ML20214D507

Final Significant Deficiency Rept SD 414/86-01 Re Emergency Diesel Engine 2B Main Bearing 7 Failure.Initially Reported on 860116.Caused by Misinstallation by Mfg,Sand Blast Grit &/Or Oil Contamination.Engine Rebuilt

ML20214D507
Person / Time
Site:	Catawba
Issue date:	02/19/1986
From:	Tucker H DUKE POWER CO.
To:	Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
SD-414-86-01, SD-414-86-1, TAC-68694, NUDOCS 8603050230
Download: ML20214D507 (4)

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. DUKE POWEn Gontwxy I*.O.150K 3318D CitAltLOTTE. N.C. 211242 IIAL !!. TUCKER TE LE PIION E m ,m m noo ara mil MTLhm PetMnTT10!W February 19, 1986 k cm C. V 2

Dr. J. Nelson Grace, Regional Administrator y U. S. Nuclear Regulatory Commission ,_,

Region II ..

101 Marietta Street, NW, Suite 2900 m Atlanta, Georgia 30323 tv Re: Catawba Nuclear Station, Unit 2 Docket No. 50-414 Significant-Deficiency no. 414/86-01

Dear Dr. Grace:

My letter of January 16, 1986, which transmitted the subject Deficiency Report, stated that a final report on the diesel bearing .

failure would be provided prior to fuel load. Attached is the final report, which contains a summary of the problem, corrective actions taken, and conclusions drawn. We believe no further action is required on this item.

Very truly yours,

b. /h/

Hal B. Tucker LTP:slb Attachment cc: Director Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission Washington, D. C. 20555 INPO Records Center Suite 1500 1100 Circle 75 Parkway Atlanta, Georgia 30339 NRC Resident Inspector Catawba Nuclear Station O

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l Final Report Catawba Nuclear Station Emergency Diesel Engine 2B No. 7 Main Bearing Failure SD 414/86-01 February 19, 1986 i

Event Description and Remedial Action On November 20, 1985 after approximately 180 hours0.00208 days <br />0.05 hours <br />2.97619e-4 weeks <br />6.849e-5 months <br /> of run time the 2B Catawba emergency diesel engine tripped due to high bearing temperature on bearing number 7. Upon disassembly, both the bottom and the top half bearing shells were found to be badly scored. The bottom half was fractured into three pieces.

As a result of this failure, the integrity of the main bearing components was verified dimensionally. Critical areas on the engine base and bearing caps were inspected to ensure that no cracking had occurred. After these inspections, several main journals were honed and new bearing shells installed.

About ninety seconds after starting the engine after the repair work mentioned above (December 5, 1985), the engine again shut down due to high bearing temperature. Inspections showed that the number seven main bearing had failed. The upper and lower bearing shells again showed severe scoring. The lower half showed one crack similar to the first failure but remained intact.

Due to this second failure, a more exhaustive investigation was conducted. This investigation included:

o mapping crankshaft diameters o gauging bearing caps for signs of distortion o inspecting the engine base for cracks or wear o

o visually inspecting all lube oil passages flushing the lube oil piping and cleaning other Lube oil System components o performing a metallurgical evaluation of all failed bearing shells o reviewing previous documentation associated with 2B diesel work The dimensions obtained were compared to TDI drawings. No inconsistencies were found. In addition the visual inspections i i revealed no problem areas.

l Oil passages and tubing that supply the main, connecting rod, and arist pin bearings were visually inspected using fiber optic techniques. All were found to be open and free of debris. All crank shaft oil passage plugs were found to be properly installed.

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F Inspection of the lube oil sump tank and the right bank strainer revealed small amounts of iron beads that were later discovered to be sand blast shot. The external lube oil piping was flushed using a temporary pump and filter arrangement capable of 900 gpm flow; about 400 gpm higher than normal system flow. Flushing continued until samples showed particulate contaminants to be less than SAE class 2 for hydraulic systems. The 4 inch internal lube oil headers and engine base were added to the flush circuit using the same cleanliness criteria.

Bearing shells from both failures were examined at the Production Support Department's metallurgy lab to determine the nature of the scoring and cracking of the aluminum castings. Numerous particles of iron from 10 to 20 mils in size were found embedded in the babbitt layer of the bearings especially at the end of deep score marks. The particles were identical to the shot found in the lube oil strainer and the sump tank and to samples of used shot taken from the floor of the construction department sand blast yard.

Cracks in the #7 bearing lower halves from both failures were probably due to fatigue. No material defects were found that would have contributed to this failure.

A review of Construction Department documents revealed that LD system piping was removed for sandblasting during the Construction phase. Main bearings 1 and 2 were opened at this time to check for possible damage due to sand blast grit contamination. None was found. There were no records of the #7 bearing ever being opened by Construction and it is thought to have been assembled by the manufacturer prior to the first failure.

Conclusions The first bearing failure appears to be due to slight misalignment during installation aggravation by localized over stress caused by the sand blast grit. A combination of the slight mis-installation by the manufacturer, the lube oil contamination and this being the most highly loaded bearing lead to the failure.

The second failure, having occurred in only 90 seconds, leads to the conclusion that the bearing was mis-installed. The scoring of the shell after only ninety seconds lead to the conclusion that there was an oil contamination problem whether by debris from the first failure or the sand blast material.

2B engine has been run successfully after having been rebuild and flushed per approved procedures. The #7 main bearing shells have been removed for inspections after one hour and after one-hundred-thirty-eight hours of operation and have been found to be in excellent condition.

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, n' At this point we have a reasonable level of confidence in the reliability of the bearing. No further corrective action is planned.

A more detailed report documenting our investigation is being prepared for the Office of Nuclear Reactor Regulation (ONRR) for review in support of the licensing effort on Catawba Unit 2. It will be submitted to ONRR prior to initial criticality.