Vibration Monitoring for Gas Turbines
Steve Sabin – SETPOINT Vibration
Jan
2015
About content…
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About SETPOINT…
20 minutes from
Lake Tahoe
Machinery Protection
Condition
Monitoring
About me…
• BSEE from Oregon State University
• 22 years with Bently Nevada
• Sales Engineer in Western Canada
• TransCanada Pipelines, NOVA Pipelines, etc.
• ORBIT magazine executive editor
• Marketing Director
• Lots and lots of articles / app notes / white papers
• 5 years with SETPOINT
• Secretary for API 670 4th and 5th editions
Links to Resources
• API 670 5th edition
http://www.api.org/publications-standards-and-statistics/standards/whatsnew/publication-updates/new-refining-publications/api_std_670
• 1Q2005 ORBIT magazine Gas Turbine Vibration Monitoring article
http://www.ge-mcs.com/download/orbit-archives/2001-2005/1st_quarter_2005/1q05_gasturbinevibmonitoring.pdf
• Georgia Tech Short Course on Combustion Instability (“Humming”)
http://soliton.ae.gatech.edu/people/tlieuwen/hummingresources/hummingoverview.ppt
• Video on how SETPOINT uses the PI System in place of
stand-alone condition monitoring software
http://www.osisoft.com/Templates/item-abstract.aspx?id=10985
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Monitoring Fundamentals
The Industry Standard – API 670
•
Details sensors, monitoring systems, documentation requirements, and
installation practices
•
Specifies accepted “good engineering practice” for machinery protection
•
Excellent starting point for company-specific vibration monitoring standards in
all industries (not just O&G)
•
Developed and refined over five successive editions since first published in
1976 by a broad community of end users, instrument manufacturers, and
machinery OEMs
•
Originally focused on bearing vibration, axial (thrust) position, bearing
temperature, and gearbox casing vibration – expanded to include surge
detection, overspeed, condition monitoring, and recip-specific measurements
Distinctions
Protection Systems
Purpose
API 670 Scope
Displays
Platform
Condition Monitoring Systems
Distinctions
Protection Systems
Purpose
API 670 Scope
Displays
Platform
Auto-Shutdown Protection
High-integrity “alert” and “danger” alarms suitable for
automatically tripping the machine – no operator
intervention required.
Condition Monitoring Systems
Distinctions
Protection Systems
Purpose
API 670 Scope
Displays
Platform
Auto-Shutdown Protection
High-integrity “alert” and “danger” alarms suitable for
automatically tripping the machine – no operator
intervention required.
Condition Monitoring Systems
Information Delivery
High-resolution data for machinery engineers to analyze for
run/don’t run decisions, outage planning, root cause
diagnostics, etc.
Distinctions
Protection Systems
Purpose
Auto-Shutdown Protection
High-integrity “alert” and “danger” alarms suitable for
automatically tripping the machine – no operator
intervention required.
API 670 Scope
Normative
Historic focus of 1st through 5th editions
Displays
Platform
Condition Monitoring Systems
Information Delivery
High-resolution data for machinery engineers to analyze for
run/don’t run decisions, outage planning, root cause
diagnostics, etc.
Distinctions
Protection Systems
Condition Monitoring Systems
Purpose
Auto-Shutdown Protection
High-integrity “alert” and “danger” alarms suitable for
automatically tripping the machine – no operator
intervention required.
Information Delivery
High-resolution data for machinery engineers to analyze for
run/don’t run decisions, outage planning, root cause
diagnostics, etc.
API 670 Scope
Normative
Historic focus of 1st through 5th editions
Informative
New in 5th edition as an “Informative Annex”
Displays
Platform
Distinctions
Protection Systems
Condition Monitoring Systems
Purpose
Auto-Shutdown Protection
High-integrity “alert” and “danger” alarms suitable for
automatically tripping the machine – no operator
intervention required.
Information Delivery
High-resolution data for machinery engineers to analyze for
run/don’t run decisions, outage planning, root cause
diagnostics, etc.
API 670 Scope
Normative
Historic focus of 1st through 5th editions
Informative
New in 5th edition as an “Informative Annex”
Displays
Basic (bargraphs / status / trends)
Intended for operators – often via DCS screens; local
display at racks are optional but frequently included
Platform
Distinctions
Protection Systems
Condition Monitoring Systems
Purpose
Auto-Shutdown Protection
High-integrity “alert” and “danger” alarms suitable for
automatically tripping the machine – no operator
intervention required.
Information Delivery
High-resolution data for machinery engineers to analyze for
run/don’t run decisions, outage planning, root cause
diagnostics, etc.
API 670 Scope
Normative
Historic focus of 1st through 5th editions
Informative
New in 5th edition as an “Informative Annex”
Displays
Basic (bargraphs / status / trends)
Intended for operators – often via DCS screens; local
display at racks are optional but frequently included
Detailed (waveforms, orbits, spectrums, etc)
Intended for machinery experts; often via remote access to a
local server in the plant collecting and storing the data
Platform
Distinctions
Protection Systems
Condition Monitoring Systems
Purpose
Auto-Shutdown Protection
High-integrity “alert” and “danger” alarms suitable for
automatically tripping the machine – no operator
intervention required.
Information Delivery
High-resolution data for machinery engineers to analyze for
run/don’t run decisions, outage planning, root cause
diagnostics, etc.
API 670 Scope
Normative
Historic focus of 1st through 5th editions
Informative
New in 5th edition as an “Informative Annex”
Displays
Basic (bargraphs / status / trends)
Intended for operators – often via DCS screens; local
display at racks are optional but frequently included
Detailed (waveforms, orbits, spectrums, etc)
Intended for machinery experts; often via remote access to a
local server in the plant collecting and storing the data
Platform
Hardware
Intended strictly for machinery protection; usually rackbased; not simply transmitters into PLCs or DCSs
Distinctions
Protection Systems
Condition Monitoring Systems
Purpose
Auto-Shutdown Protection
High-integrity “alert” and “danger” alarms suitable for
automatically tripping the machine – no operator
intervention required.
Information Delivery
High-resolution data for machinery engineers to analyze for
run/don’t run decisions, outage planning, root cause
diagnostics, etc.
API 670 Scope
Normative
Historic focus of 1st through 5th editions
Informative
New in 5th edition as an “Informative Annex”
Displays
Basic (bargraphs / status / trends)
Intended for operators – often via DCS screens; local
display at racks are optional but frequently included
Detailed (waveforms, orbits, spectrums, etc)
Intended for machinery experts; often via remote access to a
local server in the plant collecting and storing the data
Platform
Hardware
Intended strictly for machinery protection; usually rackbased; not simply transmitters into PLCs or DCSs
Software
Generally computer-based; uses Microsoft business/consumer
operating systems
Radial Vibration
Y-probe
X-probe
Displacement
(mils pk-pk)
Casing Vibration
Velocity
(in/sec 0-pk)
Axial (Thrust) Position
NORMAL
Gap (mils)
Can configure for:
• increasing gap upscale* (normal)
• increasing gap downscale (counter)
Probe
COUNTER
*increasing gap upscale depicted here
Eccentricity
• Indicates amount of shaft bow
• Typically measured at a shaft extreme
• Slow-roll speeds (well below rotordynamic effects)
Phase / Speed
Pulses/min
(rpm)
Reverse Rotation
CW Rotation
Reverse Rotation
CCW Rotation
• Peak reverse speed
• # of reverse rotations
Temperature Measurements
• Bearing metal temperature measurements are
covered in API 670 and are often included in the
machinery protection system, since they are
machinery temperatures, not process
temperatures
• Other temperatures in machinery are
sometimes measured as well:
• Electric motors – winding temperatures
• Gas turbines – exhaust temperatures
• Recip compressors – valve temperatures
Conceptual Overview
Monitors
Sensors
Bearings
Machine Cases
Machinery
Protection
System
Shafts
Turbine
Generator
Typical Probe Mounting
image courtesy of Elliott Group
Typical Transducer Arrangement
Typical System Arrangement
8 x 4-channel monitors for 30 vib’n,
thrust, speed, and phase inputs
Condition
Monitoring
SW
Redundant
MODBUS®
links with DCS
3 x 6-channel monitors
for 16 temp inputs
Local HMI
4-20mA and relay outputs
Fully redundant power
connections to 24Vdc supplies
Typical Local HMI
Typical Condition Monitoring Plots
Orbit / Timebase
Trends
Bode
Polar
Typical Condition Monitoring Plots
Spectrum
Alarm List
Waterfall
Gas Turbine Classifications
Classifications
Industrial (i.e. Heavy Duty)
Aeroderivative
•
•
•
•
•
•
•
•
•
•
Fluid-film bearings
Solely for industrial use
Heavy / Large /Foundation-mounted
Always single-spool; often single-shaft
Conventional maintenance
SGT6-2000E
(103 MW)
Rolling-element bearings
Adapted from aircraft engine design
Lightweight / Compact / Skid-mounted
Often multi-spool GG driving a PT
Swap-out maintenance
FT4000 SWIFTPAC®
(60 MW)
Sub-Classifications
“Light” Industrial
Hybrid
• All-industrial components
• Fluid-film bearings
• Skid-mounted / packaged
•
•
•
•
Centaur 40
(50 MW)
Part-aero / Part-industrial components
Mix of bearing types
Multi-spool/shaft
MS6001FA (LP compressor) + LM6000
(HP compressor and HP/IP turbine)
LMS100
(~100 MW)
Major Manufacturers
Industrial
Aeroderivative
Brands, Acquisitions, and Mergers
x
6
10
(but mostly convergence)
Monitoring Considerations
Aeroderivative Nomenclature
(Image courtesy of ORBIT magazine)
Multi-Spool Aeros
Typical 1-Spool GG
Typical 2-Spool GG
(shown in figure below)
Typical 3-Spool GG
LM2500
GE LM6000
Rolls-Royce RB211
GE LM1600
Rolls-Royce TRENT
Aerodynamically-Coupled Gas Turbine
2-Spool Gas Generator
LP
Comp
HP
HP Spool
HP
LP Spool
Comp
HP Spool
Turb
LP
Turb
Power
Turb
Driven Machine
(pump, generator,
compressor, etc.)
Monitoring Philosophies
Industrial
Aeroderivative
•
•
•
•
•
•
•
•
•
•
•
•
Fluid-film bearings  Proximity
Heavily instrumented  6-12 sensors
Conventional maintenance
Engine problem = loss of product
Relatively OEM-independent
Relatively “clean” vibration signals
Rolling-element bearings  Siesmic
Lightly instrumented  1-3 sensors
Swap-out maintenance
Engine problem = loss of life
Extremely OEM-dependent
Extremely noisy vibration signals
(lots of signal processing required)
Recommended Monitoring
INDUSTRIAL
Measurement
Description
MINIMAL TRANSDUCER SUITE
• Radial Bearings
• Thrust Bearings
• Shaft Speed / Phase
• X-Y proximity probes
• Dual-voting axial probes
• Once-per-turn phase reference probe
SUPPLEMENTAL FOR LARGE FRAME SIZES
• Casing Vibration*
• Eccentricity
• Seismic velocity at bearing caps
• Proximity probe for rotor sag or bow
* NOTE: GE frame-type gas turbines use only seismic bearing cap vibration for shutdown protection;
proximity probes on radial bearings are used only for condition monitoring.
Recommended Monitoring
AERODERIVATIVE
Measurement
Description
ENGINE
• Casing Vibration
• Shaft Speed
• Seismic at OEM-specified locations with
OEM-specified filtering (primarily 1X)
• Multi-tooth gear for each spool speed
POWER TURBINE
• Rolling Element Bearings
• Casing Vibration
• Fluid Film Bearings
• Radial Bearings
• Thrust Bearings
• Shaft Speed/Phase
• Seismic velocity at OEM-specified locations
• X-Y proximity probes
• Dual-voting axial probes
• Once-per-turn phase reference probe
Typical OEM-Specified Schema
3. Have unfiltered accel signal available
for diagnostics (not used for monitoring)
HOT
50 pC/g Accel
Field
WARM
Spool Speed x
gear ratio
2. Monitor filtered 25-350 Hz wideband
for “other” engine problems
• 10 second time delay alarm
• 10 second danger level to trip
Interface Module
Monitor
1. Monitor each rotor @ 1X for blade loss
COOL
events
 1X velocity tracked
at spool speed
• Fast (100 mS) danger level time
 Raw
Acceleration
 Wideband Velocity
delay trip
(10 mV/g)
@ 25-350 Hz (100mV/ips)
• 1 second time delay on alarm levels
Control Room
GE IDM FOR AERODERIVATIVES
Why Velocity and not Accel?
Exhaust Gas Temperature
• Ideally measured at turbine inlet,
(but usually too hot there!)
• Measured at tubine exhaust
plenum instead (via thermocouples
placed circumferentially)
• Indicates problems in hot gas path
• Can be used for both control and
monitoring
Typical exhaust gas temperature profile
(Screen capture from GE System 1 software)
Combustor Instability (Humming)
• Huge issue with DLE engines
• Excellent short course by Georgia Tech’s
Tim Lieuwen (click on screen at right for
link to course slides)
“Humming” Monitoring
• Monitored with dynamic pressure transducers observing pulsations
in combustor cans – often with stand-off tubes
• Proprietary OEM schemas for sophisticated narrow-band frequency
monitoring (often 12-pole or better roll-off required)
• Used as part of feedback control loop to adjust fuel mixture if
humming occurs
Control Target:
“As lean as possible
without humming”
Pressure
Sensor
Combustion
Control
“Humming”
Monitor
Combustor
Typical Gas Turbine Transducers
High-Temperature
Moving-Coil Velocity Sensor
(Metrix 5485C)
High-Temperature
Accelerometer Sensor
(Metrix SA6350)
Proximity Sensor
(Metrix MX2030)
High-Temperature
Pressure Sensor
(Kistler)
Recommended Reading
Q&A