Download - Vibration Issues of Diesel Engine
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Resolving Vibration Issues of Diesel EngineDriven Fire Water Pumps
in QP Offshore
Case Study
By
Isham Sudardjat Sherief Mekawey
Reliability Engineer and Principal MDS EngineerQP Offshore Operation GE-Bently Nevada
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Introduction to QP Offshore
BackgroundTechnical Data and Acceptance Criteria
Contractual Vibration Points
Vibration Measurement Locations at Field Analysis
Conclusions from Investigation
Proposed ActionsFinal Vibration Results
Lessons Learnt
Contents
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Resolving Vibration Issues of Diesel Engine Driven Fire Water Pumps in QP Offshore
Introduction to QP Offshore
WELL HEADPLATFORM
PS-3
PS-2
HALUL
TERMINAL
SBM
TANKER
WELL HEADPLATFORM
WELL HEADPLATFORM
WELL HEADPLATFORM
TOTALQPDOXY
QP Offshore Operations comprises of: Halul Storage and Loading Terminal 2 Production Platforms:
Maydan Mahzam (MM): PS-2 Bul Hanine (BH) : PS-3
3
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Resolving Vibration Issues of Diesel Engine Driven Fire Water Pumps in QP Offshore 4
BackgroundProject was started in 2004
The scopes were engineering, procurement,installation, and commissioning of:2 jockey pumps (motor driven vertical pumps)2 sea water utility pumps (motor driven vertical pumps)4 fire water pumps (diesel engine driven vertical pumps with right
angle gearbox)Jockey and Sea Water Pumps passed SAT while FireWater Pumps failed to pass SAT in 2006 due to highvibration.2 vibration consultants were involved to solve theproblems without success3rd vibration consultant was involved in Oct 2009,implementation of recommendations started in 2010,hand over in 2012.
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Resolving Vibration Issues of Diesel Engine Driven Fire Water Pumps in QP Offshore 5
Technical Data and Acceptance CriteriaPump:
Vertically suspended centrifugalpump, 3 stages
1750 rpm, water lubricated, 880cu.m/hr
Drive Shaft :
Double Universal Joint Cardan Shaft
Gearbox :
750 HP, 1750 RPM,
1:1 Ratio, Right Angle
Threaded Coupling Type
Diesel Engine :
12 Cylinders, DITA, 800HP, 1750 RPM
Acceptance Criteria:
As per NFPA 20 article 7.6.1.5which refers to HydraulicInstitute Standard (5.84 mm/srms) at Pump Head
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Contractual Vibration Points
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Vibration Measurement Locations at Field
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Foundation/supporting arrangement for Diesel Engine, Gearbox and Pump.
Reason could be: vibration isolators are not installed either underthe engine feet nor under the frame on which the engine ismounted.
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Resolving Vibration Issues of Diesel Engine Driven Fire Water Pumps in QP Offshore 10
Observation:2 Startup/coast down waterfall indicated resonance inthe speed range 1200 to 1400 rpm Most likely from the cordonshaft or coupling hub
Critical speed in the range of 1200-1400rpm
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Resolving Vibration Issues of Diesel Engine Driven Fire Water Pumps in QP Offshore 11
Pump-B
Pump-A
Pump-D
Observation:3 Bump testdata on the Gearboxstructure indicated aresonance at 22.5Hz and33 Hz, which is less than
20% separation margin(Pump Running speed28.75Hz)
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Pump-A
Pump-B
Pump-D
Observation:4 Highfrequency spectrumindicated 1X GMF withsidebands, indicatedpremature wear of gear
teeth/excessivebacklash.
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Conclusions from Investigation
Unbalance of Gearbox cordon shaft or couplinghub mounted at gearbox input shaftTransfer of vibrations from diesel engine to thegearbox and pump assembly
Structural resonances from gearbox supportassembly.Premature wear of gear teeth / excessivebacklash .
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Resolving Vibration Issues of Diesel Engine Driven Fire Water Pumps in QP Offshore 14
Proposed Actions
In situ balancing of gearbox cordon shaft and GBO/P shaft.Installation of vibration isolators below theengine feet or the base frame
Modify the Gearbox structure to shift the naturalfrequency with 30% separation margin.Inspection of Gearbox for excessive gearwear/backlash.
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Resolving Vibration Issues of Diesel Engine Driven Fire Water Pumps in QP Offshore 15
Action-1: Balancing attemptedon GB I/P and GB O/P shaft toreduce unbalance on cordonshaft and to reduce excitation onthe GB structure respectively.(coupling between Engine andGB used to balance the GB I/Pshaft. GB fan at the top used tobalance the GB O/P shaft).
Actions in Sequence
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1X componentbefore balancing
Vib component at 22Hzshown after balancing
1X component afterbalancing
Action-1 (contd): In-situbalancing resulted in reductionof 1X. However the amplitude
shifted to the frequency of 22 Hz(0.8X).
Waterfall signaturebefore balancing
Waterfall signatureafter balancing
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Action-2: The engine stand was replaced with a new stand withvibration isolators
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Action-3: Pump Head/Gearbox structure modified
Old Pump head New Pump head
GB TOP
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Resolving Vibration Issues of Diesel Engine Driven Fire Water Pumps in QP Offshore 20
Bump test on the GB and pumphead (with modified head) showednatural frequency at 41.25 Hz(achieved 41% separation margin)
GB TOP
Pump head
GB Bottom
b d d f d l h
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Action-4: Gearbox inspected and found only 70% teeth contact.GB OEM brought to site, gear backlash was checked and adjustedto conform to OEM specifications
f b b f d f h b kl h
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Before
Now
Comparison of vibration spectrum before and after the backlashadjustment on the Gearbox
High frequency GMFcomponents & side bands
Drastic reduction of High frequency GMFcomponents & side bands
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Pump-D selected as pilot, implemented all the mentioned actionitems and resulted in great improvement. Red highlighted in tablebelow is the contract specified location (Limit 5.84 mm/s rms)
Final Vibration Results
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Lessons Learned
All contractual limits must be carefully acknowledgedduring design and verified during FAT.Solving the problems in factory is much easier thandoing it on site.Get the right consultant involved at the first chance.Understand the size of problem since beginning couldsave time, cost and efforts.Major modifications might be a solution whenever theproblem is complex.