s breathing zone within an enclosure should provide useful information on the concentration levels that face a welder during confined space operations. It also provides an initial investigation condition as the basis for ventilation experiments. The use of a small enclosure provides a scaled simulation of the actual working environment. The objectives of these experiments were to: i)
Develop a sampling strategy to duplicate exposure experiments with a high degree of repeatability and replication,
ii)
To measure the breathing zone concentrations for welding performed within a controlled environment, and
iii) 4.1.2
Determine how the plume is dispersed in this restricted environment. Set Up For Initial Fume Measurements
A number of initial trials were carried out using CIGWELD ER-70S-4 0.9 mm wire (refer to §3.2.4 for specification) within the enclosure. These exploratory tests were used to optimise the measurement systems, for breathing zone and background concentration levels. The 0.9 mm wire produced uneven weld beads with an extremely high spatter ejection due to the high wire feed speed required. In addition, the tests produced a large concentration distribution between samples. An increase in the wire diameter was chosen so as to generate a reliable, stabilised welding condition hence, steady fume production. The increase in wire diameter size from 0.9 mm to a 1.2 mm electrode produced a good quality weld bead, reduced spatter levels (visual observation) as well as a stabilised fume production. Quimby and Ulrich (1999) noted that a wire diameter of 1.2 mm was commonly used, as it was readily available and the “median common standard in most GMAW.” Selecting constant welding parameters enabled a greater emphasis on how the fumes are dispersed within the working environment, rather than evaluating what parameters generate higher concentration levels. The shielding gas nozzle-to-work distance was 144
Chapter 4
fixed at 14 mm. This distance was chosen based on literature review results. Slight variations due to visual errors are negligible, as past research noted that the nozzle-towork distance has only a minor influence on fume rates. The welding input parameters of voltage and current for these experiments were measured using the ARCWATCH™ program, over a period of 5 minutes. These mean welding conditions are provided in Table 4.1. Table 4.1 Welding Conditions used during fume/breathing zone investigations. Electrode
1.2 mm ER-70S-6 (Copper coated) 1.2 mm ER-70S-6 (Non-Copper coated)
Mean Voltage (Volts)
Mean Current (Amps)
Mean Wire Feed Speed (m/min)
Power (kW)
Metal Transfer Mode
25
200
8.76
5
Mixed Mode
To ensure the consistency of the measured values, all parameters have been constrained to eliminate any misrepresentation of the recorded samples. The experiments were carried out using a flat bead deposit on a rotating mild steel pipe. The shielding gas used was BOC Argoshield 50 (82% Ar, + 13.25% CO2 + 2.75% O 2). It was expected that these investigations would provide a detailed account of breathing zone exposure under the specified welding conditions, within a confined environment. Before each test was performed, the enclosure was exhausted of any residual fume via an extraction fan located on the ceiling for a period of 15 minutes. Also, the space was swept clean to prevent any secondary aerosol characteristics (i.e. prevent the settled particles from becoming reanimated). 4.1.3
Breathing Zone Concentrations for ER-70S-6 Wire
All exposure measurements were performed in accordance with the Australian Standard for measuring fume from welding and allied processes (AS-3853.1-1991). For the general procedure, refer to §2.2.8 and §3.3.2. The breathing zone concentrations measured during the trials demonstrated that when welding is executed within the confined region, the exposure levels are several times larger than the prescribed maximum limit of 5 mg/m3. The measured mean exposure concentration of 83 mg/m3 exceeded the concentration TWA by almost 17 times (Figure 4.1). 145
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Samples were taken using three different welding electrodes during the confined space experiments. The primary investigation utilised ER70S-6 Hyundai electrodes, with both copper coated and non-coated wires. The investigation of the low fuming, non-copper coated wire was undertaken to determine the effect the electrode had on reduction of breathing zone concentrations in direct comparison with the copper coated electrode, and also the sensitivity of the measurement technique used. All exposure measurements recorded indicated the extremely high concentration levels of welding fume pollutants within the sampled breathing zone. The exposure of the welder to the fume generated by the GWAW process yielded some interesting findings.
Breathing Zone Concentration (mg/m3)
1000
100
10
1 0
5
10
15
20
25
30
35
40
Sample Number
Figure 4.1 Scatter of breathing zone concentration results for the confined space welding trials. The experiments with the ER70S-6 copper coated 1.2 mm diameter electrode produced good quality weld beads and relatively small spatter ejection. A picture of the weld bead produced is shown in Figure 4.3. Spatter ejection was determined visually through the enclosure window.
146
60 50 40 30 20 10
9 13 0-
13
012
9
9 12
011
11
10
9
9
0-
-9
10
90
-8 9 80
-7 9 70
9 -6 60
-5 9 50
9 -4 40
-3 9
0 30
Breathing Zone Concentration Percentage (%)
Chapter 4
Concentration Range (mg/m3)
Figure 4.2 Normal distribution of breathing zone exposure concentration for ER70S-6, 1.2 mm copper coated electrode
Please see print copy for Table 2.13
Figure 4.3 Weld beads were approximately 2 mm between each bead, and a thickness of 6 mm. Figure 4.2 displays the distribution of the results generated by the breathing zone experiments. Although deviations from the mean concentration of 82.7 mg/m3 (highlighted in Figure 4.1 and Table 4.2) are quite large, the overall concentration distribution demonstrates the reliable, reproducible quality of these tests. 147
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Table 4.2 Mean breathing zone concentration results measured during confined space experiments on ER70S-6 1.2 mm copper coated wire VENTILATION PARAMETER BREATHING ZONE FUME CONCENTRATIONS (mg/m3) Non-ventilated space Mean Concentration = 82.72 mg/m3 (N = 40) Standard Deviation = 11.23 mg/m3 Coefficient of Variation = 18.29 % 4.1.4
Results of the Enclosure Concentrations Within The Confined Space
In addition to the breathing zone trials, parallel enclosure background concentration samples within the enclosure were recorded during the initial breathing zone experiments. The location of the sampler was discussed in §3.3.3. Although only a few samples were taken of the enclosure concentration, the sampled results for the confined environment gave an insight into the distribution of the generated fume plume. For the 15 minute arcing period, the mean concentration was calculated over the 10 samples taken. The mean enclosure concentration was 73.4 mg/m3, with the deviations are highlighted in Figure 4.4 and Table 4.3. It is clearly visible from Figures 4.4 and 4.5 that, although only few data points were recorded, there is little divergence from the mean concentration (16.4 mg/m3 from minimum to maximum concentration). Due to the continuity of the results i.e. the limited scatter found in concentrations, the small sample number was felt to be sufficient in providing representative results. The enclosure exposure concentration in this ‘confined space’ is approximately 89% of the breathing zone exposure concentration measured. Figure 4.6 illustrates the comparison between filters used in both the breathing zone and enclosure measurements. The discolouration due to the accumulation of the welding fume is visible on both filter samples. The darker deposit on the breathing zone filter signifies the higher mass concentration (far right), while both the breathing zone and enclosure samples illustrate the effects of welding fume occupational exposure over a 15 minute period, in comparison to the pristine filter membrane on the far left.
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Background Breathing Zone Concentration (mg/m3)
1000
100
10
1 0
2
4
6
8
10
Sample Number
Figure 4.4 Background concentrations within the welding enclosure. These measurements were taken in the background area of the welding space, at a distance of 1.6 metres and height of 0.45 metres from the arc.
Background Enclosure Exposure Concentration Percentage (%)
60
50
40
30
20
10
0 55-59
60-64
65-69
70-74
75-79
80-84
85-89
Concentration Range (mg/m3)
Figure 4.5 Distribution of concentrations from background enclosure concentrations Table 4.3 Mean background enclosure concentration results measured during confined space experiments on ER70S-6 1.2 mm copper coated wire VENTILATION PARAMETER BREATHING ZONE FUME CONCENTRATIONS (mg/m3) Non-ventilated space Mean Concentration = 73.43 mg/m3 (N = 10) Standard Deviation = 6.05 mg/m3 Coefficient of Variation = 8.24 % 149
Chapter 4
Please see print copy
Figure 4.6 Photograph illustrating the continuity of the filter paper before and after collecting fume within the confined environment. 4.1.5
Breathing Zone Concentrations for ER-70S-6 (Non-Copper Coated) Wire
The removal of the copper coating from the electrode wire is claimed to reduce the total generation rates of the GMAW process. Previous studies have stated that fume emission rates can be reduced with the use of low fume generating wires. This current investigation generated a reduction on the mean breathing zone concentration, compared to the copper coated wire, by approximately 34%.
Breathing Zone Concentration (mg/m3)
1000
100
10
1 0
5
10
15
20
25
Sample Number
Figure 4.7 Breathing zone concentration results using the non-copper coated ER-70S-6 electrode.
150
Breathing Zone Concentration Percentage (%)
Chapter 4 60 50 40 30 20 10 0 30-34 35-49 40-44 45-49 50-54 55-59 60-64 65-69 70-74 Concentration Range (mg/m3)
Figure 4.8 Distribution of breathing zone concentrations from ER70S-6, 1.2 mm non-copper coated electrode As with the copper coated electrode experiments, there was a large distribution within the experimental results, as shown in Figures 4.7, 4.8 and Table 4.4. The difference between the lowest and highest measured concentrations was approximately 17 mg/m3. Along with the measured concentration, spatter ejection from the arc region differed, although an expression for the spatter was not determined. Table 4.4 Mean breathing zone concentration results measured during confined space experiments on ER70S-6 1.2 mm non-copper coated wire VENTILATION PARAMETER BREATHING ZONE FUME CONCENTRATIONS (mg/m3) Non-ventilated space Mean Concentration = 54.19 mg/m3 (N = 25) Standard Deviation = 5.91 mg/m3 Coefficient of Variation = 10.91 % 4.1.6 Summary of Confined Environment Results The exposure concentrations for all confined space breathing zone measurements significantly exceeded the occupational exposure standard. The comparison between the breathing zone and enclosure concentrations for the copper coated wire illustrates that, within the bounded environment, there is a high risk probability of excessive occupational exposure. The small difference in the total concentration exposure between the two sampling positions exhibits the high demand for an exposure control strategy.
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The introduction of the non-copper coated electrode produced a reduction in the breathing zone exposure concentration. This breathing zone concentration reduction indicates that operator exposure can be reduced by process modification. Moreover, the result of effectively reducing contaminant generation (FFR) may lead to a reduction in operator exposure.
Breathing Zone Concentration (mg/m3)
1000 Copper Coated CoatedWire Electrode Copper Non-copper Coated Solid Wire Electrode BackgroundConc. Background
100
10
1 0
2
4
6
8
10
Sample Number
Figure 4.9 Comparison between breathing zone concentrations for copper and non-copper coated electrodes, as well as the background concentration for both wires. The mean breathing zone concentration for the copper-coated electrode, non-coppercoated electrode and the background enclosure measurements are 82.72, 54.19 and 73.34 mg/m3 respectively. The closeness of the breathing zone and background enclosure concentrations indicates that within the confined environment, an individual within close proximity to a source of contaminant will be exposed to comparable concentrations to those of the operator. 4.2 Ventilated Enclosure This section reports the effects of introducing various ventilation strategies into the controlled enclosure. The breathing zone concentrations recorded during these experimental studies are presented here to aid in determining the most effective method of controlling and/or reducing welding fume exposure of the operator. These trials were
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performed in the same controlled environment as the previous confined space investigations. Section 4.2.1 examines the introduction of the first strategy of a ‘general’ ventilation system. The confined environment is ventilated via different extraction points located in the ceiling. The second condition uses natural ventilation provided by using the open door of the enclosure. It should be noted that the control of this method is extremely difficult, as it relies on the thermal properties of the source and environment and the size of the opening (§2.4.5). Section 4.2.3 introduces the localised ventilation parameters with an induced flow across the facial area of the mannequin. Section 4.2.4 further examines the local extraction strategy with the use of an extraction nozzle within close proximity to the arc. The objective of this section was to!! ! ! determine the effectiveness to controlling operator’s breathing zone exposure to excessive concentrations. This was achieved by: i)
Varying positions of extraction points for general and local extraction modes,
ii)
Using the ‘open door’ of the enclosure to measure the effect of having a large opening has on fume dispersion,
iii)
Varying extraction rates to determine concentration reduction on the operator’s exposure.
4.2.1.1
General Mechanical Ventilation
The first scenario of this investigation was focused on general ventilation of the confined space. This was achieved by means of an extraction system with inlets positioned in the ceiling of the enclosure. The initial extraction rate used was 702 l/min, which equates to an air change rate for the enclosure of 3.8 air changes per hour (ACH). Air changes per hour represents a simple function of the extraction rate divided by the volumetric size of the enclosure. Investigations were performed from two points of extraction. These two positions were chosen to investigate the effect of the extraction point location on breathing zone concentration reduction, with both inlets located in the ceiling to represent a general ventilation system. Extraction point 1 was located in the far corner of the enclosure (the furthest point from the arc), while extraction point 2 was directly above the arc and breathing regions. 153
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Relocating the extraction point to a position directly above the mannequin’s head, allowed the effect of overhead ventilation to be explored. This extraction point was investigated due to the unknown effects of extracting welding fume from directly above the operator’s breathing zone. Two scenarios were possible: 1. The plume, directed through the operator’s facial region, creates a potentially higher breathing zone exposure, or 2. The negatively pressurised environment will extract the plume at a greater rate than its volumetric flow, producing a higher velocity across the welder’s face, which may aid in reducing exposure levels. The gravimetric concentration device was again employed to evaluate the breathing zone condition. For the extraction point at position 1, the results of the fume concentration gathered produced a dramatic reduction in the exposure of welder to the pollutant, in comparison to the confined space situation (Figure 4.10). Figure 4.12 highlights the further decrease in measured concentration due to repositioning the extraction point above the welding operation (operator’s head).
Breathing Zone Concentration (mg/m3)
1000
100
10
1 0
10
20
30
40
Sample Number Figure 4.10 Breathing zone concentration results for each sample taken using general ventilation via extraction point 1 (Far corner, on the ceiling of enclosure). Extraction rate is 0.7 m3/min.
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Concentration Percentage (%)
60 50 40 30 20 10 0 9-11
12-14
15-17
18-20
21-23
24-26
27-29
Concentration Range (mg/m3) Figure 4.11 Distribution of the breathing zone concentration results for the general ventilation via extraction port in the far corner of the enclosure. Extraction rate is 0.7 m3/min
Breathing Zone Concentration (mg/m3)
1000
100
10
1 0
10
20
30
40
Sample Number Figure 4.12 Breathing zone exposure concentrations due to the relocating the ceiling extraction point. The extraction port was above the source of contaminate and the operator’s breathing zone (Extraction rate 0.7 m3/min). Figures 4.11 and 4.13 demonstrate the distribution of the measured concentration, due to the influence of the ceiling extraction ventilation strategy. 155
Chapter 4
Concentration Percentage (%)
60 50 40 30 20 10 0 1-3
4-6
7-9
10-12
13-15
16-18
19-21
Concentration Range (mg/m3) Figure 4.13 Breathing zone exposure concentration distribution due to the general ventilation at position 2 (On enclosure ceiling, above source and breathing zone). Measuring the breathing region exposure levels for the second case demonstrated a substantial reduction compared to that of the confined space experiments. The overhead extraction position yielded an average breathing zone concentration of 10.1 mg/m3, a reduction of 88% from the confined space model, and a 48% reduction compared to the first general extraction scenario. This result indicates that the control effectiveness increases as the extraction point moves closer to the source. It should however be noted that the concentrations measured are still twice that of the TWA exposure standards for welding fume (5 mg/m3). 4.2.1.2
Variation in Extractions Rates for General Ventilation
Variation of the extraction volumetric flow rate for this general ventilation strategy enabled the establishment of a relationship between extraction flow rate and breathing zone concentration. Using three different extraction flow rates, of 0.7, 0.5 and 0.3 m3/s, the measured breathing zone concentrations are illustrated below in Figure 4.14. The distribution of the measured concentration, due to the variation in the extraction rate for 0.5 and 0.3 m3/s, are illustrated below in Figures 4.15 and 4.16, respectively. The measured concentration distribution for an extraction rate of 0.7 m3/s can be seen in Figure 4.11. 156
Chapter 4
Breathing Zone Concentration (mg/m3)
100
10
0.7 m3/s
0.5 m3/s
0.3 m3/s
1 0
5
10
15
20
Sample Number
Figure 4.14 Breathing zone concentration results due to variations in extraction rate. The general ventilation was provides by an extraction port, in the far corner of the enclosure.
Concentration Percentage (%)
60 50 40 30 20 10 0 23-26
27-29
30-32
33-36
37-39
Breathing Zone Concentration (mg/m3)
Figure 4.15 Breathing zone concentration distribution due to the general ventilation of the confined space. Ventilation point was in the far the corner of the enclosure, with an extraction rate of 0.5 m3/s (2.7 ACH). The increase in extraction rate delivered lower measured breathing zone concentrations, however, these values indicate that this ventilation strategy is not effective at meeting occupational exposure regulations. The mean breathing zone concentrations for
157
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extraction rate variations, compared to the confined space are displayed below in Figure 4.17.
Concentration Percentage (%)
60 50 40 30 20 10 0 42-44
45-47
48-50
51-53
54-56
57-59
Breathing Zone Concentration (mg/m3)
Figure 4.16 Breathing zone concentration distribution due to the general ventilation of the confined space. Ventilation point was in the far the corner of the enclosure, with an extraction rate of 0.3 m3/s (1.6 ACH).
Breathing Zone Concentration (mg/m3)
1000 Mean Breathing Zone Series3 Concentration
100
10 0
0.3
0.5
0.7 3
Ventilation Extraction Rate (m /s)
Figure 4.17 Distribution of measured breathing zone concentrations, due to the effect of various extraction rates of general ventilation. The introduction of the general extraction strategy, within the confined space, produced significant reductions in the concentration of the breathing zone environment for the 158
Chapter 4
welder, for varying extraction rates. However, the measured breathing zone concentrations still exceeded the recommended average for an 8-hour working period (these experiment represent only 3% of the total duration of the ‘normal’ working day). Intuitively, further increase in the extraction rate will continue the trend of reducing breathing zone concentration. For an established fume emission rate, increasing in the extraction rate will generate an increase in the number of air changes per hour, providing more air movement. Increasing the number of air changes effectively reduces the total space concentration. Thus. at some (rather large) extraction rate, the breathing zone concentration should theoretically converge towards the regulation occupational standards. 4.2.2
General Natural Ventilation
Natural ventilation provides a fluid exchange between the internal contaminated environment and the external atmospheric conditions. Using the enclosure’s doorway gave the maximum possible area for air exchange to aid in the reduction of contaminant levels within the controlled space. The general flow through an opening such as a doorway is discussed in §2.4.5, where the warm contaminate layer will be forced out, while the clean ambient air will flow into the workspace. The large opening effectively removes the welding contaminant generated from the enclosure, however, as with the general ventilation case, the plume still ascends through the breathing region across the welder’s face. The average breathing zone concentration with the door flow is 12.3 mg/m3, a reduction of 85% from the confined space mean concentration, and produced similar exposure control to the general extraction strategies of §4.2.1.1. The measured results for these experiments are illustrated in Figures 4.18 and 4.19. The use of general ventilation to control operator’s breathing zone exposure was not effective at reducing the measured breathing zone concentrations to meet occupational regulations, but gave similar results to general extraction. The effect of combining the two above methods of general ventilation (mechanical and natural) would be a decrease in the overall concentration within the space. The combination of the two methods effectively provides a reduction in breathing zone 159
Chapter 4
exposure concentration due to an increase in exchange rate. However, only a tightly controlled system will be able to control the exposure concentration towards the occupational standards.
Breathing Zone Concentration (mg/m3)
1000
100
10
1 0
10
20
30
40
Sample Number Figure 4.18 Breathing zone concentration results using natural ventilation (doorway flow) to control welder exposure.
Concentration Percentage (%)
60 50 40 30 20 10 0 1-3
4-6
7-9
10-12
13-15
16-18
19-21
Concentration Range (mg/m3) Figure 4.19 Distribution of breathing zone concentration generated by using a doorway (natural ventilation) to reduce welding fume levels.
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4.2.3
Cross Flow (Laminar Flow) Ventilation
When laminar airflow is passed through a working environment, it creates a cross flow pattern where the contaminant is displaced from the typical vertical path, reducing the contact the welder has with the fume plume. The normal recommended air velocity for effective dispersion of welding fumes is 0.5 m/s across the welder’s face. Air forced across the welder’s face to remove the contaminate prior to operator exposure
Operator
Location of arc on workpiece Location of sampling point Figure 4.20 Schematic of cross-flow air movement, with airflow passed across the welder’s breathing zone and above the workpiece. For details of the orientation of the enclosure, refer to Chapter 3. Using a large fan, an extraction volumetric flow of 2.5 m3/s was used to generate the required cross-flow velocity (§3.6.5). 1000
Breathing Zone Concentration (mg/m3)
Crossflow (Right to Left) Crossflow (Left to Right) TWA (5mg/m3) 100
10
1
0
5
10 15 Sample Number
20
25
Figure 4.21 Breathing zone concentration results for both flow directions, using a crossdraft directed across the welder’s frontal region. The results using a crossdraft velocity of 0.5 m/s produced an average breathing zone concentration of 3.43 mg/m3 (right-to-left airflow) and 3.44 mg/m3 (left-to-right 161
Chapter 4
airflow), and are illustrated in Figures 4.21 and 4.22. The recommended 0.5 m/s air velocity did effectively reduce the average breathing zone levels to the prescribed occupational limit, however, an average of 22% of the total measured samples were 4.5 mg/m3 or higher. The right-to-left airflow 16% of the concentration fell above the 4.5 mg/m3 with 2 samples (8%) above 5 mg/m3, while the left-to-right crossdraft produced 28% above 4.5 mg/m3 (with 1 sample above 5 mg/m3). In order to reduce the exposure risk factor, the crossdraft velocity was increased by 0.1 m/s increments over two steps (0.6 and 0.7 m/s). This increase in crossdraft velocity generated a reduction in the measured breathing zone exposure concentrations. 30 Breathing Zone Concentration Percentage (%)
Crossflow (Right to Left) Crossflow (Left to Right)
25 20 15 10 5
57
5
6.
6. 6-
-6 5. 5
55. 5
55 4.
4
4. 5 4-
53.
3. 5
5
3
3-
52.
2. 2-
52
1.
1. 5
1-
51
0.
0-
0. 5
0
Breathing Zone Concentration (mg/m3)
Figure 4.22 Distribution of breathing zone concentration generated by using a cross-flow to reduce welding fume levels. The percentage represents that of the recorded concentration samples in the breathing zone. Increasing the airflow velocity across the face of the welder produced a small reduction in the breathing zone exposure concentration, with air velocities of 0.6 and 0.7 m/s generated mean measured concentrations of 2.9 mg/m3 and 2.6 mg/m3, respectively. The results of this investigation are illustrated in terms of the increased airflow velocity with respect to the measured breathing zone concentration (Figure 4.23). With the 0.6 m/s cross flow, the breathing zone concentration was consistently below the recommended TLV.
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Breathing Zone Concentration (mg/m3)
8 7 6 5 4 3 2 1 0 L to R (0.5 m/s)
R to L (0.5 m/s)
R to L (0.6 m/s)
R to L (0.7 m/s)
Cross-draft Air Velocity (m/s)
Figure 4.23 Increasing the crossdraft velocity, across the face of the operator, produced a reduction in the total breathing zone exposure to contaminants produced by the welding process. This graph indicates the measured range and the mean breathing zone concentration generated during these crossdraft trials. 4.2.4
Local Extraction Ventilation
The position of the nozzle, with respect to the arc zone, has significant effects on fume control. However, the position of the nozzle with respect to the welder has not been clearly evaluated. A nozzle positioned on the same side of the weld as the worker may produce a higher exposure rate due to the exhaust hood drawing the plume towards the operator (especially if the nozzle is not effectively located close to the source). The extraction of fume from the source will eliminate, or at least reduce the plume flow past the welder’s head, producing a lower exposure. Three positions were investigated to evaluate the effectiveness of removing contaminate from close proximity. These were: -
150 mm from the arc at 50o, welder’s side,
-
125 mm from the arc at 50o, welder’s side,
-
100 mm from the arc at 50o, welder’s side,
-
100 mm from the arc, 180o (directly opposite welder).
Figure 4.24 demonstrates the position of the extraction nozzle, with respect to the welder and the arc region, while Figure 4.25, 4.26 and 4.29 display the measured concentration results produced during this study. 163
Chapter 4
Angle (q) from welder’s centreline
Arc region
Figure 4.24 Schematic depiction of local extraction orientation, with respect to operator and source. The extraction nozzle position is relative to the welder, with the lower edge of the duct positioned horizontally from the arc. The local extraction system used an extraction rate of 0.32 m3/min, which provided an effective capture velocity of 2 m/s at 100 mm (or one diameter) from the arc. Repositioning the extraction nozzle, with respect to the welder, produced no significant beneficial effects on fume reduction (Figures 4.27 and 4.28). It has been argued that if the nozzle is on the same side of the weld as the worker, a higher exposure rate may be experienced due to the exhaust hood drawing the plume towards the welder. As expected, repositioning the extraction nozzle closer to the source produced lower breathing zone concentrations, as the efficiency of the extraction nozzle increases. 1000
Breathing Zone Concentration (mg/m3)
150 mm/ next to welder 125 mm/ next to welder 100 mm/ next to welder
100
10
1
0
5
10
15
20
25
Sample Number
Figure 4.25 Breathing zone concentration results due to varying the distance between the extraction nozzle and the contaminant source (located at 50o or adjacent to the operator). The extraction rate is maintained at 0.32 m3/min. 164
Chapter 4
60
Concentration Percentage (%)
150 mm/ next to welder
50
125 mm/ next to welder
100 mm/ next to welder
40
30
20
10
0
0-0.5
1.5-2
3.0-3.5
4.5-5
6-6.5
7.5-8
9-9.5
10.5-11 12-12.5 13.5-14
Concentration Range (mg/m3)
Figure 4.26 Breathing zone concentration distribution due to varying the extraction nozzle to source distance. 1000
Breathing Zone Concentration (mg/m3)
100 mm/ next to welder 100 mm/ opposite to welder
100
10
1 0
5
10
15
20
25
Sample Number
Figure 4.27 Breathing zone concentrations for varying the orientation of the extraction nozzle with respect to the operator, but 100 mm separation between the source of the contaminant and the extraction nozzle. As above, the extraction rate is 0.32 m3/min.
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Breathing Zone Concentration Percentage (%)
30
100 mm/ next to welder
25
100 mm/ opposite to welder 20
15
10
5
0 1
2
3
4
5
6
7
8
9 3
Concentration Range (mg/m )
10
11
12
Figure 4.28 Exposure concentration percentages for a local extraction nozzle positioned a distance of 100 mm at an angle of 50o (adjacent to) and 180o (directly opposite) to the operator. The average exposure concentration presented to the welder with the extraction nozzle at 150 mm from the arc is 10.2 mg/m3. This position is as effective at reducing the measured breathing zone concentration as the overhead general ventilation (§4.2.1) in controlling the fume. Poor positioning of the extraction nozzle results in poor reduction of breathing zone exposure. Repositioning the extraction nozzle 25 mm closer to the source (125 mm) increased the effective control of the nozzle, and reduced the measured mean exposure concentration to 4.5 mg/m3 (a 55% exposure reduction in comparison with 150 mm nozzle distance). Further reduction of the nozzle-to-arc distance by another 25 mm again generates an increase in nozzle effectiveness, and the fume exposure concentration becomes 2.3 mg/m3, a reduction from the enclosure scenario of 97%, and 77% more effective than the 150 mm nozzle position. If the position of the nozzle at an angle of 180o (directly opposite the welder) at a distance of 100 mm from the arc, the mean breathing zone concentration was 2.33 mg/m3. This method yields a 97% reduction of the exposure level of the benchmark concentration experiments. The extraction nozzle adjacent to the welder resulted in 24% of the total concentration above 3 mg/m3, while repositioning the nozzle 180o yielded 20% of the concentration above 3 mg/m3.
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Breathing Zone Concentration (mg/m3)
16 14 12 10 8 6 4 2 0 150 mm/ next to welder
125 mm/ next to welder
100 mm/ next to welder
Location of the Extraction Nozzle from Arc (mm)
Figure 4.29 Repositioning the extraction nozzle closer to the arc source produced a reduction to the measured breathing zone concentration. These results highlight the exposure ranges, and mean breathing zone concentrations measured, for various positions of the extraction nozzle. The nozzle was next to the welder during these investigations. Using the above results, a quantified relationship between the measured breathing zone concentrations and the effective capture velocity at the arc source, was derived as shown in Figure 4.30.
Breathing Zone Concentration (mg/m3)
16 14 12 10 8 6 4 2 0 150 mm/ next to welder
125 mm/ next to welder 100 mm/ 2 next 0.9 m/s 1.2 m/s m/sto welder Location of the Extraction Nozzle from Arc (mm) Capture Velocity of Nozzle (m/s) Figure 4.30 Repositioning the extraction nozzle closer to the arc source produces an increase in capture velocity, effectively reducing the measured breathing zone concentration. These results highlight the mean breathing zone concentrations measured, quantified against various capture velocities.
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4.3.1 Thermal Monitoring Of The Controlled Space For the confined space breathing zone experiments, a thermocouple array was positioned vertically inside the enclosure, within close proximity to the ceiling (with a 100 mm separation between each thermocouple), to record the temperature of the internal, thermal environment (as illustrated in Figure 4.31). This enabled the thermal gradient of the enclosure to be assessed over the arcing period. The profile of the rise in temperature was recorded via the thermocouple data acquisition system, allowing the growth of the buoyant contaminated layer to be analysed for the arcing period.
∂T•n ∂z
†
Dz
† Figure 4.31 Measuring the thermal distribution within the enclosure, thermocouples were positioned 100 mm apart, resembled in the diagram above. 4.3.2 Temperature Measurements for Confines Space Investigations The initial steady state temperatures of the enclosure prior to arc initiation, with zero air movement are shown in Figure 4.32. The mean initial thermal conditions exhibited small temperature stratification, with a difference of approximately 1.0 oC, between the lowest and highest sampling points, and an initial mean ambient thermal gradient ( ∂T• Dz ) of 1.25 oC/m. The continuous heat input from the welding arc, over the 15-minute period, increases † the temperature of the enclosed environment. This thermal growth was dependent on the arcing period and the height of the sampling point. At no time during the welding period does the enclosure’s transient temperature growth become abated. Figure 4.32 illustrates the mean initial and final sampled temperatures recorded by each thermocouple over the arcing period. The mean final temperature difference between
168
Chapter 4
the lowest and highest thermocouple was approximately 14.3 oC, providing a final mean thermal gradient of 11.5 oC/m. Using a spreadsheet for further analysis, an average linear interpolation of the recorded temperature readings gives the mean initial and final temperature gradients of the enclosure of 1.25 oC/m and 11.5 oC/m, respectively. 36.00 INITIAL FINAL Linear (FINAL)
31.00
Temperature (oC)
y = 11.486x + 14.76
Linear (INITIAL)
26.00
21.00 y = 1.2538x + 17.877
16.00 0.51
0.61
0.71
0.81
0.91
1.01
1.11
1.21
1.31
1.41
1.51
1.61
1.71
1.81
Height (m)
Figure 4.32 Average temperatures for all experiments between the initial and final states of the confined welding space. The use of different electrode wires generated a different thermal gain for the same total electrical energy input and weld period. For the copper coated electrode wire, a higher thermal gain was experienced during the arcing period. The mean temperature gain for the highest sampling height was approximately 5.6 oC higher for welding performed with the copper coated electrode compared to the non-copper coated electrode. The lower thermal mass of welding with the non-copper coated wire, due to reduction in emission, may have contributed to producing this graphic reduction in thermal growth. A sample of this result, for both the copper and non-copper coated electrodes, is highlighted in Figures 4.33 and 4.34. The mean ambient temperature used in both cases was the measured external temperature during arcing period.
169
Chapter 4 35 Mean Amb 660 560 460
30
Temperature (oC)
360 260 160 60
25
20
15 0
5
10
15
Time (Minutes)
Figure 4.33 Example of the temperature rise during the arcing period, within the enclosure for the ER70S-6 copper coated electrode wire. All heights are in relation to the position of the arc. 35 Mean Amb 760 mm 660 mm 560 mm
30
Temperature (oC)
460 mm 360 mm 260 mm 160 mm
25
60 mm
20
15 0
5
10
15
Time (Minutes)
Figure 4.34 Example of the temperature rise during the arcing period, within the enclosure for the ER70S-6 non-copper coated electrode wire. All heights are in relation to the position of the arc.
170
Chapter 4
The temperature observed at each sampling height demonstrated an approximate linear growth with arcing time. This increase in temperature was attributed to the descending thermal interface of buoyant pollutant (combination of fume and heat) through the enclosure. Baines and Turner’s (1969) investigation into the filling box model stated that this thermal growth was due to a conservation of volumetric flux. Baines (1983) further described that a relationship between the plume and the interface can be determined at each vertical position by this volumetric conservation principle (refer to §2.3.10). An example of the descending interface’s measured position is illustrated in Figure 4.35. 0.8 0.7
Height (Metres)
0.6 0.5 0.4 0.3 0.2 Dt = 0.1oC
0.1
Dt = 0.2oC
Dt = 0.5oC
0 0
50
100
150
200
250
Time (Seconds)
Figure 4.35 Graphical relationship of the interface position with respect to time for the copper coated ER-70S electrode. The interface position was determined by monitoring temperature differences of 0.1, 0.2 and 0.5oC. Alternately, utilising the temperature profile (similar to the Worster and Huppert (1983) density profile discussed in §2.3.10) the frontal development through the enclosure can be monitored. This temperature step analysis allows the development of the thermal mass within the enclosure to be visually represented with respect to time, as is depicted in Figure 4.36. The advantage of this method of thermal analysis is it does not rely on a predetermined thermal step (such as the interface); however, it is not a simple reflection of the position of the interface.
171
Chapter 4
0.7
Height Of Thermocouple (m)
0.6
0.5
0.4
0.3
0.2
0.1
30
60
Time Scale (Seconds) 120 300
600
900
0 0
2
4
6
8
10
12
14
Temperature Step - DT (oC)
Figure 4.36 Representation of the temperature step profile over the 15-minute arcing period. This representation of the temperature step can be utilised to visualise thermal levels over the arcing period. By monitoring the space prior to arc initiation, a mean local temperature (for each point) was measured. The evaluation of the “first front” temperature was achieved by observing a determined temperature step from the initial mean value. Upon arc initiation, the plume rises into the environment and disperses. Several temperature steps (DT of 0.1, 0.2 and 0.5 oC) were utilised to depict the average temperature step of the interface. Using this method made ‘locating’ the interface position with respect to time relatively straightforward. Baines and Turner stated that the “first front” will exhibit a constant temperature throughout its travel, however, this is not an ideal situation with effects such as the diffusion of the plume within the environment, heat losses to the enclosure, additional heating from the source radiation, etc all influence the internal environment. Using this temperature difference DT , the interface movement was traced through the gathered data, as it descends through the enclosure. Where the mean local temperature, at each height, grew D T, time taken for this step to occur was recorded for each † thermocouple. The total time growth of the interface is depicted in Figure 4.37 and Figure 4.38 for copper coated and non-copper coated wire, respectively.
172
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0.8 0.7
Height (Metres)
0.6 0.5 0.4 0.3 0.2 0.1 0 0
100
200
300
400
500
600
Time (Seconds)
Figure 4.37 Graphical relationship of the interface position with respect to time for various experiments using the copper coated ER-70S-6 electrode with an interface step DT = 0.5 oC. (5 Experimental 1; ; Experimental 2; ° Experimental 3)
0.8 0.7
Height (Metres)
0.6 0.5 0.4 0.3 0.2 0.1 0 0
100
200
300
400
500
600
Time (Seconds)
Figure 4.38 Graphical relationship of the interface position with respect to time for various experiments using the non-copper coated ER-70S-6 electrode, with an interface step DT = 0.5 oC. (u Experimental 1; 5 Experimental 2; Í Experimental 3; ° Experimental 4)
173
Chapter 4
One important factor to consider is that there is a period of plume travel and accumulation at the ceiling prior to thermal growth of the interface. From the experimental data, the growth of the contaminated interface through the enclosure is demonstrated in Figures 4.37 and 4.38. The copper coated electrode generated a distinguishable thermal interface at quicker rates in comparison to the non-copper coated ER-70S wire. However, development of the interface through the sampled heights demonstrated that the thermal interface generated by the non-copper coated electrode wire progressed quicker than the higher concentrated interface from the copper coated wire. 4.3.3 Determination of the Virtual Source of the Welding Fume Plume There are numerous methods of locating the virtual origin (§2.3.11), however the method employed here is that based on the use of empirical measurements. This technique estimates the location of the origin based on the scaled quantities of the interface measurements. Since results for the plume/interface volume flow have been obtained, these values are adapted to determine the position of the virtual origin. The correction method of analysis performed generated the graphical illustration (Figure 4.39 and 4.40) of the scaled properties of the interface as determined by Baines -2 3
and Turner (1969). By plotting the experimental observations as z0
against time,
correction of the measured height iteratively by adding a constant length zv until the -2 3
modified height ( z0 + zv )
scales correctly with time. The value of zv becomes the †
origin correction (position of the virtual source).
†
† the The results were fitted to † a linear regression fit. The linear regression fit utilises
gradient of the line to determine the origin correction. The virtual origin corrections, for copper coated and non-copper coated electrode wires, are noted in Table 4.5 and 4.6. For the examples depicted below, the virtual origin correction for copper coated wire was located at 0.68 metres below the actual source, while the non-copper coated experiments located the virtual source approximately 1.08 metres below the actual source. Both of these experiments were for a 0.5 oC thermal step.
174
Chapter 4
7 zv = 0
6
4
(z0+zv)
-2/3
5
3
Theoretical Linear Plot y = 0.00212x + 0.91103
2 1 Linear Regression (zv = 0.677 m) y = 0.00212x + 0.3585
0 0
100
200
300
400
500
600
Time (Seconds)
Figure 4.39 Plot highlighting interface height relationship against theoretical and actual time period to obtain the ideal virtual origin for a welding source with copper coated ER-70S-6 electrode wire (0.5 oC temperature step). 7 zv = 0
6
(z0+zv)-2/3
5 4 3
Theoretical Linear Plot y = 0.00212x + 0.91103
2 1 Linear Regression (zv = 1.075 m) y = 0.00212x - 0.00033
0 0
100
200
300
400
500
600
Time (Seconds)
Figure 4.40 Plot highlighting interface height relationship against theoretical and actual time period to obtain the ideal virtual origin for a welding source with noncopper coated ER-70S electrode wire (0.5 oC temperature step).
175
Chapter 4
Table 4.6 Mean virtual origin corrections for copper coated ER70S-6 electrode. Temperature Step Virtual Origin Correction 0.1 oC 1.31 metres 0.2 oC 1.07 metres o 0.5 C 0.64 metres Table 4.7 Mean virtual origin corrections for non-copper coated ER70S-6 electrode. Temperature Step Virtual Origin Correction 0.1 oC 1.52 metres o 0.2 C 1.34 metres 0.5 oC 1.08 metres 4.3.4 Temperature Measurements for Natural Ventilation Investigations In addition to the confined space experiments, the thermal investigations were used to assess the general extraction conditions. The first condition examined was the mechanical extraction via the opening situated in the far corner of the enclosure. Over the total arcing period, the thermal environment exhibited several conditions. Upon arc initiation the enclosure displayed a thermal growth, with a steady increase in temperature. After several minutes, the temperature began to stabilise, producing a constant thermal gradient with mild temperature fluctuations between the 0.46 and 0.56 metre thermocouple heights. This is highlighted below in Figure 4.41, where a sample of this growth is illustrated. This thermal condition suggests that the contaminant descends through the enclosure, until the extraction flow equalises with the fume plume volumetric flow, producing a stabilised thermal environment within the enclosure. This stable temperature profile continues for the remainder of the arcing period. Moving the extraction opening above the arc and breathing zone locations produced a marked reduction in the thermal growth over the arcing period. The measured concentrations (§4.2.1.1) produced a reduction of approximate 50% compared to the original extraction position, and the temperature results presented a similar effect. The final temperature difference was approximately 1 oC with a similarly stable trend, although a much longer time period was required to reach the stable condition. This is illustrated in Figure 4.42. The similar thermal trend to the original extraction location again resulted from a conservation of volumetric flow, however, repositioning the extraction opening directly over the process increased in control effectiveness, as was 176
Chapter 4
demonstrated by the reduction in the measured breathing zone concentration. Both ventilation strategies utilised an extraction rate of 0.7 m3/s. 21
Thermocouple height above arc 760 mm
660 mm
560 mm
460 mm
360 mm
260 mm
160 mm
Temperature (oC)
20
19
18
17 0
50
100
150
200
250
300
350
400
450
Time (Seconds)
Figure 4.41 Temperature measurements for the general ventilation of the enclosure through an opening away from the arc. The extraction rate utilised during monitoring was 0.7 m3/s. 21
Thermocouple height above arc 760 mm
660 mm
560 mm
460 mm
360 mm
260 mm
160 mm
Temperature (oC)
20
19
18
17 0
100
200
300
400
500
600
700
800
Time (Seconds)
Figure 4.42 Temperature measurements for the general ventilation of the enclosure through an opening above arc and breathing zone regions. The extraction rate utilised during monitoring was 0.7 m3/s.
177
900
Chapter 4
Investigating the thermal conditions of natural ventilation scenario enabled an assessment in comparison with the mechanical method of general ventilation. The doorway of the enclosure provided an ideal opening for dispersing the accumulated contaminant out of the operating environment (§2.4.5). 23
Thermocouple height above arc
Temperature (oC)
760 mm
660 mm
560 mm
460 mm
360 mm
260 mm
160 mm
21
19
17 0
20
40
60
80
100
120
140
160
180
Time (Seconds)
Figure 4.43 Temperature measurements for the natural ventilation of the enclosure via flow through the doorway. The contaminated fluid dispersed within the enclosure and is exits via the doorway (as illustrated in Figure 3.25). Several experimental runs were sampled, each giving a similar thermal pattern to that depicted in Figure 4.43. This chart represents a small sample of the enclosure conditions after a period of approximately 4 minutes from arc initiation. When the arc is initiated, the enclosure temperature rose, similar to Figure 4.41, however, the temperature rise was slightly higher (approximately 4 oC), then shallowed off to a ‘steady’ range. The final mean temperature difference between the upper and lowest most thermocouples after thermal stabilisation was 3.4 oC. These temperature measurements indicate that the thermal environment within the enclosure was relatively stable, with no significant changes for the remainder of the arcing period. This steady condition suggested the contaminant accumulation had reached a stratified condition. The thermal step between 0.46 and 0.56 metres indicates that the highly buoyant mass lies above the 0.46 metre height. This vertical range (0.45-0.55 metres) corresponds to the limits of the breathing zone used during these investigations.
178
Chapter 4
4.4.1 Shielding Gas Experimental Results The flow of the shielding gas in GMAW has an integral role in the initial dispersion of the fume. Shielding gas, ejected from the welding nozzle, generates an impingement on the workpiece, forcing the contaminant across the welded surface and impeding the rise into the working environment. The downward flow of gas adds in creating the non-ideal source conditions (along with the intense heat source). Fumes generated by the welding process are collected by this gas flow and forced across the workpiece. The problem associated with this impingement flow is how to determine the radial spread the plume travels before the thermally buoyant plume begins vertical motion. For a horizontal operation, the jet flow of gas from the nozzle acts as a barrier, preventing any direct vertical motion from the plume by forcing the hot metal vapour towards the working surface. The downward motion is translated horizontally upon contact with the boundary layer of the welded surface (neglected any convective transfer from the surface). This is referred to as a wall jet effect. The fluid will spread radially until the buoyancy forces overcome the initial momentum force, causing the plume to separate from the workpiece and begin vertical motion into the occupational environment. Figure 4.44 illustrates the affects of shielding gas used during GMAW. The first photograph (Figure 4.44a), without the presence of shielding gas displays the turbulent plume ascending with a small horizontal spread, while Figure 4.44b highlights the increased spread generated by the addition of the shielding gas. The mean measured radial spreads, from the photographs, are noted in Table 4.7 below. Table 4.7 Mean Radial Spread Results from Photographic Experiment (reference length was the welding torch nozzle D = 20 mm) Shielding Condition Mean Diameter Spread (m) Without Shielding Gas ª 0.075 With Shielding Gas ª 0.18 It is illustrated in Figure 4.44, that the welding scenario has some initial dispersion with † zero shielding gas flow, however, input of shielding † gas clearly produces an increase in the fume radial spread, by an approximate factor of 2.4.
179
Chapter 4
b)
Please see print copy for Figure 4.44
Please see print copy
Figure 4.44 Photographs of the fumes generated by FCAW a) without shielding gas, and b) with shielding gas. The shielding gas produces a larger base of fume plume. 4.4.2 Salt Water Simulations In an attempt to understand the effects of the shielding gas on initial fume dispersion of the contaminant, a simple model was developed to identify the key influencing parameters. Utilising a salt-water experiment, the main flow qualities (buoyancy, volumetric flux and height) were adopted to simulate the effects of an impinging fountain. Some of the modelling characteristics were difficult to simulate accurately, thus the effects of these parameters were determined via manipulating various nondimensional characteristics of the jetted fluid. In trying to duplicate the fluid parameters of the shielding gas into the salt-water model, a quick analysis of the key parameters was initiated. Appendix D highlights this analysis. From this analysis, it was noted that an effective simulation of the welding parameters could not be achieved with great accuracy, however, the effects of the impinging model would still provide beneficial results that could be employed to estimate the behaviour of the shielding gas. The injected salt-solution simulates the effects of the buoyant shielding gas fluid, while the fresh water represents the ambient conditions.
180
Chapter 4
Please see print copy for Figure 4.45
Figure 4.45 Images of the radial spread of an impinged fountain on an acrylic sheet. Each image represents a 0.2 second time interval of the fountain development. Due to the symmetry of the experiments, only half of these images are illustrated. The thermal length depicted by these images was L j = 0.128 m. Figure 4.45 represents an example of the radial dispersal of the fountain upon impact with the impinging surface. The experimental results are illustrated below in Figures † 4.46-4.49. During these experimental investigations, variations of salt-solution concentration and volumetric flux are included together with the modification of nozzle height. The parameters used during each experiment are highlighted within the description of each figure. 182
Chapter 4
0.12 s
o Experimental 2
0.10
Radial Spread (Rsp) - metres
Experimental 1
r Experimental 3 u Experimental 4
0.08
0.06
0.04
0.02
0.00 0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
Nozzle-to-surface height (H) - metres
Figure 4.46 Radial spread of fluid as a function of the nozzle-to-surface distance, over four experimental runs. The initial conditions of the jetted fluid are; (M0 = 3.9x10-6 m4/s2, Q0 = 1.75x10-5 m3/s, B0 = 4.7x10-7 m4/s3, L j = 0.128 m). 0.06
s
o Experimental 2
0.05
Radial Spread (Rsp) - metres
Experimental † 1
r Experimental 3 u Experimental 4
0.04
0.03
0.02
0.01
0 0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
Nozzle-to-surface Height (H) - metres
Figure 4.47 Radial spread of fluid as a function of the nozzle-to-surface distance, over four experimental runs. The initial conditions of the jetted fluid are; (M0 = 3.18x10-5 m4/s2, Q0 = 5.0x10-5 m3/s, B0 = 3.44x10-5 m4/s3, L j = 0.07 m).
† 183
Chapter 4
0.06 s
o Experimental 2
0.05
Radial Spread (Rsp) - metres
Experimental 1
r Experimental 3 u Experimental 4
0.04
0.03
0.02
0.01
0 0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
Nozzle-to-surface Height (H) - metres
Figure 4.48 Radial spread of fluid as a function of the nozzle-to-surface distance, over four experimental runs. The initial conditions of the jetted fluid are (M0 = 2.45x10-5 m4/s2, Q0 = 4.4x10-5 m3/s, B0 = 3.02x10-5 m4/s3, L j = 0.063 m). 0.06 5
†2 + Experimental
0.05
Radial Spread (Rsp) - metres
Experimental 1
0.04
0.03
0.02
0.01
0.00 0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
Nozzle-to-surface Height (H) - metres
Figure 4.49 Radial spread of fluid as a function of the nozzle-to-surface distance, over two experimental runs. The initial conditions of the jetted fluid are (M0 = 3.54x10-6 m4/s2, Q0 = 1.7x10-5 m3/s, B0 = 5.74x10-6 m4/s3, L j = 0.034 m). It is apparent that all the influencing parameters have some effect on the dispersion of the buoyant fluid away from the source condition. An increase in the height between the † nozzle and the impinging surface diminishes the radial spread of the fluid. From the 184
Chapter 4
data shown, there is an almost linear slope for radial spread as a function of the nozzleto-surface distance. This is due to the reduction in the total momentum driving the contaminated fluid. A decrease in the initial volumetric flow also decreases the initial momentum effect on motivating the radial dispersion of the fluid. The decrease in initial momentum flux generates a decrease in the jet length ( L j ) of the fluid. However, a decrease in initial buoyancy produces an increase in the radial spread of the
† to an increase in the fluid over the impinged surface. The buoyancy reduction leads thermal length of the fluid, increasing the overall influence of the initial momentum (decreasing the buoyancy induced momentum). From this analysis, an increase in the thermal length of the fluid provides an increase in total radial dispersion from the point of stagnation. The increase can result from either an increase in initial momentum, or a decrease in initial buoyancy experienced by the contaminated fluid. In addition to the source characteristic effects, the radial dispersion is also influenced as a function of the vertical offset between the nozzle and the impinging surface. A comparison between the actual effect of the shielding gas and the impinging fountain experiments shows that an increase in the input volumetric flow displaces the fluid greater distance away from the source area. The actual welding scenario has some initial dispersion with no shielding gas (Figure 4.44a) however the input of shielding gas clearly produces an increase in the fume spread. An increase in the radial spread of the experimental simulations corresponds with volumetric flow increase, as well as the decrease of buoyancy and surface-to-nozzle height. 4.4.3
Determination of the Correction Factor (y)
The downward injection of a buoyant fluid on a horizontal surface will, at some point, reverse the negative trend of its initial momentum. As stated above, the radial dispersion of the fume is proportional to a function of the residual momentum and initial buoyancy. The equation used to estimate radial spread was scaled with a correction factor d (refer to §5.3). Evaluation of this constant was achieved by plotting the empirical measurements (represented by the dimensionless parameter H + Rsp ) against the theoretical thermal length parameter L j . The linear gradient of this plot represents the correction factor from the equation, 185 †
†
Chapter 4
H + Rsp = yL j
4.2
Figure 4.50 illustrates the experimental radial dimensionless parameter as a function of theoretical radial spread. Each of†the measured results, gathered in the previous section, were plotted against their theoretical estimation, and using a linear interpolation for each set of data points, the mean gradient of the slope, with a gradient of 1.5. 0.20
0.18
0.16
(Rsp+H) metres
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0.00 0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
Jet length (Lj) metres
Figure 4.50 Corrective factor used in Equation 4.2 was determined from plotting a dimensionless comparison between the measured mean radial spread of the fluid against its theoretical prediction. The gradient of the slope y = (Rsp L j ) 1- (H L j ) represents this correction factor.
(
)
Determining a solution for this corrective factor, the model for the radial spread of an impinging fountain (in metres) becomes, †
H + Rsp = 1.5L j . The main focus on predicting radial dispersion of a contaminated fluid was to develop some method of determining † the initial spread and estimate the position of the virtual origin for a welding fume plume generated by GMAW. Evaluation of the radial spread of the fume allows the estimate to the position of the virtual source (as described in §2.3.11). Finding an approximation for the virtual source position then allows further characteristics of the welding plume to be analysed by reducing the forced plume problem into a simplified plume with a pure source of buoyancy. 186
Chapter 4
The theories behind the analytical modelling of welding fume plumes have been developed since the 1950s. The driving force of a welding plume is provided by the energy input from the arc. Due to this intense source of heat, the fume will always be positively buoyant by nature, independent of the shielding gas composition. The intense heat input of the arc is the primary source of buoyancy for the fume plume, with the addition of shielding gas and convective currents from the work-piece fuelling the buoyancy effect close to the source. The use of mechanical and natural “general extraction” ventilation systems produced a significant reduction in breathing zone exposure levels in comparison to the unventilated case. However, the introduction of a “local extraction ventilation” (LEV) system allowed the extraction airflow to interact with the welding fume plume prior to entering the breathing zone of the operator. This resulted in the greater reduction of the mean breathing zone concentrations, depending on the location of the extraction hood. Shielding gas flow can have a positive effect on breathing zone fume reduction by dispersing the fume. Simulations using the salt-water jet gave an indication to the likely effects of the shielding gas and nozzle geometry. Using the flow characteristics of the shielding gas can provide Increasing the nozzle separation from the workpiece reduces the effective dispersion of the injected fluid, allowing some form of control, in addition to the volumetric flow rate and gas characteristics.
187
Chapter 5
Chapter 5
MODELLING FUME PLUME DISPERSION WITHIN A WORKING ENVIRONMENT
This chapter discusses the flow effects associated with a GMAW fume plume and develops ideas of how to model fume plume dispersion from the arc region. The initial section of this chapter will investigate the behaviour of the source conditions. This will be done via theoretical analysis and experimental modelling. Section 5.1 predicts the fume plume’s characteristics developed from pre-existing plume theories and fume formation estimates. Section 5.2 describes certain ventilation theories that can be implemented to aid in occupational exposure control, while Section 5.3 presents a model for the shielding gas flow. The dispersion of the contaminant generated by GMAW is a critical area in understanding how concentration levels within the breathing environment of the workplace are affected. The fume plume movement can by described in three critical steps. Firstly, the initial fume dispersion away from the source. Secondly, the general plume ascent, and thirdly the required extraction rate to control the concentration levels within the occupational environment. 5.1
Welding Source Conditions
The fume plume, generated by the oxidation and condensation of the high temperature metal vapour during GMAW, disperses away from the arc region into the ambient within a thermally buoyant current. The source conditions of a GMAW operation have an integral input on the initial dispersion from the arc region, which is crucial in the establishment of the fume plume flow. The large initial heat input, generated by the GMAW process, provides the contaminated plume with a strongly buoyant motion. This high buoyancy causes the pollutant to rise into the occupational environment. The initial heat input was previously discussed in Chapter 2 As stated earlier, the origin of the welding fume plume is a finite source, rather than an ideal point source. The emissions of the welding fume plume from the source are characteristically non-Boussinesq (§2.3.3), due to the large initial heat input ( q0 ). An important factor to consider is the dispersion of the fume plume away from the arc due †
188
Chapter 5
to shielding gas influence. The use and effects of the shielding gases are outlined in §2.1.6, §2.2.5.6.1 and §2.3.7. 5.1.1 Simulation of Welding Plume Flow Within a Confined Environment Based on Pre-existing Models and Classical Plume Theories Using similar welding parameters used for the experimental investigations (arc voltage of 25 Volts, current of 200 Amperes, a stand-off length of 18 mm) the melting rate of a 1.2 mm diameter electrode is obtained from Equation 2.1.
MR = [aI + blI 2 a] mm/s
[
2
]
= 0.3(200A) + 5 ¥10-5 (18 mm)(200A) = 96 mm/s or 5.76 m/min
5.1
The melting rate of the electrode can then be utilised to determine heat input of the fume † plume (Equation 5.1), using the logarithmic relationship between the melting rate of the wire and the total heat input of the arc source. For these investigations: qT = VI = 25 ¥ 200 = 5000 W = 5 kW .
q0 = qT [-0.1787 + 0.0857In(MRv )] †
[
2
5.2
]
= (5000) -0.1787 + 0.0857In(96 ¥ p (1.2 2) ) = 1115 W
For this step, MR is converted into volumetric rate, MRv , via multiplying by the crosssectional area of the wire.†It was previously noted that the initial heat input of the fume plume lies between 7-20% of the total heat input. From this determination, the ratio † between the total heat input and initial fume plume input ( q0 /qT ) is 22.3%. Using Bosworth and Deam’s (2000) model that explored the relationship between fume † formation rate in GMAW and the droplet size, an estimate for the fume formation rate can be determined. The heat input into the droplet is proportional to the wire feed rate (and current), so the surface superheated temperature of the droplet, DTd , the metal vapour generation rate, m˙ VGR , and the estimate for fume formation rate, m˙ FFR are given by:
† †
† D DTd = 12 E 1- (Wdmm ) 2 32 12 0.817 -42924 T ¢ (g/hr) = C ( dmm ) ( 3809W ) T ¢ e 12
(Wdmm )
m˙ VGR
189 † †
5.3 5.4
Chapter 5
Ê ˆ m˙ VGR m˙ FFR = 1.29Á ˜ , (g/hr) Ë 1+ ( m˙ VGR 30) ¯
5.5
Assuming, for simplicity, that the droplet diameter is equal to the wire diameter (1.2 mm), and the wire†feed rate is 5.76 m/min, then the estimate for the GMAW fume formation rate will be DTd = 492 K T ¢ = 2305 K m˙ VGR = 9.6 g /hr m˙ FFR = 9.4 g /hr
5.6
The initial buoyancy of the welding fume plume is then estimated using the equation †
B0 ª 0.0281q0
@ 0.0281(1.115 kW ) = 0.031 m 4 s3
5.7
The fume plume characteristics are estimated using the classic plume theories developed by Morton et al. (1955) † and for ease of calculation, a top hat model was used. For this situation, the volumetric flux, momentum flux and local reduced gravity can be obtained 13 6 Ê 9a ˆ 2 3 5.8 Q( z) = c1B z , where c1 = aÁ ˜ p = 0.115 5 Ë 10 ¯ Ê 5 ˆ 2 3 Ê 6a ˆ 4 3 23 5.9 M ( z) = c 2 B0 z 4 3 , where c 2 = p Á ˜ Á ˜ = 0.294, and Ë 8ap ¯ Ë 5 ¯ † 13 1 2 G¢ = B0 z-5 . † 5.10 c1 † † Assuming the entrainment coefficient, a , is 0.1. A depiction of these parameters is 13 0
53
(
demonstrated in Figure 5.1.
)
†
190
Chapter 5 0.06
Volumetric Flow Rate (m3/s)
0.05
0.04
0.03
0.02
0.01
0 0
0.2
0.4
0.6
0.8
1
1.2
1.4
1
1.2
1.4
1
1.2
1.4
PlumeM(z) Height (Metres) 0.04
Momentum Flux (m4/s3)
0.035
0.03
0.025
0.02
0.015
0.01
0.005
0 0
0.2
0.4
0.6
0.8
Plume Height (Metres) 140
120
2
Buoyancy (m /s)
100
80
60
40
20
0 0
0.2
0.4
0.6
0.8
Plume Height (Metres)
Figure 5.1 Graphic representation of buoyancy, volumetric flux and momentum flux as a function of plume height. 191
Chapter 5
A plume released into a confined space will travel towards the ceiling, located at a height of H = 1.15 metres above source. Assuming the plume comes from a point pure source (ie zv = 0), the velocity of the plume can be estimated from the volumetric flux and the plume spread (area). The velocity of the plume, at any height, is given by the formula: † v(z) =
Ê 25 ˆ c1B01 3 Q(z) c1B01 3 z 5 3 = = Á ˜ A(z) p ((6 5)az) 2 4 Ë 9 ¯ pa 2 z1 3
5.11
5.1.2 Estimation of Fume Released into an Enclosure For a confined†environment, the dispersal height of the plume is limited. For an environment restricted by a bounded space, with a height of 1.15 metres, the plume will rise, and is predicted to behave similarly to the filling box model (§2.3.10) where the plume will impact on the upper ceiling boundary, and generate an interface of temperature and contaminant. This initial interface has characteristics that can be predicted from Equation 2.46, and the descent of the interface through an enclosure, with a effective cross-sectional area of 2.3 m x 2.3 m (5.29 m2). The density gradient across this first front is constant, and is estimated using 13 5 Ê 5 ˆ -4 3 2 3 -5 3 g¢H = Á p ˜ a B0 H . 3p Ë 18 ¯
5.12
Accordingly, the temperature difference (DT) across the interface is approximately;
†
DT T• = Dr r• G' ( z) = gDr r• = g(DT) T•
5.13
On reaching the ceiling (z = H = 1.15 m), the reduced gravity of the plume is initially 0.85 m/s2 from Equation 5.12 above. Using † the above relationship between density and temperature, the temperature difference across the interface is DT = Tint - T• = 0.85T• g .
5.14
For an ambient of 20oC (293 K), the interface temperature is 45.5 oC. The position of the interface, as it descends with time through the enclosure, can be modelling using † Baines and Turner’s filling box analysis.
192
Chapter 5
-3 2
ÈÊ 2 ˆÊ B 1 3 H 2 3 ˆ ˘ z0 = HÍÁ ˜Á 0 ˜t -1˙ A ¯ ÎË 3 ¯Ë ˚
5.15
-3 2
ÈÊ ˆÊ 0.031 1 3 1.15 2 / 3 ˆ 2 ( ) ( ) ˜t -1˘˙ = 1.15ÍÁ ˜ÁÁ ˜ 5.29 ÍÎË 3 ¯Ë ˙˚ ¯ 1.1
†
Interface Height (Metres)
1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0
100
200
300
400
500
600
700
800
900
Time (Seconds)
Figure 5.2 The height of the contaminant interface as a function of time (for a continuous source input). The time period begins when the interface layer has first developed. Figure 5.2 illustrates the estimated position of the interface with respect to time. The highly buoyant nature of the fumes generated by a welding process will ascend through the workers breathing zone, towards the ceiling. For a breathing zone within 500 mm from the welding source, the buoyant, contaminated interface will reach this level within 100 seconds of initial frontal development. An important issue worth noting is that the time period does not include the time taken for the welding plume to travel to the ceiling and form the interface. According to Baines (1983), the volumetric flow within the enclosure is conserved. That is, the volumetric flow of the ascending plume is equivalent to the volumetric flow of the descending interface layer. This is expressed as follows
QPlume ( z) = -QInterface ( z) dz 13 c1B0 z 5 3 = - 0 A dt 193 † †
5.16a 5.16b
Chapter 5
An estimate for the time taken for the interface to fill down to the source height can be done utilising this expression. Assuming the initial velocity of the descending interface remains constant for all time, the estimated time taken to fill the box will be: t=
H 1.15 = = 133 sec , dz dt 0.115 ¥ 0.0311 3 ¥1.15 5 3 5.29
5.17
The actual time frame required to fill the box will be greater than the estimated 133 seconds. The † interface velocity will decrease during the interface descent, creating a greater filling period. The estimated time for the interface to descend to height of the breathing zone (0.45 metres above the arc) will be 81 seconds, assuming the constant rate of descent in Equation 5.17. During this period, the operator will be exposed to the fumes within the plume only. Using the analysis described by Worster and Huppert (1983) regarding the time dependency of density for the filling box model, an expression for the density at a certain height can be established over a desired time frame. -3 2
È 1 Ê 18 ˆ1 3 ˘ z 0 (t ) = Í1+ Á ˜ t ˙ Î 5Ë 5 ¯ ˚
, and d = fˆ 2 3 (t )d• (z ) - c (t ) .
5.18
53
1- z 0 (t ) Where fˆ (t ) = , 1- z 0 (†t ) † Ê 5 ˆ1 3 -2 3 Ï 10 ¸ 155 2 d• = 5Á ˜ z Ì1- z z + ...˝ , and Ó 39 ˛ Ë18 ¯ 8112 1 3 Ï -2 3 1 3 4 3 ˘¸ Ê 5 ˆ z -1 † ˆ 2 3 È1- z 0 5 1- z 0 155 1- z 07 3 c (t ) = 5Á ˜ Ì 0 + 3f Í + ...˙˝ . Ë18 ¯ Ó 1- z 0 Î 1- z 0 78 1- z 0 56784 1- z 0 ˚˛ †
5.19 5.20 5.21
Finding the non-dimensional approximation of the interface density difference with † respect to enclosure height and time (from Equation 5.18-5.21), an estimate for the welding contaminant interface is illustrated in Figure 5.3. The relationship between buoyancy and temperature difference is highlighted above in Equation 5.13, thus an estimate of the local temperature rise (for a specific height),
DT ( z,t ) , can be acquired over a period of time (as illustrated in Figure 5.4a). Using simple heat transfer principles, a relationship between the convective heat output and an
† 194
Chapter 5
estimate for the concentration within the enclosure can be approximated. This is found from equating: q = rc p Q˙ DT , m˙ C = FFR ˙ Q Ê m˙ rc ˆ C = Á FFR p ˜DT . q Ë ¯ †
5.23
6 z = 0.8 z = 0.5
25
†5
20
Buoyancy g' (m/s2)
z = 0.2
15 10 5
z = 0.8 metres
4
z = 0.45 metres
3 2
z = 0.115 metres
1
0 0
2
4
6
8
10 12 14 16 18 20 22 24 26
0 0
100
200
Non-dimensional Time (t)
300
400
500
600
700
800
Time (Seconds)
Figure 5.3 Density profile of a fume release within an enclosure, as a function of time, at various heights with both non-dimensional and dimensional parameters. a) Represents the non-dimensional profile of the enclosure, while b) displays the predicted buoyancy within the enclosure for varying height z. 12
Temperature Difference DT (oC)
Non-dimensional Buoyancy (d)
30
5.22
z = 0.8 metres
10 8
z = 0.45 metres
6 4
z = 0.115 metres
2 0 0
100
200
300
400
500
600
700
800
900
Time (Seconds)
Figure 5.4a Estimated temperature difference (compared to ambient) in the welding enclosure over the 900-second arcing cycle. 195
900
Chapter 5
From this expression, a direct link between temperature difference and concentration is predicted, allowing a prediction of the local concentration (Figure 5.4b). From these approximations the space concentration, at a height of 0.45 metres above the arc source, after 900 seconds of continuous fume generation is approximately 94 mg/m3.
Concentration C(z,t) (mg/m3)
120 z = 0.8 metres
100 80
z = 0.45 metres
60 40
z = 0.115 metres
20 0 0
100
200
300
400
500
600
700
800
900
Time (Seconds)
Figure 5.4b Estimated concentration in the welding enclosure as a function of position and time. 5.2.1 Concentration Estimation within a Confined Space Although there is no direct correlation between welding fume formation rates and operator’s breathing zone exposure, an estimation of the concentration within a simple enclosure may be predicted using Equation 5.24. Intuitively, higher rates of contaminant emission will yield a higher concentration of pollutant, within a confined space. The steady-state concentration of welding fume released within a confined space can be predicted by using a simple mathematical model of the key parameters of emission and ventilation rates. For a non-ventilated, well-mixed enclosure, with a continuous source emission rate of m˙ FFR = 2.6 mg/s over a period of 15 minutes, the estimated concentration will be; †
Css =
†
m˙ FFR t (2.6 ¥ 60) ¥15 = = 384.6 mg/m3 " 6.084
196
5.24
Chapter 5
Where the volume of the enclosure, " , is 6.084 m3 (1.15 m x 2.3 m x 2.3 m). The simple model of a ventilated, single room equation 2.61 is restated below
†"dC i 5.25 = Q˙ Co + N˙ - QCi - k 2Ci" . dt Ï Ê Q˙ Ê Q˙ N˙ ˆ¸ N˙ ˆ 5.26 Ci = ÌC0 - t Á Co + ˜˝{exp[- t t ]} + t Á Co + ˜ " ¯˛ "¯ Ë" Ë" Ó † -1 ˙ Where t = (Q " + k 2 ) . From the initial steady-state condition, with no ventilation, † -1 t = (k 2 ) = 15 minutes, thus k2 = 0.067 min-1. For an extraction rate similar to that used
63% in comparison to the non-ventilated enclosure. There are no known models to predict the total breathing zone concentration of the operator, however the breathing zone concentration is expected to be lower than the total space concentration, as the operator does not ‘consume’ the total contaminant produced. Figure 5.5 illustrates the predicted enclosure concentration behaviour due to the influence of extraction rate variation. 350
SPACE CONCENTRATION (mg/m3)
†
3 † during the welding experiments (0.708 m /min), the estimated enclosure concentration after 15 minutes is 179.2 mg/m3. This is the concentration, assuming a fully mixed † environment over the total arcing period. This provides a reduction of approximately
300
250
200
150
100
50
0 0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
EXTRACTION RATE (m3/min)
Figure 5.5 Estimated enclosure concentrations after 15 minutes due to increasing an extraction flow rate. The initial parameters are m˙ FFR = 2.6 mg/s (§5.1.1), " = 6.084 m3, C˙ o = 0 mg/m3, t = 900 s and k2 = 0.067 min-1. 197 †
†
†
Chapter 5
5.2.2 Additional Ventilation Control of a Confined Environment For an enclosed environment, the management of a dispersed contaminant can be achieved through controlled ventilation strategies. The flow of a pollutant through an enclosure, with an opening on the ceiling, can be estimated through a conservation of volumetric flow (Figure 5.6). The position of the interface will determine the volumetric flow rate of the plume at that height, which is then related to extraction rate of the contaminant removed from the occupied environment. The principle of the volumetric flow conservation with a single ventilation opening on the ceiling gives the relationship: Qin = Qout
5.27
Qvent = Q( h ) = c1B1 3 h 5 3
Qvent †
Q
H
z0 ( t Æ •)
† of contaminants through an ceiling opening, with Figure 5.6 The steady extraction a continuous source, produces a displacement flow with the interface stationary with time (when the extraction rate is equal to volumetric flow rate of the contaminant at z0). For an extraction unit with known exhaust rate, the position of the interface can be predicted, or conversely, the required extraction rate can be calculated to generate an appropriate position for the interface (above occupation environment). The extraction unit used in the experimental investigations has an extraction rate of 708 l/min. Utilising this extraction rate, the predicted position of the contaminated interface will be; È 708 (1000 ¥ 60) ˘3 5 ˙ = 0.51 m z0 = Í 13 ÍÎ 0.115 ¥ (0.031) ˙˚
5.28
The predicted height of the interface will be 0.51 metres above the source, using the 708 l/min extraction rate. Alternately, the † critical extraction rate required to establish the 198
Chapter 5
contaminated interface at a height of 0.45 metres is 577 l/min. Figure 5.7 depicts the predicted contaminant interface height for increasing extraction rates. 1.4
Interface Height (m)
1.2
1
0.8
0.6
0.4
0.2
0 0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
0.045
0.05
Volumetric Extraction Rate (m3/s)
Figure 5.7 Relationship between contaminant interface height and the extraction volumetric flow. 5.2.3 Buoyancy Driven System With Enclosure Ventilated By A Side Opening The geometry applicable to welding in a confined space, with a single vertical opening in a wall is shown schematically in Figure 5.8. The focus of the present work is to determine the critical area of the vent, Acrit, required to prevent the depth of the buoyant, contaminated layer increasing such that the layer is significantly below the vent. Following the work of Linden et al. (1990) one may reasonably assume that under steady-state conditions the warm, buoyant layer will be fully mixed due to the turbulent characteristics within the upper boundary layer. Under these conditions it is also reasonable to model the incoming flow through the vent as not mixing with the outgoing contaminated air. The plume flow rate through the interface at z!=!h must then equal the exchange flow rate through the opening. Thus, 12
Qvent = Q( z = h ) = k1 Acrit ( g¢d ) = c1B1 3 h 5 3
Since the buoyant layer is fed by the plume: †
199
5.29
Chapter 5
g'= Gz= h = B 2 3 h -5 3 /c1
5.30
For an opening with aspect ratio g = D/W then:
† Acrit
c16 5 2 = 15 4 5 h g k1
5.31
Qvent
† Q
H
h
Figure 5.8 Enclosure with a point source of buoyancy and a vertical opening at a height h above floor illustrating flow with the critical vent area, Acrit, required to ensure buoyant layer remains above opening. It is interesting to note that the critical vent area is not a function of the strength of the source of buoyancy in the enclosure. This is to be expected from dimensional arguments and is consistent with other models of buoyancy-driven natural ventilation situations. The relationship between the opening height, h, and the critical vent area is illustrated in Figure 5.9.
Please see print copy for Figure 5.9
Figure 5.9 Plot of the critical vent area required to restrict the buoyant, contaminated layer above the mid-height of the enclosure opening with vent aspect ratio, g, taking values of 0.1, 0.5, 1, 2 and 10. [Slater, Cooper & Norrish, 2001]. The ventilation volume flow rate is an important parameter and can be determined simply from Equation 5.29. 200
Chapter 5
5.2.4 Buoyancy Driven System With Enclosure Ventilated By A Doorway The ventilation of an environment through a doorway opening was highlighted in §2.4.5. The breathing zone concentration effects of the doorway dispersion were investigated by these studies (§4.2.2). The area of the doorway will be greater than the critical opening area, generating a flow regime similar to a sharp-crested weir flow. The fluid flows out through the opening, in a weir like fashion, with the contaminant confined within the upper half of the enclosure. This is depicted in Figure 5.10. Qvent
H h
Figure 5.10 Enclosure with a point source of buoyancy and a vertical doorway opening, with height H, The buoyant layer remains exits the enclosure through the upper section of the opening. Using this weir theory, as presented by Winter (2001), an estimate for the doorway flow is: D1
Qout =
12
Ú c W (2g¢z) d
o
dz
5.32
0
23 2 32 = c d W o g¢1 2 D1 3 Qplume = Qout †
c1B1 3 h 5 3 =
2
32
3
5.33 12
c d W o D1 ( g¢D1 )
Ê B2 3 ˆ1 2 23 2 = c d W o D1Á 5 3 D1 ˜ 3 Ë c1h ¯ 32
c1 h 5 2 =
23 2 32 Cd W o D1 3
5.34
5.35
† Where W is the width of the doorway, and D1 is the depth of the contaminated
dispersing fluid. For † an enclosure with doorway with a width of W = 715, the depth that the contaminated fluid descends into the environment can be determined. Assuming the † 201
Chapter 5
depth is equivalent to the effective height of the enclosure minus the interface height i.e. D1 = H - h ,
23 2 32 Cd W o ( H - h ) 3 32 32 52 h = K ( H - h ) , where K = 2 3 2 Cd W o 3c1 h 5 3 = K 2 3 ( H - h) 32
c1 h 5 2 =
†
5.36 5.37
5.38 h( h 2 3 + K 2 3 ) = K 2 3 H † † From this, the interface height has two critical values. Shaw and Whyte (1974) stated †
that the coefficient for a vertical door is Cd † = 0.65. The approximate value of K 3 2 is 5. Thus, the critical values of h are 0.65 or 5.75 metres. Naturally, if the enclosure is 1.15 metres in height, the interface height will be 0.65 metres, and the depth of the † † contaminated fluid will be 0.5 metres. The volumetric flow exiting through the door, from Equation 5.32, will be 0.21 m3/s 5.3
Shielding Gas Effects
The flow of shielding gas in GMAW has an integral role in the initial dispersion of the fume. Shielding gas, ejected from the welding nozzle, generates an impingement on the workpiece, which forces the contaminant across the welded surface and delays the rise into the working environment. The downward flow of shielding gas adds in creating the non-ideal point source condition (along with the intense heat source). Fumes generated by the welding process are collected by this gas flow and forced across the workpiece. The problem associated with this impingement flow is how to determine the radial distance the plume travels before the thermally buoyant plume detaches from the surface. For a horizontal operation, the jet flow of gas from the nozzle acts as a barrier, preventing any direct vertical motion from the plume by forcing the hot metal vapour towards the working surface. The initial downward motion is translated horizontally upon contact with the boundary layer of the welded surface. This is referred to as a wall jet effect. The fluid will spread radially until the buoyancy forces overcome the initial momentum force, causing the plume to separate from the workpiece and begin vertical motion into the occupational environment (neglected any convective transfer from the surface). 202
Chapter 5
Figure 5.11 represents a simplistic definition of quantifying the initial behaviour of a GMAW fume plume. The lack of any shielding gas allows the metal vapour into the atmosphere earlier, causing earlier oxidation and condensation of the contaminant, thus producing fume within close proximity to the arc. The addition of the shielding gas prevents this initial exposure to the ambient, prolonging the metal vapour presence and pushing this vapour away from the arc region. This impulsion by the shielding gas works in these steps:
2.
1.
The flow of the shielding fluid forces the fume/vapour mixture back towards the workpeice,
Shielding gas ejected from torch nozzle (M0, Q0 Ø) The initial arc temperature present a higher positively buoyant vapour/fume (B0 ↑)
3.
Fume travels horizontally across surface
Buoyancy allows the fume to detach from the workpiece and rise into occupied environment
4.
Figure 5.11 Diagrammatic evaluation of how the shielding gas flow redistributes the fume plume generated by the GMAW process. This is known as an impinging fountain. The theoretical model of the turbulent fountain (§2.3.6) is used as the basis of modelling the source conditions of the welding fume plume. Understanding the behaviour of the initial fume plume movement can then be use to predict a virtual origin (or point source) and estimate the flow characteristics of the plume. Consider a turbulent, forced plume with initial conditions of (M0, B0, Q0) to describe the fume flow from the arc region of the torch. The fume (initially metal vapour) will be buoyant, with fluxes in both initial momentum and volume. The welding torch has a diameter of f 0 , with a nozzle-to-workpiece height of zI , assuming a perpendicular 203 †
†
Chapter 5
welding process (illustrated in Figure 5.12). It is noted that the initial buoyancy of the force plume opposes the initial shielding gas flow, due to the intense heat input of the process. GMAW Nozzle Initial Conditions B0, Q0, M0
f0 H Workpiece † † that are relevant to modelling the Figure 5.12 Parameters of a welding nozzle dispersion of the ejected fluid. These critical parameters are used to generate a simulation with a salt-water model.
The initial buoyancy of a welding process does not come from the shielding gas, however, for modelling purposes the initial buoyancy will follow the flow generated by the nozzle. As stated previously in §2.3.6, the critical height ( zcrit ) of the turbulent fountain with no flow obstructions is,
zcrit = c
†
M 03 4 = cL j , B01 2
5.39
where c is a constant of approximately 1.85, and the initial momentum flux and buoyancy flux of the ejected are defined by:† 2
2
2
2
M 0 = 4Q0 pf e = pf e V0 4 , 2 B0 = Q0 g0¢ = pf e V0 g¢ 4
5.40a 5.40b
The effective source diameter, f e , is dependant on source characteristics of the fluid, † whether the initial flow † is laminar or turbulent (Bloomfield and Kerr, 2002). For a laminar flow, f e = 3f 0 , while for a turbulent flow f e = f 0 . Obstruction of the flow by † the welded surface placed within close proximity to the nozzle ( H < zcrit ) prevents further vertical motion. However, the fluid will still have some momentum due to the † † initial flow input. This momentum flux, at the point of impingement, can be † approximated as being a function of the initial momentum flux, M 0 .
204
†
Chapter 5
The flow continues to travel horizontally, over the impinged surface, until the fluid’s buoyancy effects begin to dominate flow characteristics, causing the fluid to detach from the surface and establish upward motion into the occupational environment. The horizontal distance from the point of stagnation to plate separation is referred to as the critical spread length ( Rsp ). Determining an estimate of this critical length Rsp , assumes that the flow separation is dependent on three parameters, which include the height to impingement, and both initial parameters of momentum and buoyancy of the fume. † † From this, a relationship between the momentum and buoyancy fluxes was derived using a similar approximation to the jet length.
M 03 4 H + Rsp = y 1 2 = yL j B0
†
5.41
Rsp Ê H ˆ ª ÁÁ1˜ yL j Ë yL j ˜¯
5.42
The assumption of this analysis is that the flow of the ejected fluid is characteristically turbulent throughout its motion. For a situation with a large critical length, the initial † flow characteristic of the fluid will be dominated by laminar behaviour. This initial laminar flow will drive the fluid with no entrainment during the flow establishment phase. The transition between laminar and turbulent flow characteristics Figure 5.13 illustrates the non-dimensional relationship between the radial spread as a function of the vertical motion components of the jet length and nozzle-to-impinged surface distance (as expressed in Equation 5.42). It is interesting to note that, for any thermal length of the impinging fountain, the relationship for the non-dimensional parameter H L j has a critical value of approximately 3. There will be no radial dispersion beyond this point (the fluid will not impact the workpiece, thus there will be no radial dispersion).
205
†
Chapter 5 Non-dimensional plot of radial spread 0.60
0.40
Rsp yL j 0.20
† -0.40
-0.20
0.00 0.00
0.20
0.40
0.60
0.80
1.00
H 1yL j Figure 5.13 The non-dimensional radial dispersion of the impinging fountain, Rsp L j , as a relationship between non-dimensional height from the workpiece, † H L j , and the jet length constant, y = 1.5.
†
5.3.1 Practical Application The main focus on predicting radial dispersion † of a contaminated fluid was to develop † some method of determining the initial spread and estimate the position of the virtual origin for a welding fume plume generated by GMAW. Evaluation of the radial spread of the fume allows the estimate to the position of the virtual source (as described in §2.3.11. Finding an approximation for the virtual source position then allows further characteristics of the welding plume to be analysed by reducing the forced plume problem into a simplified plume with a pure source of buoyancy. The theories behind the motivation of a plume have been around since the 1950s. The driving force of a welding plume is provided by the energy input. The fume will always be positively buoyant by nature, independent of the shielding gas composition. The intense heat input of the arc is the primary source of buoyancy for the fume plume, with the addition of shielding gas and convective currents from the work-piece fuelling the buoyancy effect close to the source. Using the welding process from the concentration experiments, as mentioned above, M 0 = Q0V0 , nozzle diameter was 20 mm, and shielding gas flow was equal to 15 l/min
206 †
Chapter 5
2
2
or 0.00025 m3/s, V0 = 0.8 m/s, giving M 0 = pDe V0 4 , and B0 = 0.031 m4/s2. For the laminar, uniform flow of shielding gas from the welding nozzle, the effective diameter becomes De = 3D0 . From §4.6, the constant y = 1.5, so the predicted radial spread †† † becomes; † M 03 4 Rsp = y 1 2 - H B0
†
The estimated radial spread is 0.022 m, from the point of impingement. Thus, using the
z + zv = 5Rsp /6a , with z = 0. From this, the virtual origin simple virtual origin estimate, † was located 0.18 metres below the actual welding arc. 5.4
SUMMARY
†
The theoretical modelling of the welding plume itself enables the behaviour of the plume to be established, and critical ventilation parameters to be evaluated. The results, however, are useless without a direct comparison with an actual welding scenario. Comparisons between the actual and theoretical models are included in the Chapter 6. The modelled plume dispersion assumed that a welding plume, within a confined environment, behaves in a manner similar to the filling box theory. In addition, the estimated concentration of the enclosure, although useful in predicting the required ventilation rates, is vastly greater than the measured results from §4.1.2. Developing the impinging fountain model aided in developing a greater understanding of the initial fume dispersion, due to the influence of shielding gas effects. This model, to the author’s knowledge, is a new development in understanding the initial welding plumes characteristics. Determining the radial spread of the plume enables the fume to be expressed as a ideal point source (using the virtual origin correction method) as well as describing how the plume will behaviour due to the influencing effects of the shielding gas, not just the energy input from the arc.
207
Chapter 6
Chapter 6 DISCUSSIONS 6.1
Discussion of Results
This thesis describes an investigation into the breathing zone concentration of a welder, associated with GMAW of mild steel under various conditions. The first investigations involved an enclosed, “confined space” environment while the second scenario involved the introduction of various ventilation strategies to this confined space. The aim of this investigation was to evaluate which methods of ventilation can reduce operator’s breathing zone exposure concentrations to acceptable levels within the test environment and to establish a greater understanding of how welding fumes are dispersed within the occupational environment. This aim was achieved through several objectives including the experimental investigation, the identification of factors influencing particulate and gaseous welding fume levels in the working environment and modelling of the complex effects of fume plume dispersion within the workplace. In order to perform the evaluation of the breathing zone concentrations from GMAW, a rig was designed and built to facility repeatable consistent, efficient and accurate fume production experiments. The design criteria are highlighted in Chapter 3. The initial confined welding situation was chosen for two reasons. Firstly, to determine a benchmark breathing zone exposure and space concentrations so as to find the control efficiencies for the later ventilation strategies and, secondly, to investigate issues relating to fume production and dispersion within the enclosure. This breathing zone analysis generates greater practical application, as it represents an actual exposure quantity rather than an emission quantity. This study of the fume dispersion from GMAW found that the measured breathing zone concentration within a confined space exceeded the exposure recommendations: =
An average of 82.7 mg/m3 for copper coated ER70S-6 electrode wire, greater than 16 times the regulatory limits).
208
Chapter 6
=
Replacing the copper coated electrode with a non-copper ER70S coated electrode, to reduce FFR, still produced breathing zone concentrations (54.2 mg/m3 mean concentration) exceeding OHS levels (by a factor of 11).
=
The background enclosure concentration was 73.3 mg/m3, approximately 89% of the operator’s breathing zone concentration. This background exposure was based solely on the exposure to the dispersion fume, rather than direct contact with the rising fume plume.
The standard TWA exposure levels are based over a nominal working period of 8 hours, however over the 15 minute experiment period, the measured concentrations displayed the high breathing zone concentrations welders are exposed to if no preventative methods are implemented. This confirms that there must be some form of air movement employed to reduce the breathing zone concentration levels in practical situations. There is a correlation between these measured results and the WTIA fume minimisation studies (1999) (refer to Figure 2.43). The WTIA fume study of GMAW found that breathing zone concentrations ranged from 2 mg/m3 to 90 mg/m3, during an unconfined welding operation. The similarities between these two studies suggest that the measured breathing zone concentrations from these investigations represent a ‘normal’ welding scenario. The higher exposure concentration range recorded during these investigations, may be attributed to the accumulation of contaminant within confined environment. The use of a low fuming electrode reduced the breathing zone exposure concentration by 30%. From the literature survey carried out, it is noted that the reduction of fume formation rates is achieved by numerous parameter alterations, but these changes have not been linked to a reduction in breathing zone exposure. Moreover, it is the intuitive belief that lower generation of fume emissions into the welding environment lead to lower exposure levels of the welder. Modelling the space concentrations, based on the dispersion of a contaminant within a confined environment, estimated the concentration 384.6 mg/m3 while an assessment of the developing concentration through the enclosure generated an estimate, at a height of 0.45 209
Chapter 6
metres above the arc, was 93 mg/m3. The concentration estimate generated by the developing interface, with height and time, displays likeness with the measured enclosure concentrations. However, more work into the exposed concentration model, for welding fume, needs to be undertaken before it can be effectively utilised. A notable reduction in the measured breathing zone concentration was demonstrated, within the confined space, using two different ceiling extraction locations; one above the source and breathing zone, the other at a distance from the source. Repositioning the extraction point closer to the source produced greater reduction of the breathing and enclosure concentrations. However, both of these extraction positions generated mean breathing zone concentrations exceeding the regulatory limits by factors of 2 and 4, respectively. Variation in the rate of extraction from this general ventilation strategy produced a relatively intuitive result in relation to the measured breathing zone concentration. The increase in extraction rate decreased the measured breathing zone concentration during these investigations. =
An extraction rate of 0.3 m3/s produced a mean breathing zone concentration of 51.4 mg/m3.
=
Increasing the extraction rate to 0.5 m3/s yielded a reduction in breathing zone concentration, with a mean concentration of 30.7 mg/m3.
=
A further extraction increase to 0.7 m3/s (full extraction capability) produced a mean breathing zone concentration of 20.4 mg/m3.
Modelling the ventilation rate effects on space concentration illustrated that increasing the extraction rate, exhibited a similar trend by producing a decrease in total space concentration. A comparison between the measured breathing zone concentrations and modelled space concentrations demonstrated that, although the ranges differ (by a factor of 3), there are similar trends of increased extraction rates producing lower concentrations. Although there is no direct correlation between space and breathing zone concentrations, for these experimental investigations there was a similar development between the mean 210
Chapter 6
exposure concentration and extraction rate. The results generated by this study are highlighted below in Figure 6.1. 1000
Experimental Mean Breathing Zone Concentration
Concentration (mg/m3)
Theoretical Steady-state Space Concentration
100
10
1 0
0.2
0.4 0.6 3 Ventilation Extraction Rate (m /s)
0.8
Figure 6.1 The increase in extraction rates provides reductions for both the modelled space concentrations and measured breathing zone concentrations. This similar behaviour demonstrates that an increase in ventilation is beneficial to the occupational environment. The trend of reducing breathing zone concentration will, intuitively, continuing with increasing extraction rate. The more air removed from an enclosure will increase ACH, as well as the dilution of the contaminant within the enclosure. However, the fume plume dispersed into an environment will continue to pose a hazard to the operator, and they may still be exposed to excessive fume concentrations. Great care is needed to effectively control occupational environment. Utilising the enclosure’s doorway (natural ventilation) provided an inflow of fresh ambient conditions into the controlled environment. This inflow generates an air exchange with the contaminated pollutant within the enclosure with the warm interface exiting the space from the upper region while the cooler ‘fresh’ air enters from the lower region (§2.4.5).
211
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=
The presents of the air exchange via the open doorway generated a breathing zone concentration exceeded the exposure limit by just under 2.5 times, with the mean breathing zone exposure equal to 12.26 mg/m3.
=
This natural ventilation method of controlling operator exposure is comparable with that of the general extraction, via a mechanical system positioned directly over the operator (on the ceiling).
The limits of the enclosure height and doorway size have an influence on how effectively the operator’s breathing zone exposure may be controlled. For a confined space, the limited working environment and opening area greatly restrict the effective capacity of utilising natural ventilation, however, a larger workshop environment would benefit greatly from the simple use of natural airflow. The thermal investigations of the enclosure with general ventilation produced a distinctive outcome (§4.3.4). Ventilation using the mechanical extraction from position 1 produced a small thermal growth upon arc initiation, which stabilised after several minutes. A similar trend was exhibited with the use of the natural ventilation strategy. The mean steady thermal gradient experienced by these ventilation strategies was approximately 2.5 and 5.7 o
C/m, respectively. Repositioning the mechanical extraction point to directly above the arc
and breathing regions produced a similar thermal profile, however the overall growth was smaller with a mean final thermal gradient of 1.7 oC/m. The difference in thermal conditions between the mechanical extraction locations corresponds well with the measured breathing zone concentration results. The extraction point located closer to the arc produced lower breathing zone concentrations, as well as lower thermal changes within the enclosure. The combination of the general mechanical and natural ventilation strategies would result in a further increase in control efficiency, if properly implemented. As mentioned previously, any increase in the extraction rate of the system will, theoretically, reduce the contaminant by providing increased dilution of the space. Moreover, natural ventilation may provide air movement through the working environment, however great care must be taken to ensure fume is not propelled into the operator’s breathing zone. 212
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The presence of a local extraction system further reduces the concentration levels, however greater care needs to be exercise to allow benefit for the worker. Firstly, the employment of a crossdraft across the welder’s facial region must provide protection against the fume plume, yet not disturb the presence of the shielding gas. Recommendations found during the literature review indicated that a minimal crossdraft velocity 0.5 m/s was required to produce sufficient protection to the operator. These studies investigated crossdraft velocities of 0.5 – 0.7 m/s. =
The recommended crossdraft velocity of 0.5 m/s provided a mean exposure concentration of 3.53 mg/m3 (for both flow directions), however yielded several contaminant samples exceeding the occupational limit.
=
An exposure percentage of 16% was above 4.5 mg/m3 for a right-to-left crossflow direction, while left-to-right yielded almost double (28%) breathing zone concentration above 4.5 mg/m3. From this, a right-to-left airflow across the breathing zone, would benefit the operator by providing a lower distribution in breathing zone concentration. However, in a practical situation, the movement of the welder’s body will affect the breathing zone exposure rate due to disturbance of the airflow and plume’s movement.
=
Increasing the crossdraft velocity to 0.7 m/s reduced the mean breathing zone to 3.3 mg/m3, with a reduction in the total exposed concentration range. The additional increase of crossdraft velocity effectively reduced breathing zone exposure within the confined space. The required increase in air velocity may be attributed to the restriction of air movement within the confined environment, as well as the prolonged exposure period.
The implementation of the local extraction nozzle provided the best method of controlling the mean breathing zone exposure. Correctly positioning the nozzle provided greater control of the fume, while a poorly positioning did little to effectively reduce the breathing zone concentrations.
213
Chapter 6
=
When the extraction nozzle was within 100 mm of the arc source and to the side of the welder, the mean breathing zone concentration was 2.54 mg/m3, 50% of the prescribed exposure level.
=
Repositioning the nozzle opening to directly face towards the welder produced an almost identical mean exposure concentration.
=
The nozzle adjacent to the operator produced 76% of the total measured concentration below 3 mg/m3, while the nozzle opposite to the welder generated 80% of the total concentration below 3 mg/m3. The small difference represented a single measured sample, thus the two control methods produced similar results.
=
Increasing the distance between the extraction nozzle and source by 25 mm produced an increase in breathing zone concentration of 4.5 mg/m3, producing an effective capture velocity of 1.2 m/s.
=
A further increase of 25 mm (to 150 mm) once again produced an increase in exposure concentration (10.22 mg/m3), twice the exposure limit for welding, and would provide no real benefit to the operator. The effective capture velocity at this location was 0.9 m/s.
Breathing Zone Concentration (mg/m3)
14
Mean Concentration 12
Concentration Range
10 8 6 4 2 0 0.9 m/s
1.2 m/s
2 m/s
Capture Velocity (m/s)
Figure 6.2 The effective capture velocities used during the local ventilation of welding fume from GMAW. These results highlight the need of an appropriate capture velocity, to provide adequate operator conditions. 214
Chapter 6
The comparison between the initial shielding gas effects on plume dispersion, and the saltwater highlights the dispersal characteristic of the ejected shielding fluid. The input of the shielding gas in the ‘actual’ welding scenario (§4.3) demonstrated the visual dispersive effects on the fume plume. A flow of 20 l/min provided an increase of approximate 2.5 times in radial dispersion of the fume within close proximity to the arc. This could be utilised to effectively reduce operator exposure (§6.3.1). Modelling the initial fume plume dispersion, due to the interaction of the shielding gas, was aimed at developing an understanding of the initial fluid characteristics on fume plume dispersion. The salt-water modelling of an impinging fountain illustrated the overall characteristics and effects of parameter manipulation. To utilise the radial dispersion as a form of fume control requires: an increase in volumetric flow; decrease in buoyancy; or decrease in the nozzle-to-workpiece distance. This will generate greater movement across the surface, dispersing the fume away from the arc (and operator). In order to examine the dispersion of the welding fume plume within a confined space several assumption were applied. The first assumption deals with the thermal effects of the enclosure. The enclosure is assumed to be an adiabatic system. In reality the interface generated by the plume will experience heat loss to the enclosure, as well as diffusing within the environment. Another thermal influence not considered in these experiments is the effect of the workpiece convective current. A thermal current, generated by the electrical heat input into the workpiece, is emitted from the total pipe length due to the extreme heat input that the arc generates, which generates a line plume effect over the length of the pipe. This current will not only effect the plume’s flow behaviour to some extent, but also the influence a thermal change of the ambient conditions. Ignoring this characteristic limits the problem to a simple source condition of fume and heat generation, which is the dominant source of the fume plume itself. It should be noted that there was no ‘clear’ indication where the actual position of the contaminated interface was. Several visualisation techniques were employed, however, 215
Chapter 6
these proved inadequate. Due to the intense arc light, it was possible to see the initial dispersion of the fume plume close to the source (as demonstrated in Figure 4.44). However, the extreme light source conditions restricted further visualisation within the enclosure. The addition of various lighting strategies, to aid visualisation, proved unsuccessful in overcoming this intense light. Incorporating the thermocouple system to investigate the descent of the accumulated contaminant proved effective and relatively simple. Monitoring the temperature growth within the enclosure allowed the interface to be traced and utilised in determining the dispersion of the fume. The results of the temperature analysis highlight the behaviour of the fume plume within a confined environment, and how the predicted model resembles the actual plume distribution. The dispersion of the fume plume within the enclosure corresponds to the models of classic plume theories relating to convective currents from buoyant sources. The filling box model described by Baines and Turner (1969) for a fluid released into a confined region is closely related to the welding fume dispersion within the enclosure. The fume will ascend to the ceiling, accumulating into a contaminated highly buoyant interface. As long as the plume is continuous, the contaminated environment will move downward through the enclosure reducing the quality of air within the working environment. The filling box theory developed expresses the position of the developed interface with respect to time. This could be used to estimate the timeframe for the contaminated interface to reach the operator’s breathing zone (as well as working environment). However, this expression is limited in that it does not factor in the time taken for the plume to travel to the upper boundary and interface development period. The simple expression for this filling estimate is: -1 3
t = 8.2AB0
[h
-2 3
- H 2 3]
This timeframe can be utilised in designing the appropriate ventilation system to eliminate this contaminated interface † intercepting with the worker’s breathing environment. 216
Chapter 6
The temperature measurements demonstrate a continual linear growth with respect to height during the course of the arcing period. This meant that there was no sudden temperature rise as a result of the interface transition across the thermocouple, which does not following the prediction of the filling box model. The growth of the interface between the experiment and theoretical model exhibits similar trend characteristics, however the results deviate towards the lower boundary conditions. This may be attributed to the position of the arc, as it is not an actual boundary (the plume may still descend beneath the source). 0.8
0.7
Height (Metres)
0.6
0.5
0.4
0.3
0.2
0.1
0 0
100
200
300
400
500
600
Time (Seconds)
Figure 6.3 The descent of the contaminated interface for the actual welding scenario exhibits a similar trend to the theoretical model (dashed line). The intense initial conditions of the welding fume plume, and the unrestrictive environment below the arc have a drastic effect on plume and interface dispersion. The extension of the confined space investigations to incorporate the various ventilation systems presented some interesting results pertaining to the worker’s breathing zone exposure. Designing and implementing the various ventilation strategies was done in accordance with the notion of evaluating the possibility of controlling the operator’s breathing zone exposure concentration. Using theories presented in Chapter 2, the general and local extraction strategies were set in place. The initial parameters of the ventilation strategies were based on results found during the critical literature review. 217
Chapter 6
The thermal analysis of the enclosure with the addition of various general ventilation strategies generated a remarkable comparison with the modelling prediction. The general ventilation with an extraction unit yielded two outcomes due to the position of the extraction opening on the ceiling. The location of the first extraction point (Position 1 §3.6.2) generated a measured interface between the thermocouple height of 0.46 and 0.56 metres (§4.3.4). The predicted height of the contaminated interface (as calculated in the modelling section §5.2.2), utilising the same extraction rate of 0.7 m3/s, was 0.51 metres. Repositioning the extraction opening above the arc and operator drastically reduced the overall thermal gain, and it was difficult to note the position of the interface. Employing the natural ventilation (via the doorway) generated a measured interface height again between 0.46 and 0.56 metres above the arc (§4.3.5), while the predicted height from the modelling of the buoyant driven ventilation system via doorway ventilation (§5.2.4) was 0.65 metres. From this outcome, the theoretical interface height provides a beneficial approximate within a small environment. Such a theory enables the evaluation of functional extraction rates. Further studies should be performed to determine accuracy, especially within larger welding environments. The specifications of the enclosure dimensions incorporated the theory discussed in §2.3.10, dealing with the overturning nature of the plume impinging at the ceiling. This relationship between enclosure height and length was utilised to avoid any overturning of the plume, providing a highly stabilised ‘sampling’ environment. The enclosure has an approximate dimensional unity. Another consideration worth noting is that the position of the source is not in the immediate centre of the enclosure. Investigations were undertaken using fixed welding parameters (25 Volts and 200 Amps) to prevent alteration of the fume generation rates of the process and to minimise any fume concentration inconsistencies. As shown in the literature review, slight alterations to welding parameters such as welding voltage, arc current, wire feed speed, shielding gas flow, etc. all influence fume generation rates. The parameters chosen were based on the type and consistency of the weld bead produced, low spatter ejection, and fume generation. 218
Chapter 6
The study of the confined space breathing zone exposure confirms that some form of air movement must be employed to provide a safer working environment. Exposure of the operator to the high concentrations generated by this study warrants concern over the health and safety of any welding exercise performed within a restricted region. The introduction of the various control strategies to reduce welding fume concentrations, within the enclosure, has demonstrated the improvement to the quality of breathing zone air. The reduction to the respirable contaminant due to a variation in the mode of ventilation provides a substantial benefit for the welder. The general or natural ventilation of the enclosure produces a large reduction in breathing zone concentration, however the recorded exposure levels still exceeded the generic exposure levels for welding fume. Investigations into the shielding gas effects of fume dispersion noted that the injected fluid influences the initial distribution of the welding fume away from the arc region. The several welding experiments performed demonstrate that, although there is an initial radial dispersion without the addition of a shielding gas, the impinging fluid forces the plume horizontally away, twice the radial dispersion of the non-shielding gas situation. Development of the model to simulate the initial radial dispersion from the gas highlighted the initial characteristics that influence radial spread. The dimensions of the gas nozzle and nozzle-to-workpiece distance; the volumetric flow of the gas; and the buoyancy of the fume all heavily influence this initial radial spreading of the fume plume. Experiments involving the salt-water models validated these influential parameters. The model generated by these investigations produced a good approximation of radial spread over the impinged surface. The comparison between experimental and theoretical values for a non-dimensional approximation is highlighted below in Figure 6.4. The theoretical approximation predicts a similar trend of radial dispersion, in relationship to nozzle height from the impinged surface, however the estimated values are approximately 2.7 times greater than experimental values. Since a similar trend is exhibited by both methods, a simple division of the theoretical model yields a good approximation of the experimental results. 219
Chapter 6
2.5
Rsp theoretical Exp 2 Theorectical Correction
Exp 1 Exp 3
Non-dimensional Radial Spread
2
1.5
1
0.5
0 0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
Non-dimensional Impinging Height
Figure 6.4 Experimental and theoretical non-dimensional radial spread as a function of non-dimensional height. The corrective theoretical model provides a good approximate of the radial dispersion. The main purpose of modelling the initial dispersion was to predict the virtual origin correction required to enable expressing a welding fume plume as a pure source of buoyancy. Correlating the virtual origin factor from both modelling and thermal investigations, the ‘actual’ welding fume origin location was evaluated to be between 0.7-1 metres below the arc, while the model predicted a virtual origin location was 0.3 metres below actual origin. The difference between these values may be due to the correction analysis used, the turbulent conditions of the welding plume and enclosure conditions, etc. 6.2
Recommendations
6.2.1 Recommendations for Controlling Breathing Zone Concentrations The process of welding will inevitably produce fume contaminants, the dosage depending on the welding process and parameters used. There are documented ways of reducing the total fume generated via modifications to process parameters, as are detailed in the literature review (§2.2). In principle, it would be more advantages for the operator to design a welding process that yields a product of high quality, and produces the least amount of fume. 220
Chapter 6
The control of fume production by welding parameters will generate lower exposure levels, aiding fume control systems. However, any quality reduction of the final product is an undesirable response, so exposure control can be achieved by two methods. =
Remove of worker by utilising automation, or
=
Reduction of fumes from the process
Replacing the welder with an automated welding system eliminates the operator from close proximity to the welding process, and fumes, reducing the contaminant control systems required to the general work environment. Automated welding also increases higher quality and tighter parameter control of the welding procedure. The major disadvantage of introducing automation to the workshop is the immense initial outlay, programming of the system and down time due to technical difficulties. These investigations into the shielding gas influence on controlling breathing zone concentrations exposed another possible area for exposure control. The studies carried out simulated the effects of modifying gas parameters such as fluid buoyancy, volumetric flow and nozzle-to-workpiece distance. The effects of buoyancy are deemed rather futile when dealing with the extreme temperature of the arc zone. However, dispersion of the welding fume by manipulating the shielding gas flow rate, or the height of the nozzle could have benefits on the breathing zone concentrations of the operator. Decreasing the distance between the nozzle and the base plate will produce an increase in the radial spread of the ejected fluid (shielding gas), while an increase in the gas flow will result in a similar radial increase. Maybe a new gas nozzle that extends further towards the workpiece may assist initial fume dispersion away from the arc zone. The utilisation of this radial spread may also be incorporated into the gas nozzle, with either a dual gas nozzle that ejects a small gas flow towards the arc (to aid arc stability, etc) while a greater volumetric flow is ejected sideways at the end of the gas nozzle, further increasing the dispersion of the contaminant away from the arc. Another system may simply utilise the radial jet of gas to drive the fume away from the arc. This may result in greater dilution of 221
Chapter 6
the fume plume prior to coming into contact with the operator’s breathing zone, reducing the overall exposure concentration.
Figure 6.5 Utilising a radial jet of shielding gas (issued from the end of the torch nozzle) may aid in controlling breathing zone concentration exposure by displacing the contaminant away from the source. This displacement may increase dilution with the ambient, thus reducing the The use of various ventilation techniques for control and removal of pollutants, within the working environment, is a more cost-effective method of fume reduction. Under investigation conditions, the concentration of the enclosure could only be sufficiently controlled to meet the prescribed exposure levels by utilising an appropriately positioned local extraction system. The use of general and natural ventilation produced a dramatic reduction in the breathing zone concentrations, and for the general working environment can provide adequate fume control, if designed and employed properly. Most welding situations are performed in a large working environment, and proper ventilation design should consider the use natural ventilation techniques to improve fume control within the breathing zone as well as the general occupational environment. A large ceiling height aids the dispersal of the welding fume, however the stratification of the rising plume may Based on the results of the critical opening area of a confined environment (§5.2.3), the operator should be positioned so that the centreline of the window is above a preferable workable breathing zone height (2.5 metres or so). This allows room for the contaminants to disperse above the working environment. In regards to a critical opening area, the size of 222
Chapter 6
the opening is proportional to the height above the source of buoyancy, and inversely proportional to the aspect ratio of the opening. This critical area can be determined by the equation,
Acrit =
c16 5 2 h g 1 5 k14 5
Providing a risk assessment of the working area indicates there is adequate movement of air to provide reduction and control of concentration exposure to the worker, a large open † doorway is an effective (both cost and performance) method of reducing contamination of the working environment. 6.2.2 Recommendations For Further Work Further investigation into the dispersive effects of welding fume could elaborate on the information generated by this initial study. A method of correlating breathing zone measurement with the total fume generated will significantly aid the manufacturing industries to understand and appropriately assess the exposure risks of their employees. At this present time, there is no direct method of correlating these two factors. Naturally logic dictates that a higher fume production will generate a higher risk exposure to the welder, but whether this belief is founded needs to be determined. The additional work should incorporate different welding positions and geometry and what effect they have on plume distribution with respect to the breathing zone as well as the background working environment. One of the limitations noted within this study was the position of the sampling point. The static position of the mannequin did not allow a truly accurate assessment of the breathing zone, as most welders are bent over the workpiece during operations. This puts the breathing zone into a more direct path than observed during these trials. The validity of this analysis carried out demonstrates the need for greater control, as the location used during these trials will produce a smaller exposure then an actual welding position. Furthermore, a continuation of these trials should investigate the effects within a larger environment, perhaps with a greater ceiling height. The limitations of using the confined 223
Chapter 6
space, although relevant, are more to do with background environment concentrations then the actual operator’s breathing zone. The use of the confined space will generate higher operator exposure concentrations, thus any findings that allow reduction and controlled within this restricted environment will carry over into an ‘unbounded’ workspace. Another important issue for welding fume plume dispersion is the initial parameters surrounding the arc source itself. It is understood how fumes are produced from the arc process, but further work into the initial volumetric flow and velocities of the plume would aid in the development of an effective ventilation system. In addition to the work focused on the welding fume concentrations, further work on the turbulent impinging fountain should also be undertaken. The lack of literature available on this topic highlights the need for greater understanding of the dispersive effects that this fluid mechanism generates. Greater modelling analysis utilising a purpose-designed nozzle (that effectively reduces the laminar jetted fluid or the jet length) will increase the overall knowledge of impinging fountains, and better aid fume dispersal predictions from shielding gas effects.
224
Chapter 7
Chapter 7 CONCLUSIONS This thesis describes an investigation into the breathing zone concentration of a welder, associated with GMAW of mild steel under various conditions. As a result of these studies, the following conclusions were determined. =
The release of a contaminant into a confined space produced excessive exposure concentrations levels. The use of copper coated and non-copper coated ER70S-6 electrode wires generated mean concentration levels of 16 and 11 times the regulatory limits within the confined enclosure, respectively.
=
The mean background enclosure concentration was approximately 90% of the measured mean breathing zone concentration.
=
Thermal investigations of the enclosure demonstrated that the welding fume plume dispersed similarly to a filling box model, with the fume descending through the enclosure in a contaminated accumulated layer.
=
Implementation of a ceiling extraction point generated a reduction in the breathing zone concentration, within the controlled environment. Increasing the extraction rate produced reductions in the measured breathing zone concentration, however exposure levels still exceeded the recommended occupational levels (at best by a factor of 4).
=
Employing a natural ventilation strategy, via an opened doorway, the breathing zone concentration exceeded the exposure limit by just under 2.5 times, with the mean breathing zone exposure equal to 12.26 mg/m3.
=
A crossdraft velocity of 0.7 m/s resulted in a reduction in mean breathing zone concentration (3.3 mg/m3). The recommended crossdraft velocity (0.5 m/s) yielded several samples that exceeded the occupational limit. A crossflow direction of rightto-left provided more control over the distribution of the measured concentration (12% less than a left-to-right airflow direction). 225
Breathing Zone Concentration (mg/m3)
1000 Mean concentration Concentration Range
100
10 Concentration level of 5 mg/m3
1
) ) ) ce m) m) m) m) /s) /s) /s) /s) ay t2 t1 pa m m m m m m m m n n w i i r S 5 0 0 0 Po Po oo 0.5 0.7 0.5 0.6 12 15 10 10 ted (D n( n( a @ @ @ @ l @ @ @ o o @ i i i n t t t t t r r r r o ct ct lef lef lef en igh ati ra ra lde lde lde lde V r l t t o o o i e e e e t t t t x x o n w w w w t t t t en lE lE No igh igh igh ra ra eft ind ind ind lv ing r r l r e e c a h h h r n n e e e m m m m Fa tu (B (B (B Ge Ge ro ro ro ro n( n n n Na (F (F (F (F o o o o i w w w w ct cti cti cti flo flo flo flo ra ra ra tra t t t s s s s x x x x os os os os lE lE lE lE Cr Cr Cr Cr ca ca ca ca o o o o L L L L
Figure 7.1 The overall breathing zone concentrations, generated by these investigations into breathing zone exposure.
Chapter 7
=
The implementation of a local extraction nozzle provided the best method of controlling breathing zone exposure. The correct positioning the nozzle provided greater control of the fume, while a poorly positioning did little to effectively reduce the breathing zone concentrations.
=
Positioning the extraction nozzle at 100 mm resulted in a mean breathing zone concentration of 2.54 mg/m3, 50% of the prescribed exposure level. An additional 25 mm increased concentration 170%, while a further 25 mm (to 150 mm) increase yielded an exposure increase of 400% (twice the recommended levels).
=
Shielding gas parameters (flow rate, nozzle-to-workpiece distance) may be utilised to reduce breathing zone concentrations by dispersing the initial fume plume.
226
References ACGIH (1978), “Industrial Ventilation: A Manual of Recommended Practice”, American Conference of Governmental Industrial Hygienist Air Products (1999), “Welder’s Handbook – For Gas Shielded Arc Welding, Oxy Fuel Cutting and Plasma Cutting – 3rd Edition”, Air Products PLC Alpaugh EL, Phillipps K & Pulsifer C (1968), “Ventilation Requirements for Gas Metal Arc Welding vs Covered Electrode Welding”, American Industrial Hygiene Association Journal, Nov-Dec Anderson PCJ & Carter G (1996), “Pulsed MIG – A Closer Look at Productivity, Spatter and Fume”, TWI Bulletin, July/August, pp 68-71 Anderson PCJ & Wikorowicz R (1995), "Ozone Emissions During Arc Welding Pt 1", Welding and Metal Fabrication, October Anderson PCJ & Wikorowicz R (1995), "Ozone Emissions During Arc Welding Pt 2", Welding and Metal Fabrication, November ANSI/AWS F1.1-85 (1985), “Method for Sampling Airborne Particulate Generated by Welding and Allied Processes”, American Welding Society, Miami, Florida ANSI/AWS F1.2-85 (1985), “Laboratory Method for Measuring Fume Generation Rates and Total Fume Emission of Welding and Allied Processes”, American Welding Society, Miami, Florida ANSI/AWS F3.1-89 (1989), “Guide for Welding Fume Control”, American Welding Society, Miami, Florida Antonini JM, Krishna Murthy GG, Rogers RA, Albert R, Eager TW, Ulrich GD & Brian JD (1998) "How Welding Fumes Affect the Welder", Welding Journal, Vol. 77, (10), pp 55-59 AS 2812-1985, “Welding, Brazing and Cutting of Metals – Glossary of Terms”, Australian Standards AS 3853.1-1991, “Fume From Welding and Allied Processes. A Guide to Methods for the Sampling and Analysis of Particulate Matter”, Australian Standards AS 3853.2-1991, “Fume From Welding and Allied Processes. A Guide to Methods for the Sampling and Analysis of Gases”, Australian Standards AS/NZS 2865-2001, “Safe Working in a Confined Space”, Australian Standards 227
ASHRAE (1989), “1999 ASHRAE Handbook: Heating, Ventilating and Air Conditioning Applications”, American Society of Heating, Refrigeration and Air-Conditioning Engineers, Atlanta, Georgia AWS (1972), “Welding Handbook, Vol. 1. Welding Technology”, American Welding Society, Miami, Florida AWS (1973), “The Welding Environment”, American Welding Society, Miami, Florida AWS (1979), “Fumes and Gases in the Welding Environment”, American Welding Society, Miami, Florida Baines WD & Turner JS (1969), "Turbulent Buoyant Convection from a Source in a Confined Region", J. Fluid Mech., Vol. 37, pp 51-80 Baines WD (1983), "A Technique for the Direct Measurement of Volume Flux of a Plume", J. Fluid Mech., Vol. 132, pp 247-256 Batchelor GK (1967), “An Introduction to Fluid Dynamics”, Cambridge University Press, London Beaumont JJ & Weiss NS (1981), "Lung Cancer Among Welders", J. of Occupational Medicine, Vol. 23, No 12, pp 832-844. Bennett (1985), “ Ozone in the Pulsed MIG and TIG Welding of Mild Steel”, Technology Planning and Research Division TPRD/M/1536/N85, Marchwood Engineering Laboratories Bitcolov NZ, Olishevskiy AT, Agoshkov AI & Strizheusov SN (1992), "Ventilation of Welding Collection Shops", ROOMVENT ‘92, Air Distribution in Rooms, Third International Conference, Aalborg, Denmark Blakeley PJ (1995), "Welding Fume - Control and Guidance", Welding and Metal Fabrication, October Bloomfield LJ & Kerr RC (1998), “Turbulent fountains in a stratified fluid”, J. Fluid Mech., Vol. 385, 335-356 Bloomfield LJ & Kerr RC (2002), “Inclined Turbulent Fountains”, J. Fluid Mech., Vol. 451, 283-294 Bosworth MR & Deam RT (2000), "Influence of GMAW Droplet Size on Fume Formation", Journal of Physics. D, Applied Physics, Vol. 33, Pt 20, pp 2605-10
228
Bradshaw LM, Fishwick D, Slater T & Pearce N (1998), “Chronic bronchitis, work related respiratory symptoms, and pulmonary function in welders in New Zealand”, Occup. Environ Med, Vol. 55(3), pp 150-154 British Occupational Hygiene Society (1973), “Hazard From Welding Electrodes – I”, IIW Doc VIII-525-73, International Institute of Welding Brooks G, Mahboubi F, French IE & Tyagi VK (1997), "The Influence of the Consumable and Power Source Type on Welding Fume", Australasian Welding Journal, Vol. 42, 38-43s Brown WG & Solvason KR (1962), "Natural Convection Through Rectangular Openings in Partitions: 1 - Vertical Partitions", Int. J. Heat Mass Transfer, Vol. 5, pp 859-868 Carter GJ (1998), “Estimation of Exposure to Arc Welding Fume”, The Welding Institute, 7324.03/98/1004.03 Carter GJ (2002), “Evaluation of the Effect of Arc Welding Practice on Fume Emission Rate, Exposure to Fume and its Control”, The Welding Institute, 7402.01/00/1088.03 Cary HB (1979), “Modern Welding Technology’, Prentice Hall, New Jersey Castner HR & Null CL (1998), "Chromium, Nickel and Manganese in Shipyard Welding Fumes", Welding Journal, Vol. 77, (6), 223s-231s Castner HR (1996), "Fume Generation Rates for Stainless Steel, Nickel and Aluminium Alloys", Welding Journal, Vol. 75 (12), 393s-401s Castner HR (1995), "Gas Metal Arc Welding Fume Generation Using Pulsed Current", Welding Journal, Vol. 74 (2), 59s-68s Chen LC, Wu CY & Qu QS (1995), "Number Concentration and Mass Concentration as Determinants of Biological Response to Inhaled Irritant Particles", Inhal. Toxicol., Vol. 7, pp 577-588 Contreras GR & Chan-Yeung M (1997), “Bronchial reactions to exposure to welding fumes”, Occup. Environ Med, Vol. 54, pp 836-839 Cooper CD & Alley FC (2002), “Air Pollution Control: A Design Approach”, Waveland Press Inc., Illinois Cooper P & Linden PF (1996), "Natural Ventilation of an Enclosure Containing Two Buoyancy Sources", J. Fluid Mech., Vol. 311, 153-176 Dalziel SB & Lane-Serff GF (1991), "Hydraulics of doorway exchange flows", Building 229
and Environment, Vol. 26, No 2, pp 121-135 Davies GMJ (1993), “Buoyancy Driven Flows Through Openings”, PhD Thesis, Queen’s College, Cambridge Davies GMJ & Linden PF (1992), “The Effects of Headwind on Buoyancy-Driven Flow Through a Doorway”, ROOMVENT ‘92, Air Distribution in Rooms, Third International Conference, Aalborg, Denmark Deam R, Bosworth M, Chen Z, French I, Haidar J, Lowke J, Norrish J, Tyagi V & Workman A (1997), “Investigation of Fume Formation Mechanisms in GMAW”, WTIA 45th Annual Conference, November, Melbourne, Australia Deam RT, Simpson SW & Haidar J (2000), "Semi-empirical Model of the Fume Formation from Gas Metal Arc Welding", Journal of Physics. D, Applied Physics, Vol. 33, Pt 11, pp 1393-402 Deam R, Bosworth M, McAllister T, Norrish J, Brooks G, Zhou S, Haidar J, Lowke J, Farmer T & Simpson S (1998), “Understanding Fume Formation by GMAW”, Cooperative Research Centre for Welded Structures, CRC Project 97:44 Dennis J & Mortazavi SB (1996), "The Mechanism of Fume and Spatter Formation in MIG Welding", Occasional Technical Report 9608 for Metal Fume Research Unit. University of Bradford, England. Dennis JH, French MJ, Hewitt PJ, Mortazavi SB & Redding CR (1996), "Reduction of Hexavalent Chromium Concentration in Fumes From Metal Cored Arc Welding by Addition of Reactive Metals", Annuals of Occupational Hygiene, Vol. 40, No 3, pp 339344 Dennis JH, Mortazavi SB, French MJ, Hewitt PJ & Redding CR (1997), "Effects of Welding Parameters on Ultra-Violet Emissions, Ozone and Cr(VI) in MIG Welding", Annuals of Occupational Hygiene, Vol. 41, Part 1 pp 95-104 Department of Employment and Productivity (1970), “Fumes from Welding and Flame Cutting; Report on the Ship Building and Ship Repairing Industry”, Department of Employment and Productivity, London Donaldson K, Stone V, Clouter A, Renwick L & MacNee W (2001), “Ultrafine Particles”, Occup Environ Med, Vol. 58, pp 211-216 Eastaugh P (1997), "Limiting Welders' Fume Fever (Health Aspects of Metal Fume)", 230
Health and Safety at Work, Vol. 19, October, p 18(1) Emmmett EA & Horstman SW (1976), "Factors Influencing the Output of UV Radiation During Welding", Journal of Occupational Medicine, Vol. 18, Part 1, pp 41-44 Farwer A (1989a), “Ozone in the Welders Breathing Zone with Shielding Gas Arc Welding: Limits and Restrictions for the Use of Emission Data to Predict the Effects of Nitrogen Monoxide Additives in the Shielding Gas”, IIW/IIS XII-89 Farwer A (1989b), “Ozone Concentrations in the Welders Breathing Zone with GasShielded Arc Welding: Recent Investigations on the Influence of Nitric Oxide Additives in the Shielding Gas”, IIW/IIS XII-1472-89 Fishwick D, Bradshaw LM, Slater T & Pearce N (1997) “Respiratory symptoms, acrossshift lung function changes and lifetime exposures of welders in New Zealand”, Scand J.Work Environ Health, Vol. 23, pp 351-358 French IE, Tyagi VK & Brooks G (1996) “Effect of Welding Power Source Characteristics on Fume Generation Rate During Continuous Wire Welding and Surfacing and Manual Metal Arc Welding”, Technical Report No. MTA 380, CSIRO Division of Manufacturing Technology, Adelaide, Australia Goodfellow HD & Tahti E (2001), “Industrial Ventilation Design Guidebook” Academic Press, San Diego, California Gray CN, Hewitt PJ & Dare PRM (1982), “New approach would help control weld fume at source Part 2 - MIG fumes”, Welding and Metal Fabrication, October, pp 318-324 Gray CN & Sutherland R (1996), “A Dispersion Model of Exposure to Welding Fume”, Occupational Hygiene Solutions: Fifteenth Annual Conference and AGM of the Australian Institute of Occupational Hygienists, December 1-4, pp 203-207, Perth, Australia. Head IW & Silk SJ (1979), “Integral Fume Extraction in MIG/CO2 Welding”, Metal Construction, December Health and Safety Executive (1990), “Guidance Note EH55 – The Control of Exposure to Fume From Welding, Brazing and Similar Processes”, London, United Kingdom. Heile RF & Hill DC (1975), "Particulate Fume Generation in Arc Welding Processes", Welding Journal, Vol. 54 (7), 201s-210s Hewett P (1993), "The Particle Size Distribution, Density and Specific Surface Area of 231
Welding Fumes From SMAW and GMAW Mild and Stainless Steel Consumables", IIW Doc VII 1688 93, International Institute of Welding Hewitt PJ (1996), ” Occupational Health in Metal Arc Welding”, Indoor Built Environ., Vol. 5, 253-262 Hewitt PJ (1993), "Systems Approach to the Control of Welding Fumes at Source", Annuals of Occupational Hygiene, Vol. 37, Part 3 pp 297-306 Hilton DE, Plumridge PN & Green JI (1992), "Particulate Fume Generation During Gas Metal Arc Welding and Gas Tungsten Arc Welding", IIW Doc VIII-1652-1992, International Institute of Welding, London Hudson NJ, Evans AT, Yeung CK & Hewitt PJ (2001), “Effect of Process Parameters Upon the Dopamine and Lipid Peroxidation Activity of Selected MIG Welding Fumes as a Marker of Potential Neurotoxicity”, The Annals of Occupational Hygiene, Vol. 45, Part 3, pp 187-192 Hunt GR & Kaye NG (2001), “Virtual Origin Correction for Lazy Turbulent Plumes”, J. Fluid Mech., Vol. 435, pp 377-396 Hunt GR & Linden PF (2001), “Steady-state flows in an enclosure ventilated by buoyancy forces assisted by wind”, J. Fluid Mech., Vol. 426, 355-386 Hunt GR (1999), “Turbulent Plumes and Jets”, Department of Applied Mathematics and Theoretical Physics, Cambridge University, Cambridge Irving R (1992), "Inverter Power Sources Check Fume Emissions in GMAW ", Welding Journal, Vol. 71 (2), 53-57 Jenkins N (1986), “The Facts About Fume – A Welding Engineer’s Handbook”, The Welding Institute, 2nd Edition, Cambridge, United Kingdom Jin Y (1991), "Experimental Study of Plume Rise in a Stably Stratified Environment", ASHRAE Transactions, Vol. 97, Part 2, pp 340-346 Jin Y (1992), "Welding Plume Rise in a Large Building with Temperature Gradient ", ROOMVENT ‘92, Air Distribution in Rooms, Third International Conference, Aalborg, Denmark Jin Y (1994), "Fume Generation from Gas Metal Arc Welding Processes", Staub Reinhaltung der Luft., Vol. 54, (2), pp 67-70 Kalliomaki PL, Kalliomaki K, Kelha V, Sortti V & Korhonen O (1980), "Measure of 232
Lung Contamination Among Mild Steel and Stainless Steel", Welding In the World, Vol. 18, Part 3/4, pp 67 Karjalainen A, Kurppa K & Virtanen S (2000), “Incidence of occupational asthma by occupation and industry in Finland”, Am J.Ind Med, Vol 37, pp 451-458 Khoo GT (1996) “Occupational Asthma from Welding: a case report”, Ann Acad Med Sing, Vol. 25, pp 293-295 Kimura Y, Ichihara I & Kobayashi M (1974), "Some Quantitative Evaluations of Fumes Generated From Coated Arc Electrodes", IIW Doc VIII-574-74, International Institute of Welding Kimura Y, Kobayashi M & Maki S (1976), "Some Considerations about Fumes Generated in Arc Welding Processes", IIW Doc VIII-687-76, International Institute of Welding Kobayashi M, Maki S & Ohe T (1976), "Factors Affecting the Amount of Fumes Generated by Manual Metal Arc Welding", IIW Doc VIII-670-76, International Institute of Welding Kobayashi M, Maki S, Hashimoto Y & Suga T (1978), "Some Consideration About Formation Mechanisms of Welding Fume", Welding In the World, Vol. 16, No 11/12, pp 238-248 Kobayashi M, Sakai Y & Hayashi K (1979), "Development of Fume Controlled Electrodes", Welding In the World, Vol. 17 (9/10), pp 228-230 Koken Ltd (2003), “Open-type Push-Pull Ventilation System”, Koken Ltd, Tokyo, Japan Koshiishi F & Shimizu H (2001), “High-Performance, Non-copper-coated Solid Wire for MAG Welding SE Wire”, Kobelco Technology Review, No 24, October, pp 60-63 Lane-Serff GF, Linden PF & Smeed DA (1990), "Laboratory and Mathematical Models of Natural Ventilation", ROOMVENT ‘90, Oslo, Norway Lidwell OM (1977), "Air Exchange Through Doorways: The Effect of Temperature Difference, Turbulence and Ventilation Flow", J. Hyg. Camb., Vol. 79, pp 141-154 Linden PF & Simpson JE (1985), "Buoyancy Driven Flows Through an Open Door", Air Infiltration Rev., Vol. 6, pp 4-5 Linden PF, Lane-Serff GF & Smeed DA (1990), "Emptying Filling Boxes: The Fluid Mechanics of Natural Ventilation", J. Fluid Mech., Vol. 212, pp 309-335 233
Ma J & Apps RL (1982), “MIG Transfer Discoveries of Importance to Industry”, Welding and Metal Fabrication, Vol. 51, Sept, pp 307-316 McDonald JC, Keynes HL & Meredith SK (2000), “Reported incidence of occupational asthma in the United Kingdom 1989-97”, Occup. Environ Med, Vol. 57, pp 823-29 McQuiston FG & Parker JD (1994), “Heating, Ventilation and Air Conditioning: Analysis and Design”, John Wiley and Sons, New York Messler RW (1999), “Principles of Welding: Processes, Physics, Chemistry, and Metallurgy”, John Wiley and Sons, New York Metcalf J & Davies JW (1975), “An Investigation into the Levels and Effects of Toxic Fume Produced During Semi-Automated Flux-Cored Welding in Confined Spaces”, Conference Proceedings “Exploiting Welding Technology”, London Mierzwinski S, Piotrowski J & Trzeciakiewicz Z (1992), "Improvement of Efficiency of Contaminants Capture in Enclosure of an Electric Arc Furnace", ROOMVENT ‘92, Air Distribution in Rooms, Third International Conference, Aalborg, Denmark Mortazavi SB (1997), "Engineering Control of Occupational Exposure to Welding Fume by Process Modification", Welding In the World, Vol. 39, Part 6, pp 297-303 Morton BR (1957), "Buoyant Plumes in a Moist Atmosphere”, J. Fluid Mech., Vol. 2, pp 127-144 Morton BR (1959), "Forced Plumes", J. Fluid Mech., Vol. 5, pp 151-163 Morton BR, Taylor GI & Turner JS (1956), "Turbulent Convection from Mainland and Instantaneous Sources", Proc. Royal Soc. Of London, Series A, Vol. 234, pp 1-23 MUREX (1999), Welding Consumables Health and Safety Information Leaflet NOHSC (1990), “Occupational Exposure Limits”, Guidance Note EH 40/90, Health and Safety Executive, Australia Norrish (1992), “Advanced Welding Processes”, Institute of Physics Publishing Norrish J (1997), “Comments on Generic Fume Assessment Ozone Measurements”, September Norrish J (1999), “ENGG901 Introduction to Welding and Joining Processes”, Cooperative Research Centre for Welding and Joining class notes, University of Wollongong, Australia Ojima J, Shibata N & Iwasaki T (2000), "Laboratory evaluation of welder's exposure and 234
efficiency of air duct ventilation for welding work in a confined space", Industrial Health, Vol. 38, Issue 1, pp 24-29 Olander L (1985), "Welding Fume Buoyant Plumes", Aerosol Science and Technology 4, Vol. 4, pp 351-358 Olander L (1996), “Welding Fume Plumes in Industrial Workrooms”, Ventilation '85, Amsterdam, pp 153-158 Omega (1999), “DataShuttle and WB-DynaRes for Data Acquisition and Control User’s Manual”, Omega Technologies Company, England Quimby BJ & Ulrich GD (1999) “Fume Formation Rates in Gas Metal Arc Welding”, Welding Journal, April, 142s-149s Rouse H, Yih CS & Humphreys HW (1952), "Gravitational Convection from a Boundary Source", Tellus, Vol. 4, pp 201-210 Saito H, Ojima J, Takaya M, Iwasaki T, Hisanaga N, Tanaka S & Arito H (2000), "Laboratory measurement of hazardous fumes and gases at a point corresponding to breathing zone of welder during a CO2 arc welding", Industrial Health, Vol. 38, Issue 1, pp 69-78 Sandberg M & Etheridge D (1996), “Building Ventilation: Theory and Measurement”, John Wiley and Sons, New York Schmidt W (1941), “Turbulente-ausbreitung eines stromes erhizter luft”, Z. Angew. Math. Mech. Vol. 21, pp 265-278 Shaw BH & Whyte W (1974), "Air Movement through doorways - the influence of temperature and its control by force airflow", BSE, Vol. 42, Dec, pp 210-218 Shibata N, Tanaka M, Ojima J & Iwasaki T (2000), "Numerical simulations to determine the most appropriate welding and ventilation conditions in small enclosed workspace", Industrial Health, Vol. 38, Issue 4, pp 356-365 Shutt RC (1979), “Controlled Total Copper in Wire Electrodes”, Welding Journal, November, pp 30 Simpson PJ, Stares IJ & Richardson IM (1993), "Reducing Ozone and Ultraviolet Emissions from GTA Welding", Welding and Metal Fabrication, April
235
Slater G, Cooper P & Norrish J (2001), “Natural ventilation of a side-vented enclosure containing a source of welding fume”, 14th Australasian Fluid Mechanics Conference Adelaide University, Adelaide, Australia, December 2001 Smars (1980), “The Problem of Ozone in the MIG Welding of Aluminium”, AGA Research Report, GIF-0050, Stephenson D, Seshadri G & Veranth JM (2003), “Workplace Exposure to Submicron Particle Mass and Number Concentrations from Manual Arc Welding of Carbon Steel”, AIHA Journal, Vol. 64, pp 516-521 Stern RM (1979), “Perspectives for Industrial Hygiene”, Danish Welding Institute, IIWVIII-840-79 Thorton M & Stares I (1994), "Analysis of Particulate Fume Generation Rates from Gas Metal Arc Welding", Welding Review International, November, pp 363-365 Thrysin E, Gerhardsson G & Forssman S (1952), "Fumes and Gases in Arc Welding", Archieves of Industrial Hygiene and Occupational Medicine, Vol. 6, Part 5, pp 381-402 Tian Y (1997), “Low Turbulence Natural Convection in an Air Filled Square Cavity”, PhD Thesis, South Bank University Tinkler MJ (1980), “Measurement and Control of Ozone Evolution During Aluminium GMA Welding”, IIW Proceedings of Colloquium on Welding and Health, Portugal, July Tinkler MJ (1983), “Evaluation and Control of Fumes Produced During Welding, Volume 1 – Problem Survey”, Ontario Hydro Research Division, Toronto, Ontario Tinkler MJ & Ditschun A (1984), “Evaluation and Control of Fumes Produced During Welding, Volume 2 – Experimental Evaluation”, Ontario Hydro Research Division, Toronto, Ontario Turner JS (1969), "Buoyant Plumes and Thermals", Ann. Rev. Fluid Mech., Vol. 1, pp 29-44 Turner JS (1962), "The ‘Starting Plume’ in Neutral Surroundings", J. Fluid Mech., Vol. 13, pp 356-368 Turner JS (1973), “Buoyancy Effects in Fluids”, Cambridge University Press, London Turner JS (1966), “Jets and Plumes with Negative and Reversing Buoyancy”, J. Fluid Mech. Vol. 26, 779-792. Ulfvarson U (1981), "Survey of Air Contaminants from Welding", Scand. J. Work 236
Environment, Vol. 7, Suppl 2, pp 1-28 Vandenplas O, Dargent F & Auverdin JJ (1995), “Occupational asthma due to gas metal arc welding on mild steel”, Thorax, Vol. 50, pp 587-588 Voitkevick V (1995) “Welding Fumes, Formation, Properties and Biological Effects”, Abington Publishing, Cambridge Watson G (2000), "Assessment and Control of Fume and Ozone During Welding", Welding and Metal Fabrication, January, pp 10-11 Winter N (2001), “Single Sided Natural Ventilation”, Undergraduate Thesis, University of Wollongong, Australia Worster MG & Huppert HE (1983), "Time-Dependent Density Profiles in a Filling Box", J. Fluid Mech., Vol. 132, pp 457-466 WTIA (1997), “Technical Note 7: Safety and Health in Welding”, Welding Technology Institute of Australia, Sydney WTIA (1999), “Fume Minimisation Guideless”, Welding Technology Institute of Australia, Sydney www.twi.com - The Welding Institute web site www.wtia.com.au - Welding Technology Institute of Australia web site Xin H, Geng Z & North TH (2001), “Fume Generation During Solid- and Metal- Cored Wire Welding”, Welding Journal, Vol. 80 (7), pp 173s-183s Yih CS (1951), Proc. First U.S. National Congressional Applied Mechanics, pp 941 Zhivov AM (1993), "Principles of Source Capturing and General Ventilation Design for Welding Premises", ASHRAE Transactions, Vol. 99, Part 1, pp 979-986, 1993 Zhou S, Norrish J & Chen Z. (1998), "Influence of Different Metal Transfer Modes on Welding Fume Generation During Gas Metal Arc Welding", Materials 98, Wollongong, Australia, July
237
Appendix A.2
Workbench Speed (Traversing) Table A2.1 Calibration trials for traversing bed speed Control Position and Direction 20 FWD REV 30 FWD REV 40 FWD REV 50 FWD REV 60 FWD REV 70 FWD REV 80 FWD REV 90 FWD REV 1.6
RUN 1 39.6 41 20.5 20.7 13.5 13.6 10.3 10.3 8.3 8.3 6.7 6.9 5.8 5.9 5.1 5.1
RUN 2 39.5 40.1 20.6 20.6 13.5 13.6 10.4 10.3 8.2 8.4 6.8 6.8 5.8 5.7 5.1 5
RUN 3 40.1 40 20.6 20.6 13.5 13.5 10.4 10.4 8.3 8.3 6.8 6.9 5.7 5.8 5.1 5
RUN 4 39.9 40.1 20.5 20.6 13.6 13.5 10.3 10.3 8.2 8.3 6.7 6.8 5.9 5.8 5.1 5.1
Avg RUN RUN time 5 6 (sec) 40 40.1 39.87 39.8 40.1 40.18 20.6 20.5 20.55 20.5 20.5 20.58 13.5 13.5 13.52 13.5 13.5 13.53 10.3 10.3 10.33 10.4 10.4 10.35 8.2 8.2 8.23 8.3 8.2 8.30 6.8 6.7 6.75 6.9 6.8 6.85 5.7 5.7 5.77 5.8 5.8 5.80 5.1 5 5.08 5.2 5.2 5.10
Mean Speed (m/min) 0.1806 0.1792 0.3504 0.3498 0.5327 0.5320 0.6968 0.6957 0.8745 0.8675 1.0667 1.0511 1.2486 1.2414 1.4164 1.4118
Avg Overall speed (m/min) 0.180 0.350 0.532 0.696 0.871 1.059 1.245 1.414
Speed (Fwd) Speed (Rev)
1.4
Speed (m/min)
1.2 1.0 0.8 0.6 0.4 0.2 0.0 0
20
40
60
80
Controller Setting
Figure A2.1 Traversing bed speed as a function of controller setting. Measurements were recorded over a set test length of 0.12 metres.
100
Appendix A.2
Workbench Speed (Rotating) Table A2.2 Calibration trials for rotational welding bench Controller Avg Mean Mean Setting Rotation Time Trial Time Speed Speed 1 2 3 4 5 6 7 8 9 10
RUN 1 RUN 2 RUN 3 RUN 4 N/A N/A N/A N/A N/A N/A N/A N/A 15.15 14.98 15.20 15.23 18.01 18.21 18.17 18.21 20.13 20.18 20.31 20.24 22.54 22.72 22.46 22.53 24.50 24.62 24.53 24.48 27.43 27.34 27.46 27.51 29.89 29.68 29.81 29.76 33.01 33.24 33.13 32.91
(sec) N/A N/A 15.14 18.15 20.22 22.56 24.53 27.44 29.79 33.07
(rpm) N/A N/A 0.25 0.30 0.34 0.38 0.41 0.46 0.50 0.55
(m/min) N/A N/A 0.16 0.19 0.21 0.24 0.26 0.29 0.31 0.35
0.4
Rotating Speed (m/min)
0.35 0.3 0.25 0.2 0.15 0.1 0.05 0
0
2
4
6
8
10
Controller Setting
Figure A2.2 Rotational bed speed as a function of controller setting. Table A2.3 Final experimental settings used during breathing zone concentration trials. Trials were over a timeframe of 15minutes. Workbench Condition Controller Setting Mean Speed (m/min) Traversing 10 ≈ 0.1 Rotational 5 0.21 Total mean speed used during experiment = 0.23 m/min, Total weld bead length = 3.49 m
Appendix A.3
A.3 Crossdraft Extraction Analysis In order to generate the recommended crossdraft velocity of 0.5 m/s, the extraction volumetric flow rate required is: Extraction Flow Rate = Cross-sectional Area x Velocity = 4.81 x 0.5 = 2.4 m3/s A3.2
Fan selection:
The fan was selected based on two criteria: cost and effectiveness. Firstly, the fan had to be able to provide an extraction rate of 2.4 m3/s, in additional to meeting the financial budget for this project. Fan: Fantech APP0634/4 pole, three-phase, 4 Kilowatt axial fan Blades: Original 14, however due to the poor quality of some, it was reduced to 7 Diameter: 630 mm Maximum Speed: 1440 rpm An inverter was attached to modify to power input to generate the required 2.4 m3/s extraction rate. A3.3
Duct Design
To transport the fume from the enclosure, a duct system was designed to meet the guidelines provided by ASHRAE handbook (1999). ASHRAE recommended a minimum transport duct velocity of 7-10 m/s to transport fume particles. To ensure this duct velocity, with the extraction rate of 2.4 m3/s, a square duct of 500 mm x 500 mm, was chosen as the main duct system. To connect the duct system to the fan, an expansion section was design from the square ducting to the 630 mm circular fan inlet. To accommodate the confined surroundings, the duct system was designed to fit within the small working area. This required several right-angle corners to be incorporated into the design. Within these corner pieces, a single vane was included to aid fluid flow through the ducting. This provided an effective and easy extraction route.
Appendix A.3 The exhaust section from the fan used a constrictive length of ducting (630 mm to 400 mm) followed by a small length of 400 mm diameter ducting. This was then exhausted out of a side-door of laboratory, into the atmospheric environment. Due to the small size, and the actual use of the ducting system, the pressure loss over the short length was not considered significant enough to warrant effective control. The pressure drop of the system (from entry to fan) was calculated to be approximately 93 Pa, due to 2.6 m duct length (with various sizes), entry loss, two 90o bends (coefficient of 0.3), expansion to fan section (coefficient of 0.1). Total Pressure Loss to Fan = Entry Loss + (Duct Length x Press Loss/m) + Fitting Pressure Losses = 0.6x102 x 0.5 + (2.6 m x 8Pa/m) + 60 Pa (2 x 0.3 + 0.1) = 92.8 Pa
ONE SPLITTER VANE IN ELBOW
ONE SPLITTER VANE IN ELBOW 700 mm
500 mm
700 mm
700 mm 1100 mm
500 mm x 500 mm OPENING
2300 mm
SECTION FROM SQUARE TUBING 500 x 500 mm TO ROUND f = 630 mm
700 mm
ENCLOSURE
FAN SPECIFICATIONS: FANTECH AP0634 FAN DIAMETER = 630 mm No. POLES = 4 No. BLADES = 7 BLADES @ 25o MOTOR = 4.0 kW RPM = 1440
FAN
500 mm
SECTION FROM ROUND f = 630 mm TO ROUND f = 400 mm
SQUARE DUCTING => 500 mm x 500 mm 2 x 90o BENDS = 700 mm x 700 mm STRAIGHT DUCT LENGTH = 1600 mm 1 (500mm x 500mm) SQUARE DUCT TO ROUND DUCT (f = 630 mm) 1 ROUND DUCT (f = 630 mm - 400 mm) 400 mm DUCT LENGTH = 500 mm
Welding Enclosure Ducting System NOT DRAWN TO SCALE Geoffrey Reginald Slater
28/10/2002
DUCT BENDS 700 mm
EXPANSION JOINT
ONE SPLITTER VANE 700 mm 630 mm 500 mm
200 mm 500 mm
500 mm CONSTRICTION JOINT
500 mm
400 mm
630 mm
Welding Enclosure Ventilation – Part 2 NOT DRAWN TO SCALE Geoffrey Slater
28/10/2002
590 mm m
ALUMINUM BAR PERSPEX 400 mm f = 8 mm
400 mm
IMPINGING FOUNTAIN EXPERIMENT 27/09/02 1. 2. 3. 4.
Perspex Sheet: t = 12 mm; 450 x 450 mm Aluminum Bars: 590 x 15 x 15 mm (x2) Threaded Rods: l = 500 mm; O.D. = 8 mm (x4) Nut; f = 8 mm (x8) (NOT TO SCALE)
Appendix B Confined Space Concentration Measurements (Copper Coated ER70S-6 Electrode) Mass Before Welding Experiment No. grams mg 1 0.00962 9.62 2 0.00936 9.36 3 0.0099 9.9 4 0.00877 8.77 5 0.00815 8.15 6 0.00802 8.02 7 0.00816 8.16 8 0.00918 9.18 9 0.00807 8.07 10 0.00825 8.25 11 0.00849 8.49 12 0.00835 8.35 13 0.00918 9.18 14 0.00868 8.68 15 0.0089 8.9 16 0.00856 8.56 17 0.00823 8.23 18 0.0084 8.4 19 0.00921 9.21 20 0.00812 8.12 21 0.00809 8.09 22 0.00876 8.76 23 0.00864 8.64 24 0.00903 9.03 25 0.00899 8.99 26 0.00853 8.53 27 0.00824 8.24 28 0.0084 8.4 29 0.00818 8.18 30 0.00832 8.32 31 0.00893 8.93 32 0.00837 8.37 33 0.00918 9.18 34 0.0082 8.2 35 0.00859 8.59 36 0.00903 9.03 37 0.00859 8.59 38 0.00831 8.31 39 0.0086 8.6 40 0.00849 8.49
Mass After Welding grams mg 0.01103 11.03 0.01139 11.39 0.01233 12.33 0.01053 10.53 0.00965 9.65 0.01034 10.34 0.00967 9.67 0.01091 10.91 0.00979 9.79 0.00988 9.88 0.01022 10.22 0.01003 10.03 0.01061 10.61 0.0105 10.5 0.01098 10.98 0.01 10 0.00968 9.68 0.0099 9.9 0.01087 10.87 0.01058 10.58 0.00972 9.72 0.01032 10.32 0.01053 10.53 0.01037 10.37 0.01102 11.02 0.01032 10.32 0.0098 9.8 0.01026 10.26 0.01028 10.28 0.00952 9.52 0.01032 10.32 0.01022 10.22 0.01092 10.92 0.00995 9.95 0.01032 10.32 0.01027 10.27 0.01017 10.17 0.01044 10.44 0.01014 10.14 0.01042 10.42
Collected Mass mg 1.41 2.03 2.43 1.76 1.5 2.32 1.51 1.73 1.72 1.63 1.73 1.68 1.43 1.82 2.08 1.44 1.45 1.5 1.66 2.46 1.63 1.56 1.89 1.34 2.03 1.79 1.56 1.86 2.1 1.2 1.39 1.85 1.74 1.75 1.73 1.24 1.58 2.13 1.54 1.93
Appendix B Confined Space Concentration Measurements (Non-Copper Coated ER70S-6 Electrode)
Experiment No. 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
Mass Before Welding grams mg 0.0171 17.1 0.01725 17.25 0.01728 17.28 0.01723 17.23 0.01697 16.97 0.01744 17.44 0.01613 16.13 0.0163 16.3 0.01773 17.73 0.01842 18.42 0.01802 18.02 0.01792 17.92 0.01794 17.94 0.01746 17.46 0.01717 17.17 0.01756 17.56 0.01826 18.26 0.01735 17.35 0.01725 17.25 0.0163 16.3 0.01619 16.19 0.01624 16.24 0.01605 16.05 0.01663 16.63 0.01622 16.22
Mass After Welding grams mg 0.01829 18.29 0.01896 18.96 0.01884 18.84 0.01887 18.87 0.01827 18.27 0.01895 18.95 0.01793 17.93 0.01797 17.97 0.01924 19.24 0.02002 20.02 0.01975 19.75 0.01929 19.29 0.01938 19.38 0.01866 18.66 0.01875 18.75 0.01924 19.24 0.01973 19.73 0.01911 19.11 0.01885 18.85 0.01768 17.68 0.01783 17.83 0.01785 17.85 0.01778 17.78 0.01800 18.00 0.01780 17.80
Collected Mass mg 1.19 1.71 1.56 1.64 1.30 1.51 1.80 1.67 1.51 1.60 1.73 1.37 1.44 1.20 1.58 1.68 1.47 1.76 1.60 1.38 1.64 1.61 1.73 1.37 1.58
Appendix B Confined Space Background Enclosure Concentration Measurements (Copper Coated ER70S-6 Electrode)
Experiment No. 400 401 402 403 404 405 406 407 408 409
Mass Before Welding grams mg 0.01678 16.78 0.01853 18.53 0.01659 16.59 0.01702 17.02 0.01743 17.43 0.01798 17.98 0.01699 16.99 0.01807 18.07 0.01759 17.59 0.01774 17.74
Mass After Welding grams Mg 0.01875 18.75 0.02054 20.54 0.01888 18.88 0.01887 18.87 0.01962 19.62 0.02018 20.18 0.0193 19.3 0.02008 20.08 0.01982 19.82 0.01961 19.61
Collected Mass Mg 1.97 2.01 2.29 1.85 2.19 2.2 2.31 2.01 2.23 1.87
Appendix B General Ventilation Concentration Measurements (Far Corner of Enclosure) Extraction Rate of 0.7 m3/min Mass Before Welding Mass After Welding Collected Mass mg Experiment No. grams mg Weight mg 66 0.00846 8.46 0.00881 8.81 0.35 67 0.00823 8.23 0.0088 8.8 0.57 68 0.009 9 0.00952 9.52 0.52 69 0.00939 9.39 0.01006 10.06 0.67 70 0.00952 9.52 0.01003 10.03 0.51 71 0.00845 8.45 0.00893 8.93 0.48 72 0.00945 9.45 0.00994 9.94 0.49 73 0.00958 9.58 0.01025 10.25 0.67 74 0.00947 9.47 0.00995 9.95 0.48 75 0.00851 8.51 0.00923 9.23 0.72 76 0.00976 9.76 0.01043 10.43 0.67 77 0.00937 9.37 0.00997 9.97 0.6 78 0.00988 9.88 0.01042 10.42 0.54 79 0.00626 6.26 0.00686 6.86 0.6 80 0.02117 21.17 0.02176 21.76 0.59 81 0.02114 21.14 0.02178 21.78 0.64 82 0.017 17 0.01756 17.56 0.56 83 0.01705 17.05 0.01769 17.69 0.64 84 0.01676 16.76 0.01739 17.39 0.63 85 0.01668 16.68 0.01728 17.28 0.6 86 0.02104 21.04 0.02175 21.75 0.71 87 0.01728 17.28 0.01784 17.84 0.56 88 0.01733 17.33 0.01796 17.96 0.63 89 0.01697 16.97 0.0175 17.5 0.53 90 0.01744 17.44 0.01793 17.93 0.49 91 0.0171 17.1 0.01782 17.82 0.72 92 0.01725 17.25 0.01784 17.84 0.59 93 0.01858 18.58 0.01921 19.21 0.63 94 0.01749 17.49 0.01814 18.14 0.65 95 0.01698 16.98 0.01766 17.66 0.68 96 0.01735 17.35 0.01788 17.88 0.53 97 0.01768 17.68 0.0181 18.1 0.42 98 0.01723 17.23 0.01772 17.72 0.49 99 0.01764 17.64 0.01821 18.21 0.57 100 0.01707 17.07 0.01768 17.68 0.61 101 0.01673 16.73 0.01728 17.28 0.55 102 0.01716 17.16 0.01781 17.81 0.65 103 0.0176 17.6 0.01814 18.14 0.54 104 0.01812 18.12 0.0186 18.6 0.48 105 0.01782 17.82 0.01856 18.56 0.74
Appendix B
General Ventilation Concentration Measurements (Far Corner of Enclosure) Extraction Rate of 0.5 m3/min Mass Before Welding Experiment No. grams mg 106 0.01723 17.23 107 0.01738 17.38 108 0.01735 17.35 109 0.01737 17.37 110 0.01714 17.14 111 0.0173 17.3 112 0.01625 16.25 113 0.01753 17.53 114 0.01746 17.46 115 0.01755 17.55 116 0.01713 17.13 117 0.01769 17.69 118 0.01723 17.23 119 0.01693 16.93 120 0.01727 17.27 121 0.01698 16.98 122 0.01816 18.16 123 0.01797 17.97 124 0.01812 18.12 125 0.01695 16.95
Mass After Welding grams mg 0.01811 18.11 0.01828 18.28 0.01818 18.18 0.01823 18.23 0.01806 18.06 0.01807 18.07 0.01719 17.19 0.0184 18.4 0.01832 18.32 0.01841 18.41 0.01805 18.05 0.01848 18.48 0.01806 18.06 0.01777 17.77 0.01815 18.15 0.01797 17.97 0.01905 19.05 0.0189 18.9 0.01906 19.06 0.01774 17.74
Collected Mass mg 0.88 0.9 0.83 0.86 0.92 0.77 0.94 0.87 0.86 0.86 0.92 0.79 0.83 0.84 0.88 0.99 0.89 0.93 0.94 0.79
Appendix B General Ventilation Concentration Measurements (Far Corner of Enclosure) Extraction Rate of 0.3 m3/min
Experiment No. 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145
Mass Before Welding grams mg 0.01783 17.83 0.01732 17.32 0.01655 16.55 0.01823 18.23 0.01793 17.93 0.01733 17.33 0.01802 18.02 0.01753 17.53 0.01698 16.98 0.01687 16.87 0.0172 17.2 0.01703 17.03 0.01776 17.76 0.0169 16.9 0.01747 17.47 0.01804 18.04 0.01816 18.16 0.01792 17.92 0.01811 18.11 0.01704 17.04
Mass After Welding grams mg 19.26 0.01926 18.87 0.01887 17.91 0.01791 19.72 0.01972 19.48 0.01948 18.78 0.01878 19.5 0.0195 18.9 0.0189 18.52 0.01852 18.49 0.01849 18.69 0.01869 18.37 0.01837 19.23 0.01923 18.38 0.01838 18.97 0.01897 19.46 0.01946 19.55 0.01955 19.34 0.01934 19.54 0.01954 18.56 0.01856
Collected Mass mg 1.43 1.55 1.36 1.49 1.55 1.45 1.48 1.37 1.54 1.62 1.49 1.34 1.47 1.48 1.5 1.42 1.39 1.42 1.43 1.52
Appendix B General Ventilation Concentration Measurements (Central Position Within Enclosure) - Extraction Rate of 0.7 m3/min Mass Before Welding Mass After Welding Collected Mass mg Experiment No. Grams mg grams mg 146 0.01828 18.28 0.0185 18.5 0.18 147 0.01825 18.25 0.01827 18.27 0.31 148 0.01708 17.08 0.01725 17.25 0.17 149 0.01836 18.36 0.01857 18.57 0.21 150 0.01793 17.93 0.01817 18.17 0.24 151 0.01827 18.27 0.01862 18.62 0.35 152 0.0184 18.4 0.01877 18.77 0.37 153 0.01781 17.81 0.0181 18.1 0.29 154 0.01752 17.52 0.01783 17.83 0.31 155 0.01694 16.94 0.01719 17.19 0.25 156 0.01731 17.31 0.01761 17.61 0.3 157 0.01691 16.91 0.01718 17.18 0.27 158 0.01743 17.43 0.01789 17.89 0.46 159 0.01756 17.56 0.01799 17.99 0.43 160 0.01728 17.28 0.01753 17.53 0.25 161 0.01732 17.32 0.01753 17.53 0.21 162 0.01754 17.54 0.0177 17.7 0.16 163 0.01655 16.55 0.01692 16.92 0.37 164 0.01636 16.36 0.01669 16.69 0.33 165 0.01668 16.68 0.01697 16.97 0.29 166 0.01617 16.17 0.01638 16.38 0.21 167 0.01651 16.51 0.01689 16.89 0.38 168 0.01754 17.54 0.01786 17.86 0.32 169 0.01689 16.89 0.01716 17.16 0.27 170 0.01704 17.04 0.01725 17.25 0.21 171 0.01678 16.78 0.01697 16.97 0.19 172 0.01724 17.24 0.01749 17.49 0.25 173 0.01658 16.58 0.01689 16.89 0.31 174 0.01693 16.93 0.01719 17.19 0.26 175 0.0174 17.4 0.01767 17.67 0.27 176 0.01687 16.87 0.01728 17.28 0.41 177 0.01783 17.83 0.01815 18.15 0.32 178 0.01748 17.48 0.01767 17.67 0.19 179 0.01692 16.92 0.01721 17.21 0.29 180 0.01736 17.36 0.01762 17.62 0.26 181 0.1792 179.2 0.17958 179.58 0.38 182 0.01678 16.78 0.01706 17.06 0.28 183 0.01753 17.53 0.0178 17.8 0.27 184 0.01773 17.73 0.01807 18.07 0.34 185 0.01695 16.95 0.01726 17.26 0.31
Appendix B General Ventilation Concentration Measurements (Natural Ventilation via Doorway) Mass Before Welding Mass After Welding Collected Mass mg Experiment No. grams mg grams mg 186 0.0173 17.3 0.01759 17.59 0.29 187 0.01668 16.68 0.01703 17.03 0.35 188 0.01698 16.98 0.01731 17.31 0.33 189 0.01773 17.73 0.01818 18.18 0.45 190 0.01852 18.52 0.01903 19.03 0.51 191 0.01808 18.08 0.01849 18.49 0.41 192 0.01792 17.92 0.01831 18.31 0.39 193 0.01814 18.14 0.01847 18.47 0.33 194 0.01746 17.46 0.01785 17.85 0.39 195 0.01717 17.17 0.01747 17.47 0.3 196 0.01756 17.56 0.01782 17.82 0.26 197 0.01726 17.26 0.01753 17.53 0.27 198 0.01735 17.35 0.0176 17.6 0.25 199 0.01725 17.25 0.01757 17.57 0.32 200 0.0163 16.3 0.01674 16.74 0.44 201 0.01619 16.19 0.01664 16.64 0.45 202 0.01622 16.22 0.01659 16.59 0.37 203 0.01605 16.05 0.0163 16.3 0.25 204 0.01663 16.63 0.01696 16.96 0.33 205 0.01622 16.22 0.01652 16.52 0.3 206 0.01722 17.22 0.01753 17.53 0.31 207 0.01654 16.54 0.01682 16.82 0.28 208 0.01702 17.02 0.01737 17.37 0.35 209 0.0173 17.3 0.01767 17.67 0.37 210 0.01689 16.89 0.0173 17.30 0.41 211 0.01736 17.36 0.01768 17.68 0.32 212 0.01785 17.85 0.01823 18.23 0.38 213 0.01747 17.47 0.01775 17.75 0.28 214 0.01699 16.99 0.01735 17.35 0.36 215 0.01764 17.64 0.01787 17.87 0.23 216 0.01783 17.83 0.01824 18.24 0.41 217 0.01709 17.09 0.01744 17.44 0.35 218 0.01697 16.97 0.01741 17.41 0.44 219 0.01803 18.03 0.01837 18.37 0.34 220 0.017822 17.822 0.01811 18.11 0.29 221 0.01748 17.48 0.0178 17.80 0.32 222 0.01732 17.32 0.01777 17.77 0.45 223 0.01827 18.27 0.01864 18.64 0.37 224 0.01779 17.79 0.0181 18.10 0.31 225 0.01733 17.33 0.01772 17.72 0.39
Appendix B Local Ventilation Concentration Measurements (Crossdraft Right to Left Across Breathing Zone) – Crossdraft Velocity 0.5 m/s
Experiment No. 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250
Mass Before Welding grams mg 0.01702 17.02 0.01648 16.48 0.01684 16.84 0.01751 17.51 0.01817 18.17 0.01816 18.16 0.01867 18.67 0.01805 18.05 0.01702 17.02 0.01648 16.48 0.01751 17.51 0.01684 16.84 0.016 16 0.01652 16.52 0.0181 18.1 0.01817 18.17 0.01769 17.69 0.01805 18.05 0.01748 17.48 0.01788 17.88 0.01815 18.15 0.01804 18.04 0.01746 17.46 0.01769 17.69 0.01821 18.21
Mass After Welding grams mg 0.01708 17.08 0.0166 16.6 0.01689 16.89 0.01755 17.63 0.01823 18.23 0.01824 18.24 0.01877 18.77 0.01816 18.16 0.01708 17.08 0.01655 16.55 0.01759 17.59 0.01697 16.97 0.01609 16.09 0.01663 16.63 0.01819 18.19 0.01834 18.34 0.01779 17.79 0.01816 18.16 0.01757 17.57 0.01798 17.98 0.01822 18.22 0.01812 18.12 0.01757 17.57 0.01783 17.83 0.01757 18.36
Collected Mass mg 0.07 0.12 0.09 0.12 0.07 0.08 0.1 0.11 0.08 0.09 0.08 0.13 0.09 0.11 0.09 0.17 0.1 0.11 0.09 0.1 0.07 0.08 0.11 0.14 0.15
Appendix B Local Ventilation Concentration Measurements (Crossdraft Left to Right Across Breathing Zone) – Crossdraft Velocity 0.5 m/s
Experiment No. 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275
Mass Before Welding grams mg 0.01751 17.51 0.01735 17.35 0.01625 16.25 0.01827 18.27 0.01716 17.16 0.0185 18.5 0.01844 18.44 0.01757 17.57 0.01699 16.99 0.01745 17.45 0.01782 17.82 0.01803 18.03 0.01843 18.43 0.01759 17.59 0.01742 17.42 0.01777 17.77 0.01693 16.93 0.01788 17.88 0.01742 17.42 0.01751 17.51 0.01749 17.49 0.0178 17.8 0.01808 18.08 0.01631 16.31 0.01869 18.69
Mass After Welding grams mg 0.01759 17.59 0.01749 17.49 0.01639 16.39 0.01837 18.37 0.01724 17.24 0.01861 18.61 0.01852 18.52 0.01768 17.68 0.01706 17.06 0.01754 17.54 0.01795 17.95 0.01818 18.18 0.0185 18.5 0.01768 17.68 0.01747 17.47 0.01789 17.89 0.01703 17.03 0.01801 18.01 0.0175 17.5 0.01759 17.59 0.01763 17.63 0.01789 17.89 0.0182 18.2 0.01641 16.41 0.01882 18.82
Collected Mass Mg 0.08 0.14 0.14 0.1 0.08 0.11 0.08 0.11 0.07 0.09 0.13 0.15 0.07 0.09 0.05 0.12 0.1 0.13 0.08 0.08 0.14 0.09 0.12 0.1 0.13
Appendix B Local Ventilation Concentration Measurements (Crossdraft Left to Right Across Breathing Zone) – Crossdraft Velocity 0.6 m/s
Experiment No. 276 277 278 279 280 281 282 283 284 285 286 287
Mass Before Welding Grams mg 0.01751 17.51 0.01735 17.35 0.01625 16.25 0.01827 18.27 0.01716 17.16 0.0185 18.5 0.01844 18.44 0.01757 17.57 0.01699 16.99 0.01745 17.45 0.01782 17.82 0.01803 18.03
Mass After Welding grams mg 0.01759 17.59 0.01749 17.49 0.01639 16.39 0.01837 18.37 0.01724 17.24 0.01861 18.61 0.01852 18.52 0.01766 17.66 0.01708 17.08 0.01752 17.52 0.01791 17.91 0.01811 18.11
Collected Mass mg 0.08 0.08 0.07 0.07 0.08 0.11 0.08 0.09 0.09 0.07 0.09 0.08
Appendix B Local Ventilation Concentration Measurements (Crossdraft Left to Right Across Breathing Zone) – Crossdraft Velocity 0.7 m/s
Experiment No. 288 289 290 291 292 293 294 295 296 297 298 299
Mass Before Welding grams mg 0.01843 18.43 0.01759 17.59 0.01742 17.42 0.01777 17.77 0.01693 16.93 0.01788 17.88 0.01742 17.42 0.01751 17.51 0.01749 17.49 0.0178 17.8 0.01808 18.08 0.01631 16.31
Mass After Welding grams mg 0.01843 18.43 0.01759 17.59 0.01748 17.48 0.01784 17.84 0.01701 17.01 0.01794 17.94 0.01752 17.52 0.01758 17.58 0.01757 17.57 0.01787 17.87 0.01815 18.15 0.01639 16.39
Collected Mass mg 0.06 0.07 0.08 0.06 0.1 0.07 0.08 0.07 0.07 0.08 0.09 0.06
Appendix B Local Ventilation Concentration Measurements (Local Extraction Nozzle) 150 mm from arc, 50o at welder’s side Mass Before Welding Experiment No. grams mg 300 0.01669 16.69 301 0.01661 16.61 302 0.01697 16.97 303 0.01707 17.07 304 0.0176 17.6 305 0.01755 17.55 306 0.01798 17.98 307 0.0182 18.2 308 0.01737 17.37 309 0.01685 16.85 310 0.01752 17.52 311 0.01803 18.03 312 0.01749 17.49 313 0.01785 17.85 314 0.01651 16.51 315 0.01749 17.49 316 0.01706 17.06 317 0.01752 17.52 318 0.01749 17.49 319 0.01647 16.47 320 0.01723 17.23 321 0.01694 16.94 322 0.01743 17.43 323 0.01757 17.57 324 0.01711 17.11
Mass After Welding grams mg 0.01701 17.01 0.01694 16.94 0.01735 17.35 0.01738 17.38 0.01776 17.76 0.01781 17.81 0.01831 18.31 0.01844 18.44 0.01771 17.71 0.01716 17.16 0.01775 17.75 0.01831 18.31 0.01768 17.68 0.0182 18.2 0.0168 16.8 0.01779 17.79 0.01737 17.37 0.01789 17.89 0.01777 17.77 0.01681 16.81 0.01758 17.58 0.01722 17.22 0.01767 17.67 0.01783 17.83 0.01734 17.34
Collected Mass mg 0.32 0.33 0.38 0.31 0.16 0.26 0.33 0.24 0.34 0.31 0.23 0.28 0.19 0.35 0.29 0.3 0.31 0.37 0.28 0.34 0.35 0.28 0.24 0.26 0.23
Appendix B Local Ventilation Concentration Measurements (Local Extraction Nozzle) 125 mm from arc, 50o at welder’s side Mass Before Welding Experiment No. grams mg 325 0.01742 17.42 326 0.01689 16.89 327 0.0172 17.2 328 0.01737 17.37 329 0.01758 17.58 330 0.01705 17.05 331 0.01668 16.68 332 0.01782 17.82 333 0.01768 17.68 334 0.01802 18.02 335 0.01773 17.73 336 0.01669 16.69 337 0.01754 17.54 338 0.01748 17.48 339 0.01762 17.62 340 0.01856 18.56 341 0.01778 17.78 342 0.01703 17.03 343 0.01721 17.21 344 0.01799 17.99 345 0.0183 18.3 346 0.01744 17.44 347 0.01761 17.61 348 0.01713 17.13 349 0.01786 17.86
Mass After Welding grams mg 0.01751 17.51 0.017 17 0.0173 17.3 0.01748 17.48 0.01776 17.76 0.01721 17.21 0.0169 16.9 0.01793 17.93 0.0178 17.8 0.0182 18.2 0.01787 17.87 0.01685 16.85 0.01765 17.65 0.01761 17.61 0.01779 17.79 0.01865 18.65 0.01787 17.87 0.01713 17.13 0.01736 17.36 0.01813 18.13 0.0184 18.4 0.01757 17.57 0.01771 17.71 0.01725 17.25 0.01797 17.97
Collected Mass mg 0.09 0.11 0.1 0.11 0.18 0.16 0.22 0.11 0.12 0.18 0.14 0.16 0.11 0.13 0.17 0.09 0.09 0.1 0.15 0.14 0.1 0.13 0.1 0.12 0.11
Appendix B Local Ventilation Concentration Measurements (Local Extraction Nozzle) 100 mm from arc, 50o at welder’s side Mass Before Welding Experiment No. grams mg 350 0.01752 17.52 351 0.01734 17.34 352 0.01709 17.09 353 0.01745 17.45 354 0.01804 18.04 355 0.01736 17.36 356 0.01666 16.66 357 0.01649 16.49 358 0.01685 16.85 359 0.01743 17.43 360 0.01762 17.62 361 0.01684 16.84 362 0.01706 17.06 363 0.01781 17.81 364 0.0177 17.7 365 0.01688 16.88 366 0.01756 17.56 367 0.01735 17.35 368 0.0167 16.7 369 0.01725 17.25 370 0.01763 17.63 371 0.01696 16.96 372 0.01707 17.07 373 0.01734 17.34 374 0.01638 16.38
Mass After Welding grams mg 0.01755 17.55 0.0174 17.4 0.0172 17.2 0.0175 17.5 0.0181 18.1 0.0175 17.5 0.01672 16.72 0.01656 16.56 0.0169 16.9 0.0175 17.5 0.01771 17.71 0.01689 16.89 0.01714 17.14 0.01784 17.84 0.01775 17.75 0.01694 16.94 0.01764 17.64 0.01744 17.44 0.01674 16.74 0.01731 17.31 0.01769 17.69 0.01703 17.03 0.01717 17.17 0.01739 17.39 0.01647 16.47
Collected Mass mg 0.03 0.06 0.1 0.05 0.06 0.12 0.06 0.07 0.05 0.07 0.09 0.05 0.08 0.03 0.05 0.06 0.08 0.09 0.04 0.06 0.06 0.07 0.1 0.05 0.09
Appendix B Local Ventilation Concentration Measurements (Local Extraction Nozzle) 100 mm from arc, 180o to welder (directly opposite) Mass Before Welding Experiment No. grams mg 375 0.01624 16.24 376 0.01665 16.65 377 0.0162 16.2 378 0.01648 16.48 379 0.01687 16.87 380 0.01667 16.67 381 0.01708 17.08 382 0.01807 18.07 383 0.01781 17.81 384 0.01647 16.47 385 0.01733 17.33 386 0.01682 16.82 387 0.01704 17.04 388 0.01709 17.09 389 0.01821 18.21 390 0.01645 16.45 391 0.01767 17.67 392 0.01711 17.11 393 0.0166 16.6 394 0.01714 17.14 395 0.01808 18.08 396 0.01853 18.53 397 0.01678 16.78 398 0.01707 17.07 399 0.01732 17.32
Mass After Welding grams mg 0.01636 16.36 0.01668 16.68 0.01632 16.32 0.01653 16.53 0.0169 16.9 0.01672 16.72 0.01718 17.18 0.01817 18.17 0.01786 17.86 0.01651 16.51 0.01741 17.41 0.01688 16.88 0.01709 17.09 0.01717 17.17 0.0183 18.3 0.01649 16.49 0.01773 17.73 0.01718 17.18 0.01665 16.65 0.01722 17.22 0.01816 18.16 0.01859 18.59 0.01683 16.83 0.01714 17.14 0.01738 17.38
Collected Mass mg 0.12 0.03 0.12 0.05 0.03 0.05 0.1 0.09 0.05 0.04 0.08 0.06 0.05 0.08 0.09 0.04 0.06 0.07 0.05 0.08 0.08 0.06 0.05 0.07 0.06
Appendix C
35 Mean Amb 660 560 460
30
360
o Temperature ( C)
260 160 60
25
20
15 0
2
4
6
8
10
12
14
16
Time (Minutes)
Figure C.1 Thermal growth of the enclosure over the 15-minute arcing period for a copper coated electrode wire (Experiment 1) 30 Mean Amb 660 560 460 360 25 o Temperature ( C)
260 160 60
20
15 0
2
4
6
8
10
12
14
16
Time (Minutes)
Figure C.2 Thermal growth of the enclosure over the 15-minute arcing period for a copper coated electrode wire (Experiment 2) C.1
Appendix C 35 Mean Amb 660 560 460
30
360
Temperature (oC)
260 160 60
25
20
15 0
2
4
6
8
10
12
14
16
Time (Minutes)
Figure C.3 Thermal growth of the enclosure over the 15-minute arcing period for a copper coated electrode wire (Experiment 3) 35 Mean Amb 660 mm 560 mm 460 mm
30
360 mm
Temperature (oC)
260 mm 160 mm 60 mm 25
20
15 0
2
4
6
8
10
12
14
16
Time (Minutes)
Figure C.4 Thermal growth of the enclosure over the 15-minute arcing period for a copper coated electrode wire (Experiment 4)
C.2
Appendix C 30
Mean Amb 760 mm 660 mm 560 mm 460 mm 360 mm
25
Temperature (oC)
260 mm 160 mm 60 mm
20
15 0
2
4
6
8
10
12
14
16
Time (Minutes)
Figure C.5 Thermal growth of the enclosure over the 15-minute arcing period for a copper coated electrode wire (Experiment 5) 40
Mean Amb 760 mm 660 mm 560 mm
35
460 mm
Temperature (oC)
360 mm 260 mm 30
160 mm 60 mm
25
20
15 0
2
4
6
8
10
12
14
16
Time (Minutes)
Figure C.6 Thermal growth of the enclosure over the 15-minute arcing period for a copper coated electrode wire (Experiment 6) C.3
Appendix C 40
Mean Amb 760 mm 660 mm 560 mm
35
460 mm
Temperature (oC)
360 mm 260 mm 30
160 mm 60 mm
25
20
15 0
2
4
6
8
10
12
14
16
Time (Minutes)
Figure C.7 Thermal growth of the enclosure over the 15-minute arcing period for a copper coated electrode wire (Experiment 7) 35
Mean Amb 760 mm 660 mm 560 mm 460 mm
30
Temperature (oC)
360 mm 260 mm 160 mm 60 mm 25
20
15 0
2
4
6
8
10
12
14
16
Time (Minutes)
Figure C.8 Thermal growth of the enclosure over the 15-minute arcing period for a copper coated electrode wire (Experiment 8) C.4
Appendix C 30
Mean Amb 760 mm 660 mm 560 mm 460 mm 360 mm
25
Temperature (oC)
260 mm 160 mm 60 mm
20
15 0
2
4
6
8
10
12
14
16
Time (Minutes)
Figure C.4 Thermal growth of the enclosure over the 15-minute arcing period for a non-copper coated electrode wire (Experiment 41) 30
Mean Amb 760 mm 660 mm 560 mm 460 mm 360 mm
25
Temperature (oC)
260 mm 160 mm 60 mm
20
15 0
2
4
6
8
10
12
14
16
Time (Minutes)
Figure C.42 Thermal growth of the enclosure over the 15-minute arcing period for a non-copper coated electrode wire (Experiment 42) C.5
Appendix C 35
Mean Amb 760 mm 660 mm 560 mm
30
460 mm
260 mm 160 mm
o
Temperature ( C)
360 mm
60 mm
25
20
15 0
2
4
6
8
10
12
14
16
Time (Minutes)
Figure C.43 Thermal growth of the enclosure over the 15-minute arcing period for a non-copper coated electrode wire (Experiment 43) 30
Mean Amb 760 mm 660 mm 560 mm 460 mm 360 mm
25
Temperature ( C)
260 mm
o
160 mm 60 mm
20
15 0
2
4
6
8
10
12
14
16
Time (Minutes)
Figure C.44 Thermal growth of the enclosure over the 15-minute arcing period for a non-copper coated electrode wire (Experiment 44)
C.6
Appendix C
0.8 0.7
Height (metres)
0.6 0.5 0.4 0.3 0.2 0.1 0 0
50
100
150
200
250
300
350
400
450
Time (Seconds)
Figure C.13 Graphical relationship of the interface position with respect to time for the copper coated ER-70S electrode. The interface position was determined by monitoring temperature differences of 0.5oC. (Investigation 1) 0.8 0.7
Height (Metres)
0.6 0.5 0.4 0.3 0.2 0.1 0 0
50
100
150
200
250
300
350
400
450
Time (Seconds)
Figure C.14 Graphical relationship of the interface position with respect to time for the copper coated ER-70S electrode. The interface position was determined by monitoring temperature differences of 0.5oC. (Investigation 2) C.7
Appendix C
0.8 0.7
Height (Metres)
0.6 0.5 0.4 0.3 0.2 0.1 0 0
50
100
150
200
250
300
350
400
450
Time (Seconds)
Figure C.15 Graphical relationship of the interface position with respect to time for the copper coated ER-70S electrode. The interface position was determined by monitoring temperature differences of 0.5oC. (Investigation 3) 0.8 0.7
Height (Metres)
0.6 0.5 0.4 0.3 0.2 0.1 0 0
50
100
150
200
250
300
350
400
450
Time (Seconds)
Figure C.16 Graphical relationship of the interface position with respect to time for the copper coated ER-70S electrode. The interface position was determined by monitoring temperature differences of 0.5oC. (Investigation 4)
C.8
Appendix C
0.8 0.7
Height (Metres)
0.6 0.5 0.4 0.3 0.2 0.1 0 0
50
100
150
200
250
300
350
400
450
Time (Seconds)
Figure C.17 Graphical relationship of the interface position with respect to time for the copper coated ER-70S electrode. The interface position was determined by monitoring temperature differences of 0.5oC. (Investigation 5) 0.8 0.7
Height (Metres)
0.6 0.5 0.4 0.3 0.2 0.1 0 0
50
100
150
200
250
300
350
400
450
500
Time (Seconds)
Figure C.18 Graphical relationship of the interface position with respect to time for the copper coated ER-70S electrode. The interface position was determined by monitoring temperature differences of 0.5oC. (Investigation 6)
C.9
Appendix C
0.8 0.7
Height (Metres)
0.6 0.5 0.4 0.3 0.2 0.1 0 0
50
100
150
200
250
300
350
400
Time (Seconds)
Figure C.19 Graphical relationship of the interface position with respect to time for the copper coated ER-70S electrode. The interface position was determined by monitoring temperature differences of 0.5oC. (Investigation 7) 0.8
0.7
Height (Metres)
0.6
0.5
0.4
0.3
0.2
0.1
0 0
50
100
150
200
250
300
350
400
450
500
Time (Seconds)
Figure C.20 Graphical relationship of the interface position with respect to time for the non-copper coated ER-70S electrode. The interface position was determined by monitoring temperature differences of 0.5oC. (Investigation 1)
C.10
Appendix C 0.8
0.7
Height (Metres)
0.6
0.5
0.4
0.3
0.2
0.1
0 0
50
100
150
200
250
300
350
400
450
500
Time (Seconds)
Figure C.21 Graphical relationship of the interface position with respect to time for the non-copper coated ER-70S electrode. The interface position was determined by monitoring temperature differences of 0.5oC. (Investigation 2) 0.8
0.7
Height (Metres)
0.6
0.5
0.4
0.3
0.2
0.1
0 0
50
100
150
200
250
300
350
400
450
500
Time (Seconds)
Figure C.22 Graphical relationship of the interface position with respect to time for the non-copper coated ER-70S electrode. The interface position was determined by monitoring temperature differences of 0.5oC. (Investigation 3)
C.11
Appendix C 0.8
0.7
Height (Metres)
0.6
0.5
0.4
0.3
0.2
0.1
0 0
100
200
300
400
500
600
Time (Seconds)
Figure C.23 Graphical relationship of the interface position with respect to time for the non-copper coated ER-70S electrode. The interface position was determined by monitoring temperature differences of 0.5oC. (Investigation 4) 0.8
0.7
Height (Metres)
0.6
0.5
0.4
0.3
0.2
0.1
0 0
50
100
150
200
250
300
350
400
450
Time (Seconds)
Figure C.24 Graphical relationship of the interface position with respect to time for the non-copper coated ER-70S electrode. The interface position was determined by monitoring temperature differences of 0.5oC. (Investigation 5)
C.12
Appendix D
Appendix D: Buoyant Fountain Experimental Analysis D.1
Shielding Gas Calculations
Assuming Argon has a mean temperature of 15 oC (From BOC guide).
r = 1.6906 kg/m3 m = 2.1979 ¥10-5 kg/m3 u = 1.30 ¥10-5 m2 /s c p = 521.68 Q = 15 L/min = 0.015 m3/min = 0.00025 m3/s
Gas flow rate:
Diameter of gas nozzle†exit: D = Do – Di = 0.02-0.0012 m = 0.0188 m A = 3.13 x 10-4 m2
Area of gas nozzle exit:
Nozzle-to-workpiece distance = 0.015 m Non dimensional height, Do/H = 0.02/0.015 = 1.33 Exit shielding gas velocity = Q/A = 0.00025/0.00031 = 0.81 m/s The exit conditions are slightly different, due to the electrical heat input from the arc. Thus:
qconv
†
qconv = rQc p DT = 0.223 ¥ 25 ¥ 200 = 1115W Thus, ∆T = 5057 K
† P 101.325 r 0Ar = 0 = = 0.07 kg/m3 , RT0Ar 0.287 ¥ 5057
The fluid conditions of the shielding gas flow: The buoyancy†of the initial conditions becomes
g¢0 = g
Ê1.2 - 0.07 ˆ r• - r 0Ar 3 = 9.81Á ˜ = 9.24 kg/m Ë ¯ r• 1.2 B0 = g¢0Q0 = 0.00231 m4 /s3 M 0 = V 2 A = 2.03 ¥10-4 m4 /s2 Re = VD /u = 1171 L j = M 0 3 / 4 /B01/ 2 = 0.74 D.1
†
Appendix D
D.2
Salt-water simulation calculations, Nozzle Diameter = 0.01 m Nozzle Area = 7.86 x 10-5 m2
To generate similar buoyancy conditions to the shielding gas, the required buoyancy for the simulation was
Dr =
rg¢ 994.16 ¥ 9.81 = = 1055.45 g 9.24
Note: The salt-water simulations are opposite in buoyancy compared to the welding scenario. That is,†the salt-solution is negative buoyant, with respect to ambient, while the welding scenario is positively buoyant. Table D.1 Salt-water concentrations used during turbulent buoyant fountain experiments. BRIX Density Buoyancy 3 (kg/m ) (m4/s3) 0.4 997.35 0.027 5.1 1029.51 0.344 10.2 1064.41 0.688 -3 Assuming a constant kinematic viscosity = 1 x 10 kg/m3. From Fox and McDonald (1994), the kinematic viscosity for seawater (Specific Gravity of 1.025) was within 5% of fresh water. Converting Brix to density was done via the relationship r = 6.8428(Brix) + 994.61 Using non-dimensional to match the fluid conditions of the shielding gas with the saltwater simulations, the key parameters used for this model will be the thermal length ( L j ), † Reynold’s number (Re) and the non-dimensional height (D/H).
Re = VD /u SG = VD /u sim = 1171
†
D /H SG = D /H sim = 1.33 L j = M0
3/4
1/ 2
/B0
SG
= M0
3/4
1/ 2
/B0
sim
= 0.74
For a nozzle with a diameter of 0.01 m, the simulated height to match welding conditions will be 0.0075†m. D.2
Appendix D
Table D.2 Salt-water conditions based on matching the key parameters from the actual shielding gas conditions. BRIX Velocity Volumetric Flux Buoyancy Flux Momentum Flux (m/s) (m3/s) (m4/s3) (m4/s2) 0.4 117.1 9.197 x 10-3 0.393 0.358 5.1 10.2 Based on the equations within Chapter 5, and the flow is in a laminar condition.
The closeness of the nozzle to the workpiece and the large exit velocity prove difficult to accurately model the shielding gas conditions, with available equipment. Construction of a specific rig to effectively assess this condition would substantial benefit the accuracy of this hypothesis. The problem associated with the height of the nozzle to the impinging surface, with a laminar exit flow limited the working model. The theory behind the impinging flow still was investigated, as there are few studies available into this phenomena, and (although not accurately modelled) may contribute to controlling initial welding fume plume dispersion and ultimately, breathing zone conditions. Table D.3 Parameters used during the impinging fountain experimental investigations. 2 Reduced Gravity (m/s ) 0.027 0.688 0.688 0.331 Volumetric Flux (m3/s) 1.75E-05 5.10E-05 3.84E-05 4.39E-05 Initial Buoyancy Flux (m4/s3) 4.73E-07 3.51E-05 2.64E-05 1.45E-05 Initial Momentum Flux(m4/s2) 3.91E-06 3.32E-05 1.88E-05 2.45E-05 Jet length (m) 0.128 0.074 0.055 0.091
D.3
Appendix D D.3
Rotameter Calibration for various salt solutions [except for Winter (2001)]
The method used for calibrating rotameter was as follows: 1. Begin with the initial flow through rotameter to set on 5 2. Measure the time it takes to fill a measuring cylinder to a determined volume 3. Measure the Brix value of the solution 4. Repeat steps 1-2 for flows of 10, 15 and 20 5. Repeat steps 1-4 for different salt concentrations. The results are shown in table D.4
12 brix salt 8 brix salt solution solution
4 brix salt solution
TABLE D.4 Rotameter calibrations flow volume time ml s 5 100 310 10 200 310 15 200 135 20 250 147 5 100 310 10 200 285 15 200 135 20 250 120 5 100 315 10 200 250 15 200 135 20 250 120
D.4
flow rate ml/s m3/s 0.323 3.23E-07 0.645 6.45E-07 1.481 1.48E-06 1.701 1.70E-06 0.323 3.23E-07 0.702 7.02E-07 1.481 1.48E-06 2.083 2.08E-06 0.317 3.17E-07 0.800 8.00E-07 1.481 1.48E-06 2.083 2.08E-06
Appendix D D.4 DigImage Procedures D4.1 Starting the Program 1. Turn on the TV monitor and the VCR before turning on the computer 2. The computer will ask what mode to be set up in, pick the first one, for 25 buffers. 3. Create a folder in the appropriate DigImage directory where the files will be stored. 4. Start up the Dos Prompt program from the Start menu 5. Type in the following commands (in BOLD) to start DigImage from the desired directory At C:\windows>cd\Img (then enter) At C:\Img>cd digimage\GeoffS\Tape* (then enter) At C:\Img\digimage\GeoffS\Tape*>digimage (then enter) If it a new directory that hasn’t been used before a start up screen comes up. Press Q (quit) to get to the main menu). D4.2 Setting up World Co-ordinates This is required for each experiment as the camera may not be in exactly the same position as the last one. 1. Position the tape to the desired image and pause. 2. Store the image into a buffer, From the main menu use the following commands G – (Grab/ display) G – (grab a single frame) Then State buffer – i.e. 0 Then press play on the VCR and press any key to grab the frame 3. Copy the buffer into 1 using the Grab/display menu using the following commands C – (Copy buffer) Then answer the screen commands to copy buffer 0 to buffer 1. 4. Set up the world coordinates starting from the main menu P – (coordinate mapping system) W – (world coordinates) I – initialise world coordinate mapping State that the units will be mm L – (Locate world coordinate points) Choose Buffer 1 as the image for locating the points on Buffer 1 will then appear on the TV and using E to zoom in and then either P (maintains present zoom and exits) or R (reset to no zoom and exit) to select the cursor point define the following positions. Choose N (for no) when all points have been determined S – (save world coordinate mapping) State the file name i.e. TapeA5 (Experiment 5 on tape A)
D.5
Appendix D D4.3 Carrying out Time Series function From the main menu carry out the following commands: T – (time series) L – (time series of a line or column) Choose the buffer image to determine the column – 1 Now when the cursor is at the desired location for the column press P State which buffer the time series is to be placed in - 2 State whether a line or column – C Press N – for no to another line or column State the time the time series is to accumulate for in minutes i.e. 00:45 is zero minutes and 45 seconds, while 10:00 represents 10 minutes and zero seconds. This is determined by the time of the experiment. Record the information on the screen as it is used to determine the time scale fields = * seconds 1 sample taken every * fields = * seconds for * fields = * seconds State whether manual or computer control. This is control over the VCR and should choose manual – M When the video is in the correct location press any key to start Write down the experiment start count and the flow start count from the VCR D4.4 Save Time Series Image From the main menu carry out the following commands: K – (save restore buffer) G – (save as GIF. Image State the buffer image to save –2 State the file name – i.e. TapeA5ts Write out the whole screen not window – S Press enter twice D4.5 Collect Data Points from Time series From the main menu carry out the following commands: P – (Co-ordinate system mapping) P – (Determine co-ordinates of a point) State the buffer of the time series image - 2 State the file name – i.e. TapeA5dp Buffer 2 will then appear on the TV and using E to zoom in and then either P (maintains present zoom and exits) or R (reset to no zoom and exit) to select points on the trend
D.6
Appendix E
Appendix E: Measured Welding Parameters The following samples of the welding parameters were measured by the ArcWatch data acquisition system. These samples represent a portion of the total data collected per arcing cycle (15 minutes), however they highlight the mixed metal transfer mode utilised during the concentration investigations. These conditions were the same for both electrode wires (copper and non-copper coated) used. Table E.1 Mean welding parameters utilised during breathing zone concentration investigations Welding Parameters Mean Results Voltage
23.1 Volts
Current
197.6 Amperes
Wire Feed Rate
8.33 m/min
The input parameters for these investigations were V = 25 Volts and I = 200 Amperes
The results were used to monitor the welding conditions during arcing process, and assess the chosen welding parameters that were selected. The chosen voltage and current generated an ideal weld quality for these study (good quality bead with low spatter ejection) and generated adequate fume quantity for analysis. The assessment of spatter ejection was determined visually through the acrylic wall of the enclosure, while the concentration investigations were assessed on the amount of fume generated and the close replication of these results (these are demonstrated in Chapter 4 and Appendix B).
E.1
Appendix E Sample No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44
Voltage (VOLTS) 30.82 30.76 25.82 26.86 29.11 30.03 25.39 29.24 26.06 7.02 27.28 30.4 24.78 30.03 25.57 6.71 26.49 26.92 24.23 29.36 28.14 28.99 26.18 24.72 26.61 25.88 33.57 25.88 31.43 25.7 28.14 25.7 26.49 29.17 5.19 26.43 27.16 31.25 25.7 25.33 4.88 25.27 6.84 31.56
Current (AMPERES) 294.59 170.83 210.42 151.9 257.24 162.86 243.3 161.62 244.54 172.82 159.87 175.06 190.75 175.06 199.72 184.53 150.41 263.47 297.33 210.18 146.67 188.76 172.57 222.38 179.79 193.24 186.77 278.16 170.83 199.97 289.12 199.22 266.21 289.12 185.52 264.21 251.26 169.09 193.99 229.1 178.55 297.08 208.93 174.07 E.2
Wire Feed Rate (m/min) 10.85 9.44 8.52 7.56 9.04 8.81 8.75 8.26 8.63 8.3 7.21 7.63 7.67 7.9 7.81 8.32 6.65 9.47 10.63 10.63 6.81 8.6 7.35 8.57 8.44 7.68 8.51 9.69 8.83 7.89 10.23 9.23 10.18 11.43 9.23 10.33 10.21 9.3 8.47 8.98 8.27 10.42 9.02 9.19
Appendix E Sample No. 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88
Voltage (VOLTS) 26.79 26.37 24.54 28.81 18.37 25.39 25.82 30.15 27.04 27.95 28.14 29.72 5.62 26.55 4.21 25.27 25.51 28.38 25.02 31.49 26.55 26.98 24.54 26.06 29.85 26.67 24.6 26.43 25.27 27.28 26 25.39 25.76 31.07 27.89 26 5.55 25.39 29.97 29.6 26.61 24.66 24.84 25.51
Current (AMPERES) 152.65 224.87 211.42 181.54 163.61 197.72 269.69 178.05 166.35 156.39 342.41 149.41 176.56 320 191 297.58 251.51 160.87 317.75 180.04 170.08 267.95 168.59 229.6 162.61 309.79 149.91 248.77 215.41 215.16 196.23 216.9 283.89 157.13 243.3 162.36 192 187.51 149.66 273.68 243.05 221.63 321.24 184.03 E.3
Wire Feed Rate (m/min) 7.43 8.24 8.14 8.25 7.49 8.5 9.38 8.48 7.47 7.79 10.86 8.38 7.68 11.13 9.28 11.11 10.4 8.7 10.98 9.79 7.45 9.83 8.48 8.8 8.55 10.46 8.83 9.01 8.51 9.11 9.16 9.1 10.05 8.22 10.12 7.8 8.24 7.95 6.6 9.57 9.81 9.98 11.42 9.75
Appendix E Sample No. 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132
Voltage (VOLTS) 27.34 26.25 6.16 7.02 25.7 23.8 26.25 25.88 26.86 7.69 26.92 26.37 25.45 26.98 25.45 30.03 25.76 4.46 26.06 26.55 26.55 28.02 26.79 24.6 26.43 4.82 5.74 26.12 22.95 5.37 23.38 26.49 30.15 26.43 25.39 26.61 28.08 5.13 25.51 26.43 5.43 26.25 5.43 6.29
Current (AMPERES) 160.62 183.03 184.28 177.06 197.48 242.3 147.42 231.34 241.05 175.56 232.34 223.87 252.51 316.01 264.46 258.24 339.92 186.27 231.34 212.42 265.96 309.29 160.37 184.53 202.71 266.7 179.55 238.07 183.03 173.57 193.24 250.52 290.11 147.42 143.94 259.23 230.6 184.28 182.04 215.16 203.45 251.51 187.76 188.26 E.4
Wire Feed Rate (m/min) 8.6 7.36 7.52 8.05 8.17 9.1 7.34 8.68 9.31 8.53 9.27 9.44 9.77 11.84 10.95 11.28 12.6 9.87 9.69 9.4 10.08 11.94 8.85 8.92 7.74 10.18 8.73 10.06 7.96 8.16 8.47 8.87 11.02 8.3 6.86 9.02 9.06 9.24 8.52 8.45 8.75 9.46 8.6 9.08
Appendix E Sample No. 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176
Voltage (VOLTS) 25.51 24.11 4.64 25.27 29.85 25.57 6.29 29.97 26.92 24.66 26.73 3.91 19.29 26.12 31.25 24.78 25.21 7.51 26.06 25.33 24.54 26.79 6.96 8.73 25.63 24.84 17.33 26.18 29.24 27.4 26.25 29.6 27.1 26.49 5.8 26.55 24.9 25.21 7.32 26.73 25.7 29.6 25.02 5.98
Current (AMPERES) 240.31 378.02 177.8 165.6 163.61 255.25 199.72 167.09 193.99 149.91 258.74 177.3 188.01 246.78 173.57 182.04 183.53 184.78 222.38 318.25 247.78 231.84 163.11 177.55 217.65 223.37 149.17 256 256.74 159.13 274.67 222.38 149.41 196.23 176.06 202.21 193.24 240.56 207.19 153.4 211.42 161.62 184.28 178.05 E.5
Wire Feed Rate (m/min) 8.51 13.07 9.94 8.59 7.27 9.83 7.88 8.12 7.74 8.1 8.33 9.1 8.01 9.35 8.11 8.45 7.69 7.25 8.79 11.23 11 9.82 8.1 8.47 8.26 8.94 7.87 9.26 9.75 9.2 9.81 9.98 7.07 8.33 7.02 8.99 8.24 9.08 9.17 7.67 7.95 7.76 7.11 8.43
Appendix E Sample No. 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220
Voltage (VOLTS) 25.27 30.15 25.21 24.72 25.76 27.53 25.57 25.63 26.31 29.48 30.46 30.94 29.66 27.59 5.07 5.8 17.09 13.73 6.04 27.53 25.88 32.59 25.45 26.67 29.24 24.66 5.49 29.36 26.92 27.83 24.72 27.65 6.84 25.45 24.41 30.09 28.5 25.33 32.59 29.85 26.73 26.06 25.21 5.13
Current (AMPERES) 229.85 171.33 250.77 199.72 198.72 153.65 207.69 184.53 148.92 261.72 167.84 166.6 237.82 211.92 183.03 177.3 271.93 164.36 166.6 161.87 263.72 170.33 184.03 258.24 169.09 209.43 204.2 165.35 180.04 243.79 211.42 220.39 172.32 299.58 343.4 171.08 165.1 199.72 176.81 156.88 215.9 217.65 309.54 192 E.6
Wire Feed Rate (m/min) 8.1 8.93 8.78 9.31 7.98 7.91 8.56 8.58 6.03 9.09 7.75 7.69 8.47 9.82 7.84 8.46 9.17 8.64 7.03 7.95 8.57 8.69 7.3 9.73 8.36 8.6 8.07 7.87 7.47 9.44 8.56 9.39 8.34 10.68 12.44 9.48 8.26 8.49 7.31 7.87 8.7 9.25 10.22 9.1
Appendix E Sample No. 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256
Voltage (VOLTS) 26.43 9.09 32.35 25.39 27.28 24.23 24.29 30.88 25.7 25.7 6.71 25.88 24.84 26.25 24.9 29.79 29.42 26.61 25.02 6.04 28.14 27.59 26.55 5.49 8 24.11 29.91 7.81 24.78 24.66 31.74 25.33 6.47 25.39 6.9 28.02
Current (AMPERES) 223.13 186.77 178.3 214.66 203.45 371.79 258.49 152.65 188.76 212.67 208.68 158.13 195.98 314.77 288.62 157.13 150.41 202.95 181.54 205.44 163.36 205.69 207.44 236.32 178.05 263.22 161.62 188.76 212.17 184.78 169.09 240.81 186.27 196.48 206.19 210.42
E.7
Wire Feed Rate (m/min) 8.94 8.68 8.73 8.43 8.17 13.01 11 9.62 7.25 8.75 9.41 7.7 7.84 10.91 10.9 9.1 7.19 8.69 7.76 8.07 7.39 8.53 8.12 9.38 7.72 10.09 7.65 9.01 8.18 8.08 8.01 9.15 8.44 7.97 8.88 9.53
Appendix E Sample No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44
Voltage (VOLTS) 33.94 22.28 27.59 29.79 26.06 27.1 28.38 4.88 6.23 23.44 25.7 29.3 7.63 10.68 31.8 27.4 7.32 29.42 31.68 23.99 6.71 26.49 25.82 6.29 26.86 29.48 8.73 29.72 24.78 29.42 27.1 29.79 6.84 29.17 6.1 5.55 27.1 31.92 29.79 26.86 29.66 6.84 26.55 29.17
Current (AMPERES) 159.38 200.21 135.97 171.08 181.29 165.35 176.06 178.8 150.41 292.35 230.6 271.93 204.45 149.66 219.64 284.14 164.11 270.69 153.65 168.59 154.15 178.3 229.6 157.88 185.77 192.74 149.17 233.58 203.95 211.42 257.99 132.98 192 216.15 249.77 181.29 259.48 134.72 269.44 251.76 213.16 165.1 172.57 170.58 E.8
Wire Feed Rate (m/min) 7.96 8.49 7.07 6.91 7.18 7.21 7.14 7.67 7.08 9.55 9.39 10.59 9.29 8.45 8.08 9.99 8.04 10.3 8.4 7.65 7.37 6.75 7.97 8.31 7.09 8.43 7.37 7.96 8.4 9.26 9.27 7.36 7.43 8.86 9.6 8.47 9.39 7.43 9.54 9.99 9.29 9.25 7.25 7.59
Appendix E Sample No. 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88
Voltage (VOLTS) 25.09 25.39 27.28 34.18 27.65 29.36 5.86 7.14 28.14 28.32 5.13 27.22 6.29 28.81 25.82 30.58 27.59 27.22 16.17 8.36 34.55 6.53 28.69 28.44 28.2 23.5 29.72 25.27 28.14 27.65 27.95 33.26 27.89 27.34 28.93 6.1 5.68 28.69 26.55 29.17 23.86 26.25 33.02 25.76
Current (AMPERES) 208.18 278.16 188.01 144.93 200.71 150.16 228.6 169.09 205.2 183.28 206.69 178.05 212.92 174.81 236.82 188.76 205.2 271.93 250.27 270.69 242.55 287.37 155.39 176.81 183.78 219.14 160.62 157.88 200.46 223.87 196.98 173.32 180.79 166.6 259.48 187.51 220.14 204.45 240.81 162.61 275.92 193.74 143.19 182.29 E.9
Wire Feed Rate (m/min) 7.31 10.15 8.73 7.98 7.46 7.66 7.79 7.9 8.65 7.68 8.39 8.17 7.86 7.78 9.55 8.53 8.09 10.36 10.35 10.32 10.33 11.61 8.15 8.26 7.17 8.88 7.75 6.9 7.93 8.49 8.51 8.79 6.48 7.53 8.94 8.88 8.84 9.06 8.85 8.39 9.62 9.02 7.09 7.62
Appendix E Sample No. 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132
Voltage (VOLTS) 30.03 27.95 29.3 6.77 30.4 22.64 5.62 25.15 5.07 5.43 33.87 7.63 26.18 23.13 26.73 24.35 28.56 5.07 25.7 25.76 36.93 25.09 8.79 6.9 6.9 22.46 29.72 9.52 7.57 30.52 28.5 27.1 31.92 5.62 26.55 5.92 31.86 28.26 27.16 28.08 26.25 25.39 29.3 27.89
Current (AMPERES) 174.81 231.09 184.78 286.13 236.07 352.87 140.2 171.08 159.13 176.56 151.66 159.87 197.72 205.2 169.09 157.13 228.6 153.9 167.84 300.57 242.05 188.76 169.09 147.17 147.92 313.27 362.83 152.9 303.31 224.37 270.19 247.28 168.59 215.16 211.17 215.16 139.2 201.46 168.84 194.49 177.55 255 186.02 167.84 E.10
Wire Feed Rate (m/min) 7.53 9.04 7.53 10.99 9.4 13.05 7.99 8.22 6.96 7.72 6.78 7.89 7.09 8.44 7.06 7.69 7.89 7.8 6.53 10.18 10.12 8.77 7.47 7.01 6.55 10.9 12.26 9.02 11.16 9.97 10.69 10.58 9.43 8.45 8.18 8.69 7.73 8.45 6.6 8.63 7.42 9.75 7.76 8.28
Appendix E Sample No. 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176
Voltage (VOLTS) 25.82 28.81 30.76 26.18 6.29 9.09 25.02 28.08 30.21 35.03 6.04 23.86 29.11 4.82 4.94 27.65 28.81 26.43 5.55 29.6 5.55 25.57 29.36 5.13 5.13 7.08 24.35 30.4 5.8 27.71 6.65 7.39 4.52 26.98 26.55 29.36 30.09 7.69 29.24 7.81 26.86 5.92 28.5 26.25
Current (AMPERES) 196.23 289.61 152.9 230.6 144.18 265.71 257.74 165.6 215.41 200.96 148.42 204.7 184.53 158.88 217.65 259.23 210.67 177.06 268.2 188.76 258.74 160.12 150.16 162.11 193.49 200.46 242.05 136.46 264.46 184.28 244.29 249.27 240.06 240.06 296.09 224.12 187.02 240.31 188.76 162.61 182.04 238.56 179.55 317.01 E.11
Wire Feed Rate (m/min) 7.25 10.37 7.99 8.65 7.49 9.59 9.97 8.29 8.38 8.99 7.19 8.09 8.2 6.92 7.72 10.47 9.06 8.27 9.94 8.5 9.74 9.22 6.28 7.13 7.2 8.36 9.11 7.53 8.81 8.6 9 10.06 9.59 10.18 11.08 10.4 8.77 9.86 8 7.87 7.7 8.8 7.9 11.56
Appendix E Sample No. 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220
Voltage (VOLTS) 24.17 32.84 6.96 24.11 6.77 29.11 8.3 28.14 6.53 28.38 5.07 28.63 6.16 31.62 29.6 31.07 28.99 30.03 27.34 29.11 27.59 4.46 24.54 31.8 26.25 6.04 26 25.02 27.89 27.28 27.95 28.26 27.53 30.21 25.09 6.1 5.37 29.72 29.05 31.01 30.94 28.32 22.95 26.67
Current (AMPERES) 190 216.9 165.85 190.5 157.88 206.94 170.33 175.81 162.11 178.05 200.71 211.42 152.4 205.69 250.27 153.15 163.11 223.87 181.29 166.6 341.91 217.9 188.51 262.72 177.06 227.11 166.85 147.17 246.78 217.9 195.98 232.59 361.08 188.51 222.88 198.47 159.13 187.27 147.67 204.7 147.67 244.54 256.99 207.93 E.12
Wire Feed Rate (m/min) 8.8 9.53 8.05 7.93 6.93 8.4 7.92 7.64 6.48 7.55 7.63 8.55 7.18 8.66 9.13 8.03 7.2 8.73 7.89 8.24 10.38 9.64 8.61 9.9 8.64 9.2 7.98 8.43 7.85 9.35 7.5 9.37 12.07 10.16 9.18 9.16 7.02 8.07 6.75 7.79 6.7 9.44 9.58 9.33
Appendix E Sample No. 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256
Voltage (VOLTS) 6.1 30.58 26.37 23.25 28.32 31.43 27.83 7.93 25.57 29.11 25.76 31.13 6.04 26.79 31.8 28.32 5.55 27.95 27.16 6.53 26.31 7.26 26.79 24.6 20.02 25.57 26.67 28.32 26.37 6.53 5.55 5.07 26.49 27.34 5.07 29.11
Current (AMPERES) 216.15 230.6 236.07 288.37 223.37 159.62 301.07 174.32 205.69 223.87 189.26 182.78 179.79 243.79 225.12 170.08 194.24 206.94 226.61 213.91 174.07 192 182.29 267.45 221.88 215.9 154.15 240.56 140.2 235.83 179.55 183.53 196.98 263.22 183.03 270.44
E.13
Wire Feed Rate (m/min) 8.58 10.02 9.61 10.57 10 8.22 10.22 9.72 7.66 9.03 8.89 7.88 7.49 9.35 8.94 9.06 7.19 8.67 8.77 9.46 7.6 8.29 7.45 10.31 9.25 10.05 6.48 8.96 7.04 9.33 7.8 8.65 7.26 9.94 8.19 10.46
Appendix E Sample No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44
Voltage (VOLTS) 31.07 32.29 9.7 27.83 25.76 32.29 22.52 27.1 5.86 27.1 24.96 27.1 15.26 5.98 7.39 5.13 30.09 5.13 29.6 25.33 6.35 29.54 5.49 28.44 26.79 26.25 27.53 29.6 27.59 30.64 27.71 5.92 26.31 29.42 26.37 27.4 28.75 28.56 31.43 7.45 6.41 23.86 26.25 30.33
Current (AMPERES) 162.36 164.11 248.03 134.22 357.85 125.51 314.27 247.03 153.65 190.5 247.78 213.16 181.29 256 188.26 172.57 207.19 193.24 154.64 208.43 169.58 227.86 235.08 194.99 220.39 161.62 172.57 172.57 166.1 268.95 317.26 214.91 204.95 125.01 278.66 173.82 166.85 190.75 166.35 203.95 243.05 145.68 191.75 250.02 E.14
Wire Feed Rate (m/min) 6.68 6.66 8.82 7.67 11.41 7.48 11.08 10.97 8.54 8.22 9 8.85 8.9 9.42 9 8.19 8.11 7.73 7.77 7.53 8.13 8.17 9.38 8.44 9.79 8.04 8.25 6.26 7.37 9.11 11.76 10.18 9.72 7.21 9.75 7.65 8.01 7.94 7.48 8.16 9.59 7.34 8.38 8.4
Appendix E Sample No. 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88
Voltage (VOLTS) 28.08 27.59 26.31 30.94 11.72 28.38 29.72 27.95 28.02 5.8 33.69 28.75 32.35 7.26 23.07 26.55 27.95 26.79 28.02 30.82 23.86 24.96 7.02 31.86 26.55 7.75 31.07 27.22 27.22 31.56 28.56 7.57 27.77 7.45 29.48 27.47 27.22 31.86 5.8 6.84 28.56 30.94 28.44 6.04
Current (AMPERES) 236.82 245.29 182.04 197.48 147.42 200.71 125.76 260.73 265.96 198.97 156.88 142.44 188.26 248.03 225.37 176.81 178.8 195.23 173.57 142.94 363.82 276.91 152.65 164.85 162.36 190.25 152.9 278.16 186.02 142.94 251.26 167.84 271.19 159.13 177.3 255.75 177.8 166.6 221.88 167.34 190.5 240.31 117.54 148.67 E.15
Wire Feed Rate (m/min) 10.07 9.72 9.43 8.2 7.2 8.07 7.65 8.35 10.19 8.47 7.51 6.86 8.01 9.05 9.07 8.02 8.24 7.78 8.78 6.14 11.67 11.03 8.76 8.04 7.17 7.91 7.52 9.65 8.56 7.55 8.97 7.52 9.88 8.25 9.34 8.59 8.52 7.2 9.2 7.12 7.8 8.68 7.44 6.04
Appendix E Sample No. 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132
Voltage (VOLTS) 22.77 24.48 5.43 26.67 6.04 26.55 9.46 28.14 28.99 28.14 28.38 22.71 27.28 26.92 17.58 26.73 33.08 25.33 31.31 9.03 8.91 26.49 27.22 28.26 24.54 21.97 4.82 6.16 6.04 29.85 29.3 29.17 6.41 6.29 29.72 7.63 5.86 26.43 26.61 6.84 26.37 24.84 21.61 27.22
Current (AMPERES) 166.6 220.39 172.08 212.67 204.7 238.32 206.19 260.23 170.58 189.01 178.55 156.88 123.76 166.35 284.14 155.14 276.17 242.55 162.61 158.63 177.3 273.43 164.11 186.27 263.22 262.47 230.84 150.91 147.42 192.5 188.51 230.1 165.1 280.4 231.09 194.99 156.88 222.63 205.2 184.78 174.81 247.03 249.02 129.99 E.16
Wire Feed Rate (m/min) 7.33 8.34 7.96 7.81 9.09 8.79 9.08 10.04 9.32 7.3 8.12 7.12 6.39 6.41 9.55 8.17 9.98 9.45 9.27 6.61 8.01 9.01 8.65 8.63 9.22 10.45 10.39 7.89 6.94 7 8.68 8.47 8.09 9.41 9.75 8.94 7.67 8.53 8.57 8.19 8.05 9.23 9.67 8.16
Appendix E Sample No. 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176
Voltage (VOLTS) 28.32 24.84 24.48 31.98 28.44 30.82 5.86 25.63 26.98 29.36 26.61 25.88 28.81 23.62 25.63 25.76 6.1 31.43 28.44 5.55 18.62 25.88 26.55 28.26 27.77 26.73 32.23 30.52 33.2 5.74 28.26 30.94 18.19 24.41 28.87 30.4 27.1 26.73 29.72 27.65 28.81 7.81 27.04 8
Current (AMPERES) 171.83 218.14 164.11 138.21 182.53 157.63 214.66 206.19 184.53 125.51 235.08 261.97 288.87 390.97 186.27 220.88 155.14 173.07 306.05 143.19 156.14 177.3 197.48 190 239.56 193.99 204.2 151.9 160.87 179.3 241.8 165.85 197.97 192.25 235.58 166.1 170.58 204.7 193.24 217.9 247.53 157.88 168.09 192.99 E.17
Wire Feed Rate (m/min) 7.2 8.56 8.91 5.31 7.24 6.24 8.08 8.59 8.34 6.38 9.48 9.48 11.08 13.69 11.06 9.77 7.93 8.42 9.89 7.63 7.78 7.79 7.81 8.09 9.59 8.13 8.25 7.25 8.11 6.79 8.65 7.9 9.03 7.69 8.86 8.88 7.88 7.91 8.67 7.62 10.13 7.51 7.42 7.62
Appendix E Sample No. 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220
Voltage (VOLTS) 30.46 27.34 29.17 27.47 28.26 32.41 26.67 7.08 24.78 27.77 6.1 27.53 26.98 29.3 27.71 8.85 26.73 5.98 30.88 29.11 5.55 31.25 4.82 7.2 29.05 29.79 27.1 29.24 22.77 31.86 23.56 27.77 27.04 24.23 27.89 27.89 24.17 27.34 27.04 27.83 28.63 27.16 26.98 29.3
Current (AMPERES) 161.12 213.91 196.73 169.58 218.14 233.58 154.39 202.21 258.49 169.58 288.12 179.55 205.94 234.08 237.07 177.06 231.59 168.84 142.69 165.1 164.11 237.07 173.57 236.82 199.47 227.11 210.42 195.23 277.66 143.69 191.75 183.03 282.39 191.25 175.81 151.41 211.42 277.91 209.43 182.29 136.46 177.55 345.15 212.92 E.18
Wire Feed Rate (m/min) 8.55 7.68 8.14 7.39 8.82 8.8 8.29 7.9 9.92 8.32 10.06 8.25 8.94 8.97 10.3 8.87 9.43 7.75 6.79 6.95 7.1 8.76 7.85 8.77 8.55 9.58 8.78 8.54 10.28 7.59 9.16 7.59 10.63 7.67 8.04 6.95 8.4 9.93 9.71 8.83 7.46 7.59 10.75 9.44
Appendix E Sample No. 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256
Voltage (VOLTS) 26.98 30.82 29.42 11.35 24.17 5.98 28.2 30.09 27.53 23.68 5.43 24.84 31.74 28.2 33.2 4.64 26.49 25.02 6.35 27.16 5.8 23.99 7.45 4.7 22.52 26.06 26.37 8.61 26.73 25.45 31.25 30.52 27.89 27.47 6.47 30.82
Current (AMPERES) 346.64 201.21 171.58 182.04 293.6 147.92 202.71 163.36 215.41 173.57 175.81 305.55 269.19 133.48 236.57 248.77 320.24 316.26 192.99 186.77 249.27 161.62 161.12 152.15 285.88 182.29 218.64 228.11 177.3 213.41 138.21 156.88 169.83 173.07 163.86 210.42
E.19
Wire Feed Rate (m/min) 12.32 9.95 8.52 7.87 10.81 7.83 8.64 8.82 7.9 7.62 7.85 10.03 10.59 8.23 9.24 9.46 11.76 12.54 10.29 8.56 10.1 7.83 7.64 6.97 9.78 8.3 9.31 9.49 8.06 7.96 7.41 7.29 6.76 7.75 6.78 8.22
Appendix E Sample No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44
Voltage (VOLTS) 25.51 27.65 5.07 27.28 9.58 25.7 10.38 25.76 25.45 30.82 30.27 25.21 12.7 25.27 29.54 25.51 25.82 28.14 24.84 31.98 28.32 25.76 29.24 7.14 26.92 25.45 31.56 30.82 25.63 28.14 24.66 26.55 30.64 26.18 29.48 30.64 24.78 7.26 28.69 25.39 24.78 6.84 9.46 25.33
Current (AMPERES) 237.82 141.45 173.57 192.74 266.95 250.27 184.28 169.83 242.3 161.12 161.37 187.76 213.66 160.12 166.85 190 217.65 299.58 254.5 148.67 185.52 229.6 242.3 196.48 197.97 324.48 170.33 163.11 191.75 148.67 230.84 286.13 208.18 227.61 163.11 164.6 192 206.94 145.93 341.41 277.66 177.06 189.26 240.31 E.20
Wire Feed Rate (m/min) 7.9 7.88 7.03 7.64 9.91 10.07 8.64 8.77 8.36 8.15 7.41 7.8 8.45 7.7 6.78 8.08 7.73 11.14 10.13 8.51 8.19 8.77 9.73 9.33 8.4 11.32 8.4 8.75 7.12 7.29 8.46 10.63 9.82 9.23 7.73 7.86 7.88 8.16 7.12 11.26 11 9.05 8.86 9.45
Appendix E Sample No. 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88
Voltage (VOLTS) 6.96 26.49 6.1 27.59 5.92 8.12 27.34 5.68 27.04 27.77 26.61 28.08 24.96 26.55 31.49 25.51 29.36 25.88 27.22 30.09 31.25 26.18 32.1 25.7 20.08 29.97 6.65 25.94 10.01 25.45 26.92 25.82 26.92 26.37 24.96 6.96 28.63 25.51 25.51 26.06 29.72 29.24 30.64 32.23
Current (AMPERES) 172.08 228.85 168.34 216.9 170.58 204.45 197.97 180.79 263.22 145.93 144.43 155.64 207.69 289.37 156.88 254 150.16 134.72 139.7 166.1 171.58 129.49 167.09 252.26 133.73 311.53 180.54 175.31 182.53 231.34 170.33 139.2 143.44 137.96 326.97 173.82 137.21 188.26 217.15 219.39 168.09 177.55 162.61 238.56 E.21
Wire Feed Rate (m/min) 8.4 9.49 7.01 9.12 7.3 8.56 8.08 9.42 8.74 8.06 6.56 6.91 7.85 10.1 8.37 9.44 8.11 7.72 5.03 6.62 7.79 5.7 7.2 8.87 6.78 10.56 9.29 7.63 8.06 8.82 8.18 8.01 6.25 5.64 9.99 8.41 6.96 8.19 8.55 8.63 7.43 7.84 7.23 9.42
Appendix E Sample No. 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132
Voltage (VOLTS) 26.98 27.65 25.45 27.95 25.57 28.69 28.02 27.34 29.42 8.42 33.26 26.61 26.61 28.87 26.98 7.2 25.45 25.39 30.88 31.86 28.14 25.45 5.49 25.51 27.34 28.32 27.4 26.73 7.32 25.63 6.53 25.57 29.54 29.42 25.7 26.25 24.72 30.27 27.22 26.98 25.57 30.46 5.86 26.49
Current (AMPERES) 252.26 138.96 209.68 217.9 184.53 290.61 137.46 311.78 146.92 232.84 160.62 172.57 188.51 219.64 325.47 203.45 171.33 256.49 184.03 151.16 214.16 282.14 160.12 254.75 134.72 185.52 144.68 209.43 175.56 197.48 161.37 170.83 167.09 145.43 128.99 249.27 243.54 152.9 135.97 129.74 194.74 144.68 181.29 167.84 E.22
Wire Feed Rate (m/min) 9.12 7.69 7.83 9.77 8.18 10.21 7.56 10.88 8.42 8.81 7.64 8.4 6.86 8.78 11.11 10.68 8.11 9.68 8.32 7.1 9.03 10.14 7.92 9.62 7.14 8.26 6.39 8.69 7.54 8.46 7.32 7.11 6.79 7.27 6.4 8.11 9.46 8.7 6.88 5.37 6.4 7.16 7.44 7.5
Appendix E Sample No. 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176
Voltage (VOLTS) 28.69 28.26 6.65 26.67 27.28 22.46 28.38 26.92 27.4 30.15 5.19 26.55 26 25.94 25.94 25.57 26 30.46 26.31 26.37 6.23 5.68 30.27 30.03 28.63 28.44 29.48 27.4 10.56 29.24 26.43 30.33 8.18 5.37 7.02 30.21 5.43 27.1 28.99 25.57 29.36 5.31 25.63 6.04
Current (AMPERES) 247.53 274.42 159.38 146.43 244.04 256.99 215.41 236.07 312.77 148.67 172.08 170.83 188.26 212.42 193.49 134.72 199.47 229.6 185.52 202.95 176.06 145.18 139.2 142.19 233.83 286.38 227.36 133.73 191.75 134.22 165.6 209.43 173.07 155.89 157.88 142.94 161.62 298.08 205.69 211.92 159.13 159.62 174.81 205.69 E.23
Wire Feed Rate (m/min) 8.48 10.76 7.85 7.43 8.37 10.6 9.05 9.77 11.19 8.98 7.28 8.06 7.52 9.43 7.76 7.44 6.89 9.66 7.45 9.29 7.84 6.85 5.98 6.41 7.87 10.6 9.97 7.91 7.1 7.36 6.42 8.09 7.38 7.33 6.32 6.91 7.3 9.67 8.92 8.9 7.8 7.55 6.61 8.27
Appendix E Sample No. 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220
Voltage (VOLTS) 31.8 26.31 26.55 7.02 30.88 7.14 30.94 5.13 12.7 29.24 27.4 5.25 28.02 28.56 25.15 27.53 28.93 30.94 29.17 32.17 29.6 31.74 31.43 26.55 25.45 28.56 25.88 8 29.85 29.6 29.17 5.37 6.53 29.48 28.26 26.25 26.12 27.16 28.02 28.14 7.69 24.84 7.32 6.47
Current (AMPERES) 146.67 171.83 206.19 251.51 156.14 332.45 136.96 183.03 208.43 282.39 253.75 225.37 132.73 286.38 211.67 271.19 168.34 274.92 221.88 144.43 162.61 177.8 143.19 123.02 158.88 179.79 178.55 215.16 134.97 186.02 236.82 171.58 162.11 140.95 209.43 208.43 189.51 240.56 271.93 222.63 148.42 235.58 152.4 159.38 E.24
Wire Feed Rate (m/min) 7.54 7.2 8.59 9.34 8.23 10.88 7.74 8.68 7.59 10.31 10.04 10.01 7.32 10.28 9 10.75 8.32 10.44 9.45 7.95 7.31 7.66 7.37 5.71 5.9 7.61 6.9 8.49 6.5 7.49 8.74 8.53 7.36 6.44 7.89 9.32 8.07 8.62 9.8 9.89 7.92 9.26 7.4 7.48
Appendix E Sample No. 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256
Voltage (VOLTS) 29.48 32.1 5.37 31.74 27.89 27.28 26.61 25.39 25.76 6.35 32.1 6.23 26.86 28.75 26.98 5.43 25.94 25.82 27.71 31.13 32.59 26.12 27.89 26.12 27.59 25.88 26.43 6.71 6.9 28.14 26.73 27.22 8.06 27.89 30.21 30.27
Current (AMPERES) 189.01 144.18 266.7 136.71 184.53 252.01 182.29 167.09 165.85 161.87 206.94 159.13 214.16 241.3 160.12 175.81 155.14 163.86 317.01 287.62 256 189.01 211.92 176.06 183.78 175.56 186.52 157.63 193.99 198.72 176.31 173.32 218.64 264.96 139.45 134.72
E.25
Wire Feed Rate (m/min) 6.9 7.1 8.91 8.07 7.33 9.27 8.75 7.99 7.2 7.12 8.24 7.17 7.52 9.75 7.56 8.03 7.18 6.92 10.12 11.27 11.54 9.38 8.37 8.67 7.18 8.65 7.68 7.11 7.17 8.37 7.75 7.84 7.84 10.1 7.36 6.75
Appendix E Sample No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44
Voltage (VOLTS) 27.77 7.63 4.7 25.76 27.22 26.49 27.71 26.55 27.89 29.36 26.61 9.95 30.82 27.71 29.54 30.03 27.89 6.65 8.67 25.88 31.43 6.29 29.66 27.53 25.7 6.35 29.6 6.23 6.71 27.59 25.76 27.53 26.18 15.75 27.16 26.61 25.82 10.8 25.21 30.58 26.12 27.04 5.68 28.32
Current (AMPERES) 168.34 160.37 162.36 174.07 215.65 269.69 200.21 134.47 195.23 156.64 224.12 152.4 319.25 298.83 237.07 218.89 307.29 169.09 165.1 265.46 150.91 289.61 168.34 210.18 203.95 161.12 297.83 204.95 158.88 133.23 185.27 255 254.25 234.08 201.21 139.95 172.82 159.62 164.85 248.28 215.65 194.99 174.07 152.65 E.26
Wire Feed Rate (m/min) 8.78 7.85 7.34 7.15 8.68 9.67 9.28 7.5 7.21 8.2 7.84 7.1 10.63 11.39 10.58 9.8 11.64 8.56 7.89 9.71 8.15 10.5 8.28 9.19 8.86 7.33 10.12 9.48 7.43 7.21 7.02 9.34 11.05 9.99 8.83 6.99 7.36 7.09 6.81 9.14 8.72 9.11 7.67 6.98
Appendix E Sample No. 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88
Voltage (VOLTS) 28.38 25.45 5.49 28.81 24.84 28.26 4.58 28.93 27.22 27.77 27.28 31.25 27.16 25.45 9.46 31.68 29.66 26.31 26.79 6.77 25.27 25.39 31.49 5.86 26.61 7.45 30.94 26.25 31.49 26.55 27.34 31.56 28.56 25.33 25.21 28.08 32.65 31.07 26.06 30.76 27.89 28.99 4.94 28.99
Current (AMPERES) 301.57 230.6 170.58 195.48 192 135.22 289.37 235.83 261.23 193.74 164.36 158.38 141.69 202.21 171.83 167.09 153.15 250.77 196.73 200.21 334.19 251.76 154.64 153.9 124.76 182.29 237.57 179.79 266.95 211.92 221.38 170.33 140.7 192.99 195.23 197.97 157.38 144.93 188.01 164.6 137.96 233.83 210.67 140.2 E.27
Wire Feed Rate (m/min) 10.88 10.27 7.93 8.36 7.52 6.55 9.84 10.34 10.07 8.9 7.95 7.63 6.64 7.3 7.26 7.11 7.87 8.52 9.09 8.24 11.56 10.44 8.77 7.77 6.09 7.02 9.2 7.91 9.49 9.51 8.93 7.76 7.25 8.3 8.11 7.46 7.62 6.51 7.74 7.24 6.17 8.17 8.57 7.57
Appendix E Sample No. 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132
Voltage (VOLTS) 26.12 25.76 30.64 24.84 22.71 29.72 30.27 7.14 26.73 28.75 6.53 25.7 7.02 25.09 26.37 27.89 26.43 25.7 26.25 31.43 5.74 26.06 30.58 7.2 30.33 26.86 27.04 29.72 26.18 5.43 28.08 28.99 5.07 9.16 29.66 16.66 25.76 31.25 5.31 6.47 25.51 32.1 30.09 25.7
Current (AMPERES) 207.69 261.72 175.31 306.05 219.14 159.62 154.64 208.18 153.65 258.49 156.39 185.27 172.32 198.22 272.18 181.79 237.32 200.96 211.67 172.08 177.06 145.43 219.39 167.59 157.13 245.79 134.97 176.56 182.53 183.78 142.94 146.67 185.27 164.85 208.68 177.8 190 197.72 175.56 164.36 179.79 158.88 324.48 209.43 E.28
Wire Feed Rate (m/min) 8.38 9.44 8.31 10.86 9.62 8.26 6.88 8.1 7.72 9.26 7.88 8.28 7.62 8.57 9.27 8.83 9.93 7.93 8.66 8.32 8.48 6.23 8.06 7.17 8.04 8.73 7.08 7.7 8.05 6.86 6.67 6.47 7.55 7.14 8.15 7.72 8.05 7.8 7.9 7.29 7.55 6.85 10.83 9.88
Appendix E Sample No. 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176
Voltage (VOLTS) 13.18 5 5.68 31.68 25.39 5.37 7.26 6.04 8.24 28.08 27.65 27.28 28.08 25.39 28.32 6.53 26.25 23.86 29.97 28.87 26.25 25.15 28.2 26.31 27.1 26.18 7.87 27.95 5.31 5.49 27.28 4.7 25.76 26.31 28.87 28.14 25.76 26.43 9.22 26.67 29.6 29.97 7.32 25.33
Current (AMPERES) 157.13 174.81 172.08 159.62 188.51 173.07 162.11 164.11 249.27 273.18 222.63 211.17 213.66 210.67 246.53 168.09 214.66 210.92 171.33 150.66 190.5 284.38 142.94 197.97 223.62 227.11 192.74 138.46 176.06 195.23 140.95 176.06 217.9 263.47 268.45 157.13 243.79 329.46 203.45 136.71 254.75 355.36 171.08 225.62 E.29
Wire Feed Rate (m/min) 7.96 7.37 7.68 7.06 7.93 7.64 6.9 6.78 8.88 10.44 9.66 8.91 9.74 8.68 9.56 8.78 8.57 8.4 8.4 6.92 7.76 10 8.12 8.2 9.33 8.58 8.3 7.04 7.98 7.88 6.65 7.54 8.68 8.99 10.47 8.37 10.28 11.08 10.02 7.27 9.37 12.38 9.8 9.88
Appendix E Sample No. 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220
Voltage (VOLTS) 26 26.67 25.82 7.32 25.76 5.43 26.49 26.67 28.14 24.9 5.98 25.15 29.91 29.36 29.17 27.34 5.25 26.31 26.61 4.7 26.37 26.98 27.65 26.37 26.73 26.43 29.97 32.23 28.14 5.43 8.36 28.81 27.65 29.85 24.9 6.59 30.46 27.04 25.76 28.99 24.84 28.32 26.73 26.61
Current (AMPERES) 194.74 262.72 276.91 161.62 198.72 178.8 199.72 157.13 142.69 263.72 203.7 245.04 171.58 157.13 168.84 140.45 177.55 196.48 200.71 213.16 141.2 223.37 240.06 207.44 254 313.77 156.14 175.81 177.3 161.62 162.86 166.35 146.92 154.64 197.23 236.32 167.84 131.48 241.3 271.93 243.54 248.77 148.67 305.55 E.30
Wire Feed Rate (m/min) 8.35 10.41 10.54 8.68 8.56 7.47 8.18 8.46 6.62 8.41 9.64 8.8 8.28 7.56 8.17 5.95 7.28 7.18 8.19 9.55 6.8 7.82 10.32 8.42 10.77 10.93 8.36 7.69 8.03 7.44 7.29 7.87 6.25 6.43 7.59 8.55 8.9 6.34 8.16 9.97 10.15 10.31 9.24 10.03
Appendix E Sample No. 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256
Voltage (VOLTS) 26.37 27.28 29.66 7.51 25.27 31.07 28.87 28.14 25.57 6.96 5.37 26.79 27.1 29.3 31.07 10.86 6.47 30.33 25.57 26.43 7.69 8.3 26.25 29.91 5.37 28.02 25.63 26.98 27.16 25.15 7.93 26.92 30.21 8.97 4.58 27.1
Current (AMPERES) 245.54 232.09 243.05 204.95 261.72 162.86 242.05 146.43 351.87 220.88 180.79 267.7 286.13 265.46 170.83 260.23 178.8 177.06 247.78 244.54 259.73 175.81 201.46 210.67 193.99 148.42 160.87 142.94 320.74 201.46 251.02 238.07 179.79 205.94 230.84 143.19
E.31
Wire Feed Rate (m/min) 10.47 9.72 9.93 9.56 10.02 8.7 9.17 7.6 11.61 9.99 9.69 9.33 10.96 11.01 9.61 9.38 8.33 8.75 9.83 9.3 10.08 8.98 8.76 8.53 8.4 7.06 7.17 7.28 10.15 8.73 9.9 9.81 9.19 8.24 9.53 7.84
Appendix E Sample No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44
Voltage (VOLTS) 30.88 24.29 5.49 28.38 6.29 5.07 5.8 26.18 29.91 29.17 25.88 30.15 25.27 26.43 27.22 25.45 24.96 25.88 26.98 30.94 25.21 4.21 28.08 26.49 28.02 30.58 26.43 23.68 24.72 28.81 27.28 27.22 26.86 30.21 26.61 4.39 27.4 27.1 27.65 7.2 4.7 26.67 27.77 27.04
Current (AMPERES) 164.11 200.21 171.33 316.51 173.32 177.3 192 269.44 311.03 161.12 303.06 196.98 204.95 208.43 136.96 283.39 185.52 200.71 286.13 165.6 205.69 246.78 155.64 193.74 233.58 162.86 267.2 269.69 211.42 293.85 242.55 281.4 307.29 160.87 259.98 191 235.33 141.94 297.33 202.71 183.78 250.77 150.66 277.41 E.32
Wire Feed Rate (m/min) 6.9 7.9 7.94 10.34 9.14 7.7 8.81 9.25 11.53 9.16 10.79 9.54 9.11 9.07 7.42 9.39 8.93 7.86 10.62 8.96 8.15 9.38 8.74 7.67 9.02 8.37 9.29 10.25 9.51 11 10.95 10.93 12.12 9.86 9.65 9.18 8.92 7.41 10.31 9.28 8.86 9.23 8.36 9.59
Appendix E Sample No. 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88
Voltage (VOLTS) 28.69 6.35 25.33 26.61 27.89 27.1 25.21 27.71 5.31 29.54 25.76 30.4 28.44 21.61 26.31 5.31 30.64 26.49 26.31 28.5 6.53 25.94 26.61 7.14 24.9 6.47 28.56 26.37 28.32 27.1 5.25 27.34 26.06 26.92 28.2 23.68 26.49 24.9 7.08 29.3 6.1 5.55 7.2 30.7
Current (AMPERES) 167.34 219.89 210.42 278.91 144.43 228.35 196.48 180.04 180.29 162.36 335.68 155.14 238.32 176.06 247.78 329.46 177.06 213.16 224.62 268.2 202.46 264.71 267.7 198.72 175.81 165.1 159.87 224.37 224.87 139.95 180.79 205.2 180.54 255 152.15 165.1 161.12 182.04 180.29 158.88 187.02 169.09 174.81 160.87 E.33
Wire Feed Rate (m/min) 8.24 9.34 8.38 10.79 7.8 8.68 8.48 8.48 7.46 7.3 11.13 7.93 9.66 8.59 9.55 11.59 9.98 8.39 9.25 10.26 9.98 9.81 10.67 9.54 8.31 7.6 7.98 7.65 9.24 7.28 7.13 8.24 8.43 9.96 7.36 7.11 6.84 7.27 7.33 7.21 7.85 7.37 7.08 7.19
Appendix E Sample No. 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132
Voltage (VOLTS) 24.48 26.92 27.16 28.38 30.09 8.91 25.02 31.62 25.09 5.31 27.89 28.81 26.55 30.52 26 6.53 26.79 5.31 22.16 29.91 26.49 30.33 28.56 6.96 25.57 5.13 25.39 26.25 26.55 28.38 27.47 28.08 24.96 30.88 25.57 5.8 26.73 25.88 29.11 28.69 29.3 28.44 24.9 26.37
Current (AMPERES) 212.92 248.03 231.09 283.14 169.09 182.29 353.36 150.16 193.49 194.49 224.37 219.39 268.7 173.82 211.92 254 259.98 169.34 259.98 170.08 222.13 314.27 161.37 160.62 223.13 177.3 234.08 192 200.96 272.93 296.84 258.49 258.98 163.36 190.5 169.83 194.74 269.94 142.44 246.04 208.93 155.89 178.8 193.49 E.34
Wire Feed Rate (m/min) 8.87 9.12 9.35 10.54 9.56 7.98 11.67 9.02 8.43 7.66 8.89 9.08 10.29 9.19 9.42 9.11 10.08 8.65 9.8 8.87 8.49 11.14 8.85 7.64 8.39 8.44 9.39 8.79 8.68 9.29 11.14 10.87 11.28 8.58 8.56 7.47 8.45 9.23 7.57 9.03 9.01 7.65 7.57 8.08
Appendix E Sample No. 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176
Voltage (VOLTS) 26.18 25.21 26.55 27.59 7.14 27.22 27.77 33.08 6.77 30.94 5.19 8.48 6.04 27.04 27.47 27.59 27.1 8 30.76 8.48 25.09 26.31 30.7 22.64 31.98 26.06 28.14 7.14 6.16 26.92 26.98 26.25 27.04 8.3 28.2 6.04 27.22 24.41 26.06 5.62 7.26 33.69 26.73 25.33
Current (AMPERES) 323.48 187.02 178.8 228.6 187.02 230.84 147.17 220.39 170.58 153.9 175.06 156.88 212.67 249.27 291.86 235.33 189.51 190.75 186.77 200.21 171.08 179.05 175.06 171.83 163.36 246.04 170.83 164.36 173.82 219.89 219.14 198.97 230.84 181.54 135.97 211.17 188.26 180.79 176.06 170.08 178.05 169.34 183.03 289.37 E.35
Wire Feed Rate (m/min) 11.34 9.09 8.7 8.45 8.22 9.5 7.54 8.49 7.94 7.02 7.38 6.52 9.33 8.8 10.76 9.95 9.54 8.34 8.04 8.48 7.92 6.99 8.04 6.91 8.2 8.33 8.16 7.44 7.35 8.01 9.88 7.96 9.11 8.44 7.12 8 8.01 7.77 7.84 7.14 7.17 7.42 7.88 10.32
Appendix E Sample No. 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220
Voltage (VOLTS) 30.27 7.14 29.72 27.59 27.34 26.98 27.65 26.31 31.8 30.82 5.31 27.22 31.86 5.98 26.12 27.04 29.91 6.35 7.08 29.6 7.14 7.39 31.13 7.14 27.71 27.47 28.81 25.63 5.74 28.56 26.73 31.25 28.02 25.76 30.15 29.66 5.49 28.75 25.33 26.31 26.67 5.43 6.04 26.12
Current (AMPERES) 135.72 155.64 280.9 258.74 245.79 216.4 203.95 205.2 151.16 159.38 168.34 156.39 305.8 184.03 193.74 251.02 171.83 243.54 164.6 146.18 296.34 166.85 181.29 195.23 282.39 172.82 202.21 169.09 174.32 264.71 192.74 283.39 223.13 178.05 155.14 149.91 153.65 239.31 180.79 203.45 178.3 163.36 173.82 189.51 E.36
Wire Feed Rate (m/min) 7.55 6.87 9.54 10.05 10.28 9.71 9.29 8.78 7.48 6.9 7.21 6.86 10.29 9.31 8.47 9.24 8.49 9.04 7.77 7.04 10.17 8.37 8.05 7.85 10.74 8.59 8.92 7.84 7.54 9.42 8.73 9.87 10.25 8.18 7.37 6.71 6.78 9.13 7.92 8.4 8.2 7.45 7.54 7.58
Appendix E Sample No. 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256
Voltage (VOLTS) 30.09 29.05 6.35 5.49 31.13 29.11 28.63 26.67 25.76 5.31 29.66 26.67 9.03 25.82 33.14 28.69 27.59 25.88 26.37 26.79 6.35 7.2 29.79 27.83 28.87 27.28 27.16 29.05 28.63 26.92 26.37 25.57 25.51 26.31 10.62 27.1
Current (AMPERES) 184.28 233.83 164.85 150.91 140.95 313.27 277.16 186.27 170.33 156.88 274.67 220.63 176.31 155.14 139.45 258.24 244.54 166.1 235.83 198.22 158.13 149.66 248.03 237.32 280.15 207.93 230.35 300.57 257.99 192.25 179.05 168.84 166.6 193.99 165.1 205.69
E.37
Wire Feed Rate (m/min) 7.38 9.45 7.85 6.75 6.25 10.06 11.43 9.45 8.12 6.89 9.42 9.71 8.36 7.48 6.34 8.64 9.84 8.59 9.81 8.59 7.34 6.54 8.83 9.15 10.78 10.11 9.16 11.1 11.36 9.4 8.49 7.46 7.92 7.96 7.69 7.43
Appendix E Sample No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44
Voltage (VOLTS) 27.34 25.94 26.55 31.74 6.41 31.68 7.63 27.22 26.73 26.37 26.79 30.09 28.87 28.75 33.45 27.77 26.61 8.24 28.63 28.2 26.55 25.82 34.67 26.43 30.33 27.28 26.61 8.85 30.03 28.44 30.88 6.71 25.57 27.95 29.42 32.17 25.7 6.53 31.8 25.88 26.37 26.25 27.28 30.03
Current (AMPERES) 212.67 157.38 126.01 310.53 196.98 257.24 267.2 256.74 180.04 227.61 257.74 146.18 159.13 175.56 155.14 266.95 191.75 188.26 177.06 192.99 183.03 157.88 140.2 116.79 151.16 228.11 242.8 149.91 260.23 295.84 149.91 165.6 224.12 204.7 161.87 149.66 233.83 160.62 141.94 180.54 179.55 122.02 256 173.57 E.38
Wire Feed Rate (m/min) 8.77 7.55 5.73 10.03 8.9 9.94 10.8 10.88 9.47 8.76 9.93 7.89 7.35 7.39 7.11 10.02 8.6 7.81 7.56 8.07 8.41 6.94 6.7 5.28 7.1 7.62 8.94 7.68 9.37 11.27 8.4 7.91 8.25 8.41 7.67 7.02 9.05 7.34 6.88 7.47 8.1 5.39 8.46 7.8
Appendix E Sample No. 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88
Voltage (VOLTS) 26.25 5.98 25.7 25.39 31.98 29.48 8.79 8.3 4.88 6.47 28.14 31.92 28.75 28.93 30.88 10.01 25.57 27.22 28.87 31.19 25.88 26.12 5.37 26.73 27.1 25.57 27.4 28.14 26.31 8.73 26.73 27.04 29.79 25.39 25.57 27.47 29.36 32.65 6.59 25.7 26.86 27.53 28.26 26.43
Current (AMPERES) 167.34 223.87 187.02 170.08 139.95 132.48 141.2 147.67 153.65 144.93 137.21 146.92 141.69 134.22 166.85 167.34 168.84 256.99 224.12 145.93 209.43 189.26 187.27 223.13 218.64 244.04 274.17 258.49 190.25 153.65 192.74 289.61 133.73 167.34 217.4 271.19 226.61 134.72 176.06 184.03 206.44 255 137.96 143.44 E.39
Wire Feed Rate (m/min) 7.44 8.61 8.59 7.36 6.59 5.98 6.36 6.33 6.98 5.86 5.62 6.04 6.14 6.27 7.28 7.21 6.41 8.77 9.18 8.11 8.43 8.3 8.4 8.08 8.56 9.46 10.71 10.64 9.67 7.55 7.73 10.23 7.84 8.09 7.87 9.83 9.72 7.8 7.9 7.89 8.16 9.06 7.5 7.36
Appendix E Sample No. 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132
Voltage (VOLTS) 26.67 11.66 8.42 7.57 15.14 26.49 28.14 28.26 7.75 5.49 25.76 26 33.02 5.68 26.18 26.86 27.59 29.17 29.91 7.26 5.19 25.82 25.88 29.91 31.43 30.94 8.79 8 25.45 26.37 26.43 28.38 31.49 25.15 26 29.11 8.36 25.94 28.2 32.35 8.48 26.67 26.06 28.5
Current (AMPERES) 172.82 214.41 293.35 155.64 156.88 221.63 251.51 131.48 148.42 166.85 217.65 351.12 148.92 161.12 190.5 251.51 219.64 208.68 137.46 144.68 158.63 180.54 213.41 137.96 141.45 155.64 161.37 167.34 184.78 214.66 241.3 226.11 148.67 173.32 261.97 304.31 155.64 186.77 226.36 138.46 148.67 169.34 241.8 209.18 E.40
Wire Feed Rate (m/min) 6.4 8.82 10.11 8.44 7.41 7.9 9.58 7.3 7.03 7.44 8.64 11.38 8.68 8.16 7.79 8.65 9.11 8.83 7.32 6.71 7.21 7.47 7.69 6.85 6.49 6.58 6.98 7.35 7.28 7.88 9.3 9.37 7.97 7.79 9.07 11.12 9.09 7.7 8.85 7.43 7.33 6.95 8.32 8.6
Appendix E Sample No. 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176
Voltage (VOLTS) 32.78 6.77 26.73 29.79 6.47 26.67 28.38 6.53 26.92 5.25 23.86 25.63 27.77 26.25 28.56 31.13 25.21 31.37 25.82 29.24 21.42 29.6 8.73 26 26.49 29.24 25.82 26.73 5.31 27.4 29.79 29.36 28.56 28.38 28.87 32.41 8.91 25.88 28.81 9.89 26.37 28.87 33.57 7.69
Current (AMPERES) 212.67 192.25 261.47 215.65 159.38 233.33 129.49 159.62 262.47 184.53 391.71 254.25 129.49 205.69 132.73 138.46 253.75 143.69 232.34 141.45 252.26 168.59 144.93 162.61 192.5 131.48 180.04 256 161.12 287.62 131.73 148.92 193.24 308.79 226.36 131.73 135.97 187.51 223.87 162.11 213.66 219.64 127.25 149.41 E.41
Wire Feed Rate (m/min) 8.92 9 9.38 9.26 8.53 8.29 7.06 7.13 8.9 8.02 13.27 11.45 8.97 7.61 6.76 6.62 8.62 7.69 8.33 7.06 9.22 7.89 7.03 7.27 7.36 6.62 7.83 8.85 8.2 9.58 7.59 6.75 7.59 10.42 9.84 7.65 7.04 7.23 8.43 8.23 7.86 8.85 6.99 7.31
Appendix E Sample No. 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220
Voltage (VOLTS) 25.63 29.97 32.65 7.32 30.52 6.53 25.39 30.76 5.86 26.43 31.31 25.39 29.48 6.84 27.28 25.33 25.02 27.83 26.61 28.38 25.82 29.72 29.3 29.05 26.92 29.17 25.76 26.73 29.48 25.94 31.13 26 29.11 25.57 32.29 6.71 25.02 25.82 25.94 28.81 8.18 26.18 32.1 34.48
Current (AMPERES) 191.5 132.98 138.46 239.31 323.48 140.2 169.09 146.18 173.32 301.32 140.45 163.11 137.96 194.24 309.04 305.3 292.1 213.91 265.21 123.02 233.09 138.46 181.79 136.22 164.85 123.02 203.95 249.52 135.97 261.97 143.94 225.86 187.02 179.79 137.21 187.76 146.67 155.39 190 125.76 148.67 157.13 142.19 160.37 E.42
Wire Feed Rate (m/min) 6.87 6.36 6.2 8.15 11.46 8.56 7.55 6.77 7.55 9.87 7.84 6.88 6.76 7.48 10.84 11.47 11.74 10.68 10.29 8.08 8.44 7.15 7.38 7.01 6.57 6.04 7.25 9.05 8.15 8.82 7.72 8.23 8.56 8.03 6.81 7.11 6.76 7.29 6.88 6.46 6.59 6.68 6.35 7
Appendix E Sample No. 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256
Voltage (VOLTS) 26.25 31.01 26.86 34.36 8.12 30.52 7.57 27.16 7.69 26.86 27.1 27.16 27.77 26.43 27.04 33.51 26.86 8.36 26.98 31.13 27.53 28.5 9.28 25.7 25.76 26.12 27.89 29.85 29.79 32.1 5.55 26.55 27.4 7.2 27.71 27.89
Current (AMPERES) 240.31 149.41 159.13 136.46 193.24 263.22 117.79 148.92 142.44 117.54 191 200.71 157.38 183.78 223.62 139.95 267.45 161.12 297.58 129.99 226.11 280.9 144.18 165.1 191 218.14 198.22 198.47 225.62 143.94 147.42 193.24 120.03 163.61 245.54 173.82
E.43
Wire Feed Rate (m/min) 8.07 7.87 6.73 5.67 7.28 9.45 7.88 6.31 6.26 6.59 7.11 6.8 7.64 7.4 8.28 7.99 8.9 8.23 10.02 8.69 7.84 9.95 8.34 7.36 7.74 8.25 8.61 8.36 9 7.45 7.47 6.91 6.97 6.89 8.05 7.64
Appendix E Sample No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44
Voltage (VOLTS) 8.85 27.16 30.7 6.41 26.73 28.38 26.92 12.94 10.86 26.92 8 26 24.96 32.1 8.42 26.25 5.62 24.23 7.08 26.86 9.16 26.67 24.96 26.98 30.46 24.29 31.31 29.6 9.4 15.56 26.31 25.57 27.04 29.97 7.57 26.31 30.52 5.86 26.61 9.95 25.27 29.48 29.54 28.02
Current (AMPERES) 156.88 206.19 135.97 140.7 236.07 127 208.18 174.32 159.87 109.57 141.94 251.51 175.56 132.23 150.91 207.19 141.94 309.54 192.99 164.6 207.69 350.63 223.13 239.81 229.85 304.06 278.16 122.52 157.13 162.61 165.85 259.98 249.02 126.25 139.2 253.75 133.73 174.07 302.07 140.95 174.07 119.28 223.13 196.98 E.44
Wire Feed Rate (m/min) 8.32 7.16 6.67 6.44 8.17 7.73 7.24 7.16 8.35 5.23 6.38 8.36 7.37 6.18 7.38 7.66 6.66 10.17 9.89 7.37 8.07 11.91 10.29 9.9 9.88 11.46 11.7 7.83 7.79 7.3 7.06 8.73 9.62 7.42 7.56 8.23 7.32 7.36 10.18 7.72 7.64 5.9 7.85 8.28
Appendix E Sample No. 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88
Voltage (VOLTS) 25.15 27.77 8 27.77 35.4 27.34 7.02 32.41 30.52 25.63 28.44 33.2 25.21 28.63 25.15 27.59 6.71 5.8 6.9 26.37 25.39 9.52 26.31 26.37 26.06 24.96 26.67 25.09 30.7 28.93 26.06 26.12 7.81 31.8 32.78 24.54 29.17 8.12 26.37 8.24 26.55 26.86 27.16 27.1
Current (AMPERES) 147.67 218.39 148.92 203.95 132.48 245.79 224.37 136.22 130.24 159.13 249.27 157.38 225.86 247.28 180.79 215.41 154.64 161.87 177.8 180.04 162.86 150.41 208.93 183.53 168.34 233.33 196.23 139.45 145.43 137.96 174.07 227.86 139.2 254 153.15 279.65 169.34 138.96 173.07 145.68 187.02 241.3 185.52 203.7 E.45
Wire Feed Rate (m/min) 8.01 8.58 7.29 7.3 6.69 8.99 8.83 6.94 6.64 6.73 8.52 7.8 8.34 10.09 8.62 8.92 7.56 6.36 7.52 7.9 7.64 6.69 7.45 8.33 7.06 8.73 8.49 6.93 6.52 6.77 7.26 7.9 6.93 8.66 7.73 9.8 8.4 7.57 7.18 6.9 6.82 9.31 8.98 8.45
Appendix E Sample No. 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132
Voltage (VOLTS) 6.23 30.76 30.88 25.76 26.25 29.11 5.98 26.98 5.43 32.47 6.65 27.95 27.1 29.79 25.45 26.86 8.3 27.65 9.7 25.94 31.19 26.49 30.33 27.95 26.18 25.82 29.24 25.88 28.75 25.63 27.4 28.14 27.22 5.98 6.65 33.08 30.58 29.72 28.08 30.33 25.88 27.53 7.87 10.25
Current (AMPERES) 148.42 145.18 127 165.35 221.88 198.72 147.17 125.76 150.66 146.67 175.56 290.11 185.77 128.25 172.08 173.07 280.9 195.73 159.38 170.08 151.66 229.6 135.22 218.89 123.27 176.06 127.25 163.36 128.99 160.62 270.19 264.96 231.59 155.89 150.66 136.22 124.76 258.49 236.32 137.96 179.55 279.65 189.76 160.12 E.46
Wire Feed Rate (m/min) 6.76 6.3 6.31 6.96 7.59 8.37 7.67 6.01 6.38 6.18 6.54 10.48 8.15 6.8 7.31 7.33 9.72 9.04 7.94 7.59 7.45 7.61 6.82 8.62 6.63 7.36 6.16 5.8 6.39 6.7 8.9 9.99 10.38 7.89 7.17 6.19 5.78 8.5 9.4 7.48 7.44 9.76 8.56 8.09
Appendix E Sample No. 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176
Voltage (VOLTS) 25.88 31.37 5.55 29.85 28.38 28.2 8.67 25.02 29.79 27.04 6.04 26.79 27.53 11.6 27.47 5.55 25.57 7.08 5.62 31.31 5.37 26.25 27.59 32.53 26 28.63 33.75 5.62 5.98 25.63 28.87 5.31 26.86 28.14 31.49 26.73 25.94 27.4 30.27 6.29 25.39 27.71 9.22 5.98
Current (AMPERES) 386.48 127.5 193.74 272.93 307.54 202.46 135.72 161.62 136.46 241.8 198.22 210.92 135.47 179.3 145.18 165.1 227.36 151.16 156.88 138.46 154.39 242.8 163.61 149.91 179.3 265.21 138.21 147.92 149.17 316.51 258.49 146.67 178.3 128.5 138.46 185.27 242.05 255 135.47 146.67 272.43 251.51 149.17 185.77 E.47
Wire Feed Rate (m/min) 12.41 8.31 8.17 9.79 11.68 9.87 7.9 6.63 7.47 7.99 8.39 8.43 7.16 7.37 6.9 7.73 7.97 7.23 6.9 6.2 7.25 7.98 7.55 7.76 6.55 9.13 7.74 7.29 6.28 10.05 10.61 8.58 7.6 6.24 6.77 7.49 8.36 9.62 7.66 7.15 9.06 10.33 8.27 7.58
Appendix E Sample No. 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220
Voltage (VOLTS) 27.53 35.1 26.06 27.71 26.79 26.12 27.77 31.01 25.88 8.12 25.82 28.63 8.42 5.25 27.22 7.02 25.82 26.18 27.89 6.16 26.18 28.63 28.87 25.09 26.73 31.56 26.06 9.46 10.68 27.28 24.35 25.45 24.41 26.73 29.3 32.04 6.71 6.47 26.49 28.26 30.52 25.51 23.86 32.78
Current (AMPERES) 277.66 158.63 212.17 266.7 177.3 190.25 253.01 136.46 237.57 194.74 211.67 253.01 146.92 170.33 249.02 161.37 190.5 212.67 193.24 175.81 190 292.6 168.34 192.25 228.11 155.39 176.81 162.61 172.57 226.86 210.42 304.31 175.81 282.39 132.48 145.18 175.31 161.12 243.79 172.57 142.94 275.92 298.58 142.19 E.48
Wire Feed Rate (m/min) 9.55 8.59 8.19 10.8 8.78 7.76 9.41 8.07 8.57 8.69 8.23 9.65 7.88 7.59 8.85 8.39 7.86 8.04 8.86 8.26 7.39 10.23 8.61 8.44 8.81 8.26 7.69 6.63 7.09 8.44 8.75 11.03 10 9.95 7.61 6.93 7.69 6.83 8.61 7.67 7.11 9.28 11.18 9
Appendix E Sample No. 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256
Voltage (VOLTS) 26.43 17.03 26.06 25.57 27.16 7.81 25.94 27.47 29.24 5.8 26.37 26.92 6.41 26 27.28 30.33 24.84 27.04 13.85 26.86 27.04 27.71 21 24.9 14.65 25.39 5.31 28.63 8.73 30.03 8.18 27.71 30.4 8.85 28.63 29.54
Current (AMPERES) 126.01 135.22 192.5 204.45 134.47 146.67 195.73 230.1 139.95 161.87 216.4 287.87 158.63 192.99 207.69 153.65 227.61 220.14 187.27 259.73 281.89 223.87 147.17 313.27 154.15 200.96 139.2 172.57 159.87 175.06 159.87 173.32 277.41 144.93 223.87 153.9
E.49
Wire Feed Rate (m/min) 6.36 6.34 7.76 7.35 6.7 7.23 7.33 8.34 7.36 7.72 7.38 10.05 8.82 7.84 8.31 7.39 9.18 8.74 8.97 9.07 10.71 9.84 7.61 11.04 8.73 9.18 7.16 7.76 6.62 7.6 6.56 7.62 9.49 7.41 8.97 7.11
Appendix E Sample No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44
Voltage (VOLTS) 30.4 5.74 7.87 6.71 6.53 26.43 27.53 30.64 6.1 25.82 5.49 26 25.7 30.09 30.4 27.34 27.47 29.3 27.04 27.77 27.77 27.16 26.73 25.94 5.98 30.52 31.43 30.64 28.56 29.42 28.87 29.79 10.13 4.82 5.62 22.77 7.26 5.37 6.41 29.54 29.91 26.73 26.55 26.25
Current (AMPERES) 277.41 151.66 167.09 177.55 157.63 118.78 306.3 134.22 197.23 161.12 156.88 164.36 175.81 204.95 268.7 196.98 265.96 231.59 256 211.42 202.95 217.65 194.74 183.78 168.59 146.67 138.46 267.2 273.18 259.23 237.32 240.06 142.44 154.15 147.92 158.88 135.72 168.59 145.18 238.32 277.41 193.74 187.27 163.36 E.50
Wire Feed Rate (m/min) 9.49 7.44 6.96 7.18 6.94 6.69 8.85 7.46 7.86 7.56 7.01 7.14 6.44 8.07 9.53 9.26 9.94 11.01 9.5 10.03 8.27 9.87 8.06 8.64 7.43 6.93 6.04 9.05 10.05 10.71 9.86 10.91 7.49 7.44 6.3 7.07 5.96 7.16 6 8.56 10.07 9.78 8.53 7.47
Appendix E Sample No. 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88
Voltage (VOLTS) 5.49 6.1 22.58 25.94 6.47 13 32.1 30.03 26.12 32.9 30.52 27.59 27.04 27.1 26.12 30.46 8 22.4 5.92 30.4 5.74 28.2 30.03 8.12 28.87 27.34 31.25 31.74 31.43 7.39 27.95 25.09 8.42 29.05 27.89 26.31 25.27 6.1 10.62 26.43 26.25 26.31 26.12 5.86
Current (AMPERES) 144.18 211.42 194.99 157.88 151.16 133.73 143.19 231.59 170.83 260.48 157.38 194.74 222.63 192 177.8 251.02 155.89 171.83 149.41 187.76 158.63 185.77 134.47 138.21 266.95 196.98 174.32 133.48 246.53 140.7 203.95 155.64 136.96 258.98 188.51 160.87 157.38 153.15 147.17 174.32 184.03 188.51 159.87 154.89 E.51
Wire Feed Rate (m/min) 6.24 8.73 8.15 7.06 6.47 6.26 5.77 8.59 7.87 9.37 7.47 8.06 8.77 9.44 7.72 9.27 7.56 8.22 6.28 8.1 6.89 7.52 6.15 6.39 8.66 9.37 8.07 6.53 8.91 6.86 8.12 7.24 6.04 9.08 8.87 8.04 6.74 6.87 6.81 7.43 7.17 7.24 6.98 7.28
Appendix E Sample No. 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132
Voltage (VOLTS) 5.49 32.04 30.52 28.69 31.8 28.02 26.73 21.06 28.38 8.79 30.88 27.16 29.97 27.59 27.77 26.18 25.57 26.86 7.32 5.19 25.82 5.55 28.63 26.73 7.69 29.91 27.04 25.57 28.44 27.22 28.02 27.53 26.86 6.04 25.94 27.95 28.75 29.11 29.54 30.52 29.6 28.32 26.49 27.83
Current (AMPERES) 146.43 136.22 133.48 227.86 176.06 215.41 203.7 207.69 261.47 146.18 191 158.13 173.32 245.29 222.88 177.3 161.62 172.82 183.53 180.04 157.13 144.93 247.78 330.45 138.71 258.98 211.92 178.05 226.86 261.23 217.4 244.54 281.4 190.5 194.74 234.83 308.29 127.75 132.73 136.46 257.74 215.41 185.52 238.07 E.52
Wire Feed Rate (m/min) 6.05 6.26 5.61 8.22 7.37 9.51 8.43 8.44 9.49 8.05 7.49 7.47 6.99 9.13 9.13 8.88 7.46 7.59 7.27 8.3 6.98 6.38 8.98 11.54 7.94 9.94 8.92 8.83 8.35 10.24 9.03 10.37 10.64 9.91 8.14 9.4 11.09 8.15 6.5 6.41 8.55 9.07 8.25 9.43
Appendix E Sample No. 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176
Voltage (VOLTS) 28.56 30.21 29.91 9.34 25.57 27.95 26.55 25.21 30.27 5.8 28.5 25.7 28.99 27.4 26.31 24.11 29.66 28.38 30.4 29.97 30.33 30.4 8.42 29.17 29.05 29.36 28.44 26 27.95 26.18 15.32 25.27 4.94 6.53 6.47 30.27 31.07 7.02 7.45 7.63 8.18 7.63 27.89 26.25
Current (AMPERES) 248.53 211.42 193.24 144.93 220.88 247.78 194.99 182.78 148.42 138.96 193.99 288.62 217.15 232.84 147.92 161.62 132.48 167.09 184.78 134.97 244.54 164.6 139.2 240.06 230.35 233.33 221.38 269.94 194.49 162.61 151.66 164.6 149.17 141.2 151.9 144.43 139.45 144.43 144.18 142.69 139.7 216.9 209.68 185.02 E.53
Wire Feed Rate (m/min) 9.91 9.34 8.42 7.5 7.96 9.79 9.02 8.61 6.78 6.43 8.09 9.71 9.57 9.66 7.4 7.53 5.95 7.19 7.12 6.65 8.22 7.96 6.39 8.8 9.02 9.61 9.86 10.24 9.68 7.87 6.98 7.1 6.44 6.37 6.42 6.41 5.9 6.23 5.91 6.43 5.9 7.82 8.78 8.67
Appendix E Sample No. 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220
Voltage (VOLTS) 27.28 7.26 5.43 7.93 30.76 30.21 25.39 24.48 31.13 29.17 28.08 11.96 29.17 5.43 6.35 7.51 26.55 25.76 27.16 6.04 24.11 27.71 27.65 25.76 7.2 29.91 7.81 27.89 25.88 26.43 30.15 22.71 26.49 7.2 29.05 26.49 25.88 6.41 30.58 25.57 22.09 28.93 28.69 15.93
Current (AMPERES) 180.79 149.91 159.62 145.18 132.73 174.81 150.41 154.15 135.22 121.52 122.52 152.4 133.73 159.62 146.18 154.15 193.49 175.31 150.16 151.66 266.95 245.29 206.44 174.32 139.45 154.39 291.36 241.55 186.77 158.38 134.72 227.61 197.48 137.96 210.42 213.41 192.5 133.97 258.74 156.39 223.62 128.99 194.99 151.66 E.54
Wire Feed Rate (m/min) 7.55 6.84 6.57 6.66 5.79 7.13 6.57 6.67 5.81 6.52 4.93 6.36 5.54 6.71 6.41 7.08 7.5 7.31 6.46 6.63 8.8 9.84 9.77 8.08 6.54 6.77 9.45 10.79 8.94 7.5 6.23 9.05 8.3 6.63 8.18 9.16 7.59 6.61 9 7.99 8.34 6.75 8.09 6.88
Appendix E Sample No. 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256
Voltage (VOLTS) 28.69 30.88 30.76 28.44 31.07 8.48 29.79 28.63 30.58 28.87 26.25 26.18 29.48 30.03 30.33 27.59 27.53 7.02 30.52 8.42 30.58 28.08 27.53 25.94 6.41 6.16 29.97 5.86 6.04 9.46 29.97 29.05 29.48 27.83 25.51 25.63
Current (AMPERES) 268.7 213.41 193.24 205.44 138.71 139.45 251.02 216.9 130.99 212.42 177.06 155.64 202.46 210.67 267.7 206.19 200.71 160.37 145.93 140.45 226.11 241.55 191 162.11 159.62 144.43 152.9 147.92 155.64 136.96 257.49 138.46 257.99 191.25 193.99 177.06
E.55
Wire Feed Rate (m/min) 8.98 9.24 8.27 8.87 6.96 6.66 8.4 9.2 6.83 8.11 8.55 7.39 7.36 8.32 9.65 9.24 8.8 8.37 6.32 6.47 7.74 9.52 9.1 7.66 6.86 6.63 6.53 6.6 6.47 6.18 8.43 7.38 9.42 9.1 8.29 7.6
Appendix E Sample No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44
Voltage (VOLTS) 29.79 33.08 26.55 5.68 31.62 6.04 6.9 26.98 26.73 25.51 25.7 5.86 6.41 30.21 30.33 30.27 29.36 27.59 27.28 26 26.61 26.92 9.95 6.23 31.07 30.46 29.79 28.32 28.87 28.44 25.88 25.94 25.27 29.11 6.71 30.82 30.82 31.01 28.44 30.94 32.41 29.48 29.24 26.73
Current (AMPERES) 277.66 166.1 153.65 156.39 186.27 150.41 175.06 172.82 195.98 177.8 159.87 146.92 142.69 166.1 133.97 148.67 251.51 226.36 223.13 212.92 195.23 175.31 149.17 148.92 138.46 148.42 202.95 237.32 223.87 204.7 178.3 163.11 152.65 144.43 142.44 135.72 139.45 152.9 255.5 170.08 153.4 145.18 175.56 172.57 E.56
Wire Feed Rate (m/min) 9.95 9.2 6.66 6.61 7.14 7.17 7.28 7.75 7.68 8.15 6.89 6.67 6.04 6.97 5.86 6.23 8.44 9.14 9.37 9.36 8.32 8.39 6.76 6.66 6.02 6.34 7.36 9.06 8.99 9.5 8.39 7.43 6.65 6.39 6.07 6.26 5.76 6.34 8.81 8.2 6.66 6.64 7.54 6.9
Appendix E Sample No. 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88
Voltage (VOLTS) 28.81 28.63 27.53 28.08 25.33 26.12 8.3 5.37 27.47 16.05 5.62 30.15 7.69 26.06 26 6.9 30.03 6.29 7.39 6.84 21.48 28.32 29.11 18.01 30.27 5.92 5.25 6.29 8.42 30.15 28.87 27.22 28.63 29.6 29.91 26.92 29.48 29.72 8.54 29.48 29.91 31.86 30.33 30.09
Current (AMPERES) 215.41 252.01 244.29 197.97 206.94 179.79 144.93 226.11 215.9 145.68 155.89 136.96 134.97 174.07 161.37 150.16 244.79 168.09 143.44 142.19 160.12 249.77 247.03 256.25 141.2 152.65 152.15 152.4 153.15 208.43 258.98 215.65 196.98 258.24 129.74 189.51 269.44 176.81 262.97 268.45 139.45 164.36 145.68 188.01 E.57
Wire Feed Rate (m/min) 8.64 9.07 9.48 9.68 9.11 8.38 6.91 8.03 9.04 7.13 6.76 6.47 5.89 7.44 6.63 6.41 9.15 7.85 6.41 6.39 6.6 8.77 9.43 10.31 8.22 7.67 6.43 6.49 6.48 7.72 9.26 9.46 8.49 10.1 8.31 7.32 9.39 8.34 9.67 10.6 7.98 7.49 6.57 7.4
Appendix E Sample No. 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132
Voltage (VOLTS) 28.44 30.27 26.92 26 27.53 26.79 26.67 28.81 26.55 25.94 25.94 26.06 7.75 32.29 28.63 31.07 31.31 28.02 17.33 28.2 30.58 27.77 6.29 30.7 31.86 29.42 27.59 26.55 26.06 31.8 29.11 6.65 30.21 26.37 6.9 6.84 26.31 26.67 24.96 25.45 26.67 26.12 26.49 30.7
Current (AMPERES) 240.81 181.04 203.45 195.73 211.17 190 217.65 206.69 181.79 154.89 187.76 156.64 137.96 262.72 154.89 174.81 223.37 209.93 159.13 130.49 216.9 229.35 176.31 135.72 169.34 275.92 200.46 221.13 178.3 276.42 228.6 149.17 270.69 180.79 148.92 165.35 208.18 166.1 176.56 183.53 189.76 211.42 287.87 157.13 E.58
Wire Feed Rate (m/min) 8.94 9.07 7.97 7.9 8.57 9.14 8.07 8.97 8.52 7.2 7.99 6.83 6.07 8.83 7.62 7.63 8.13 8.79 7.73 6.42 7.7 9.47 8.35 6.63 6.6 9.51 9.19 9.34 8.52 9.82 9.86 7.62 9.62 8.97 7.03 7.62 8.28 7.55 7.29 7.68 7.46 8.81 10.05 8.2
Appendix E Sample No. 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176
Voltage (VOLTS) 30.58 7.08 29.24 30.52 5.25 5.13 5.92 6.1 30.21 30.4 30.64 30.03 30.52 29.11 7.02 5.98 30.52 27.95 6.96 6.16 30.27 6.35 5.98 25.27 25.21 29.79 28.38 29.36 31.01 27.4 26.67 24.54 28.38 26.06 27.04 29.54 31.07 30.82 9.34 30.76 29.17 27.28 25.94 5.25
Current (AMPERES) 175.81 145.93 139.2 136.71 170.58 171.08 158.88 153.9 220.88 205.44 227.36 156.88 232.09 280.9 156.39 155.14 142.69 152.9 156.88 149.41 241.55 165.6 154.15 314.27 235.08 220.39 225.37 149.66 143.19 147.17 181.54 190.25 127 231.09 174.07 132.98 139.7 142.94 147.42 140.45 251.26 213.66 176.31 161.37 E.59
Wire Feed Rate (m/min) 7.69 7.02 6.33 6.4 7.18 7.25 6.66 6.63 7.87 8.4 8.93 7.78 8.79 10.71 8.16 7.35 6.46 6.6 6.96 6.49 9.15 7.66 6.68 10.3 9.69 9.57 9.41 7.7 6.98 6.51 7.56 7.52 6.68 7.9 7.51 6.66 6.27 6.36 6.26 6.15 8.55 9.35 8.1 7.48
Appendix E Sample No. 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220
Voltage (VOLTS) 21.42 7.63 30.64 29.85 28.44 28.56 26.49 29.17 26.43 25.63 28.38 31.8 7.2 30.88 30.64 25.02 25.57 5.62 26.49 27.59 29.66 7.14 22.89 30.46 26.31 25.45 26.55 28.32 28.5 30.03 24.29 26.79 25.88 27.04 25.57 27.59 6.47 30.58 29.48 28.56 32.47 28.56 23.8 5.25
Current (AMPERES) 162.11 146.18 182.04 192.5 216.9 254 247.78 270.44 185.27 273.18 270.44 147.42 150.41 142.69 151.41 171.83 178.8 171.83 250.02 245.54 237.82 148.67 149.41 141.94 177.06 197.72 218.14 135.22 174.07 135.72 197.23 210.42 176.06 248.77 219.14 163.61 147.67 147.67 237.57 222.88 150.16 134.72 281.15 168.34 E.60
Wire Feed Rate (m/min) 6.84 6.45 7.04 7.73 8.48 9.86 9.9 11.33 9.32 9.89 10.96 8.05 7.17 6.52 6.67 6.94 7.79 7.33 8.64 9.85 9.74 8.04 6.86 6.81 7.42 7.42 8.17 7.1 7.09 6.7 7.5 8.97 7.61 8.98 9.01 8.12 7.16 6.41 8.4 8.91 7.14 6.65 9.66 7.88
Appendix E Sample No. 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256
Voltage (VOLTS) 26.06 31.13 25.51 25.57 28.32 26.37 28.69 6.9 25.21 25.76 5.86 31.01 30.76 27.34 26 25.63 7.39 32.35 26.86 29.97 29.48 31.13 26.37 5.55 27.53 27.53 31.43 26.49 26.31 26.18 25.94 5.25 26.25 7.39 27.89 27.22
Current (AMPERES) 231.09 145.43 171.33 270.94 264.71 211.67 129.99 171.33 169.34 220.63 229.6 140.2 286.88 238.81 194.24 166.1 152.65 168.34 213.41 136.71 222.63 142.69 199.47 167.59 300.82 135.72 153.65 173.07 212.67 185.27 173.07 163.36 178.3 154.39 268.95 269.94
Wire Feed Rate (m/min) 9.09 7.87 7.93 9.16 10.72 9.55 7.09 7.53 7.52 8.15 8.97 7.03 9.9 10.65 8.98 7.58 6.9 8.07 7.41 6.61 8.19 7.02 8.48 7.45 10 7.64 7.08 6.88 8.36 8.48 7.94 7.51 7.03 6.7 9.05 10.23
These samples are just a small portion of the total measured welding parameters utilised during breathing zone concentration trials. These results highlight the trend of the welding process.
E.61
