Case StudiesGas Injection Compressors are critical for offshore oil production facilities. A compressor downtime lowers oil production. This case study is about a Gas Injection Compression train at an offshore platform in the Middle East. This case study focuses on how the gradual increase in vibrations was successfully diagnosed, pinpointing the root cause for the high vibration, and finally how it was resolved. The Compression train is equipped with an online vibration monitoring and protection system in addition to a condition monitoring software that was used to diagnose the issue

Ganesh, Sankar

Sharma, Amit

English

Texas A&M University

Case Study on resolving high vibration issue of 
a centrifugal compressor at an offshore 
platform
Amit Sharma
Lead Engineer, Machinery Diagnostics Services
Baker Hughes GE-Digital Solutions, Bently Nevada
Sanker Ganesh
Technical Leader, MENAT, Machinery Diagnostics Services
Baker Hughes GE-Digital Solutions, Bently Nevada
• Amit Sharma – Lead Engineer, MENAT
- Lead Engineer, BHGE-BN, Machinery Diagnostics Services, Abu Dhabi, U.A.E.
- B.Tech Mechanical Engineering (2003) from Jamia Millia Islamia University, Delhi, India
- 10 years with GE-Bently Nevada Machinery Diagnostics Services since 2007
- Project Engineer- Rockwell Automation-Entek IRD
• Sankar Ganesh – Technical Leader, MENAT
- Technical Leader for GE Bently Nevada Machinery Diagnostics Services, MENAT region
- Bachelor Mechanical Engineering (1993) from Bharathidasan University, India.
- Over 20 years experience in vibration field and 10 years with GE Bently Nevada, 
including rotating equipment balancing, vibration analysis, diagnostics and root cause 
analysis
- Published case studies in METS and Turbomachinery symposium
Authors
Gas Injection Compressors are critical for offshore oil production facilities.
A compressor downtime lowers oil production.
This case study is about a Gas Injection Compression train at an offshore
platform in the Middle East.
This case study focuses on how the gradual increase in vibrations was
successfully diagnosed, pinpointing the root cause for the high vibration,
and finally how it was resolved.
The Compression train is equipped with an online vibration monitoring
and protection system in addition to a condition monitoring software that
was used to diagnose the issue.
Abstract
• Problem Statement
• Machine Details
• Observation & Analysis
• Conclusions & Recommendations
• Machine Inspection Findings
• Corrective Actions & Lesson Learned
Contents
Problem Statement
• 26th July 2015 The gradual rise in shaft vibration towards Non-Drive 
End (NDE) bearing began from startup onwards
• October 2015 Readings on Gas Injection Compressor Train were 
observed touching vibration alarm limits, 51 𝜇𝑚pp 
(microns peak to peak) towards LP compressor NDE 
bearing at higher speed/load condition.
• October 2015 From here onwards, the vibration amplitudes of LP 
onwards Compressor NDE bearing intermittently reached 
alarm limits & Machine availability became a concern 
for the customer.
Machine  Details
LP & HP Compressors
- 10270 rpm
- Direction of rotation- CW 
(PT to compressor)
- Tilting Pad Bearings
Speed Increaser GB
- Gear Ratio- 2.139
- Input/Output- 4800/10270 
rpm
Aero Derivative  Engine
Gas Generator & Power 
Turbine
- 5100/4800 rpm
Observations & Analysis
Shaft Vibration Amplitudes- LP Compressor Bearings, Oct 2015
Startups after 26th July 2015, the NDE bearing amplitudes shows gradual 
rise approaching alarm levels (51 𝝁𝒎pp)
DE Bearing
NDE Bearing
11 umpp
28 umpp
48 umpp
31 umpp
Observations & Analysis
Bode Plots- 1st March 2015 Startup- LP Compressor Bearings
Normal startup observed for both bearings, only Drive End (DE) bearing 
observed high (in line with machine history after Aug 2014 maintenance)
1X Phase
Amplitudes
1X Phase
Amplitudes
1X Phase
Amplitudes
1X Phase
Amplitudes
Observations & Analysis
Bode Plots- 30th September 2015 Startup- LP Compressor Bearings
Startup shows steep rise in amplitudes at NDE bearing, especially above  
12000 rpm. DE bearing Vibrations  reduces with rise in speed/load.
1X Phase
Amplitudes
1X Phase
Amplitudes
1X Phase
Amplitudes
1X Phase
Amplitudes
Observations & Analysis
Full Spectrum Cascade Plots Comparison- LP Compressor DE Bearing
1st March 2015 start up 30th September 2015 start up
Rise in reverse 1X component indicative of increased DE pre-load forces.
Frequency
S
p
e
e
d
A
m
p
lit
u
d
e
S
p
e
e
d
Frequency
A
m
p
lit
u
d
e
Observations & Analysis
Full Spectrum Cascade Plots Comparison- LP Compressor NDE Bearing
Rise in reverse 1X component indicative of increased NDE pre-load 
forces.
Frequency
S
p
e
e
d
A
m
p
lit
u
d
e
S
p
e
e
d
Frequency
A
m
p
lit
u
d
e
1st March 2015 start up 30th September 2015 start up
Observations & Analysis
Direct / 1X Orbit Plots: LP Compressor Bearings
Highly elliptical orbit observed, with higher amplitudes at NDE Bearing 
Observations & Analysis
Shaft Centerline Plots -LP Compressor Bearings
As speed increased above 12000 rpm, the rotor shows downward movement.
Amplitude Amplitude
Conclusions:
• As speed increased above 12000 rpm, the vibrations at NDE bearing 
reached alarm limits (51 𝜇𝑚pp) while the DE bearing showed 
reduction in vibration.
• Due to improper DBSE (distance between shaft ends), instead of thrust 
bearing taking the load, the load was absorbed by the coupling, 
resulting in rise in shaft vibration amplitudes at the NDE bearing.
• Abnormal movement of shaft centerline and increased ellipticity of 
orbit shape with speed/load rise indicates DBSE or alignment related 
issue.
Recommendations:
• DBSE & coupling pre-stretch shall be checked across both 
ends of LP compressor as per protocol values.
• Verify the alignment condition of the machine train.
Conclusions & Recommendations
Machine Inspection Findings
Evidence of hot spots observed on the bearing pads which might be due
to pre-load on the bearing.
• Coupling Pre-stretch between LP & HP compressor was found to be
1.72 mm compared to the recommended 1.32 mm.
• The bearings pads were observed with minor carbon deposits which
might be due to burned oil in the pads.
Corrective Actions & Lesson Learned
Corrective actions:
• Coupling pre-stretch between LP & HP compressor was found 1.72 
mm against recommended 1.32 mm. Hence a shim of 0.4 mm was 
added.
• LP Compressor NDE bearing was replaced with new one with 
clearances maintained at 203 𝜇𝑚. Alignment of the machine train was 
done as per design values.
Lessons learned:
• Maintaining coupling pre-stretch is an important aspect of the 
maintenance, to avoid loading of the coupling instead of thrust 
bearings, especially during higher load conditions.
• Availability of historical information from online condition monitoring 
system enabled identification of the root cause. 
Considerable improvement in LP compressor NDE bearing vibration 
amplitudes observed.
Post Maintenance Data Plots
LP Compressor NDE Bearing Vibration:
13 umpp23 umpp
Ellipticity of the NDE bearing improved significantly
Post Maintenance Data Plots
LP Compressor NDE Bearing Direct/1X Orbit Plots:
Before Oct 2015
After Oct 2015
QUESTIONS…


Case Study on Resolving High Vibration Issue of a Centrifugal Compressor at an Offshore Platform

Texas A&amp;M Repository

Case Study on resolving high vibration issue of a centrifugal compressor at an offshore platformAmit SharmaLead Engineer, Machinery Diagnostics ServicesBaker Hughes GE-Digital Solutions, Bently NevadaSanker GaneshTechnical Leader, MENAT, Machinery Diagnostics ServicesBaker Hughes GE-Digital Solutions, Bently Nevada• Amit Sharma – Lead Engineer, MENAT- Lead Engineer, BHGE-BN, Machinery Diagnostics Services, Abu Dhabi, U.A.E.- B.Tech Mechanical Engineering (2003) from Jamia Millia Islamia University, Delhi, India- 10 years with GE-Bently Nevada Machinery Diagnostics Services since 2007- Project Engineer- Rockwell Automation-Entek IRD• Sankar Ganesh – Technical Leader, MENAT- Technical Leader for GE Bently Nevada Machinery Diagnostics Services, MENAT region- Bachelor Mechanical Engineering (1993) from Bharathidasan University, India.- Over 20 years experience in vibration field and 10 years with GE Bently Nevada, including rotating equipment balancing, vibration analysis, diagnostics and root cause analysis- Published case studies in METS and Turbomachinery symposiumAuthorsGas Injection Compressors are critical for offshore oil production facilities.A compressor downtime lowers oil production.This case study is about a Gas Injection Compression train at an offshoreplatform in the Middle East.This case study focuses on how the gradual increase in vibrations wassuccessfully diagnosed, pinpointing the root cause for the high vibration,and finally how it was resolved.The Compression train is equipped with an online vibration monitoringand protection system in addition to a condition monitoring software thatwas used to diagnose the issue.Abstract• Problem Statement• Machine Details• Observation & Analysis• Conclusions & Recommendations• Machine Inspection Findings• Corrective Actions & Lesson LearnedContentsProblem Statement• 26th July 2015 The gradual rise in shaft vibration towards Non-Drive End (NDE) bearing began from startup onwards• October 2015 Readings on Gas Injection Compressor Train were observed touching vibration alarm limits, 51 𝜇𝑚pp (microns peak to peak) towards LP compressor NDE bearing at higher speed/load condition.• October 2015 From here onwards, the vibration amplitudes of LP onwards Compressor NDE bearing intermittently reached alarm limits & Machine availability became a concern for the customer.Machine  DetailsLP & HP Compressors- 10270 rpm- Direction of rotation- CW (PT to compressor)- Tilting Pad BearingsSpeed Increaser GB- Gear Ratio- 2.139- Input/Output- 4800/10270 rpmAero Derivative  EngineGas Generator & Power Turbine- 5100/4800 rpmObservations & AnalysisShaft Vibration Amplitudes- LP Compressor Bearings, Oct 2015Startups after 26th July 2015, the NDE bearing amplitudes shows gradual rise approaching alarm levels (51 𝝁𝒎pp)DE BearingNDE Bearing11 umpp28 umpp48 umpp31 umppObservations & AnalysisBode Plots- 1st March 2015 Startup- LP Compressor BearingsNormal startup observed for both bearings, only Drive End (DE) bearing observed high (in line with machine history after Aug 2014 maintenance)1X PhaseAmplitudes1X PhaseAmplitudes1X PhaseAmplitudes1X PhaseAmplitudesObservations & AnalysisBode Plots- 30th September 2015 Startup- LP Compressor BearingsStartup shows steep rise in amplitudes at NDE bearing, especially above  12000 rpm. DE bearing Vibrations  reduces with rise in speed/load.1X PhaseAmplitudes1X PhaseAmplitudes1X PhaseAmplitudes1X PhaseAmplitudesObservations & AnalysisFull Spectrum Cascade Plots Comparison- LP Compressor DE Bearing1st March 2015 start up 30th September 2015 start upRise in reverse 1X component indicative of increased DE pre-load forces.FrequencySpeedAmplitudeSpeedFrequencyAmplitudeObservations & AnalysisFull Spectrum Cascade Plots Comparison- LP Compressor NDE BearingRise in reverse 1X component indicative of increased NDE pre-load forces.FrequencySpeedAmplitudeSpeedFrequencyAmplitude1st March 2015 start up 30th September 2015 start upObservations & AnalysisDirect / 1X Orbit Plots: LP Compressor BearingsHighly elliptical orbit observed, with higher amplitudes at NDE Bearing Observations & AnalysisShaft Centerline Plots -LP Compressor BearingsAs speed increased above 12000 rpm, the rotor shows downward movement.Amplitude AmplitudeConclusions:• As speed increased above 12000 rpm, the vibrations at NDE bearing reached alarm limits (51 𝜇𝑚pp) while the DE bearing showed reduction in vibration.• Due to improper DBSE (distance between shaft ends), instead of thrust bearing taking the load, the load was absorbed by the coupling, resulting in rise in shaft vibration amplitudes at the NDE bearing.• Abnormal movement of shaft centerline and increased ellipticity of orbit shape with speed/load rise indicates DBSE or alignment related issue.Recommendations:• DBSE & coupling pre-stretch shall be checked across both ends of LP compressor as per protocol values.• Verify the alignment condition of the machine train.Conclusions & RecommendationsMachine Inspection FindingsEvidence of hot spots observed on the bearing pads which might be dueto pre-load on the bearing.• Coupling Pre-stretch between LP & HP compressor was found to be1.72 mm compared to the recommended 1.32 mm.• The bearings pads were observed with minor carbon deposits whichmight be due to burned oil in the pads.Corrective Actions & Lesson LearnedCorrective actions:• Coupling pre-stretch between LP & HP compressor was found 1.72 mm against recommended 1.32 mm. Hence a shim of 0.4 mm was added.• LP Compressor NDE bearing was replaced with new one with clearances maintained at 203 𝜇𝑚. Alignment of the machine train was done as per design values.Lessons learned:• Maintaining coupling pre-stretch is an important aspect of the maintenance, to avoid loading of the coupling instead of thrust bearings, especially during higher load conditions.• Availability of historical information from online condition monitoring system enabled identification of the root cause. Considerable improvement in LP compressor NDE bearing vibration amplitudes observed.Post Maintenance Data PlotsLP Compressor NDE Bearing Vibration:13 umpp23 umppEllipticity of the NDE bearing improved significantlyPost Maintenance Data PlotsLP Compressor NDE Bearing Direct/1X Orbit Plots:Before Oct 2015After Oct 2015QUESTIONS…

https://oaktrust.library.tamu.edu/bitstream/1969.1/172467/1/24_Peton.pdf

Case Study on Resolving High Vibration Issue of a Centrifugal Compressor at an Offshore Platform

Abstract

Similar works

Full text

Available Versions

Texas A&M University

Texas A&M Repository

Case Study on Resolving High Vibration Issue of a Centrifugal Compressor at an Offshore Platform

Abstract

Similar works

Full text

Available Versions

Texas A&M University

Texas A&amp;M Repository

Texas A&M Repository