February 2005

Outline Fluid Film Thrust Bearings: Fundamentals, Damage Evaluation, & Repair VIBRATION INSTITUTE MEETING CHARLOTTE, NC Pioneer Motor Bearing May 2006

n Basic

Design Criteria n Thrust Bearing Monitoring n Damage investigation n Damage mechanisms n Inspection n Repair

(c) 2006, Pioneer Motor Bearing Company

(c) 2006, Pioneer Motor Bearing Company

History

History

n Without

n However,

question the most significant mechanical invention in the world was:

Slide 2

almost immediately upon discovery of the wheel, the need for bearings was also discovered:

The Wheel

(c) 2006, Pioneer Motor Bearing Company

Slide 3

(c) 2006, Pioneer Motor Bearing Company

History

History

n Which

n As

has led to one of the most elusive searches in human history

Slide 4

one can observe from this wooden wheel dating to 2700 BC, axels where used to allow support by radial and thrust bearings:

(c) 2006, Pioneer Motor Bearing Company

Slide 5

(c) 2006, Pioneer Motor Bearing Company

Slide 6

1

February 2005

Load Orientations: radial/thrust

Thrust Bearing n Support n e.g.

axial load from the process

Water or steam pressure

n Thrust

runner surface

n Generally

flat ( 1000 psi) psi) at the location of the highest loading n Hydrostatic film is developed through pressure, film thickness is controlled by flow n Quite often, many bearings are fed by a common high pressure header (c) 2006, Pioneer Motor Bearing Company

Slide 34

Hydrostatic Lift System

Hydrostatic Lift System n Introduce

externallyexternally-pressurized oil into bearing cavity for operation at low surface speeds and high loads n Forms

hydrostatic bearing on lower half

Hydrostatic lift in tilting pad thrust shoes. (c) 2006, Pioneer Motor Bearing Company

Slide 35

(c) 2006, Pioneer Motor Bearing Company

Slide 36

6

February 2005

Sample Hydrostatic Lift Oil System Schematic of TurbineTurbineGenerator Hydrostatic Lift System

Main oil pump is shaft driven

AC & DC pumps

Each radial bearing #3#3-8 has a separate pressurized hydrostatichydrostaticlift supply (1500 psig), separate supply pump with a gravity (or slight vacuum) drain back to the reservoir.

(c) 2006, Pioneer Motor Bearing Company

upgrading specific design features of the assembly n Directed lubrication n Alternative materials n Offset pivots

(c) 2006, Pioneer Motor Bearing Company

Slide 39

n Temperature

(c) 2006, Pioneer Motor Bearing Company

Slide 40

Thrust Temperature Monitoring n Embedded

n Load

Sensors

n Thermocouples

Collar Position

n RTD’ RTD’s

n Oil

(c) 2006, Pioneer Motor Bearing Company

Slide 38

Effect of ChromeChrome-Copper Alloy Backing Material

Thrust Bearing Monitoring n Thrust

n Consider

Slide 37

Effect of Pivot Offset

(c) 2006, Pioneer Motor Bearing Company

OK smart guy, I’ I’ve already got a tilting pad thrust bearing, Now what?

Slide 41

Inlet and Exit Temperature

(c) 2006, Pioneer Motor Bearing Company

Slide 42

7

February 2005

Tilt-Pad Thrust Profiles

Embedded Sensors n Proper

Temperature profiles show influence of pressure peak over the pivot (dashed circle), as well as radial and circumferential flow. (c) 2006, Pioneer Motor Bearing Company

Location

Ref. Kingsbury sales literature, EQHEQH-1.

Slide 43

(c) 2006, Pioneer Motor Bearing Company

Slide 44

Thrust Load Measurement

Thrust Load Measurement

n Basic

n Leveling

Bearing Design

(c) 2006, Pioneer Motor Bearing Company

Slide 45

Plates

(c) 2006, Pioneer Motor Bearing Company

Slide 46

Thrust Load Measurement

Thrust Position Measurement

n Strain

n Eddy

Current Probes n Dual Voting

Gage Load Cell

(c) 2006, Pioneer Motor Bearing Company

Slide 47

(c) 2006, Pioneer Motor Bearing Company

Slide 48

8

February 2005

Thrust Position Measurement

Damage Investigation n Generic

Elements

n Visual

examination n Background information n Photographic records n Event reconstruction n Laboratory analysis

Slide 49

(c) 2006, Pioneer Motor Bearing Company

Damage Investigation

(c) 2006, Pioneer Motor Bearing Company

Slide 50

Damage Investigation

n Visual

Examination

n Generic

Elements

n Visual “Say, is all that babbitt supposed to be on the bottom of the bearing housing like that?” that?”

(c) 2006, Pioneer Motor Bearing Company

examination n Background information n Photographic records n Event reconstruction n Laboratory analysis

Slide 51

Visual Examination

(c) 2006, Pioneer Motor Bearing Company

Slide 52

Where is the damage? n Babbitt

Surface

n Centered

over pivot n More toward trailing edge n More toward leading edge n Supporting n Leveling

n Thrust

(c) 2006, Pioneer Motor Bearing Company

Slide 53

structure

plates

collar

(c) 2006, Pioneer Motor Bearing Company

Slide 54

9

February 2005

Babbitt Surface Damage

Damage located primarily along the trailing edge is indicative of of debris, electrolysis, or other trauma that occurred while the bearing was was otherwise operating in a normal condition

(c) 2006, Pioneer Motor Bearing Company

Babbitt Surface Damage

Damage located primarily opposite the pivot is indicative the bearing bearing operating in an overloaded condition

Slide 55

Babbitt Surface Damage

(c) 2006, Pioneer Motor Bearing Company

Slide 56

Support Structure Damage n Damage

to the leveling plates, base ring, or other support structure is usually indicative of thrust collar runout problems n Collar may be installed improperly, or may have come loose in service Damage located primarily along the leading edge is indicative of a lack of lubrication, either during start up, or during operation

(c) 2006, Pioneer Motor Bearing Company

Slide 57

(c) 2006, Pioneer Motor Bearing Company

Collar Damage

Damage Mechanisms

n Circumferential

n Mechanisms

scoring or scratching of the thrust collar is usually indicative of debris in the oil system

(c) 2006, Pioneer Motor Bearing Company

Slide 59

Slide 58

are the same as those covered earlier by Dr. Branagan n Specific thrust bearing photographs may help

(c) 2006, Pioneer Motor Bearing Company

Slide 60

10

February 2005

Minor Overload

(c) 2006, Pioneer Motor Bearing Company

Babbitt Fatigue

Slide 61

Overheating

(c) 2006, Pioneer Motor Bearing Company

Slide 62

Gross Overheating

Slide 63

Anisotropy

(c) 2006, Pioneer Motor Bearing Company

(c) 2006, Pioneer Motor Bearing Company

(c) 2006, Pioneer Motor Bearing Company

Slide 64

Tin / Copper Migration

Slide 65

(c) 2006, Pioneer Motor Bearing Company

Slide 66

11

February 2005

Pivot Fretting

(c) 2006, Pioneer Motor Bearing Company

Leveling Plate Fretting

Slide 67

Babbitt Erosion

(c) 2006, Pioneer Motor Bearing Company

Slide 68

Bearing Inspection n Bearing

Surface Subsurface n Thrust Collar n Assembled End Play n Bearing

(c) 2006, Pioneer Motor Bearing Company

Slide 69

(c) 2006, Pioneer Motor Bearing Company

Slide 70

Thrust Bearing Surface

Thrust Bearing Subsurface

n Portion

n Ultrasonic

of bearing designed to carry the load must be clean and flat n Inspect for embedded debris with a single edged razor blade n Inspect surface with straight edge n Inspect contact with Prussian bluing with a calibrated plate and finally with the mating thrust collar (c) 2006, Pioneer Motor Bearing Company

Slide 71

Inspection n Dye Pen Inspection n Brass Dowel Ring Test

(c) 2006, Pioneer Motor Bearing Company

Slide 72

12

February 2005

Thrust Collar Inspection

Assembled Runout Check

n Surface

n Can

finish 16 RMS or better n Surface flatness less than .001 inch n Assembled runout less than .001 TIR

(c) 2006, Pioneer Motor Bearing Company

not be measured with a single indicator as rotor float will impact measurement n Temporary blocking may be required to limit rotor float during inspection n Requires 2 Mag base indicators with sufficient travel to stay in contact with collar face

Slide 73

Indicator position

(c) 2006, Pioneer Motor Bearing Company

Slide 74

Typical Measurement record Rotation

A

B

0

0.0000

-0.0010

45

0.0015

-0.0005

0.0020

90

0.0060

0.0050

0.0010

135

0.0030

0.0030

0.0000

180

0.0010

A-B

0.0020

0.0010

-0.0010

225

0.0005

0.0025

-0.0020

270

-0.0020

-0.0010

-0.0010

315

-0.0010

-0.0010

0.0000

360

0.0030

0.0020

0.0010

Column of calculated AA-B values gives twice the TIR runout readings for the thrust collar. In this example, the collar is running out .002 TIR

(c) 2006, Pioneer Motor Bearing Company

Slide 75

(c) 2006, Pioneer Motor Bearing Company

Assembled End Play

Repairs

n Best

n Many

to first measure available space and stacked height of the bearing assemblies n Difference should be the assembled end play n After assembly, bump test the rotor to confirm measurement

(c) 2006, Pioneer Motor Bearing Company

Slide 77

Slide 76

minor thrust bearing repairs can be accomplished on site n The level of repair that should be attempted is directly proportional to the experience level of the technicians available

(c) 2006, Pioneer Motor Bearing Company

Slide 78

13

February 2005

Babbitt Surface Repairs n

n

Babbitt Puddling

Minor imperfections can be removed by lapping or scraping Larger scratches can be repaired by first locally puddling babbitt and followed by peening and then lapping or scraping

(c) 2006, Pioneer Motor Bearing Company

Slide 79

Hand Scraping

(c) 2006, Pioneer Motor Bearing Company

(c) 2006, Pioneer Motor Bearing Company

Power Scraping

Slide 81

(c) 2006, Pioneer Motor Bearing Company

Thrust Collar Repair

Conclusions

n Minor

n Remember

damage and glazing can be repaired by hand stoning n Use a fine 600 grit oil stone n More serious repairs can be corrected by turning, lapping, or grinding n Many of these operations can be conducted in place (c) 2006, Pioneer Motor Bearing Company

Slide 80

Slide 83

Slide 82

that that the babbitt surface is a SOFT, sacrificial layer. n Look at your babbitt surface to better understand the likely cause of the bearing damage and reduce rere-occurrence. n Remanufacture (repair) or redesign bearing depending on the nature, severity, and probability of future damage. (c) 2006, Pioneer Motor Bearing Company

Slide 84

14