Vibration Issues of Diesel Engine

8/10/2019 Vibration Issues of Diesel Engine

1/24

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


2/24

Resolving Vibration Issues of Diesel Engine Driven Fire Water Pumps in QP Offshore 2

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


3/24

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


4/24


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.


5/24


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


6/24


Contractual Vibration Points


7/24


Vibration Measurement Locations at Field


8/24


9/24


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.


10/24


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


11/24


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)


12/24


Pump-A

Pump-B

Pump-D

Observation:4 Highfrequency spectrumindicated 1X GMF withsidebands, indicatedpremature wear of gear

teeth/excessivebacklash.


13/24


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 .


14/24


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.


15/24


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


16/24


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


17/24


Action-2: The engine stand was replaced with a new stand withvibration isolators


18/24


19/24


Action-3: Pump Head/Gearbox structure modified

Old Pump head New Pump head

GB TOP


20/24


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


21/24


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


22/24


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


23/24


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


24/24


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.

Documents

Vibration Issues of Diesel Engine