Case Study on Bearing Failure

8/10/2019 Case Study on Bearing Failure

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BEARING FAILURE OF BITUMEN PUMP

13P14

EQPT NO : 13P14

MODEL/MAKE : M/S RUSSIAN

MECH. SEAL MAKE : M/S EPIL

MECH. SEAL TYPE : 1502-52 SPL

BEARING TYPE : 6216, 7414

SERVICE : BITUMEN

TEMPERATURE : 220deg C


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13P14

ASSEMBLY OF PUMP WAS DONE ON 22/7/2000, AFTERRECEIPT OF SEAL.

PUMP WAS STARTED ON 10/09/2000 AND PUMP THRUSTBEARING FAILED JUST AFTER 4 HOURS OF ITS RUN.

PUMP AGAIN SENT TO WORKSHOP AND ITS BEARINGSWERE REPLACED & SEAL FITTED AFTER CLEANING.

PUMP AGAIN SENT TO SITE AND STARTED ON 25/09/2KAND AFTER 3-4HRS OF ITS OPERATION, ITS THRUSTBEARINGS AGAIN FAILED.

PUMP AGAIN SENT TO WORKSHOP FOR BEARING

REPLACEMENT.


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13P14

OBSERVATION MADE AT WORKSHOP AFTEROPENING:

BOTH THE THRUST BEARINGS BRASS CAGES WERE

FOUND BROKEN AND ITS BALLS GOT DEFORMED.

ALL OTHER COMPONENTS OF PUMP AND SEAL WERE

FOUND INTACKED.

THERE WAS 10MM GAP FOUND ON OD OF RADIALBEARING AND ID OF BRG. HOUSING, RADIAL BEARINGWAS NOT RESTING AT ALL ON HOUSING.

ANALYSIS:

SLEEVING ON HOUSING WAS DONE ON RADIAL BEARINGPORTION , WHICH WAS CAME OUT WHILE REMOVAL OFBEARING FROM HOUSING. AS PUMP WAS KEPT OPENEDAT WORKSHOP FOR ALMOST 6MONTHS ,


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13P14

ANALYSIS:

SLEEVE WAS MISSED AND BOTH THE OCCASIONBEARING WAS FITTED WITHOUT SLEEVE. SINCE RADIALBEARING WAS NOT RESTING ON HOUSING TOTALRADIAL LOAD TRANSMITTED TO THRUST BEARINGS. ASTHRUST BEARINGS ARE DESIGNED FOR AXIAL LOADAND NOT FOR RADIAL LOAD , ITS WAS FAILEDIMMEDIATELY.

REPAIR /REPLACEMENT CARRIED OUT:

BEARING HOUSING WAS REPLACED WITH SPAREBEARING HOUSING AND BOTH THE BEARINGS WERE

REPLACED. NOW PUMP IS RUNNING NORMAL


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D M GE TO RET INER


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BEARING FAILURE OF BITUMEN PUMP13P14


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REPEATED BEARING FAILURE OF BARARI

PUMP 603P3

EQPT NO :603P3

MAKE :M/S KIRLOSKAR BROTHERSERVICE :TREATED EFFULENT

WATER (BOOSTER)

TEMPERATURE :AMBIENTBEARING :3311,6311

Past Failure Event:1996 -New pump provided in BARARI minor Pump

house for boosting up the fire water pressure.Pump is taking suction from discharge of603P2 pump.

16/10/96 -Thrust Bearing failed & oil seal damaged.

04/12/97 -Both the bearing (radial & thrust )damaged,wear ring loose.


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PUMP 603P3

15/01/98 -Shaft key way damaged, welding & M/C done.19/06/98 -Sleeve damaged, gland leak, sleeve made in

workshop.10/06/99 -Thrust bearing seized & shaft damaged.25/10/99 -Both the radial & thrust bearing damaged.08/02/2000 -Bearing & oil seal damaged.both the bearing &

oil seal changed.06/03/2000 -Bearing & oil seal damagedObservation-

1. Bearing housing cover bush, provided for fixing ofoil Seal,found detached from cover and got rotated.2. Oil seal found damaged.3. Radial bearing races found rubbed against rollers4. Thrust bearing clearances increased.

5. Bearings got rotated and found loose on housing.


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PUMP 603P3

09/05/2000 -Overhauling done, bearing Replaced.

24/05/2000 -Bearing damaged.Bearing housing supportplate replaced with thicker plate andperpendicularity maintained.

19/07/2000 -Bearing failed.Heavy love-joy couplingreplaced with lighter shim pack type coupling.

26/08/2000 -Bearing failed.Pump manufacturer M/sKirloskar Brother called and assembly done in

their presence.

18/09/2000 -Bearing failed.Elect.cabling checked, as motorwas tripping at high load.


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FL KING


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PUMP 603P3

23/09/2000 -Bearing damaged.foundation boltswelding done.

10/10/2000 -Bearing failed. Foundation RCC

filling done, to strengthen thebase plate.

28/11/2000 -Bearing & oil seal damaged.Askedoperation to run the pump withfull opening of discharge valve.

08/01/2001 -Overhauling Done, bearing

changed.


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PUMP 603P3

29/01/2001 -Pump bearing again failed.Impeller diameterchecked with the data folder of the pump andfound that impeller OD is 14mm higher thanthe rated diameter of the impeller

Impeller OD trimmed to required rateddiameter and pump was assembled withtrimmed impeller and new bearing.Now pump isrunning since 05/02/2001.

Cause of failure:Due to higher impeller diameter of the pump it wasdeveloping high axial thrust, which was causing repeated

thrust bearing failure of the pump.


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REPEATED BEARING FAILURE OFBARARI PUMP 603P3

REPEATED BEARING FAILURE OF VDU PUMP 12P5S


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EQPT. DETAIL :

Tag. No.. : 12P5S Column bottom pump Eqpt. type : Centrifugal pump

Make : M/S Sulzer pump (I) ltd.

Model : ZE-100-4500 Service : Short residue Working temp. : 380-400 Deg. C. Bearing - Thrust : 7312 BG 2 nos

- Radial : NU312 Capacity Rated : 200 m3/hr

Minimum : 90 m3/hr



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PAST HISTORY AND CHAIN OF EVENTS:

Old Russian Pump 12P5S was replaced in year2000 revamp shutdown.

Pump 12P5S was attended due to bearing failure on 25/08/2000 andfollowing spares were replaced.a- Bearing 7312 (2nos) & NU 312 (1 no)b- Complete Mech. Seal .

Pump 12P5S was commissioned at 17.00hrs on 28/8/01.

At 19.00 hrs. pump bearing failed after a run of 2hrs. As perproduction log book Pumpbearing housing was found abnormally hot

& steam was coming out from CW out let line. Immediately pumpwas stopped & 12P5A was put on service.

Pump 12P5S was opened and sent to work shop for maintenance. thepump thrust and radial bearings were found badly damaged and

seized on shaft. The following spares were replaced.



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a. Bearing 7312 (2nos) & NU 312 (1 no)b. Complete Mech. Seal .c. Pump Shaft.d. Bearing housing cover repaired

On 5/9/2001 at 9hrs pump was started and its bearings again failedat 1645hrs. event before failure of the pump bearing is as follows

as per production log book. Pump 12P5S started at 9hrs in presence of MLE. Informed to

SELE. Vibration checked by MLE and found normal at 9.15hrs.12P5A stopped.

12P5S tripped at 10.10hrs. motor bearing temperature is also high.

12P5A started again. 12P5S again started at 11.15hrs informed to MLE and SELE. 12P5A

also running. 12P5 stopped at 14.30hrs and the load checked from sub station

for 12P5A & 5S and found 250 & 260 A respectively. As per SELE

12P5S load not to be kept beyond 250Amp. So 12P5 restarted at15.00hrs. all the 3pumps kept running.



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At 16.45hrs, 12P5S bearing housing found smoking,its lube oil

burnt out, oil cup was out and fumes were coming. Pumpstopped immediately in presence of SPNM(U). M/M & E/Mkept informed.

Observation

-Before opening of pump.

a)Lube oil was found burnt and having bearing wear particle.b)Coupling DBSE is found 190mm against 180mm.c)Coupling shims were found distorted and broken.d)Coupling spaces was found damaged.

-After opening at work shop.a)both the thrust and radial bearings are found damaged andseized with shaft ( identical to earlier failure).b)Shaft found 0.20mm bent at radial bearing seating.



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c)Bearing cover labyrinth found rubbed with bearing inner race

got damaged.d)Mech. seal collar found rubbed with purge bush.e)Deep rubbing marks on Wear ring observed and clearance1.5mm and 1.0mm found in front & back respectively.

f)Throat bush clearance 1.0mm found.

g)Ovality of 0.05mm found in outer thrust bearing seating.

Repair replacement done.

1.All the thrust and radial bearing replaced with new one.

2.Bearing housing cover labyrinth repaired.

3.Bearing housing ovality removed and bearing center checked.4.Pump shaft replaced with new one.5.All the wear rings except case wear ring replaced and itsclearance maintained. Throat bush also replaced andclearance maintained.



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6.Mech. Seal faces are lapped and reused as new bellow is

not available,7.New coupling is issued and hub boring is done, which is to bereplaced along with its spacers.

Suspected cause of failure:

Thrust bearing failure may be due to following reason.1.Lack of lubrication in housing.2.Excessive hydraulic thrust on bearings.3.Improper mounting of bearings.4.Improper loading of thrust bearing during operation.

Lack of lubrication in housing.The possibility of lack of lubrication is ruled out as afterfailure of bearing there was oil found in housing and it has runfor approx.7 hrs.



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Excessive hydraulic thrust on bearings.

The pump is single stage and fitted with both side wear ringsand balancing holes and its clearances are also not abnormallyhigh, which can not create that much thrust load on bearing.However during starvation of pump thrust balancing of rotorwill be disturbed.

Improper mounting of bearings.As the pump has run for approx. 7hrs on load and no abnormalsound or vibration was observed. This possibility may be ruledout.

Improper loading of thrust bearing during operationDue to high Distance between shaft ends 190mm (DBSE)maintained, compared to recommended DBSE of 180mm,coupling will cause pulling of pump rotor in motor side, whichwill result in improper loading of outer thrust bearing.



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Improper loading of thrust bearing will cause sliding of rolling

elements. As sliding friction of bearing elements, will causehigh heat generation and continue rise in bearing temperatureand subsequent failure of thrust bearings. The failure ofthrust bearing will allow the pump rotor assembly moving inpump side and it will cause rubbing of cover, purge bush and

case wear ring.


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CCRU RGC TURBINE 15KT1

THRUST BEARING FAILURE

The Recycle Gas Compressor (15-K-1) of CRU is

driven by a back pressure type steam turbine.

EQPT. DETAIL :-TAG NO. : 15KT1

MAKE : EBARA JAPAN

MODEL : SBHEG4-4

SPEED : 7446 RPMTYPE OF BLADE : 4 STAGES CURTIS WHEEL

STEM INLET PR. : 60 KG/CM2

STEAM OUT LET PR. : 4 KG/CM2



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PAST HISTORY AND CHAIN OF EVENT ON 28-2-01, 15K1 COMPRESSOR TRIPPED ON HIGH AXIAL

DISPLACEMENT.

ON 28-2-01, 19.10HRS COMP. ROLLED AFTER CHECKING.TRIPPED AT 6000 RPM ON HIGH THRUST BEARING TEMP &AXIAL DISPLACEMENT.

AFTER ANALYSIS THE PROBLEM, DECIDED TO OPEN THETHRUST BEARING FOR CHECKING.

OBSERVATION THRUST PAD (ACT.SIDE) FOUND COMPLETELY WIPED OFF.

NO OTHER ABNORMALITY OBSERVED.



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REPAIR REPL. DONE ALL THE 6NOS ACTIVE SIDE THRUST PADS REPLACED.

COMPLETE LUBE OIL REPLACED AND FILTER CHANGED.

SOLO RUN OF TURBINE CHECKED.

TURBINE ROLLED ON 6-3-01 AND FOLLWINGPARAMETER WERE OBSERVED

AXIAL DISP. : 0.23/.19

TH. BEARING TEMP : 85,91,85OC

CHEST PR. : 25 KG/CM2

1STSTAGE PR. : 19 KG/CM2

FROM 1STWEEK OF MAY THESE READINGS HAVE STARTEDINCREASING WITH OUT ANY CHANGE IN OPERATING

PARAMETER

CCRU RGC TURBINE 1 KT1


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ON 29-6-01 TURBINE TRIPPED, DUE TO HIGHTHRUST BRG. TEMP. AND AXIAL THRUST. DECIDEDTO OPEN THE TURBINE.

OBSERVATION MADE AFTER OPENING:

THRUST(ACT.SIDE) FOUND DAMAGED. 3RD& 4THROW BLADES OF TURBINE FOUND 80% CHOCKED

DUE TO SEVERE SILICA DEPOSITION. DIAPHRAGM NOZZLES WERE FOUND ERODED.

REPAIR REPL. DONE ROTOR AND DIAPHRAGM OF TURBINE WERE CLEANED BY

HYDRO-SAND BLASTING . ERODED PORTION OF DIAPHRAGM NOZZLES WERE WELD

BUILD UP AND GRINDED OFF. ACTIVE SIDE THRUST BEARING REPLACED WITH NEW

ONE.



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AFTER REPAIR / REPLACEMENT TURBINE ROLLEDON 12-7-01 AND TURBINE IS RUNNING WITHFOLLOWING PARAMETER.

AXIAL DISP. : (-)0.02/(+).01TH.BEARING TEMP. : 50,51,53 DEG. CCHEST PR. : 21KG/CM2

1ST

STAGE PR. : 13 KG/CM2

THRUST BEARING FAILURE OF CCRU RGC


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THRUST BEARING FAILURE OF CCRU RGCTURBINE 15KT1

REASON OF REPEATED FAILURE OF THRUST BEARING:

Brief on Existing systemThe HP steam requirement of CRU RGC turbine (Ebaramake) is met partly from captive generation with thebalance (about 45%) thru import from TPS. The

turbine is designed for an inlet steam temperature of420oC @60 Kg/cm2g. However, the actual steamtemperature remains in the range of 360-370oC.

Reasons of failures

The rise in thrust bearing temperature and high axialdisplacement of turbine rotor were due to deposition onthe moving and static blades of the turbine.

The suspected reasons for metal erosion of turbinediaphragm nozzles is the supply of steam at lower

temperature and impurities present in it


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a) Lab test on regular basis for DM water and BFWseparately to monitor silica concentration. This will alsohelp detection of possible contamination of condensatethrutube leaks of STG condensers.

b)

The exhaust at the turbine to be maintained at4.0+kg/cm2g on sustained basis to retard silica rejectionby steam. All the MP to LP PRDS are being checked forperformance so that LP steam header pressure is alwaysmaintained.

c) Action being initiated for providing improved insulationto ensure steam availability to RGC at design level.Steam generator at 15 F-1 of CRU are being lookedintofor ascertaining reasons for low superheat temperatureof steam generated.



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CHOKAGEOFBLADES EROSION ON DIAPHRAGM

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Case Study on Bearing Failure