GE Oil & Gas
Heavy Duty Gas Turbine Monitoring & Protection Bently Nevada* Asset Condition Monitoring Table of Contents 1 Purpose......................................................................................................2
7 Protection /Management Systems..................................................... 18
2 Scope..........................................................................................................2
7.1 3500 Series Monitoring System Overview................................................18
3 References.................................................................................................2
7.2 3500 Vibration/Thrust/Temperature/Dynamic Pressure...................18
4 Basic Operation of the Heavy Duty Gas Turbine.................................3
7.3 3701 Protection/Monitoring System.............................................................28
5 Transducer Overview...............................................................................4
7.3.1 Overview of System................................................................................28
5.1 Measured Parameters.............................................................................................4
7.3.2 System Components..............................................................................29
5.2 General Installation Considerations................................................................5
7.4 Bently Nevada Configuration Application.................................................32
5.3 Sensor Signal Path Recommendations...........................................................5
7.5 Management System............................................................................................36
6 Gas Turbine Measurements....................................................................6
8 Related Systems for Consideration ................................................... 39
6.1 Keyphasor Probe for Speed & Phase Measurements.............................6
9 Appendix 1 – Thrust Voting Considerations..................................... 40
6.2 Overspeed Fundamentals.....................................................................................6
10 Appendix 2 – Voting Truth Tables....................................................... 42
6.3 Thrust Transducers – Fluid Film Thrust Bearings......................................9 6.4 Radial and Thrust Bearing Temperature........................................................9 6.5 Vibration Transducers – Radial Journal Bearings...................................11 6.6 Bearing Housing Vibration.................................................................................12 6.7 Lube Oil Temperature...........................................................................................13 6.8 Combustor Monitoring.........................................................................................13 6.9 Exhaust Gas Temperature..................................................................................14 6.10 Process Variable Measurements....................................................................16
application note
application note 1 Purpose The purpose of this document is to identify best practices and recommendations for the selection and installation of Bently Nevada transducers, monitoring, protection, and management systems on heavy duty gas turbines. These recommendations apply to both new and existing machines targeted for retrofit installations.
2 Scope The scope of this document is limited to applications for heavy duty gas turbine mechanical systems, and addresses those gas turbines specifically with a single shaft. The recommendations contained herein can be extended to multi-rotor heavy duty gas turbine utilizing the relevant sections for the additional mechanical components. This best practice is not applicable to aeroderivative gas turbines, which are covered in a separate document. The single rotor gas turbine (GT), as the name implies, contains both the GT compressor section and GT turbine section on the same single rotor that is mechanically coupled directly to the driven equipment such as a gearbox and electrical generator. In the case of the two rotor design, the same configuration of compressor and turbine on the first rotor (also known as the
gas generator) coexists with a second rotor which supports the GT power turbine (also known as the reaction turbine) that is driven by the exhaust gas from the gas generator section. The GT power turbine is mechanically coupled to the driven component such as a compressor, pump, or generator. In the case of the single rotor and two rotor designs, these heavy duty gas turbines typically use fluid film sleeve or tilt pad bearings. The recommended products are based on those available at the time of this writing. As new technologies become available, they should be evaluated for application.
3 References 1.
American Petroleum Institute (API) Standard 670 Machinery Protection Systems, Fifth Edition, November 2014, American Petroleum Institute
2.
API Standard 616 Gas Turbines for the Petroleum, Chemical and Gas Industry Services Fifth Edition, January 2011, American Petroleum Institute
3.
International Organization for Standardization (ISO) Standard 7919-4 Mechanical vibration of non-reciprocating machines – Measurements on rotating shafts and evaluation criteria – Part 4 Gas Turbine Sets, 1996 E.
4.
Gas Turbine Engineering Handbook, 4th Edition, Meherwan P. Boyce
GE Frame 7 Heavy Duty Gas Turbine
2
application note 4 Basic Operation of the Heavy Duty Gas Turbine A gas turbine is an internal combustion rotary engine that converts fuel into mechanical output power to drive equipment such as electric generators, pumps, and compressors. Gas turbines are widely used in the power generation and the oil and gas industry in production, midstream and downstream applications. A typical gas turbine contains three main sections: the compressor, the combustor, and the turbine. The compressor is connected to the turbine by the same rotor.
The basic functions of the three sections are: 1.
Compressor – Compresses the incoming atmosphere to a high pressure into the combustion area.
2.
Combustion area – Mixes a fuel with the compressed atmospheric air and burns the air - fuel mixture and produces high-pressure, high-velocity gas that passes through the turbine section.
3.
Turbine (Expander) – Extracts the energy from the highpressure, high-velocity gas flowing from the combustion chamber. The extracted energy is converted to a mechanical output resulting in the rotation of the turbine rotor.
The mechanical output of the turbine rotor is used to drive the driven machine directly or sometimes through a gear box. The mechanical output also drives the compressor section of the gas turbine which brings in high-pressure air to mix with the fuel for combustion to continue the cycle over again. Roughly 50 percent (ranging from 40 to 80 percent) of the power generated by the turbine section is consumed by the compressor.
External power is required to get the compressor section rotating before the combustion section and turbine section can perform their tasks. The startup of a gas turbine is often accomplished with an external starting mechanism such as an electric motor or hydraulic motor, which is temporarily applied to initially turn the gas turbine rotor. The gas turbine (compressor and turbine) rotor is accelerated to approximately 20 to 25 percent of rated speed before the combustor is fired. Then an additional 40 to 60 percent of the rated speed is necessary for the gas turbine to fully start and become self-sustaining. This cranking of the gas turbine is also held for a period of a few minutes to purge the gas turbine of any possible unwanted gases that may be in the turbine. A wide variety of fuel types can be used, such as natural gas, diesel oil, residual oils, crude oil, syngas from refineries, and the gasification of solid fuels such as coal and other organic matter. The fuel type governs the need for any fuel treatment skids, and the combustor design needs to also be matched to the fuel type for proper combustion. The formal name of the thermodynamic process is as the Brayton Cycle. This cycle can be broken down into three individual thermodynamic processes know as isentropic compression, isobaric (constant pressure) combustion, and isentropic expansion. The gas turbine is a fairly complex system operating at high speeds and high temperatures that place significant demands on the direct mechanical system and support systems. As such, the gas turbine can benefit from protection and condition monitoring systems to identify problematic conditions, avoid significant machine damage, and enable planned maintenance to be performed.
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application note 5 Transducer Overview 5.1 Measured Parameters The following table summarizes the transducer selection for heavy-duty gas turbines:
1
Measurement
Sensor
Location
Monitor
Rotor radial vibration
Proximity probes
Best mounted on the bearing face or bearing support in an orthogonal pair
3500/42 or 3701/40
Bearing housing vibration
High temperature seismic
Best mounted on the bearing housing in an orthogonal pair
3500/42 or 3701/40
Rotor axial (thrust) position
Proximity probes
Mounted parallel to the rotor with a minimum target surface of 0.6 inches or 16 mm
3500/42 or 3701/40
Rotor axial (thrust) vibration
Proximity probes
Used for thrust bearing diagnostics and surge detection
3500/42 or 3701/40
Combustion dynamics
High temperature dynamic pressure sensor
Mounted on each of the combustor cans, radially mounted for annular combustors, one each for silo combustors
3500/64 or 3701/40 or 3701/442
Radial bearing temperature
RTD/TC
Two measurements in the upper half and 2 in the lower half
3500/60 3500/61
Axial bearing temperature
RTD/TC
Four measurements radially spaced on active and inactive bearings
3500/60 3500/61
Phase reference
Proximity probes
Physical reference of the rotor speed and vibration phase (Keyphasor signal)
3500/25 or 3701/40
Exhaust gas temperature
RTD/TC
Minimum of one measurement per combustor can
3500/60 3500/61
Lube oil supply
RTD/TC
For each lube oil supply
3500/60 3500/61
Lube oil drain temperature
RTD/TC
One measurement per oil drain
3500/60 3500/61
Tachometer
Proximity probes
Phase reference can be fed to the tachometer
3500/50 or 3701/40
Blade Health
Magnetic pickup
Measures the timing of the blade tips to look for blade structural problems
3701/68
Overspeed
Proximity probe or magnetic pickup1
Three probes in an array to detect a rotor overspeed condition
3500/533 or 3701/55
The sensor selection is dependent on speed wheel geometry. Proximity probes are recommended for a square tooth wheel of appropriate dimensions. When the target is a trapezoidal gear tooth, a magnetic pickup may provide the best speed signal (see the Overspeed Detection Application Guide for further details on speed target requirements.)
Supported by the ADAPT 3701/40 and /44 Aero Monitor only
2 3
4
The 3500/53 product has been included in this application guide to support our existing installed base where the 3500/53 product is in operation. The 3500/53 is no longer available for new installations and 3701/55 ADAPT.ESD should be considered for all Bently Nevada Overspeed Detection and Emergency Shutdown applications moving forward.
application note
5.2 General Installation Considerations Sensors need be installed per original equipment manufacturer (OEM) approved methods to avoid damage to bearings or other critical components. The API 670 standard for sensor installation can be applied for gas turbines. Standardizing on 1.0 meter or 0.5 meter proximity probe lengths can cut down on the number of extension cables that need to be stocked for spares. Using the Extended Temperature Range (ETR) proximity probe systems with FluidLoc* cable sealing increases the life of the probe system in many gas turbine applications. Probe replacements for obsolete parts should be done carefully; some older parts have a different thread pitch than the current models. If bracket or “quill” replacement is necessary, the bearing housing must be removed in many cases. For “hot end” bearings, choose sensor cable exits and routing carefully to avoid temperatures above the product ratings. Sensor extension cable routing out via the bearing lube oil drain line has been incorporated in some designs. FluidLoc should be used when routing cables in the bearing lube oil drain as oil can wick up the probe cables. Since some synthetic turbine lubricants have additives that can attack certain materials used for o-rings and seals, be sure to check compatibility prior to installation. Protect the probe to extension cable connection and insulate it from the ground using either the connector protection kits or 3M stretch tape. For simplified installation and component replacement, mount the proximity sensors in a DIN-rail and the junction block in junction boxes. Leave room in the junction box to coil excess proximity extension cables as they are built to an electrical length and cannot be cut to length.
Instrument air should be run into any junction box that will exceed 85° (185° F). Ambient temperature plus machine temperature at the mounting location should be considered. Process data points do not need to be replicated, but can be imported from the distributed control system (DCS) or plant historian.
5.3 Sensor Signal Path Recommendations The recommendation for wiring of the sensor back to the monitoring system and the control system depends on where the shutdown functions will be executed. ONLY buffered outputs, Modbus*, Ethernet Global Data (EGD), or 4-20 mA loops should be used to interface between the control system and GE’s Bently Nevada system. Avoid splitting the signal directly from the sensor as signal loading can degrade the signal and may introduce an additional potential point of failure. If the tripping function is done through the relays of the Bently Nevada system then the sensors should be wired to the Bently Nevada system and then to the control system for operator indication. If the tripping function is done in the control system then the sensors should be wired to the control system first then buffered outputs taken to the Bently Nevada system for condition monitoring.
Instrument Diagnostics: Every Gas Turbine 3500 or 3701 instrumentation package has extensive self-testing that is performed continuously. Self-test failures are displayed to the end user in several ways, such as the green OK LED being extinguished or the instrument rack OK relay/ protection fault (normally energized) changing state, in the operator display (if supplied) and in the monitor events list. It is extremely important that end users are aware of and take advantage of these self-test indicators so that instrumentation problems can be addressed before a false or missed alarm event occurs.
5
application note 6 Gas Turbine Measurements
Component
Description
MFR Part Number
Sensor
Bently Nevada 3300XL 8mm proximity probe system (probe, extension cable, Proximitor sensor)
Typical
6.1 Keyphasor Probe for Speed & Phase Measurements A Keyphasor* transducer is necessary for accurate speed and phase information. It must be mounted on the rotor of the driver machine. The target notch or protrusion should be suitable to generate the correct signal during all machine operating states, however the machinery manufacturer should confirm that an appropriated Keyphasor target is provided. •
•
At least one non-contact proximity transducer should be installed for once-per-rev phase reference measurements. For machines with internally mounted transducers, a spare Keyphasor transducer should be installed, with extension lead delivered to the transducer interface housing, external to the machine. As per API 670, the Keyphasor probe should be located near the thrust bearing. At this location, the thermal growth of the rotor is reduced, and mounting at this location helps ensure the notch or protrusion target does not move out of view of the probe. For machines with multiple rotors, each rotor requires its own Keyphasor probe.
33010X-aa-bb-cc-dd-ee 330130-aaa-bb-cc (ext. cable) 330180-aa-bb (Proximitor sensor)
Probe Housing
Bently Nevada explosion-proof stainless steel probe housing assembly
CA24701-aa-bb-cc
Alternative housing may be selected when explosion-proof rating is not required. Standard housing part number: 31000 or 21000 or 24701-aa-bb-cc-ddd-ee-ff Monitor
Bently Nevada 3500/25 Keyphasor Module
3500/25-aa-bb-cc
Monitor1
Bently Nevada 3500/50 Tachometer Module
3500/50-aa-01-cc
Note: When applicable, all components are supplied with “multiapprovals” to ensure complete hazardous area documentation is supplied with the order. The Tachometer module may be used in lieu of the Keyphasor module when advanced speed monitoring functionality is needed. The system vendor should provide recommended installation instructions as required.
1
If the routing for these proximity probe cables passes through an environment that exceeds 177° C (350° F), Extended temperature range (ETR) probes must be substituted for all speed or tachometer sensors. ETR probes have a a maximum rating of 260° C (500° F). Filtering – Not applicable Units – Speed and phase Machine Shutdown – Condition monitoring application only Note: A Keyphasor signal is a once-per-turn or multiple-eventper-turn pulse from a rotating shaft or gear used to provide a precise timing measurement. This allows 3500 monitor modules and external diagnostic equipment to measure shaft rotative speed and vector parameters such as 1X vibration amplitude and phase. The installation of a spare Keyphasor sensor is highly recommended because the Keyphasor is a vital element in performing machine management and diagnostics. It is a recommended practice, where possible, to input the Keyphasor signal(s) into one channel(s) of a 3500/42 monitor to allow capture of the Keyphasor signal waveform(s). The 3701 system has waveform capability for the speed and Keyphasor signals. Items listed in the following table meet this best practice. The specific ordering details of thread size and probe length should be confirmed in collaboration with the machinery manufacturer.
6
6.2 Overspeed Fundamentals Overview Overspeed of critical machines due to operational error or other system failures is a serious personnel safety risk and can cause catastrophic damage to the machinery and the plant. Since overspeed is one of the most dangerous conditions that can occur in a turbine, it is essential that overspeed protection systems are properly installed. GE’s Bently Nevada product line includes eddy current proximity transducers and monitors that constitute an electronic overspeed detection system. Such a detection system is one part of an overall overspeed protection system. (See separate Overspeed Protection Application Guide for more details.)
application note •
An Overspeed Protection System (OPS) is the complete electro-mechanical system (hydraulic-mechanical or electro-pneumatic) that senses the onset of an overspeed condition and automatically shuts the unit down by closing (or opening) valves, solenoids, and other devices necessary to bring the unit to a safe halt (see Appendix C).
•
An Overspeed Detection System (ODS) is one part of the larger OPS. It is responsible only for sensing the onset of overspeed and providing a signal suitable for triggering the rest of the OPS, which then removes energy from the machine and brings it to a safe halt. The ODS supplies this signal in the form of activation of one or more electrical relays.
mounted in the same axial plane, but with an angular offset. Three corresponding overspeed detection monitors should also be supplied. The speed sensing surface should never be located on an auxiliary rotor where there is an intervening gearbox or coupling that could potentially fail, isolating the speed sensing surface from the actual machine speed. •
If there’s enough room/physical space an additional/spare probe can be installed for use in case an operational probe fails. The additional probe should be installed with the extension cable and Proximitor sensor, so the end user can just move the field wiring cable from the Proximitor sensor related to the failed transducer to the Proximitor sensor of the additional/spare probe.
•
The speed signal must meet speed sensing signal quality at all operating speeds. This is done by qualifying the proposed installation using the Commercial Quotation Tool. It is advisable to observe the output signal of the transducer during commissioning. Keep in mind that a magnetic pickups performance improves with machine speed, and is unusable at slow speeds, while a proximity probe performs better at lower speed and the performance may degrade as speed increases. Magnetic pickups are a simpler design and less likely to fail; however, the failure modes are not visible. Proximity probes are more complicated, however almost all failure modes are guaranteed to be detected.
•
The ODS speed sensors must always observe the driver machine on the main rotor. No secondary rotors or gears are allowed, and sensors must not be placed on the driven side of any coupling. In some cases, the power turbine is also equipped with an ODS, because it can also experience overspeed conditions.
•
The turbine control system is the primary overspeed protection system. The 3500/53 or 3701/55 overspeed detection systems are part of the emergency backup to the primary control system overspeed protection in the event of a control system failure. End users may elect to remove the mechanical overspeed bolt upon the successful installation and qualification of the emergency backup overspeed protection system.
•
The 4-20 mA output must NEVER be used to control the speed of the machine. It is designed to provide speed trending information only.
•
Keyphasor signals (single notch speed signals) are NOT to be used for closed loop control or overspeed protection.
•
The overspeed detection system operates independently of the rest of the monitoring system, therefore a separate phase-reference Keyphasor or Tachometer system is required.
Overspeed Detection System A SIL-3 rated electronic overspeed detection system can be provided if the end user requires a SIL-3 certified installation. API 670 calls for a segregated electronic overspeed detection system with three independent sensors, monitors and relays, with a 40-millisecond or faster response time. This means that a dedicated rack with 3500/53 ODS monitors or a 3701/55 ADAPT Emergency Shutdown Device (ESD) should be applied for overspeed detection. The rotor target may be a multi-event wheel, but approval for the speed detection and probe mounting arrangement must be obtained by using of the Commercial Quotation Tool – Big Machines where the quality of the speed signal can be evaluated.
Note: Although 3500 and 3701 systems are capable of monitoring other variables such as vibration and thrust position, as well as overspeed, a dedicated ODS is highly recommended as the best practice. Gas turbines must have a two-out-of-three (2oo3) voting logic Triple Modular Redundant Overspeed Protection System. This entails three probes, three Proximitor sensors, and three 3500/53 channels or one 3701/55 ESD system with three processor modules and three relay modules installed. Best practices for specifying a ODS are: •
The governor speed sensors should be independent of the ODS speed sensors.
•
Three proximity transducers or magnetic pickups should be installed on the driver of each machine train
The following items meet this Specification. The specific ordering details of thread size and probe length need to be confirmed in collaboration with the machinery manufacturer.
7
application note Transducer Installation for Electronic Overspeed Detection System Two options are currently available for overspeed detection – the 3500/53 system and the 3701/55 system.
Or
Component
Description
MFR Part Number
Component
Description
MFR Part Number
Sensor
Bently Nevada 3300XL 8mm Proximity probe system (probe, extension cable, proximitor sensor)
330101/330103AA-BB-CC-DD-EE (typical)
Sensor
Bently Nevada 3300XL 8mm proximity probe system (probe, extension cable, Proximitor sensor)
330101/330103AA-BB-CC-DD-EE (typical)
Or Sensor
Magnetic pickup
Probe Housing
Bently Nevada explosion-proof stainless steel probe housing assembly
Or CA24701AA-BB-CC (if applicable)
Sensor
Magnetic pickup
Probe Housing
Bently Nevada explosion-proof stainless steel probe housing assembly
Alternative housing may be selected when explosion-proof rating is not required. Standard housing part number: 31000 or 21000 or 24701-aa-bb-cc-ddd-ee-ff Monitor
Bently Nevada 3500/53 Overspeed Detection Module in triple modular redundant (TMR)
3500/53-03-01
Note: When applicable, all components are supplied with “multi-approvals.” If the routing for these proximity probe cables passes through an environment which reaches 177° C (350° F) during operation, extended temperature range probes and extension cables must be substituted for all speed or tachometer sensors. (See related documents.)
8
CA24701AA-BB-CC (if applicable)
Alternative housing may be selected when explosion-proof rating is not required. Standard housing part number: 31000 or 21000 or 24701-aa-bb-cc-ddd-ee-ff Monitor
Bently Nevada 3701/55 Emergency Shutdown Device
3701/55 ESD
Note: When applicable, all components are supplied with “multi-approvals.” If the routing for these proximity probe cables passes through an environment which reaches 177° C (350° F) during operation, extended temperature range probes and extension cables must be substituted for all speed or tachometer sensors. (See related documents.) •
Filtering – Not applicable
•
Units – Speed and peak speed in RPM
•
Machine Shutdown – Yes, a shutdown application
application note 6.3 Thrust Transducers – Fluid Film Thrust Bearings A thrust bearing failure can lead quickly to major machine failure. API 670 recommends the installation of dual thrust transducers at each thrust bearing in order to detect thrust bearing degradation and/or failure. For SIL-3 rated applications, three probes should be installed and connected to triple modular redundant monitors.
The following items meet this best practice. The specific ordering details of thread size and probe length should be confirmed in collaboration with the machinery manufacturer. Component
Description
MFR Part Number
Sensor
Bently Nevada 3300XL 8mm proximity probe system (probe, extension cable, Proximitor sensor)
Typical
Probe Housing
The preferred mounting arrangement for the thrust probes is directly through the thrust bearing; however, the machine design does not always permit this. Thrust probe installation may also be engineered to observe the end of the rotor (within 300 mm of the thrust collar), or another collar on the rotor within a similar proximity to the thrust bearing.
33010X-aa-bb-cc-dd-ee 330130-aaa-bb-cc (ext. cable) 330180-aa-bb (Proximitor sensor)
Bently Nevada stainless 21022-aa-bb-cc steel dual axial probe housing assembly (or equivalent)1
Alternative housing may be selected when physical limitations prevent the use of the recommended housing. Monitor
Bently Nevada 3500/42M Proximity Seismic Monitor
3500/42M-aa-bb or 3701/40
Best practices for specifying thrust monitoring include:
Note: When applicable, all components are supplied with “multi-approvals.”
•
1 If housing is needed
•
Two non-contact proximity displacement transducers in a dual-voting configuration to be installed in accordance with API Latest Edition, at each hydrodynamic thrust bearing. For a SIL-3 rated installation, three probes must be installed in a 2oo3 voting configuration. Thrust Bearing Monitoring: Unless otherwise stated, axial position (thrust) modules should be provided in dual redundant configuration. Many years of field experience has shown that the best practice is dual voting thrust (2oo2 logic) for shutdown. This voting requires both sensors to exceed their danger setpoint to initiate a shutdown. API STD 670 section 7 covers this consideration in detail. Note 1: When dual voting is applied, if the two channels show different readings, immediate action should be taken to determine root cause driving the difference and corrective action taken. Note 2: When dual voting thrust is applied, a channel “Not OK” caused by a transducer fault will drive that channel’s alarms, resulting in a vote for shutdown. A second vote from the remaining channel will activate the shutdown relay. (API 670 7.4.2.5 b). Note 3: The end user is encouraged to thoroughly understand and verify voting logic at the time of commissioning and after any change in configuration. Note 4: Installation, calibration and setup should only be done by qualified and experienced personnel. Improper installation may compromise safe operation and require a machine shutdown to correct the installation.
(See appendix for further discussion on voting.)
•
Filtering – Not applicable
•
Units – Displacement
•
Machine Shutdown – Yes, typically a shutdown application
6.4 Radial and Thrust Bearing Temperature Radial Bearing Temperature Monitoring Benefits – Elevated radial bearing temperature can indicate problems related to fluid-film journal bearings, including overload, bearing metal fatigue, insufficient or no lubrication, or contaminated lubricant. Measuring radial bearing temperatures and correlating them with other process variables can assist in determining the overall condition of the machine. Applications – For fluid-film journal bearings, API 670 specifies the number of sensors to use and how to apply them based on the length to diameter ratio of the bearing. API 670 also specifies the sensor application for tilting pad bearings. The sensors should be spring loaded to assure good contact between the sensor and bearing metal. It is strongly recommended that transmitters not be used because they decrease system reliability. The most common temperature sensor types are resistance temperature detectors (RTDs) and thermocouples (TCs). The RTD functions as a change of resistance for changes in temperature. This temperature sensitive variable resistor is then used as a component in the monitoring channel circuitry. The TC comprises two dissimilar metals that create a very small electromotive force (EMF) or voltage that is then input measured by the monitor channel.
9
application note Installation – The transducer installation should be performed in accordance with the practice specified in API 670 Latest Edition. Bearings are often modified to accept embedded temperature probes during the manufacturing process. If machining is not done during manufacturing, the bearings can be removed and drilled to accept the temperature probes after machine installation, during an overhaul or retrofit. Designs for sensor installation must be approved by the OEM prior to modification. It is strongly recommended that dual sensors/cables be installed. One sensor should be connected and the second sensor and cable function as a spare. Sensor selection should take into account grounding practices for the instrumentation. Improper grounding can cause noise in the sensor circuit that can affect the monitoring channel signal conditioning and result in erroneous reading. For this reason, when utilizing thermocouples, the best practice is to select non-grounded tip TCs. RTDs, by design, are isolated and do not pose a risk to the sensitive grounding practices. For radial bearings, API 670 uses the definition of short and long bearings to define where to place the temperature measurement sensors. For a long bearing, two-plane temperature measurements are important if a misalignment between the bearing and the shaft occurs. In this case OR-logic should be applied since different temperature readings can occur for both temperature sensors Thrust bearing temperature should use OR-logic because each sensor is installed in the active and inactive pads. API 670 recommends that the bearing temperature shutdown monitor should be field changeable to shutdown when either: 1.
A single sensor exceeds the danger alarm setpoint (single or 1oo1 logic)
2.
Dual voting between predetermined pairs when both sensors exceeding their danger alarm set-points (dual voting or 2oo2 logic)
3.
Exception: Dual voting bearing temperature sensors are standard when two sensors are installed in the load zone of the same bearing.
System
Monitor
Transducer
3500
3500/65 (16 channel)
Customer/site standard TC/RTD with cable and extension cable
3500/60 (6 channel) 3500/61 (6 channel)
All monitoring system components should be specified/ordered with approvals unless specifically declined by the end user. •
Filtering – Not applicable
•
Units – Degrees temperature
•
Machine Shutdown – Condition monitoring and sometimes a shutdown application, most notably on the exhaust end bearing
10
Thrust Bearing Temperature Monitoring Benefits – Elevated thrust bearing temperature can indicate problems related to fluid-film thrust bearings, including overload, bearing metal fatigue, or lubricant issues. Measuring thrust bearing temperatures and correlating them with other process variables can assist in determining the overall condition of the machine. Applications – For fluid-film thrust bearings, API 670 specifies the number of sensors to use and how to apply them. The most common temperature sensor types are resistance temperature detectors (RTDs) and thermocouples (TDs). The RTD functions as a change of resistance for changes in temperature. This temperature sensitive variable resistor is then used as a component in the monitoring channel circuitry. The TC comprises two dissimilar metals that create a very small electromotive force (EMF) or voltage that is then input measured by the monitor channel. Installation – The transducer installation should be performed in accordance with the practice specified in API 670 Latest Edition. The active and inactive thrust bearings should be instrumented. Thrust bearing pads may be drilled to accept temperature sensors during the manufacturing process. If machining is not done during manufacturing, the bearing pads can be removed and drilled to accept the temperature probes after machine installation, during an overhaul or retrofit. Designs for sensor installation must approved by the OEM prior to modification. Sensor selection should take into account grounding practices for the instrumentation. Improper grounding can cause noise in the sensor circuit that can affect the monitoring channel signal conditioning and result in an erroneous reading. For this reason, when utilizing thermocouples, the best practice is to select nongrounded tip TCs. RTDs, by design, are isolated and do not pose a risk to the sensitive grounding practices. System
Monitor
Transducer
3500
3500/65 (16 channel)
Customer/site standard TC/RTD with cable and extension cable.
3500/60 (6 channel) 3500/61 (6 channel)
Unless Customer declines, all monitoring system components are to be specified/ordered with approvals. •
Filtering – Not applicable
•
Units – Degrees temperature
•
Machine Shutdown – Condition monitoring and sometimes a shutdown application
Application Advisory: When 3701 ADAPT is used for the vibration monitoring portion of an installation, temperature monitoring will be performed by the 3500 standard temperature offering. The 3701 and 3500 systems work together with the System 1* software to provide a complete view of the machine vibration and temperature conditions. Note: The thrust bearing position measurement should never be voted with thrust bearing temperature for the Danger Alarm. This voting was promoted in the past based on the premise that excessive thrust motion also generated
application note elevated bearing temperature. There are two reasons not to do this. First, temperature measurements can have a long lag time because of the time it takes for surface heat to heat the bearing babbitt and reach the sensor. This can produce a significant time lag that will delay protection alarming. Second, an internal rub occurs frequently at the limit of the thrust motion which will unload the bearing and cause the temperature to fall below the alarm level and prevent a Danger Alarm resulting in damage that could have been prevented by tripping on thrust position.
from the end user to rectify the cause of the “Not OK” condition. Failure to rectify a “Not OK” condition may result in either having unprotected operation or reverting to a single logic protection (1oo1) based on the remaining “OK” channel. Field changeable options allow the end user to establish the correct response based on operational need. Note 4: End users should be aware that logically OR-ing the “Not OK” channel with the channel alarm in relay logic could lead to false shutdown if an event causes a momentary “Not OK” condition on one channel (if 1oo1 voting is applied) or both channels (if 2oo2 voting is applied). A nearby lighting strike or other fast electrical disturbance could cause this condition. The input spike event is capable of exceeding the channel’s “OK” limits nearly instantly, while that same channel’s alarms may not be driven due to the momentary nature of the disruption combined with the inherent measurement delay, and the configured Alarm Time Delay. The “Not OK” response of the channel has no delay.
6.5 Vibration Transducers – Radial Journal Bearings The thin fluid film that supports the rotor, in a fluid-film bearing, permits rotor movement relative to the bearing. Two orthogonally mounted proximity transducers are required to observe this rotor motion.
“Y” Proximity Probe
“X” Proximity Probe Rotor
Bearing
Protection parameters related directly to machinery internal clearances can be enabled using simply the overall amplitude and DC position measurement. A range of chronic problems and acute fault conditions (such as misalignment, unbalance, and rotor rub) can be diagnosed effectively using the dynamic signal output from the proximity probes.
(See appendix for further discussion on voting.)
Axial Vibration: In many cases, there are vibration issues with the turbine in the axial direction. The end user should be able to view the dynamic activity of the shaft in the axial direction. Axial instabilities, compressor surge or coupling issues can manifest in the axial direction. The following items meet this best practice. The specific ordering details of thread size and cable connector options length should be confirmed in collaboration with the machinery manufacturer. Component
Description
MFR Part Number
Sensor
Bently Nevada 3300XL 8mm proximity probe system (probe, extension cable, Proximitor sensor)
Typical
Note 1: Voting a radial vibration X/Y pair increases the risk of failing to shutdown on high vibration if the machine is experiencing a severely elliptical orbit, which can occur due to a heavy preload condition. Note 2: When 2oo2 dual voting is applied, if one channel shows an alarm and the other does not, the end user should immediately determine the root cause of the alarm and take appropriate corrective action. Note 3: When 2oo2 dual voting is selected, a channel “Not OK” with one of the vibration signals demands immediate action
330130-aaa-bb-cc (ext. cable) 330180-aa-bb (Proximitor sensor)
Radial Vibration: Radial shaft vibration is monitored with orthogonal X/Y paired proximity sensors. The vibration shutdown system is field changeable to shutdown when either a single sensor exceeds the danger alarm setpoint (single 1oo1 logic) or when both sensors are exceeding their danger alarm set-setpoints (dual 2oo2 voting logic). The end user must make an informed decision to use single logic or dual voting logic based on a risk analysis and economic impact of a missed shutdown compared to a false shutdown. An excellent discussion of this trade-off consideration is presented in Section 7.4.1 of the API STD 670.
33010-aa-bb-cc-dd-ee
Probe Housing
Bently Nevada explosionproof stainless steel probe housing assembly
CA24701-aa-bb-cc
An alternative probe housing may be selected when explosion proof rating is not required Monitor
3500 Series or 3701 Series 3500/42M-aa-bb may be selected when or explosion-proof rating is 3701/40 not required
Note: When applicable, all components are supplied with “multi-approvals.” •
Filtering – High-pass: 4Hz / Low-pass: 4kHz
•
Units – Displacement pk-pk
•
Machine Shutdown – Condition monitoring and sometimes a shutdown application
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application note 6.6 Bearing Housing Vibration Bearing Housing The bearing housing is a pedestal and strap used to provide support for a rotor with the help of compatible bearings and various accessories. It is to primarily mount bearings that allow for the rotation of the rotor. The housing is bolted to a foundation through the holes in the base.
Bearing Housing Vibration Monitoring In gas turbines the bearing housing can exhibit a high degree of compliance. In this case seismic vibration transducers should be installed, in conjunction with non-contacting proximity probes, in order to monitor the absolute (relative to free space) bearing housing or structural vibration. •
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Two orthogonal Velomitor* Piezo-velocity sensors should be installed at each turbine bearing and inside the bearing housing. If possible, the transducers should be aligned with the internally mounted proximity probes. The standard Velomitor 330500 can be applied.
In cases where there is no available room/physical space to install the sensors inside the bearing housing, the sensors should be installed outside the bearing housing. If possible, the externally mounted seismic vibration transducers should be aligned with the internally mounted proximity probes. On the exhaust bearing, the sensors may be exposed to elevated temperatures, and should be selected by considering the operational temperature range compatible with temperature exposure: •
Sensors should be supplied with a mounting plate or thread adapter, and the bearing housing should be drilled and tapped suitably to accept the sensor or housing thread.
•
To maintain site consistency and interchangeability of parts, all drilling thread for casing mounted sensors should be unified (for instance, 1/2-20 UNF, 1/4-28 UNF, or M8x1).
•
A phenolic isolator block should be considered for the Velomitor mounting in the case where the generator bearings are not isolated in order to avoid the Velomitor picking up the spikes generated in the rotor.
•
The location of the bearing housing vibration may be hot and an evaluation should be made to ensure sensor survivability.
The following items meet this best practice. The specific ordering details of thread size and cable connector options length should be confirmed by the OEM, or during the Design and Installation Services (D&IS) phase for retrofits.
application note Component
Description
MFR Part Number
Sensor
330500 Velomitor Piezo-velocity sensor (transducer, mounting stud, cable)
330500-AA-BB
Cable
High temperature sealed Velomitor cable
02100036
3500 Monitor
3500/42M Proximitor/seismic monitor
3500/42M-AA-BB
Or 3701 Monitor 3701/40 ADAPT Machinery Dynamics Monitor
Application – No known restrictions. Installation – Temperature sensors should be mounted in each lube oil supply and return line. This allows monitoring the lube oil temperature and helps to isolate which component may be affected if the lube oil temperature rises at one component and not the others. Assure that the temperature sensor is mounted such that the element is in the flow of oil. Filtering – Not applicable Alarm / Shutdown – In the absence of OEM recommendations or engineering data the recommended* initial alarm and danger setpoints are: Alarm: 74° C (165° F)
3701/40
Note 1: When applicable, all components are supplied with “multiapprovals.” Note 2: HTVS/HTVAS should not be considered due to length limitations of the cable between the high-temperature sensing element to the signal conditioning electronics. It is applied for the bearing in the exhaust side for large machines where the cable route length is usually longer than the maximum available integral cable length option.
Danger: 80° C (175° F) *These setpoints should be adjusted based on actual operating conditions System
Monitor
Transducer
3500
3500/60 (No recorder output)
RTD / Thermocouple
3500/61
RTD / Thermocouple
3500/65 (No recorder output)
RTD / Thermocouple*
•
Filtering – High-pass: 10Hz / Low-pass: 2kHz
* – Only supports isolated (non-grounded) thermocouples
•
Units – Velocity 0-pk should be considered
•
Filtering – Not applicable
•
Machine Shutdown – Yes, typically a shutdown application
•
Units – Degrees temperature
•
Machine Shutdown – Condition monitoring and sometimes a shutdown application
6.7 Lube Oil Temperature Benefits – Lubricating oil or Lube Oil is the lifeblood of machinery, and heavy duty industrial gas turbines are no exception. Lube oil deterioration results in the loss of the ability to function as intended. When the lube oil is not able to function properly the gas turbine can be in a critical situation. There are four main reasons lube oil deteriorates: oxidation, thermal degradation, contamination, and additive depletion or loss. The best way to maintain a functioning lubricant is a monitoring program. Lube oil deterioration is typically the result of the length of time in use, temperature exposure, and several other conditions. The rate at which lube oil oxidizes is a function of temperature exposure. The deterioration rate for a typical mineral oil doubles for every 10°C (18°F) rise above 60°C (140°F). Synthetic oils generally have a higher resistance to oxidation. It is important to maintain the lube oil temperature at or below these temperatures. If this isn’t possible it is important to maintain the lube oil at temperatures that are as cool as possible. This is accomplished by monitoring the lube oil temperature and using heat exchangers to cool the oil prior to circulating it back to the machine components. Lube oil supply pressure and temperature and bearing oil drain temperature should be monitored. An abnormal temperature rise of 10° C (50° F) between the supply and drain should be investigated. Low lube oil pressure should be an alarm parameter.
6.8 Combustor Monitoring Benefits Flame Sensing: Combustion flame monitoring can indicate problems related to the combustors’ tuning and operation. Typical gas turbines will have several combustors that burn the fuel and air mixture creating the high temperature gas that then is expanded through the turbine section. A faulty burn from one or more combustor will cause an increase in undesirable emissions and a decrease in overall gas turbine efficiency. Loss of flame detected on one or more combustors will initiate a shutdown of the unit through the control system. This typically occurs during a startup sequence. If a unit is running and loses flame, something major has occurred, such as an anomaly in the fuel system. Flame sensors are located in each combustor. These devices send signals back to the control system to indicate that the flame meets characteristics such as “flicker”, “color”, and “intensity”. Flame sensors are provided by the OEM as a standard offering. GE Flame Tracker products can be applied to many non-GE gas turbines and may provide an improved solution as aftermarket replacement parts.
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application note For more details on Flame Sensing see the Reuter Stokes products at: https://www.gemeasurement.com/ Combustion Dynamics/Acoustics: With modern Dry Low NOx combustors, the fuel to air ratio has become very lean. This lean combustion can lead to conditions that set up an acoustic resonance in the combustor can, silo or annulus, sometimes called humming. If left unchecked, this resonance can create pressure pulsations in the combustor and/or transition piece that are large enough to create mechanical damage to the components. If these components are liberated and ejected downstream, severe mechanical damage can result. Each gas turbine has different acoustic resonant frequencies of concern. The individualities usually boil down to the granularity of the type of combustor for that specific machine. A similar model machine may have different kits for combustion depending on customer requirements and government regulators for emissions. All OEMs know what the frequencies of interest are for each model of combustor and can set up the monitoring systems to filter the dynamic pressure sensor signals for each frequency of interest. Often there are two or three frequencies of concern and band pass filters are set around them. Many systems are installed permanently because gas turbines need to be retuned for differing ambient conditions, fuel qualities, and fuel types. Online combustion dynamics monitors take on a role of more importance as fuel quality changes and can cause a gas turbine to experience acoustic pulsations unexpectedly. If necessary a shutdown can be initiated under extreme conditions.
Applications Combustion acoustic sensor numbers and locations are determined by the OEM depending on the combustion dynamics experience.
Installation System
Monitor
Transducer
3500/3701
3500/64, 3701/40
350501 Dynamic Pressure Charge Amp Dynamic Pressure Sensor not provided by GE.
•
Filtering – Determined by OEM
•
Units – mbar/psi dpp, pp, rms, 0-pk and so on
•
Machine Shutdown – Condition monitoring, load control, and possible shutdown application
6.9 Exhaust Gas Temperature Benefits – Exhaust gas temperature (EGT) is a primary indicator of gas turbine engine health and a critical parameter of engine operation. Elevated EGT can indicate deteriorated internal parts, excessive leaks, or a fouled air compressor. Excess EGT of a few degrees can reduce turbine blade life as much as 50 percent. Low EGT materially reduces turbine engine efficiency and causes emissions exceedances. Thus, the EGT can provide insight into the engine’s internal operating conditions. EGT spread can indicate problems with specific combustor cans or nozzles in addition to transition piece deterioration. Deviations around the annulus of the EGT in either the hot or cold direction may be an indication of these problems. Application – EGT plots are available from the System 1* Basic Optimization and Diagnostic Software and are used to monitor and display the EGT temperature spread of the gas turbine. The EGT plot is capable of displaying up to 100 temperature values in three (3) graphic formats: a temperature bar graph, a temperature spread bar graph, and an EGT polar plot. In the polar plot the temperature values can be plotted in reference to the combustor cans and rotated to the gas swirl angle. Decision Support is a component of the System 1* Basic Optimization and Diagnostic Software, which allows end users to develop rules to trigger alarms for a temperature excursion that deviates too far from the average of the other EGT in the array or spread. Included below are some example EGT plots. Bently PERFORMANCE*SE* Software, is another component of the System 1* Basic Optimization and Diagnostic Software which allows additional variables to be monitored along with EGT for overall gas turbine operational performance. Installation – In some gas turbine engine designs it may be possible to monitor the turbine inlet temperature, but this requires a larger number of thermocouples versus monitoring the EGT. Because turbine inlet temperature can be as high as 1800° C (3272° F), so making penetrations in the gas stream and sourcing sensing elements that can survive these extreme temperatures is difficult. Therefore, thermocouples are usually installed at the turbine discharge. An array of thermocouples is used, with the thermocouples spaced at intervals around the perimeter of the engine exhaust duct near the turbine exit. A gas temperature thermocouple is mounted in a ceramic insulator and encased in a metal sheath; the assembly forms a probe which projects into the exhaust gas stream. The thermocouple is made from chromel (a nickel/chromium alloy) and alumel (a nickel/aluminum alloy). The hot junction protrudes into a space inside the sheath. Transfer holes in the end of the sheath allow the exhaust gases to flow across the hot junction. Alarm/Shutdown/Operation – Large variation in the exhaust gas distribution from the average value can indicate combustion problems that can lead to increased thermal stress in the power turbine. These variations need to be identified early and addressed proactively. The data provides information on how to change operating conditions to reduce the deviation and help avoid turbine
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application note operational problems.
15
application note EGT Plot •
Filtering – Not applicable
•
Units – Degrees temperature, max, min, spread
•
Machine Shutdown – Condition monitoring application only
well as to correlate with other measurements. Typically the DCS Tag Description is “Compressor Inlet Temperature” and the units are in degrees Celsius (C) (or Fahrenheit (F)). •
Dew Point Temperature This is a calculated measurement (scalar value) from ambient temperature, ambient pressure and humidity measurements taken locally at site. The dew point is a water-to-air saturation temperature that is associated with relative humidity. A high relative humidity indicates that the dew point is closer to the current air temperature. Relative humidity of 100 percent indicates the dew point is equal to the current temperature and that the air is maximally saturated with water. When the dew point remains constant and temperature increases, relative humidity decreases. It is important to monitor this to calculate air charge density.
•
Ambient Humidity This is a direct measurement (scalar value) of the ambient air humidity. It is important to monitor this to understand the atmospheric conditions and to calculate air charge density.
•
Compressor Inlet Filter Delta Pressure/Pressure Drop This is usually a direct measurement (scalar value)of the pressure inside the combustion inlet chamber subtracted from the ambient pressure. It is important to take delta pressure measurements to watch for inlet filter clogging. This calculated value is provided as an input to the control logic. This further enables the condition management in System 1 software. Typically, the DCS Tag Description is “Compressor Inlet Pressure Transducer” and the units are in inches of water (inH2O).
•
Compressor Inlet Mass Flow This is a direct measurement (scalar value) of the inlet air density into the compressor section of the gas turbine. It is important to monitor this to calculate fuel injection into the combustor cans as well as to correlate with other measurements during diagnostics of Compressor Surge/Stall or other malfunctions. The usual DCS Tag Description will be ‘Compressor Inlet Mass Airflow’ and the units will be in lb-m/s.
•
Compressor Inlet Pressure This is a direct measurement (scalar value) of the inlet air pressure into the Compressor section of the Gas Turbine. It is important to monitor this to understand the mass charge of air and to calculate the compressor inlet filter delta pressure as well as to correlate with other measurements during diagnostics of Compressor Surge/Stall or other malfunctions.
•
Compressor Inlet Temperature This is a direct measurement (scalar value) of the inlet air pressure of the compressor section of the gas turbine. It is important to monitor this to understand the mass charge of air, as as well as to correlate with other measurements during diagnostics of Compressor Surge/Stall or other malfunctions. Typically the DCS Tag Description is “Compressor Inlet Temperature” and the units are in degrees Celsius (C) (or Fahrenheit (F)).
•
Compressor Discharge Pressure This is a direct measurement (scalar value) of the discharge pressure after the compressor section of the gas turbine. It is important to monitor this to measure the effectiveness
6.10 Process Variable Measurements In addition to the measurements described in the above sections, it is important to monitor process data/process variables for conducting advanced analytics and performance monitoring, as well as making condition assessments by correlating the data with other measurements. Almost always, the process data are readily available in other plant systems like Unit Control System/DCS that can be imported (via Modbus or OPC) to the System 1 condition monitoring system. Process variables from DCS can also be a direct measurement (Scalar Values) from a device like a pressure transmitter or can be a calculated value like load (measured in megawatts, mega VARs, and so on). If any required process variable is not available in any plant system, it can be brought into the Bently Nevada 3500 Series Machinery Monitoring System via a transmitter into a 3500 Process Variable Monitor. Early Warning – As part of condition monitoring, process variables are used alone or as part of a logical rule with other variables (within a RulePaks or simple rules in System 1 software or in Proficy* SmartSignal predictive analytics software) for generating soft alarms to alert about a condition change that requires attention or some preventive or corrective action by operators or maintenance personnel. These process variables are usually imported from Unit Control, DCS or other plant systems enabling RulePaks and Bently PERFORMANCE SE Software diagnostic modules in System 1 software. The following are the process variables recommended to be monitored and brought into condition monitoring system. •
Inlet Flow Differential Pressure (IFDP) The pressure rise across the inlet filter to the compressor is a key measurement for condition monitoring. High differential pressures can indicate a clogged filter and cause the overall pressure capability to decrease by the pressure ratio of the compressor. Low IFDP can indicate a hole in the filter media that can lead to foreign object damage or increased fouling.
•
Ambient Pressure This is a direct measurement (scalar value) of the ambient air pressure. It is important to monitor the ambient pressure to better understand atmospheric conditions, calculate air charge density, and correlate with other measurements. Typically the DCS Tag Description is “Flow Inlet Barometric Pressure Transducer” and the units are in inches of mercury (in Hg, inHg, or “Hg).
•
Ambient Temperature This is a direct measurement (scalar value) of the ambient air temperature. It is important to monitor this to understand the atmospheric conditions and to calculate air charge density, as
16
application note of the compressor, as well as to correlate with other measurements during diagnostics of Compressor Surge/Stall or other malfunctions. Typically the DCS Tag Description is “Compressor Discharge Pressure Max” and the units are in inches of mercury (in Hg or inHg). •
•
•
•
•
Compressor Discharge Temperature This is a direct measurement (scalar value) of the temperature of the discharge gas after the compressor section of the gas turbine. It is important to monitor this to understand the effectiveness of the compressor, as well as to correlate with other measurements during diagnostics of Compressor Surge/Stall or other malfunctions. Typically, the DCS Tag Description is “Compressor Discharge Temperature” and the units are is degrees Celsius (C) (or Fahrenheit (F)). Combustor Dynamic Pressure This is usually a direct measurement (steady-state waveform value) of the Dynamic pressure inside the combustion chamber. It is important to do combustion monitoring as a measure of the efficiency of the combustion can. This high temperature dynamic pressure sensor provides input to the control logic. As raw dynamic pressure signal is necessary for condition monitoring, a buffered signal should be provided from the control system to the Bently Nevada 3500 Series Machinery Monitoring System. This further enables the condition management capability within the System 1 software. Inlet Guide Vane (IGV) Angle The purpose of the inlet guide vanes is to direct the air into the first stage of the compressor at the proper angle for the most efficient compression. Most inlet guide vanes are fixed, but in some engines their angle can be changed by hydraulic actuators controlled by the fuel control unit. Movable guide vanes direct the air into the compressor at the correct angle as the operating conditions inside the engine change. IGV angle is usually measured by LVDT and the scalar value is supplied to the DCS. IGV monitoring provides vital feedback about how the system is functioning and indicates the expected power increase. This further enables the condition/performance monitoring of the gas turbine using the System 1 software. Typically, the DCS Tag Description is “IGV Angle in deg” and the units are in degrees (deg). Variable Stator Vane (VSV) Angle Variable stator vanes permit the angle of incidence of the exiting air onto the rotor blades to be corrected to angles which the rotor blades can tolerate without flow separation. The use of variable stator vanes permits the angle of one or more rows of stator vanes in a compressor to be adjusted, while the engine is running, in accordance with the rotational speed and mass flow of the compressor. VSV angle is usually measured by LVDT and the scalar value is supplied to the DCS. VSV monitoring provides vital feedback about how the system is functioning and indicates the expected power increase. This further enables the condition/performance monitoring of the gas turbine using the System 1 software. Combustor Fuel Flow (Gas or Liquid) This is a direct measurement (scalar value) of the fuel flow into the Combustor. It is important to monitor this to understand
and control the fuel flow as well as to correlate with other measurements during diagnostics of Compressor Surge/Stall or other malfunctions. The usual DCS Tag Description is ‘Gas Fuel Validated Fuel Mass Flow’ and the unit is lb-m/s. •
Fuel Gas Pressure This is a direct measurement (scalar value) of the fuel pressure into the combustor. It is important to monitor this to understand and control fuel flow, as well as to correlate with other measurements during diagnostics of Compressor Surge/ Stall or other malfunctions. Typically, the DCS Tag Description is “Fuel Gas Inlet Pressure Transducer” and the units are in pounds per square inch (psi).
•
Fuel Gas Temperature This is a direct measurement (scalar value) of the fuel temperature into the combustor. It is important to monitor this to understand and control fuel flow, as well as to correlate with other measurements during diagnostics of Compressor Surge/Stall or other malfunctions. Typically, the DCS Tag Description is “Gas Fuel Voted Gas Temperature Turb” and the units are in degrees Celsius (C) (or Fahrenheit (F)).
•
Fuel Lowest Heating Value (LHV) This is a manual input (scalar value) of the fuel provided by the fuel supplier, and it changes if the fuel supplies change. It is important to monitor LHV to understand and control fuel flow.
•
NOx Injection Flow (Steam or Water) This is usually a direct measurement (scalar value) of the steam or water injection flow to reduce the NOx emissions. NOx emissions are very critical for certain applications/customers and hence any change in water/steam injection flow affects performance as well as emissions to the environment.
•
Load The load as computed by the DCS, should be supplied to the System 1 Condition Monitoring System for correlation to other data points. For example, if temperature and vibration suddenly change, but there is no change in the load, this is convincing information of a real concern. However, if the vibration change corresponds to a load change, this explains the vibration and eliminates any unmerited concerns. Overlaying the load on trend plots for other sensors can be a powerful diagnostic tool.
•
Fuel Cost This is a manual input of the fuel cost to calculate performance degradation in money terms, as well as to determine the optimal time to advice a compressor wash of the gas turbine.
•
Turbine Inlet Pressure This is a direct measurement (scalar value) of the inlet air pressure into the gas turbine. It is important to monitor this to understand the condition of the inlet air filter, as well as to correlate with other measurements during diagnostics of Compressor Surge/Stall or other malfunctions.
•
Turbine Discharge Pressure This is a direct measurement (scalar value) of the discharge pressure of the turbine section of the gas turbine. It is important to monitor this to measure efficiency and turbine function, as well as to correlate with other measurements
17
application note during diagnostics of Compressor Surge/Stall or other malfunctions. •
•
Turbine Discharge Temperature (#1 to #18) This is a direct measurement (scalar value) of the exhaust air temperature typically from multiple (sometimes up to 18) temperature sensors. It is important to monitor this to calculate the unit efficiency. Once mapped to specific combustor cans, this information can be used to balance the combustor cans as well as to correlate with other measurements during diagnostics. Cooling Air Temperature This is usually a direct measurement of the air extracted from the compressor section of the turbine and used to keep sensitive areas of the turbine skid cool. If this temperature gets too high the sensitive areas can overheat and cause malfunction.
•
Lube Oil Pressure This is a direct measurement of the oil pressure being fed to the bearings to supply lift and lubrication to the bearings. It is important to monitor this value as a drop in pressure can lead to bearing damage.
•
Lube Oil Filter Differential Pressure This is a calculated measurement of the pressure drop across the oil filter. It is important to monitor this to indicate filter condition (time to replacement/cleaning) as well as to correlate with other measurements to indicate or verify other machine problems.
•
•
Start Stop Count This is a count of how many times the gas turbine has started and stopped. This is used in estimating fatigue and wear on machine components. Run Time This is a clock that runs when the machine is running and is used to initiate time-based preventative maintenance and inspections.
7 Protection /Management Systems 7.1 Bently Nevada 3500 Series Machinery Monitoring System Overview Machinery protection is implemented when vibration (or other) instruments are installed permanently onto a gas turbine and connected to a dedicated Bently Nevada 3500 Series Machinery Monitoring System. The 3500 series monitoring system has alarm setpoints, which are set by the machinery OEM or the end user to automatically raise an alarm when the predetermined alarm level is reached. The system has alarm relays for alert and danger conditions that can initiate an automatic shutdown or trip of the machine; alternatively instructions to shut down the machine may be acted upon by an operator when an alarm occurs. Machinery protection is necessary and valuable since it may prevent or minimize machine damage and consequential losses in the event that a sudden machinery or process malfunction occurs.
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The Bently Nevada 3500 Series Machinery Monitoring System is a rack-based machinery protection and condition monitoring system that provides the information you need to protect and assess the mechanical condition of rotating and reciprocating machinery. The 3500 system continuously measures and monitors various protection and supervisory parameters and can provide important information for early identification of machinery problems such as imbalance, misalignment, shaft crack, and bearing failures. A 3500 system consists of a stainless steel chassis containing a backplane circuit board and card guides on both the front and rear of the chassis that are used for insertion of monitors and their associated input/output (I/O) modules into the chassis and backplane. The monitoring system is typically installed in a cabinet, a panel, or an enclosure and can be located in a Zone 2 hazardous area if a certified system has been supplied. The system is available with a variety of I/O options including support of external zener safety barriers, external galvanically isolated safety barriers, and internal zener safety barriers. The use of appropriately rated safety barriers allows installation of intrinsically safe transducer systems in Zones 0 or 1.
7.2 3500 Vibration/Thrust/ Temperature/Dynamic Pressure In order to comply with best practices for gas turbine machinery management, the following specific requirements must be met by the monitoring and protection system. GE’s Bently Nevada 3500/15 Power Supply Modules are half-height modules that must be installed in the specially designed slots on the left side of the rack. The 3500 rack can contain one or two power supplies (any combination of AC or DC) and either supply can power a full rack. The second supply is highly recommended and acts as a backup for the primary supply. When two power supplies are installed in a rack, the supply in the lower slot acts as the primary supply and the supply in the upper slot acts as the backup supply. Removing or inserting either power supply module does not disrupt operation of the rack as long as a second power supply is installed. The 3500/15 Power Supply Modules accept a wide range of input voltages and convert them to voltages acceptable for use by other 3500 modules. Three power supply versions are available with the Bently Nevada 3500 Series Machinery Monitoring System as follows: •
AC Power Supply
•
High-voltage DC Power Supply
•
Low-voltage DC Power Supply
Best Practice Recommendation: •
Use two 3500/15 Power Supply Modules with separate power feeds for highest failure tolerance. In this scheme, the rack continues monitoring in the event of loss of a single power feed, or loss of a single power supply module due to failure or removal of the module.
application note •
240 – 240,000 cpm
Use of two 3500/15 Power Supply Modules with a single power feed coupled to both inputs is also possible, and is a suitable solution when the single power feed is from a an uninterruptable power supply (UPS). In this case, the benefit of having two power supplies is for continued operation if a single module fails or is removed from service.
3500/22M Transient Data Interface (TDI) GE’s Bently Nevada* 3500/22M TDI is the interface between the 3500 Series Monitoring System and System 1* Basic Optimization and Diagnostic Software. The TDI operates in conjunction with the M series monitors (such as the 3500/42M monitor and the 3500/64M monitor) to continuously collect steady-state and transient waveform data and pass this data through an Ethernet link to the System 1 software.
–
Filtering configuration: Not applicable
–
Full-Scale Range (FSR) configuration: 200 µm (typically). The same FSR should be applied for 1X Amp, 2X Amp, Not 1X Amp and Smax Amp
–
Setpoint configuration: according to OEM recommendations or engineering data
A typical configuration is shown below.
The TDI communicates with the data acquisition computer using Ethernet. It can support the following physical media: 10 Base-T, 100 Base-TX or 100 Base- FX (fiber). The TDI is designed to work as a standard network device and should be compatible with any Ethernet structure. Typically the 3500 rack cabinet is installed in a Control Room which the Ethernet port is the preferred option. A typical TDI configuration is shown below.
•
Bearing Housing Vibration –
For the two radial bearings design, one 3500/42M monitor should be used to receive the signals from four Velomitor sensors (two sensors per bearing)
–
For the three radial bearings design, two 3500/42M monitors should be used to receive the signals from six Velomitor sensors (two sensors per bearing)
–
Corner Frequencies configuration: High-Pass=10 Hz / Low-Pass=2,500 Hz. For gas turbines operating at design speeds between 3,000 rpm and 5,200 rpm this provides accurate and stable bearing housing vibration measurements under all on-load operating conditions.
–
Full-Scale Range (FSR) configuration: 20 mm/s RMS (typically). The same FSR should be applied for 1X Amp and 2X Amp
–
Setpoint configuration: according to OEM recommendations or engineering data
3500/42M Proximitor/Seismic Monitor GE’s Bently Nevada 3500/42M Proximitor/Seismic Monitor is a 4-channel monitor that accepts input from proximity and seismic transducers. It receives signals from the proximity transducers to monitor radial vibration. It is also used to monitor bearing housing vibration through signals received from the Velomitor sensors and to monitor thrust position from signals received from the proximity transducers. •
Radial Vibration –
For the two radial bearings design, one 3500/42M monitor should be used to receive the signals from four proximity transducers (two probes per bearing)
–
For the three radial bearings design, two 3500/42M monitors should be used to receive the signals from six proximity transducers (two probes per bearing)
–
Direct Frequency Response configuration:
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application note a more positive thrust reading (for example upscale on a bar graph). If “Toward Probe” is selected, then movement of the rotor toward the thrust probe causes the thrust position direct proportional value to increase and go upscale on a bar graph.
A typical configuration is shown below:
–
Full-Scale Range (FSR) configuration: -1.0 to 1.0 mm (typically)
–
Setpoint configuration: according to OEM recommendations or engineering data
A typical configuration is shown below:
•
20
Shaft Axial (thrust) Position –
One 3500/42M monitor should be used to receive the signals from two proximity transducers (two probes for thrust bearing). Channels 1 and 2 should be configured for thrust position. If there are two 3500/42M monitors adjacent in the rack, channel 1 in each monitor can be configured for Thrust Position to protect against an unlikely monitor failure causing a false trip.
–
Corner Frequencies configuration: Not applicable
–
Normal Thrust Direction configuration: The OEM/customer should be consulted to determine what the normal shaft movement is during operation. This defines whether the normal thrust direction (toward the active thrust bearing) is toward or away from the probe mounting. Movement of the rotor toward or away from the thrust probe corresponds to
•
Shaft Axial (thrust) Vibration –
Channel 3 and 4 from the 3500/42M monitor applied for shaft axial (thrust) position should be configured for radial vibration and receiving the signals from the two Proximity transducers used for thrust position.
application note –
Some gas turbine malfunctions (for example, misalignment) can also cause axial vibration. Monitoring the axial vibration through the sharing of thrust position probes is an economical solution because there is no need to install additional probes.
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Direct Frequency Response configuration: 240 to 240,000 cpm
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Filtering configuration: Not applicable
–
Full-Scale Range (FSR) configuration: 200 µm (typically). The same FSR should be applied for 1X Amp, 2X Amp, Not 1X Amp and Smax Amp
–
Setpoint configuration: The same as that applied for radial vibration
A typical configuration is shown below: 3500/64 Dynamic Pressure Monitor The Bently Nevada* 2500/64 Dynamic Pressure Monitor from GE is a single slot, 4-channel monitor that accepts input from various high temperature pressure transducers and uses this input to drive alarms. The monitor’s one proportional value per channel is bandpass dynamic pressure. The 3500 Rack Configuration Software can be used to configure the bandpass corner frequencies, along with an additional notch filter, if needed. The monitor provides a recorder output for control system applications. Each channel typically conditions its input signal into various parameters called “proportional values”. The user can configure Alert and Danger setpoints for each active proportional value. Combustion instabilities in industrial gas turbines can produce intolerably large pressure waves, which lead to fatigue, detachment of components, and costly outages and repair. The measurement of dynamic pressure amplitudes within the combustion chamber may be used in condition monitoring analyses to detect and correct instabilities before they cause serious damage. Frame machines usually have a can-type, or cannular combustor configuration in a series of individual, can-shaped combustors placed around the circumference of the engine. Each can has a series of burners located on its cover. These mix fuel with compressor air and introduce it into the combustor, where it is ignited. The resultant flame is confined to the single can. The hot gas flow is then channeled to the first stage of the turbine via a transition piece, where it joins the flow from the other cans located around the circumference. •
Combustor Dynamic Pressure –
Typically the quantity of sensors is defined by the OEM and always part of the control system. Cannular design requires one dynamic pressure sensor per combustor. But the common practice is to have at most four sensors in a 3500/64 monitor.
–
One 3500/64 monitor should be used to receive the signals from four high temperature pressure transducers.
–
Direct Frequency Response configuration: Not applicable
21
application note –
Filtering configuration: High-Pass=15 Hz / Low-Pass=4,000 Hz
–
Signal Conditioning Filter: Low mode
–
Full-Scale Range (FSR) configuration: 3400mbar pk
–
Setpoint configuration: according to OEM recommendations or engineering data
–
Setpoint configuration: according to OEM recommendations or engineering data
A typical configuration is shown below:
A typical configuration is shown below:
3500/25 Enhanced Keyphasor Module
3500/61 Temperature Monitor GE’s Bently Nevada* 3500/61 Temperature Monitor is a six channel monitor for temperature monitoring that accepts either resistance temperature detectors (RTD) or thermocouple (TC) temperature inputs. The module conditions these inputs and compares them against user-programmable alarm setpoints. •
22
Bearing Temperature –
Applied to radial and thrust bearings
–
For the two radial bearings design, one 3500/61 monitor should be used to receive signals from six temperature sensors. These signals are: the input of two sensors per radial bearing (one active and one spare) and two sensors for the thrust bearing (one for active pad [shoe] and another one for inactive pad).
–
For the three radial bearings design, two 3500/61 monitors should be used to receive the signals from eight temperature sensors as follows: the input of two sensors per radial bearing (one active and one spare) and two sensors for the thrust bearing (one for active pad [shoe] and another one for inactive pad)
–
Both resistance temperature detector (RTD) and thermocouple (TC) can be applied.
–
Direct Frequency Response configuration: Not applicable
–
Filtering configuration: Not applicable
–
Full-Scale Range (FSR) configuration: 150º C (typically)
The Bently Nevada 3500/25 Enhanced Keyphasor Module from GE is a half-height, two-channel module used to provide Keyphasor signals to the monitor modules in a 3500 rack. The module receives input signals from proximity probes or magnetic pickups and converts the signals to digital Keyphasor signals that indicate when the Keyphasor mark on the shaft coincides with the Keyphasor transducer. The Bently Nevada 3500 Series Machinery Monitoring System can accept up to four Keyphasor signals. A transducer produces a voltage pulse (called the Keyphasor signal) for each turn of the shaft. This signal is used primarily to measure shaft rotative speed and serves as a reference for measuring vibration phase lag angle. It is an essential element in measuring rotor slow roll bow or runout information. •
Keyphasor reading –
The Keyphasor signal is a once-per-turn voltage pulse provided by a transducer (normally a proximity probe). The Keyphasor signal is used for monitoring, diagnostic, and management systems to generate filtered vibration amplitude, phase lag, speed, and a variety of other information. Keyphasor generated information can help the operator or machinery specialist identify developing machine problems or distinguish serious problems from less serious ones. The Keyphasor signal is used to generate more than one third of the information regarding the condition of the machine. Phase (relative and absolute) is a critical part of this information.
–
The signals from a Keyphasor transducer observing a multi-tooth gear (except for Recip Multi-Event Wheel) can only be used for speed measurements and not for phase measurements.
–
Each Keyphasor module accepts up to two transducer signals from proximity probe transducers or magnetic
application note business philosophy. Voting schemes, configuration, permissive, and logic are the responsibility of the machinery OEM or the end user.
pickups. Proximity probe is always preferred because magnetic pickup is reliable only for shaft rotative speeds greater than 300 rpm –
Direct Frequency Response configuration: Not applicable
–
Filtering configuration: Not applicable
–
Full-Scale Range (FSR) configuration: 5,000 rpm (typically)
–
Setpoint configuration: Not applicable
A typical configuration is shown below:
–
Both the Normal and Voting options should be used. This is the default voting used for a standard 4-channel relay. With the Normal and Voting option selected, if a single alarming parameter is defeated by a channel Not OK condition or bypassed (either by user selection or monitor failure), then the parameter is handled using OR logic in the equation. (See appendix for further details.)
–
Latching Relays should not be selected since all machinery information is currently available in the DCS, so there is no reason to latch a relay only to identify the reason for the machine trip.
3500/94 VGA Display The Bently Nevada 3500/94 VGA Display from GE uses a standard color VGA monitor with touch screen technology to display 3500 data. This product has two components, the 3500/94 VGA module and its I/O card, and secondly, the VGA display monitor. The display monitor, with standard cabling, can be mounted up to 8 m (25 ft.) from the rack. Users configure the 3500/94 modules for language and for the type of VGA display using the 3500 Rack Configuration Software. All other types of data configuration are done locally at the display, giving the operator control over the displayed data. Users may configure nine custom screens locally.
Note: The installation of a spare Keyphasor sensor is highly recommended because the Keyphasor module is a vital element in performing machine management and diagnostics. It is a recommended practice, where possible, to input the Keyphasor signal(s) into one channel(s) of a 3500/42 monitor to allow capture of the Keyphasor signal waveform(s). 3500/32M 4-Channel Relay Module GE’s Bently Nevada 3500/32M 4-Channel Relay Module is a fullheight module that provides four relay outputs. Any number of 3500/32M modules can be placed in any of the slots to the right of the Transient Data Interface Module. Each output of the 3500/32M module can be independently programmed to perform needed voting logic. Each relay utilized on the 3500/32M module includes “Alarm Drive Logic”. Programming for the Alarm Drive Logic uses AND and OR logic, and can use alarming inputs (Alert and Danger statuses), Not- OK, or individual PPLs from any monitor channel or any combination of monitor channels in the rack. Users program this Alarm Drive using the 3500 Rack Configuration Software to meet the specific needs of the application. The traditional role of gas turbine instrumentation includes a machine protection function. •
Relays –
Only normally energized relays are allowed for use for protection.
–
The decision to enable alarm relays for alert and danger conditions is based on the customers operating and
As an example, one custom screen may show all the 1X measurements, while another shows all the gaps or the custom screens may be organized into train groupings. Users can organize all system data into specified sets of data according to their preference through a custom screen. An API 670 compatible screen is also selectable. This screen is similar to a 3300 view of the rack. Each slot shows the Direct or Gap value on the face of the module with OK and Bypass LEDs. Selecting the 3500/94 Display Router Box provides an additional viewing feature. This feature allows users to view a maximum of four racks with one display. Each rack must be individually viewed, but the rack address and alarm status of each rack is always visible in the upper right corner of the screen. The Display Router Box must be located within 6 m (20 ft.) of each 3500 rack.
Display –
RS Power Station should be used.
–
Typically the display is installed in the same 3500 cabinet. If necessary it can be installed in another place using a longer cable and power supply according to datasheet.
3500/92 Communication Gateway GE’s Bently Nevada* 3500/92 Communication Gateway module provides extensive communication capabilities of all rack monitored values and statuses for integration with process control and other automation systems using both Ethernet TCP/IP and serial (RS232/RS422/RS485) communications capabilities. It also permits Ethernet communications with 3500 Rack Configuration Software
23
application note and Data Acquisition software. The Ethernet connection to the 3500/92 module is an RJ45 connection for 10BASE-T configuration Ethernet networks.
monitoring via Modbus or use of scanning systems verses online monitoring does not conform to machinery protection best practices. The localized protection system should integrate to the plant DCS using Modbus over TCP/IP.
Supported protocols include: •
Modicon* Modbus protocol (via serial communications)
•
Modbus/TCP protocol (a variant of serial Modbus used for TCP/IP Ethernet communications)
•
Proprietary Bently Nevada protocol from GE (for communication with 3500 Rack Configuration and Data Acquisition Software packages)
•
Modbus –
–
Modbus over TCP/IP is always preferred.
–
The 3500/92 Communication Gateway can communicate with up to six hosts via Ethernet. Hosts can be devices that use Modbus protocol or computers that run 3500 Rack Configuration and Data Acquisition software. You can configure only one 3500/92 module per 3500 rack to accept Rack Configuration or Data Acquisition hosts.
Machines ranked as Critical require online localized protection to reduce consequences of failure. Remote
Example 1: A two radial bearing gas turbine driving an electric generator. Machine Train Block Diagram
Referencing the train block diagram above, we see the need to monitor the two generator and two gas turbine radial bearings with XY proximity sensors, XY velocity sensors, and two Temperature sensors at each bearing. The gas turbine thrust bearing will be monitored with a dual voting thrust monitor and two Temperature sensors. The Gas Turbine will have one or more dynamic pressure sensors on the combustors. Finally a Keyphasor sensor will monitor the phase and speed of the gas turbine (it is recommended to also
24
install a spare Keyphasor probe). This configuration will require five 3500/42 monitors, 2 3500/61 Temperature Monitors. A table shown below relates the monitored location to the proper monitor and slot location in the 3500 System Rack. Given this table, the 3500 Rack Configuration can be used to generate the complete data set to configure the monitoring system. Measurement
Location
application note Gas Turbine Keyphasor Speed/phase
GT Shaft
Prox
3500/25
S12 upper
Gas Turbine Dynamic Pressure
Dynamic Pressure
Gas Turbine Combustor
High Temp Pressure Sensor
3500/64
S7 C 1-4
Disp p/p
GT Outboard
Gas Turbine Bearing 1
Gas Turbine Bearing 2
X Prox
3500/42
S2 C1
Disp p/p
Y Prox
3500/42
S2 C2
Velocity
Y Prox
3500/42
S2 C3
Velocity
V vert
3500/42
S2 C4
Temp
RTD
3500/61
S7 C1
Temp
RTD
3500/61
S7 C2
X Prox
3500/42
S3 C1
Disp p/p
GT Inboard
Disp p/p
Y Prox
3500/42
S3 C2
Velocity
V horiz
3500/42
S3 C3
Velocity
V vert
3500/42
S3 C4
Temp
RTD
3500/61
S7 C3
RTD
3500/61
S7 C4
X Prox
3500/42
S4 C1
Y Prox
3500/42
S4 C2
Temp Gas Turbine Thrust Bearing
Thrust Position
Gas Turbine Thrust Bearing
Thrust Position
Gen Bearing 2
Temp
RTD
3500/61
S7 C5
Temp
RTD
3500/61
S7 C6
X Prox
3500/42
S3 C1
Y Prox
3500/42
S3 C2
Disp p/p
Generator Inboard
Disp p/p
Gen Bearing 2 Sensor
Monitor
Velocity
V horiz
3500/42
S3 C3
Velocity
V vert
3500/42
S3 C4
Temp
RTD
3500/61
S7 C3
Temp
RTD
3500/61
S7 C4
Disp p/p
Generator Outboard X Prox
3500/42
S3 C1
Disp p/p
Y Prox
3500/42
S3 C2
V horiz
3500/42
S3 C3
Velocity
Slot
Velocity
V vert
3500/42
S3 C4
Temp
RTD
3500/61
S7 C3
Temp
RTD
3500/61
S7 C4
Sensor to 3500 Rack Slot mapping (typical – actual slot assignments may vary due to customer preference)
25
application note
Below is the complete 3500 system rack for two radial bearing gas turbines driving a generator. Component
Description
Part Number
Qty
System Rack
Bently Nevada 3500 19 inch system rack Monitor Rack Configuration utility
3500/05-01-01-02-00-01 3500/01-01 (typical)
1
Power Supply
Bently Nevada 3500 Dual Power Modules
3500/15-01-02-02 (typical)
1
Transient Data Interface*(TDI)
Bently Nevada 350022M Rack Interface Module with Transient Data 3500/22-01-01-02 (typical) Internal interface, TMR Version (as applicable)
1
Bently Nevada 3500/42 Monitoring Card
WARNING: For measurements applicable for Hydrogen Cooled Generators can be required cards with special protection
3500/42-01-02 (typical)
5
Monitoring Card
Bently Nevada 3500/64 Combustor Dynamic Pressure
3500/64-01-02 (typical)
1
Monitoring Card
Bently Nevada 3500/61 Temperature
3500/61-01-02 (typical)
2
Monitoring Card
Bently Nevada 3500/25 Keyphasor
3500/25-01-01-02 (typical)
1
Protection Rack Local Bently Nevada 3500/94 Display Display Unit ***
3500/94-03-00-01 (typical)
1
Relay Card **
Bently Nevada 3500/32 Six Channel Relay
3500/32-01-01 (typical)
1
Relay Card **
Bently Nevada 3500/32 Six Channel Relay
3500/32-01-01 (typical)
1
Communication Gateway Card
Bently Nevada 3500/92 Communication Gateway
3500/92-04-01-02 (typical)
1
If EGD protocol is needed then 3500/91 can to be used
Note: All components to be ordered with “multi-approvals” to ensure complete hazardous area documentation is supplied with order. * The TMR version of the TDi Rack Interface Module (RIM) must be used in the case where SIL 3 protection functionality is required, otherwise the standard TDi RIM module should be used. ** Ensure the number of available relay channels meets the requirements. Relay Card should be configured as DPDT to meet API 670 requirements. *** One display panel to be installed in each location (ie: adjacent Bently Nevada cabinets = 1 location)
26
application note Below is the completed 3500 Rack configuration for a two bearing gas turbine driving a generator. (typical – actual slot assignments may vary due to customer preference)
Example 2: A three radial bearing gas turbine driving an electric generator. 3 Bearing Gas Turbine GT Bearing 1 Gen Bearing 1
Gen Bearing 2 2 Bearing Generator
Gen B2
GT Bearing 2
Thrust Bearing 1
Gen B1
X, Y Disp p/p
X, Y Disp p/p
X, Y Velocity
X, Y Velocity Radial Bearing Temp 1 and 2
Radial Bearing Temp 1 and 2
GT Bearing 3
GT TP
GT B3
Dual Thrust Sensors
X, Y Disp p/p X, Y Velocity Thrust Bearing Temp 1 and 2 Radial Bearing Temp 1 and 2
GT B2
GT B1
1 Keyphasor Sensor and spare
X, Y Disp p/p X, Y Disp p/p X, Y Disp p/p Radial Bearing Temp 1 and 2
X, Y Velocity Radial Bearing Temp 1 and 2 Dynamic Pressure Sensor(s)
Machine Train Diagram 3 bearing Driving a 2 bearing generator Referencing the three bearing GT machine train block diagram above, we see the need to monitor the two generator and three gas turbine radial bearings with XY proximity sensors, XY velocity sensors, and two Temperature sensors at each bearing. The gas turbine thrust bearing will be monitored with a dual voting thrust monitor and two Temperature sensors. The Gas Turbine will have one or more dynamic pressure sensors on the combustors. Finally a Keyphasor sensor will monitor the phase and speed of the gas
turbine (it is recommended to also install a spare Keyphasor probe). This configuration will require 6 3500/42 monitors, 2 3500/61 Temperature Monitors A table shown below relates the monitored location to the proper monitor and slot location in the 3500 System Rack. Given this table, the 3500 Rack Configuration can be used to generate the complete data set to configure the monitoring system.
27
application note Measurement
Location
Sensor
Monitor
Slot
Gas Turbine Keyphasor
Speed/phase
GT Shaft
Prox
3500/25
S12 upper
Gas Turbine Dynamic Pressure
Dynamic Pressure
Gas Turbine Combustor
High Temp Pressure Sensor
3500/64
S8 C 1-4
Gas Turbine Bearing 1
Disp p/p
GT Outboard
X Prox
3500/42
S2 C1
Y Prox
3500/42
S2 C2
Disp p/p
Gas Turbine Bearing 2
Gas Turbine Bearing 3
Velocity
V horiz
3500/42
S2 C3
Velocity
V vert
3500/42
S2 C4
Temp
RTD
3500/61
S9 C1
Temp
RTD
3500/61
S9 C2
X Prox
3500/42
S3 C1
Disp p/p
Disp p/p
GT Inboard
Y Prox
3500/42
S3 C2
Velocity
V horiz
3500/42
S3 C3
Velocity
V vert
3500/42
S3 C4
Temp
RTD
3500/61
S9 C3
Temp
RTD
3500/61
S9 C4
X Prox
3500/42
S4 C1
Disp p/p
GT Inboard
Disp p/p
Y Prox
3500/42
S4 C2
Velocity
V horiz
3500/42
S4 C3
Velocity
V vert
3500/42
S4 C4
Temp
RTD
3500/61
S9 C5
RTD
3500/61
S9 C6
X Prox
3500/42
S7 C1
Y Prox
3500/42
S7 C2
Temp Gas Turbine Thrust Bearing
Thrust Position
Gas Turbine Thrust Bearing
Thrust Position
Gen Bearing 2
Temp
RTD
3500/61
S10 C5
Temp
RTD
3500/61
S10 C6
X Prox
3500/42
S5 C1
Disp p/p Disp p/p
Y Prox
3500/42
S5 C2
Velocity
V horiz
3500/42
S5 C3
Velocity
V vert
3500/42
S5 C4
Temp
RTD
3500/61
S10 C1
Temp Gen Bearing 2
28
Generator Inboard
3500/61
S10 C2
Disp p/p
Generator Outboard X Prox
RTD
3500/42
S6 C1
Disp p/p
Y Prox
3500/42
S6 C2
Velocity
V horiz
3500/42
S6 C3
Velocity
V vert
3500/42
S6 C4
Temp
RTD
3500/61
S10 C3
Temp
RTD
3500/61
S10 C4
application note Component
Description
Part Number
System Rack
Bently Nevada 3500 19 inch system rack Monitor Rack Configuration utility
3500/05-01-01-02-00-01
Power Supply
Bently Nevada 3500 Dual Power Modules
3500/15-01-02-02 (typical)
1
Transient Data Interface(TDI) *
Bently Nevada 350022M Rack Interface Module with Transient Data Internal interface, TMR Version (as applicable)
3500/22-01-01-02 (typical)
1
3500/01-01 (typical)
Qty 1
Bently Nevada 3500/42 Monitoring Card
WARNING: For measurements applicable for Hydrogen Cooled Generators can be required cards with special protection
3500/42-01-02 (typical)
6
Monitoring Card
Bently Nevada 3500/64 Combustor Dynamic Pressure
3500/64-01-02 (typical)
1
Monitoring Card
Bently Nevada 3500/61 Temperature
3500/61-01-02 (typical)
2
Monitoring Card
Bently Nevada 3500/25 Keyphasor
3500/25-01-01-02 (typical)
1
Protection Rack Local Bently Nevada 3500/94 Display Display Unit ***
3500/94-03-00-01 (typical)
1
Relay Card **
Bently Nevada 3500/32 Six Channel Relay
3500/32-01-01 (typical)
1
Communication Gateway Card
Bently Nevada 3500/92 Communication Gateway
3500/92-04-01-02 (typical)
1
If EGD protocol is needed then 3500/91 can to be used
Note: All components to be ordered with “multi-approvals” to ensure complete hazardous area documentation is supplied with order. * The TMR version of the TDi Rack Interface Module (RIM) must be used in the case where SIL 3 protection functionality is required, otherwise the standard TDi RIM module should be used. ** Ensure the number of available relay channels meets the requirements. Relay Card should be configured as DPDT to meet API 670 requirements. *** One display panel to be installed in each location (ie: adjacent Bently Nevada cabinets = 1 location)
Below is the completed 3500 Rack Configuration for a three bearing gas turbine driving a generator. (typical – actual slot assignments may vary due to customer preference)
29
application note Three radial bearings design – typical 3500 configuration
•
3500/53 Electronic Overspeed Detection System GE’s Bently Nevada* 3500/53 Electronic Overspeed Detection System provides a highly reliable, fast response, redundant tachometer system intended specifically for use as part of an overspeed protection system. It is designed to meet the requirements of API Standards 670 and 612 pertaining to overspeed protection. The one channel 3500/53 modules are designed to be used in either two- or three- module groups (recommended) for overspeed protection applications. The module accepts a speed pulse input from either a proximity transducer (recommended) or a magnetic pickup and uses the input to drive alarms. The module provides four fast response alarm relay outputs for machinery protection purposes. The 3500 Overspeed Detection System can be configured in a two module set for 1 out of 2 (1oo2) voting or a three module set for 2 out of 3 (2oo3) voting. The system requires the use of a 3500 rack with redundant power supplies. Note: The best practice is to provide a separate 3500 rack dedicated to overspeed detection. A typical configuration is shown as follows:
30
application note •
Test mode should be enabled – start rpm: 400 rpm / end rpm: FSR
•
Direct Frequency Response configuration: Not applicable
•
Filtering configuration: Not applicable
•
Overspeed mode should be configured as Non-latching
•
•
Group voting should be Dependent Voting
Full-Scale Range (FSR) configuration: 5,000 rpm (for 3,600 rpm machine)
•
Not Ok Voting should be “OR Channel Not OK Voting with Overspeed Voting”
•
•
Inter Module Comparison should be enabled: 1 percent
Setpoint configuration: set according to OEM recommendations or engineering data. As a reference, note that the alarm setpoint is usually configured as 5 percent of nominal speed. The danger setpoint is usually configured as 10 percent of nominal speed.
The table below and the following instrument rack image show the typical components required to configure the 3500 Series Machinery Detection System. Component
Description
Part Number
System Rack
Bently Nevada 3500 19 inch system rack
3500/05-01-01-02-00-01
Monitor Rack Configuration utility
3500/01-01 (typical)
Bently Nevada 3500 Dual Power Modules
3500/15-01-02-02 (typical)
1
Transient Data Interface(TDI)
Bently Nevada 3500/22M Rack Interface Module with Transient Data Internal interface, TMR Version (as applicable)
3500/22-01-01-02 (typical)
1
Monitoring Card
Bently Nevada 3500/53 Electronic Overspeed Detection System
3500/53-03-02 (typical)
1
Protection Rack Local Display Unit2
Bently Nevada 3500/94 VGA Display – shares the same display used for the vibration rack
3500/94-14-00-01 (typical)
1
Communication Gateway Card
Bently Nevada 3500/92 Communication Gateway
3500/92-04-01-02 (typical)
1
Power Supply 1
Qty 1
If EGD protocol is required, the 3500/91 gateway can be used. Note: All components should be ordered with “multi-approvals” to ensure complete hazardous area documentation is supplied with order. The TMR version of the TDI Rack Interface Module (RIM) provides SIL-3 protection. If SIL-3 protection functionality is not required, use the standard TDI RIM module.
1
One display panel should be installed in each location (adjacent Bently Nevada cabinets are considered to be one location)
2
Overspeed Detection System – typical 3500 configuration
31
application note 7.3 3701 Protection/Monitoring System
The monitor is also well-suited for monitoring accessory equipment associated with the turbine such as vibration on motors and pumps and their driven and accessory equipment. The monitor is configured using Bently Nevada Monitor Configuration software from GE. The monitoring system consists of: ADAPT 3701/40 Monitor with network connection to the control system Bently Nevada Monitor Configuration software Sensors and interface module as needed to accommodate the asset configuration
ADAPT 3701/55 Emergency Shutdown Device
7.3.1 Overview of System ADAPT 3701/40 Machinery Dynamics Monitor GE’s Bently Nevada* ADAPT 3701/40 Machinery Dynamics Monitor provides continuous online monitoring of heavy duty gas turbines using sophisticated signal processing algorithms. The ADAPT 3701/40 monitor provides protection by continuously comparing monitored parameters against configured alarm setpoints to drive alarm statuses to the control system. In addition to alarms, the monitor provides essential machine vibration information to both operator and maintenance personnel. Each ADAPT 3701/40 monitor has two dedicated speed channels that accept input from either proximity probes or magnetic pickup type speed sensors. With some limitations, any of the dynamic channels can accept speed signals. The ADAPT 3701/40 monitor can accept up to 12 dynamic inputs. Depending on the system hardware and configuration selection, each dynamic channel within the monitor can perform the following measurements or functions: •
Radial Vibration
• Acceleration • Velocity • Thrust •
Dynamic Pressure
These measurements and their corresponding levels are used to drive alarms or relay logic. The ADAPT 3701/40 monitor is available in two different configurations: a simplex version and a duplex version. The duplex version has dual redundant processor modules to offer a higher level of reliability. The ADAPT 3701/40 monitor is designed to meet recommended requirements for monitoring heavy duty gas turbines and their driven equipment such as gear boxes, generators, and compressors.
32
GE’s Bently Nevada ADAPT 3701/55 Emergency Shutdown Device (ESD) uses a triple modular redundant architecture. In this configuration each processor module physically connects to a speed input. The Bently Nevada Monitor Configuration software allows the user to configure combinations of logic blocks in order to manage the system trip logic. This logic dictates how the trip mechanisms for the system are driven. The ADAPT 3701/55 ESD system can drive 12 independent trip relays. Of the 12 relays, six of these signals can be configured for 2oo3 voting. For the highest safety, the system should be configured in “de-energize to trip”, or “normally energized” mode so that loss of power does not result in a machine running unmonitored. (See the discussion on 3701/55 redundancy above) The degradation response upon a channel failure of a 2oo3 voted ADAPT 3701/55 Emergency Shutdown Device (ESD) will depend on its specific trip logic configuration. Using the most basic trip logic, a direct connect, between the Overspeed Detection System alarm and the 2oo3 voted relay, results in a system that degrades to a 2oo2 scheme in the event of the first fault and an unprotected state in the event of a second fault (2oo3 -> 2oo2 -> unprotected). This voting configuration can be augmented through voting the basic channel trip logic with the channel “Not OK.’ With the channel direct connection “OR” voted with the channel “Not OK” a channel failure, “Not OK,” will result in the 2oo3 configuration degrading to a 1oo2 configuration upon a single failure and from 1oo2 to a trip upon a second channel failure. (2oo3 -> 1oo2 -> trip). With the ADAPT 3701/55 Emergency Shutdown Device (ESD) system it is not readily possible to achieve the traditional 2oo3 degradation response (2oo3 -> 1oo2 -> 1oo1 -> trip). Due to the extremely open and unrestricted configurability of the 3701/55 ESD Overspeed Detection System, it is imperative that the specific logic configuration of the Overspeed Detection System trip function be completely understood, documented, and tested. Thorough validation is necessary in order to be certain that the system responds as desired to all possible input scenarios under all machinery operational conditions. The 5th relay in each relay module is a protection fault relay that de-energizes upon detection of a microprocessor module failure. The output of this relay must be made visible to the end user operator so that corrective action can be initiated upon the detection of a fault. (See separate Overspeed Application Guide for more details about overspeed detection.)
application note 7.3.2 System Components This section describes the basic features of each ADAPT Monitor system component.
Figure 7 - 2: 3701/40 Duplex System Features
Processor Modules Input Modules Figure 7 - 1: 3701/40 Simplex System Features
Output Module Sensor Wiring Terminal Blocks
ADAPT 3701/40 Machinery Dynamics Monitor
Processor Module
The next figure shows the ADAPT 3701/40 monitor’s features. This is an example of the simplex termination base. There is also a duplex termination base available.
The Processor module does all signal processing, alarming, data storage, and communication for the monitor system.
Ethernet Ports
Input Modules
Input Modules
Input modules provide power and input interfaces for six dynamic-signal sensors supporting a mixture of velocity, acceleration, displacement, and dynamic pressure measurement types. The input modules also provide power and interface for one Keyphasor sensor which can be a proximity probe or magnetic pickup type. The ADAPT 3701/40 system can house up to two input modules which can each be one of three different types. Each type is described in more detail below. Each of the three input module options support 3-wire proximity and/or acceleration connections.
Output Module
3701 PAV Input Module
Terminal Base Connectors. One each side (unused).
The Proximitor*/Accelerometer/Velomitor (PAV) input module is a 6-channel plus Keyphasor input module that accepts inputs from a variety of proximity, acceleration, and velocity transducers. The 3701 PAV module also provides sensor power, current limiting, and sensor input impedance. The PAV module is unique in that it is the only input module type that supports (2-Wire input connection) the use of transducers that require constant current for their power. These transducers are typically velomitors or accelerometers. Each channel dynamic and keyphasor of the 3701 PAV input module may be configured independently.
Discrete Contact Inputs External Keyphasor (speed outputs) Ground/Chassis Switch Auxiliary Power Input Earth Ground Connection Processor Module
Power Input Connector Terminal Block Locking Screw External Keyphasor Input Connector (speed inputs) Tag Name Pull-Out Card Sensor Wiring Terminal Blocks
3701 PAS Input Module The Proximitor/Accelerometer/Seismic (PAS) input module is a 6-channel plus Keyphasor input module that accepts inputs from a variety of proximity, acceleration, and velocity transducers. The 3701 PAS module also provides sensor power, current limiting, and sensor input impedance. The PAS module is unique in that
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application note sensors such as: +24 V Proximitor sensors, +24 V Interface modules, and 2-wire IEPE sensors using 3.3 mA constant current.
it is the only input module type which supports (2-wire input connection) the use of seismic or moving coil transducers that are passive devices that require a special biasing circuit interface. These are typically velocity transducers. Each channel (dynamic and keyphasor) of the 3701 PAS input module may be configured independently.
Any of the 3701 PoV module’s six channels (1-6) can be independently configured for one of the supported transducers. Each PoV module supports one dedicated negatively powered Keyphasor or speed measurement on channel 7 that is configurable for Proximitor sensors or magnetic pickups.
3701 PoV Module (Supported by the ADAPT 3701/44 Aeroderivative Monitor only)
The following table summarizes which sensor types and measurement types are supported on each of the input modules available.
The 3701 PoV module is a 6-channel plus Keyphasor/speed input module that interfaces to a variety of positively powered
Table 7-1: Sensor Types and Measurement Types Supported
Sensor Type Supported
Input Module Type
Measurement Type
Power
X
Radial Vibration Displacement
-24 VDC
X
Acceleration
-24 VDC
PAV
PAS
3-Wire Proximitor
X
3-Wire Accel
X
PoV1
3-Wire Proximitor
X
Radial Vibration Displacement
+24 VDC
3-Wire Interface Modules
X
Acceleration
+24 VDC
Bently HTVAS
Acceleration Velocity
-24 VDC
86517, 86497 Interface Modules
Acceleration Velocity Dynamic Pressure
-24 VDC
350500 Charge Amplifier
Dynamic Pressure
-24 VDC
X
Acceleration
-24 VDC
X
Velocity
Passive w/Bias
Velocity
-24 VDC 3.3 mA Constant Current
Acceleration Velocity Dynamic Pressure
+24 VDC 3.3 mA Constant Current
Speed
Passive
350501 Charge Amplifier
X
Seismoprobe* (2-Wire) Velomitor (2-Wire)
X
2-Wire IEPE
X
KPH Mag Pickup (2-Wire) KPH Mag Pickup (3-Wire)
X
X
X
Speed
Passive
KPH Proximitor (3-Wire)
X
X
X
Speed, Gap
-24 VDC
Supported by the ADAPT 3701/44 Aero Monitor only
1
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application note Output Module Slot
Auxiliary Power Connector
The output module communicates with the Processor Module to annunciate protection and user configurable events with built-in relays. The output module provides a double-pole double-throw (DPDT) protection fault relay and up to eight configurable-logic single-pole double-throw (SPDT) relays.
Auxiliary power is intended for future expansion to allow for the use of various sensors that require different power levels other than what is generated from primary and secondary power inputs. This feature is not currently used.
Protection Fault A protection fault occurs when there is a fault that is impacting alarm determination.
Power Input Connector This is a connector for +24 Vdc nominal power inputs. The ADAPT 3701/40 monitor allows for dual power supply connection to the power terminal. The ADAPT 3701/40 monitor is designed to operate from either the primary or the secondary power input. The redundancy is intended to avoid interruption of critical machine monitoring in case of either power supply failure.
Sensor Terminal Blocks The sensor terminal blocks provide wiring options for various types of sensors. The blocks are removable for ease of wiring. A multi-pin connector (DSUB-44 pin) provides simple connection to external test rigs or external terminal blocks in marshaling cabinets.
Ground/Chassis Switch and Ground Connector The ground chassis switch should always be closed (down position) for typical installations. When the installation mandates that the instrumentation reference (COM) of the ADAPT 3701/40 monitor be connected to a different ground than the safety Earth / Machine Earth, this connector breaks the connection of instrumentation COM to safety earth when in the “UP position.” When this switch is in the UP position (COM is not connected to Chassis or safety Earth), make sure an alternate ground connection is made to the terminal of this connector. Refer to the Installation section for more details.
Earth Ground Connection This is the lug for attaching a low impedance connection to protective earth.
Tag Name Pull Out Card The tag name pull out card (or tag sheet) can be used to document.
Sensor Connector Block Locks Sensor connector block locks are used to secure the removable terminal blocks.
Terminal Base Connectors Terminal base connectors share signals between multiple 3701 terminal bases plugged together. This feature is not currently supported. Monitors should not be connected together in this release as you could see unexpected behavior.
External Keyphasor Input Connector These input connectors are used for connecting a conditioned external Keyphasor signal from another 3701 monitor. The external KPH connections (inputs and outputs) will be used on future phases. This feature is not currently used.
Ethernet Ports Ethernet Port A (lower connector) and Ethernet Port B (upper connector) are independent Ethernet ports for communication to the 3701/40 monitoring system. There is one set of ports for the simplex terminal base and two sets of ports for the duplex terminal base.
Discrete Contact Inputs Six contact inputs connect to dry contact relays to give the operator control to various aspects of monitoring, configuration, and alarming. The contact inputs are: IP/PW RESET, ALARM/RELAY INH, TRIP MULTIPLY, SPECIAL ALARM INH, and CONFIG LOCK.
External Keyphasor Output Connectors These driven conditioned Keyphasor signals connect to another 3701 monitor’s external Keyphasor inputs. This feature is not currently used.
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application note 7.4 Bently Nevada Configuration Application GE’s Bently Nevada* Monitor Configuration (BNMC) software is used to configure the ADAPT 3701/40 Machinery Dynamics Monitor. This application can be used to configure a wide variety of 3701/40 channel mixtures and setups. It is used to build a custom configuration which is highly selectable and can allow the user to configure the ADAPT 3701/40 system to meet specific needs.
for a 3-wire input, any of the six dynamic transducer channels on one of these input modules will function in this mode. This connection or interface consists of three signals including Power (-24VDC), Common (COM), and Signal (SIG). This type of connection is primarily used with proximity transducers as well as certain accelerometers. However, any transducer that can function with the following constraints could be connected to this type of channel: •
Accept nominal power input of ground referenced -24 V DC
•
Consume typical current not exceeding 25 mA
Each input module and connection was designed with specific transducers or transducer types in mind. However, when using the custom configuration option, each channel can be configured or customized to fit specific needs and requirements.
•
Have a typical output impedance of 50 ohms
•
Support 3-wire connection as described above (PWR, COM, SIG)
•
Output signal range is within 0VDC to -24 V DC
The use of non-standard transducers and misconfiguration of options can introduce installation problems and functional challenges. Because this tool is highly flexible and configurable, the end user can also make undesirable choices. Specific attention should be paid to filter corner settings. Low- Pass corners should always be more than four times (4X) the High-Pass corner as a rule of thumb. Setting the corner(s) incorrectly alters the signal used for alarming. The following sections are meant to be used as a guide in understanding which transducers should be connected or mated with which type of input on each input module.
•
Typical frequency range from 0 Hz to 40 kHz
Sensors Custom Configuration Dynamic Sensors Each type of connection is designed to function with a specific set of transducers. The following sections explain each connection type and the transducers it was designed to support.
-24 VDC 3-Wire Proximitor/Accelerometer Connections Typical sensors include: Proximity: 3300XL NVS, 3300XL 5mm, 3300XL 8mm, 3300XL 11mm, 3300XL 25mm Accelerometer: 330400, 330425 Terminal block connections are shown below.
Figure 2 - 3: 3-Wire Proximitor/Accelerometer Terminal Block Connections
The PAS, PAV, PoV (Keyphasor), and PAA input modules are all designed to accept transducers of this type. Once configured
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Positive 24V 3-Wire Proximitor/Accelerometer Terminal Block Connections The PoV module is designed to power and receive signals from positively powered transducers. It is wired the same as the negative 3-wire transducer with the exception that the PWR connection now outputs +24 V DC instead of -24 V DC. This is the only module that has positive power outputs. Any transducer that can function with the following constraints could be connected to this type of channel: •
Accept nominal power input of ground referenced +24 V DC
•
Consume typical current not exceeding 20 mA
•
Typical output impedance is 50 ohms
•
Support 3-wire connection as described above (PWR,COM,SIG)
•
Output signal range is within 0 V DC to +24 V DC
•
Typical frequency range is between 0 Hz and 40 kHz
2-Wire Velomitor Connection Typical sensors include: Seismoprobe: 9200, 74712, 77224 Terminal block connections are shown shown below.
Figure 2 - 4: 2-Wire Velomitor Terminal Block Connections
This connection type is only available on the PAV input card. 3701 users with a PAV input module in one or both of the input slots
application note can configure any of the six dynamic channels on a given input module to function in this mode. This interface consists of two signal connections which are A/+ (positive) and B/– (negative). This connection type is designed to function with 2-Wire 3.3mA constant current transducers. Specifically, this input circuit is meant to be used with various Piezo type Velomitor transducers. Other transducers may also function if the following constraints are met: •
Device is powered by -24 V DC based 3.3 mA constant current connection
•
0 V DC to -24 V DC 50 ohms (less than 400 ohms)
•
Output signal range is within 0 V DC to -24 V DC
•
Typical frequency range is from 0 Hz to 15 kHz
2-Wire Seismoprobe Connection Typical sensors include: Seismoprobe: 9200, 74712, 77224 Terminal block connections are shown below.
velocity, acceleration, dynamic pressure or strain. They are typically powered by +24 V DC and use an approximately 3 mA constant current source. This is supplied by the PoV two wire input labeled A/+ and B/-.
Speed Sensors The ADAPT 3701/40 monitor accepts speed signal inputs from typical proximity type sensors or from a magnetic pickup type sensor. The magnetic pickup wires are connected to the ‘+ / -‘ terminals of the speed channel on the PAA and the COM/SIG inputs for the PAS and PAV input modules. The connection of a typical proximity type sensor uses the PWR, SIG and COM terminals. The PAS, PoV (Keyphasor), or PAV input modules can all be used for proximity Keyphasor types. The PoV module is supported only by the ADAPT 3701/44 aeroderivative monitor monitor. If you require isolated inputs for magnetic speed sensors, contact your local sales or service representative.
Figure 2 - 5: 2-Wire Seismoprobe Terminal Block Connections
This connection type is only available on the PAS input card. ADAPT 3701/40* Machinery Dynamics Monitor and ADAPT 3701/46 Hydro Turbine Monitor users with a PAS input module in one or both of the input slots can configure any of the six dynamic channels on a given input module to function in this mode. This interface consists of two signal connections which are A/+ (positive) and B/– (negative). This connection type is designed to function with 2-wire moving coil type transducers such as GE’s Bently Nevada* 9200 or 74712 Seismoprobes. To function with these transducers, a special biasing circuit is provided through the A/+ and B/- connections of the PAS input module. Other transducers may also function if the following constraints are met: •
Device is passive and expects a -6.5 V DC to -5 V DC bias
•
(-1 V DC differential from A/+ to B/-)
•
Typical output impedance is 100 ohms
•
Output signal range is within 0 V DC to -24 V DC
•
Typical frequency range is between 0 Hz and 7.2 kHz
Note: Single ended (SIG, COM) signals coming from transducers or buffered transducer outputs from other system equipment should NOT be connected to the PAA 2-wire connection meant for magnetic pickup inputs. They should always be connected to kph/speed COM and SIG connections if power is not required. If power is required the PWR connection can also be utilized. This is the case even when the buffered transducer signal is a buffered output of a magnetic pickup. Making these incorrect connections will yield unpredictable results related to the various functions associated with the speed readings due to the ground isolation discussed above. KPH Terminal block connections are shown below.
2-Wire IEPE Transducers Integrated Circuit Piezoelectric Sensors (IEPE) can measure Figure 2 - 6: Keyphasor/Speed Terminal Block Connections
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application note Note: ADAPT 3701/40 field wire diagrams (Document 100M0771) provide a list of standard transducers supported and tested during development. Any transducer not specifically called out within these diagrams should be investigated through a custom products or technical inquiry. Failing to do so could cause unexpected channel and/or system results or readings.
Relays There are several ways to configure the relay behavior. There are both normally-open or normally-closed contacts to hook up for each of the relay modules. Relays also may be set to ‘energize to trip’ or ‘de-energize to trip’ via a dip switch on the hardware. When the CPU card is pulled or is rebooting, the ADAPT 3701/40 monitor will drive the relays active. NOTE: Relay outputs should be configured ‘de-energize to trip’ in order to achieve the most reliable system. This causes the relays to trip when the monitoring device loses power. This setting may be mandatory for many safety installations.
Available Data – Measurements Band-pass The band-pass measurement can be configured to have a frequency range between 0.0625 Hz and 40,000 Hz. The number of poles for the low and high pass filters are configurable for 1, 2, 4, 6, or 8 poles. Band-passes can be configured for rms in addition to peak or peak to peak (pp). The statistical measure of the signal magnitude— rms—is less sensitive to data spikes. magnitude and is less sensitive to data spikes.
Direct Direct is another band-pass measurement. It is configured the same as a standard band-pass.
Bias The transducer bias voltage is in volts DC (V DC).
Gap The transducer gap voltage in volts DC (V DC). This is used in order to gap the distance between the probe and the turbine on proximity probes.
nX In a complex vibration signal, nX is the notation for the amplitude component that occurs at N times the shaft rotation speed. These variables reference a certain shaft through their associated speed. The nX values can be configured for derived rms (drms) in addition to peak or peak-to-peak (pp). The drms value is not calculated by using the root mean square algorithm for the nX values, but simply by scaling the peak or peak-to-peak calculation.
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1X This is an nX with the n set to 1, used to extract the amplitude component that occurs at the rotation speed frequency. These variables reference a certain shaft through their associated speed.
2X In a complex vibration signal, 2X is the notation for the amplitude component that occurs at two times the shaft rotation speed. These variables reference a certain shaft through their associated speed.
Amplitude Extraction This allows the user to home in on a specific frequency and pull the amplitude of the energy at that point. This is very similar to an nX value, except it is derived from an asynchronous spectrum and does not require a speed signal to calculate. The spectrum is calculated from a set in the associated spectrum field.
Pressure Pressure is a band-pass measurement that is configured the same as a standard band-pass. This is only available on dynamic pressure channels.
Dynamic Data The ADAPT 3701/40 monitor supports both synchronous and asynchronous waveforms and spectrums. These are used to diagnose signal integrity issues and for spectral measurements such as amplitude extraction.
Module Status The module statuses reflect the combined statuses of all channels. This status is available through the EGD protocol.
Channel Status Channel statuses apply to a specific channel. These statuses can be viewed in GE’s Bently Nevada Monitor Configuration System Event lists or through supported industrial protocols (such as Modbus and EGD).
Measurement Statuses Measurement statuses apply only to the specific measurement. Use GE’s Bently Nevada Monitor Configuration software to view these statuses on the Verification Bar Graph and Tabular List screens.
LED Descriptions The LEDs on the front panel of the 3701/40 ADAPT monitor, as shown in the Front Panel LEDs figure, indicate the operating status of the module.
application note Input Module LED Only one LED is present on each input module. This is the “MODULE OK” LED. When On, this LED indicates that the input module hardware is functioning properly without any critical or non-critical hardware faults. This LED does not indicate channel status as related to configuration or external wiring faults.
Output Module LEDs When the “MODULE OK” LED on the output moudle is on, it indicates that the module hardware is functioning properly without any critical or non-critical hardware faults. This LED does not indicate output relay status as related to configuration or external wiring faults.
Figure 7 - 7: Front Panel LEDs Table 2-2: LED Descriptions
LED
Indicates..
Module OK
The module is powered and functioning properly (no critical or non-critical hardware faults)
Protection Fault
A hardware fault that is impacting alarm determination (in conjunction with this LED being ‘On’, the “Protection Fault” Relay (on the back of the output module is also actuated/tripped )
User Inhibit
A user initiated action, such as Alarm Inhibit or Channel Bypass, is impacting alarm determination.
Attention
This LED is not used at this time.
Danger
A measurement amplitude has exceeded a danger setpoint.
Alert
A measurement amplitude has exceeded an alert setpoint.
Kph 1 OK
Onboard Speed signal 1 is triggering.
Kph 2 OK
Onboard Speed signal 2 is triggering
NetA
Network A has a valid link.
TX/RX A
Network traffic is flowing on Network A.
Net B
Indicates that Network B has a valid link.
TX/RX B
Network traffic is flowing on Network B.
Pwr 1 OK
External Power 1 input is present and within the specified range.
Pwr 2 OK
External Power 2 input is present and within the specified range.
The output module has eight additional LEDs labeled “Ch 1” through “Ch 8.” These LEDs indicate the status of each of the relays. When an LED for a channel is on, it indicates that the corresponding relay has tripped (actuated). If this LED blinks, it indicates that there is an internal hardware failure that is affecting the corresponding relay.
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application note 7.5 Management System
•
Inclusion of a knowledge-based decision support root-cause fault diagnostic rule library for automated detection and communication of commonly experienced machinery fault conditions, including a customizable machine and process diagnostic rule generator.
•
Creation of user advisories and a customizable communication plan that can be tailored to one of several available local languages as applicable and feasible.
•
Integrated electronic documentation management, electronic operator journal, and automated electronic report capabilities.
•
Capability to allow for a predetermined amount of concurrent users.
Machine Condition Monitoring Platform Recommendations Machine condition monitoring systems provide tremendous value to asset owners in heavy duty gas turbines applications due to the unique operating conditions usually experienced. In the majority of heavy duty gas turbines installations, remote location, limited technical and maintenance resources, and spares lead times are key drivers for online machinery analysis and predictive maintenance support systems. GE’s Bently Nevada* System 1* condition monitoring software platform is recommended as the correct solution for heavy duty gas turbines monitoring applications.
System 1 Software
Component
Description
OEM Part Number
System 1 software from GE takes advantage of a platform for real-time optimization of equipment and selected processes, condition monitoring, and event diagnostics. Similar in concept to a process control system that allows users to understand, diagnose, and control their process conditions in real time, the System 1 platform provides this capability for the assets that drive your process. System 1 software can also be applied to selected processes not normally addressed by a process control system, such as fuel management, combustion optimization, and many others. Listed below are typical characteristics of a System 1 software installation.
Hardware
Bently Nevada High Performance System 1™ DAQ Platform Server with flat panel display
To be confirmed during the time of order
Hardware
Bently Nevada Professional Workstation with flat panel display and laser printer
To be confirmed during the time of order
Software
System 1 software
3060/00-01
Software
System 1 software and licenses (w/Machine Library & DAQ Based Training CD)
3060/01-01-01-01-01….
Software
System 1 Enterprise Application Package (Turbo Machinery)
3060/10-01
Software
System 1 Display
3060/12-05-00
Software
System 1™ Data Export (OPC A&E)
3060/13-**
Software
System 1 DAQ
3060/14-01-01-00
Software
System 1 Data Importer
3060/15-**….
Software
System 1 System Extender
3060/16-**….
Software
System 1 Technical Service (2 extra years)
TSA_EXTENSION-**
•
Data analysis made available for hard-to-reach locations through the use of remote access ((such as offshore platforms and remote unmanned locations).
•
Trip and spurious shutdown analysis performed with the use of alarm event files.
•
Root cause analysis (RCA) using transient and dynamic data.
•
Capability to create profiles for different users and plant assets to allow access only to the desired data, menus, graphical plots and displays, and alarms and events.
•
Integration with other machinery and process data systems using standard protocols such as OPC.
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** Indicates adding the additional dash numbers to specify the product from the data sheet.
application note Decision Support GE’s Decision Support Studio* Developer Edition integrates with System 1 software to help improve business operations, giving early detection of mechanical, operational, instrument, or business events. It offers easy-to-use graphical tools to write rules comprised of equations and algorithms to enable users to easily acquire, capture, disseminate and leverage their knowledge of equipment, processes, and their business. Component
Description
OEM Part Number
Software
Decision Support Studio* Developer Edition
3060/36-01
System 1 RulePaks GE’s RulePaks* software works to extend the capabilities of System 1 software. They consist of a pre-configured set of rules designed specifically to perform real-time data validation, calculations and analysis, and detection of specific events and malfunctions. RulePaks software provides the following benefits:
Component
Description
OEM Part Number
Software
Decision Support RulePak: Heavy Duty Gas Turbines
3061/03-xx
Software
Decision Support RulePak: Generator
3061/18-xx
Software
Decision Support RulePak: Gearbox
3061/50-xx
Bently PERFORMANCE* SE*
GE’s Bently PERFORMANCE* SE* software compliments System 1 software by extending its functionality to include online thermodynamic performance monitoring of machinery. Bently PERFORMANCE SE software provides comprehensive information on the condition of machines in combined mechanical and thermodynamic formats. Characteristics of this software for heavy duty gas turbines and compressors include, but are not limited to, the following: •
Gas turbine performance calculations are performed in accordance with ASME PTC 22* 1997 in respect of heat rate and thermal efficiency parameters.
•
Corrections available for site standard or ISO standard conventions.
•
Gas turbine compressor calculations are performed using Real Gas Equation of State for air gas mixture including moisture content derived from relative humidity input (automatic from DCS/met station or manual input).
•
Ambient temperature and pressure inputs are also included in the database.
•
Enhance plant availability
•
Improve plant maintainability
•
Mitigate operational risks
•
Allow for rapid application of expertise from outside your business
•
Inlet filter screen differential pressure is accounted for in inlet pressure drop performance correction.
•
Extend asset life
•
Compressor performance calculations are computed using both isentropic and polytropic analysis for head and efficiency. Compressor pressure ration is also included in the list of displayed parameters.
RulePaks software offers the following capabilities: •
Configurable advisories
•
Robust IT security
•
Easy plug-in to the System 1 platform
•
Deployment across your business
•
Actionable information to drive user notifications
Component
Description
OEM Part Number
Software
Bently PERFORMANCE SE
Software is sold as part of a services project.
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application note SmartSignal
GE’s Proficy SmartSignal statistical modeling software provides automated and accurate early warning of a wide range of plant asset abnormalities by utilizing vibration and process data collected from DCS/Data Historians and Bently Nevada monitoring racks. With these early warnings, users can take a “deeper-dive” into diagnostic and analytical techniques using System 1 software. Process data needed for adequate modeling includes, but is not limited to load, temperature, speed, vibration, and pressure.
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SmartSignal software brings added value in terms of: •
Early detection and diagnosis
•
Immediate localization
•
High true positives
•
Ability to work across all assets: rotary, reciprocal, and fixed
•
Discovery of sensor issues to reduce doubt about your data
•
Fast implementation using engineered templates that can be customized to fit your data
•
Early and confident discovery of impending equipment issues
Component
Description
OEM Part Number
Software
Proficy SmartSignal software
To be determined…
application note 8 Related Systems for Consideration The heavy duty gas turbine should not be considered in isolation, but instead along with driven equipment, other machine trains, auxiliaries, and other plant systems as required based on the industry in which it will be deployed. Some of the related systems and the considerations are indicated below. Note: Refer to Best Practices of SIE for details about integration with other plant systems as well as ISS (Industry Specific Specifications) application notes for more information about measurements and monitoring of related systems. Gearboxes A gearbox (mostly speed reducing) can be coupled to the heavy duty gas turbine. If a gearbox is used, the monitoring system must be selected based on the number and type of bearings in the gearbox. Gearboxes require a Keyphasor sensor on each shaft for once-per-rev phase reference measurements (unless already installed on the driver or driven machine on the same shaft). If the gearbox is fitted with fluid film bearings a single axial proximity displacement transducer should beinstalled on each pinion shafts without a thrust bearing. (Most API compliant gearboxes are manufactured with pre-machined probe mounting locations at the pinion shafts) Specialty sensor designs such as “Button probes” may be considered for this purpose when the geometry of the machine prohibits conventional sensors. If the gearbox is fitted with rolling element bearings, localized protection is required, along with periodic machinery monitoring. Casing mounted acceleration transducers should be used. Overall machinery status should be monitored using an integrated velocity
measurement, while the enveloped acceleration spectrum (as applicable) should be used for identifying specific machinery defects such as developing bearing and gear problems. One casing mounted piezo-velocity transducer should be installed at each bearing, or at the input and output bearings on a gearbox. The transducer axis should be aligned with the principal bearing l oad direction. Acceleration measurement on the gearbox can provide the proactive maintenance planning system with a valuable source of information on progressive damage to gear elements. Specific mechanical fault symptoms related to gear wear or sudden damage can be detected through online vibration analysis. General purpose accelerometers installed in accordance with API 670 are suitable for this application. Bearing metal temperatures, oil analysis, and decision support for gearboxes should also be considered for creating a full-fledged condition monitoring program for gearboxes connected to a heavy duty gas turbine. Steam Turbine Generators, Boiler Feedwater Pumps, Fans, Heat Recovery Steam Generators The systems related to a heavy duty gas turbine used in a combined cycle power plant (integrated gasification type), can be quite complex. Many plants are simpler than the following diagram that points out a variety of possible complexities. Steam turbine generator sets should be monitored using turbine supervisory instrumentation connected to System 1 condition monitoring software. Compressors pumps and fans should be monitored using online continuous/periodic measurements based on criticality, failure modes, and failure cycles of those machines. Decision Support software can also be used to provide actionable
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application note advisories and thermodynamic performance monitoring. Process variables monitoring either at DCS level or within the condition monitoring platform should be considered for all assets. Lube System, Cooling Towers Process variable monitoring (fluid temperature, pressure, and flow) at various points should be used detect developing malfunctions. This is usually available at the DCS, and the data should be imported into the condition monitoring platform for proactive alarming and early warnings. Unit Control Systems There should be integration between the monitoring system and the unit control systems (such as Mark* VIe systems) for import and export of machinery condition data and process data. Appropriate/pre-approved communication gateways and protocols should be considered, including the interconnections and geographical location of connection points system. A system should be developed and approvals obtained before ordering. Plant DCS & Historian The monitoring system can interface with a plant control system/historian to import process data and export condition data (if required for operator-driven reliability practices). Appropriate/pre-approved communication gateways and protocols such as OPC should be considered, including the interconnections and geographical location of connection points. A system architecture drawing should be developed and approvals obtained before ordering. Computerized Maintenance Management System (CMMS) The value of condition monitoring can be realized only if the right work is identified early and the necessary corrective/preventive actions are taken in a proactive manner. In many plants a CMMS such as SAP™ or MAXIMO™ is used to manage maintenance activities. A condition monitoring system can identify work and automatically (or manually) initiate a work order in the CMMS. This interface and workflow should be considered while designing the condition monitoring platform for the plant. Plant Condition Monitoring System A plant condition monitoring system such as GE’s Bently Nevada System 1 software should be the heart of the proactive work identification program for the heavy duty gas turbine as well as all related systems in the plant. This system acts as a platform where all condition monitoring technologies converge and a database is created. The system should be able to provide data in various plots/formats for diagnostic purposes, as well as acting as a knowledge repository including the heavy duty gas turbine manuals, manual entries of notes, and more. This system should support the maintenance strategy of the plant for the heavy duty gas turbine as well as all related systems. Lube Oil Monitoring Permanent oil sampling fittings should be installed in each machine as well as the gearbox to enable representative samples to be
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drawn from the working fluid inside the machines. Oil analysis is a very important condition monitoring measurement and the analysis report should be imported to the condition monitoring platform for availability based on asset Tag ID of the heavy duty gas turbine as well as related machines along with other condition monitoring information. Remote Monitoring, Diagnostic, and Supporting Services External support from OEMs and consultants can provide extra expertise to set up, maintain, and use condition monitoring technology. These services can build understanding of the condition of the heavy duty gas turbine and related machines for added reliability and performance. The system architecture should show how this is going to be achieved including secure IT set-up. Modeling Software Early warnings of potential failures should also be obtained by adding modeling tools like GE’s SmartSignal software along with System 1 software. A data link may be required to the historian and/or other plant systems to create the model based on historical data as well as to validate whether the measured values fall within acceptable models. If not, an anomaly is notified locally to the plant or to a remote monitoring and performance center. If modeling software is needed to support plant maintenance strategy, the system architecture should identify the required interfaces.
9 Appendix 1 – Thrust Voting Considerations Bently Nevada 3500 Series Measurement and API 670 Compliance The design of a monitoring system must strike a careful balance between false trips of the machine and missing conditions should result in the machine being tripped. Obviously missing a machine trip can be a serious event, but incorrectly tripping a machine is also an event that could compromise safety, especially considering the complex processes that most of the machinery covered by API 670 supports. In both missed trip and false trip cases safety may be compromised and there is the risk of potential negative financial impact to the end user.
API 670 Requirements API 670 outlines requirements for axial position measurements, calling for paired channels. The requirement allows for one transducer signal (single voting logic, 1oo2) or two transducer signals (dual voting logic, 2oo2), to exceed the danger setpoint to initiate shutdown relay actuation. Specifically, with regard to 2oo2 dual voting logic applications, the standard indicates that shutdown relay actuation should occur when: •
Both axial position transducers or circuits fail
•
One channel has failed and the other has exceeded its danger setpoint
•
Both channels exceed the danger setpoint.
application note Transducer System Faults The axial position measurement is distinct from other measurements covered by API 670 due to the critical nature of the measurement and the possibility that the transducer element can be destroyed under extreme machinery conditions. There is the possibility that the probe target can shift suddenly in the direction of the probes with sufficient magnitude to contact and destroy the transducer. This may occur before the monitoring system measurement is capable of detecting the sudden shift and generate a trip signal. In this scenario, if the protection system were to defeat alarming upon probe failure, the alarming capability would be defeated at the time that the machine is experiencing what is highly likely to be an operating condition requiring shutdown – the very type of situation that the measurement is put in place to protect against. The possibility that the loss of a transducer is very likely to have been caused by the machine resulting in the overall protection function being defeated is what is fundamentally behind the standard’s requirement to trip upon loss of protection circuit function.
Monitoring System Faults
To accommodate for the possibility of monitoring system faults, the monitoring system has extensive diagnostic capability to self-diagnose and annunciate internal faults. In the event of an internal monitoring system fault the system responds by providing visibility to the condition by means of a number of mechanisms to annunciate the condition. This provides for a more effective alternative response to a fault than simply tripping the machine or voting to trip. Visibility mechanisms include: monitor LED states, monitor channel states (available in Modbus registers, local and remote system displays, and in System 1 software), 4 to 20 mA outputs, and the 3500 rack OK relay. These allow for visibility by plant personnel to immediately be informed and attend to a protection system malfunction. In the case of a single point monitoring system fault, the second channel supporting the recommended dual channel 1oo2 configuration continues to protect the machinery without the user suffering a false trip of the machinery and the associated safety risk and process interruption.
Summary
The design of the Bently Nevada 3500 Series Machinery Monitoring System thrust channel type considers the protection circuit outlined in API 670 section 5.4.3, to only include the probe and transducer system that are susceptible to machine-induced faults. The 3500 system is capable of differentiating between faults that occur with the transducer system and those that occur in the monitoring system itself. While the system drives for trip in the case of a transducer system fault, a fault at the monitoring system does not. Rather than driving for machine trip, the system design annunciates the fault, providing an opportunity for plant personnel to respond to the problem condition.
The axial position measurement is critical and is adapted to the application specific possibility of a probe fault being induced by a catastrophic machinery condition. Because of this possibility, API 670 requires that a transducer system fault result in that path’s protection relay actuation or voting for trip in dual logic applications. The 3500 system meets these requirements by driving for trip in the event of a transducer system malfunction. The possibility of a catastrophic machinery condition compromising the protection function does not extend to the monitoring system portion of the protection path. Therefore the 3500 system does not generate a trip signal in the case of a monitoring system fault.
A protection system designed such that it generates a trip signal in the event of a system fault condition has a significantly increased tendency for false tripping of the machine, unless the fault can credibly be linked to a machine emergency condition such as is the case with axial position transducers. If those elements of the monitoring system that are “out of harm’s way” were to drive a trip relay actuation upon failure (single logic), or drive a vote for trip in dual voting logic, the system would contribute significantly to reducing machinery availability. This is especially relevant considering the relative complexity of a typical monitoring system architecture.
The 3500 system configured for thrust measurement is capable of differentiating between a fault at the transducer level and one that occurs within the monitoring system itself. This allows the system to avoid false trips that may otherwise result from monitoring system malfunctions. The 3500 monitoring system internal diagnostic coverage and numerous fault annunciation methods all support the availability of the protection function by making the status of the monitoring system channels known to plant personnel in real time. The protection function is maintained without potentially compromising availability of the monitored machine and the associated process.
In effectively all cases, a fault at the monitoring system will not coincide with, nor be driven by a safety critical machine operating condition. Unlike the transducer portion of the protection path, there are no known credible cases where the machine is capable of compromising, or generating a fault in the monitoring system. Therefore, driving for a trip in the event of a monitoring system fault results in a false machine trip in effectively all cases for single logic applications, and has serious potential negative impact on the availability of the machinery in dual logic cases.
The 3500 system’s axial position measurement is compliant to the requirements of API 670.
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application note 10 Appendix 2 – Voting Truth Tables Voting Truth Tables for Normal AND and True AND voting A. True AND Voting – Radial Vibration
C. Normal AND Voting – Radial Vibration
Trip logic: CHAdanger AND CHBdanger = Trip
Trip logic: CHAdanger AND CHBdanger = Trip
B.
Channel A
Channel B
Result
Channel A
Channel B
Result
OK
OK
NO ALARM
OK
OK
NO ALARM
OK
NOT OK
NO ALARM
OK
NOT OK
NO ALARM
OK
DANGER
NO ALARM
OK
DANGER
NO ALARM
DANGER
OK
NO ALARM
DANGER
OK
NO ALARM
DANGER
NOT OK
NO ALARM
DANGER
NOT OK
ALARM
DANGER
DANGER
ALARM
DANGER
DANGER
ALARM
NOT OK
OK
NO ALARM
NOT OK
OK
NO ALARM
NOT OK
NOT OK
NO ALARM
NOT OK
NOT OK
NO ALARM
NOT OK
DANGER
NO ALARM
NOT OK
DANGER
ALARM
True AND Voting – Radial Vibration with Not OK
D. Normal AND Voting – Radial Vibration with Not OK
Trip logic: CHAdanger OR CHANot OK AND CHBdanger OR CHBNot OK= Trip
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Trip logic: CHAdanger OR CHANot OK AND CHBdanger OR CHBNot OK= Trip
Channel A
Channel B
Result
Channel A
Channel B
Result
OK
OK
NO ALARM
OK
OK
NO ALARM
OK
NOT OK
NO ALARM
OK
NOT OK
NO ALARM
OK
DANGER
NO ALARM
OK
DANGER
NO ALARM
DANGER
OK
NO ALARM
DANGER
OK
NO ALARM
DANGER
NOT OK
ALARM
DANGER
NOT OK
ALARM
DANGER
DANGER
ALARM
DANGER
DANGER
ALARM
NOT OK
OK
NO ALARM
NOT OK
OK
NO ALARM
NOT OK
NOT OK
ALARM
NOT OK
NOT OK
ALARM
NOT OK
DANGER
ALARM
NOT OK
DANGER
ALARM
application note Observations: 3500 RV and TP Voting 1. E.
Normal AND or True AND Voting – Thrust Position
A. RV True AND
Trip logic: CHAdanger AND CHBdanger = Trip
F.
Four truth tables define voting an RV XY pair and two truth tables define voting a TP pair. These are: B.
RV True AND OR-ed with channel OK
C. RV Normal AND
Channel A
Channel B
Result
OK
OK
NO ALARM
D. RV Normal AND OR-ed with channel OK
OK
NOT OK
NO ALARM
E.
OK
DANGER
NO ALARM
TP True AND as well as TP Normal AND (note: these are identical)
DANGER
OK
NO ALARM
F.
DANGER
DANGER
ALARM
TP True AND OR-ed with channel OK as well as TP Normal AND OR-ed with channel OK (note: these are identical)
DANGER
NOT OK
ALARM
NOT OK
OK
NO ALARM
NOT OK
NOT OK
ALARM
NOT OK
DANGER
ALARM
Normal AND or True AND Voting – Thrust Position with Not OK
Trip logic: CHAdanger OR CHANot OK AND CHBdanger OR CHNot OK= Trip Channel A
Channel B
Result
OK
OK
NO ALARM
OK
NOT OK
NO ALARM
OK
DANGER
NO ALARM
DANGER
OK
NO ALARM
DANGER
NOT OK
ALARM
DANGER
DANGER
ALARM
NOT OK
OK
NO ALARM
NOT OK
NOT OK
ALARM
NOT OK
DANGER
ALARM
2.
Timed OK Channel Defeat (TOKCD) prevents a trip on simultaneous loss of OKs (lightening, etc.) for voted RV channels when OK is not OR-ed for both True and Normal voting as shown in truth table A and C.
3.
If RV is OR-ed with the channel OK, a trip occurs as shown in truth table B and D.
4.
The nature of the TP measurement does not allow TOKCD to be applied to that measurement (see Appendix 5).
5.
If TP is OR-ed with the opposite OK, the OR-ed OKs will trip upon a momentary instantaneous loss of OK as shown in truth table F. A long term loss of OK (greater than 0.1 second) will cause a trip as shown in the truth table.
6.
If TP is not OR-ed with the OK as shown in truth table E, a momentary instantaneous loss of both transducer OKs will most likely not cause a trip because of the time required by the monitor to calculate perceived axial position shift and the normal 0.1 second TP time delay. A long term loss of both transducer OKs (greater than the 0.1 second time) will result in a trip as shown in the truth table E.
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© 2015 General Electric Company. All rights reserved. Information provided is subject to change without notice. Best practices and recommendations herein are applicable to most aeroderivative gas turbines contingent on OEM design and adherence to OEM guidelines.
GE Oil & Gas 1631 Bently Parkway South Minden, NV 89423
*Denotes a trademark of Bently Nevada, Inc., a wholly owned subsidiary of General Electric Company. The GE brand, GE logo, Bently Nevada, System 1, Keyphasor, Proximitor, Velomitor, RulePaks, Bently PERFORMANCE SE, ADRE, SPEEDTRONIC, Mark, SmartSignal, SAP and MAXIMO are trademarks of General Electric Company.
24/7 customer support: +1 281 449 2000 geoilandgas.com/
Modbus, Modicon, and Teflon are trademarks of their respective owners.
GEA32129A (12/2015)
