ML20005E188

Special Rept:On 891128,valid Failure of Diesel Generator Occurred.Caused by Improperly Drilled Oil Passage on Master Rod.Remedial Actions to Restore Standby Diesel Generator 22 Includes Crankshaft Straightening & Remachining

ML20005E188
Person / Time
Site:	South Texas
Issue date:	12/27/1989
From:	Vaughn G HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
ST-HL-AE-3326, NUDOCS 9001040040
Download: ML20005E188 (8)

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The Light i company .--,,---.- --(

P.O. Box 1700 Houston Texas 77001 713 228 9211 Houston Lighting & Power _ _ --- ~~ -- -- .m. -~)~- -

December. 27,-1989 'I ST-HL-AE-3326 File No.: G02 'l 10CFR50 .J U. S. Nuclear Regulatory Commission .

Attention: Document Control Desk Washington, DC 20555

.v-South Texas Project Electric Generating Station Unit 2 Docket No. STN 50-499 Interim Special Report Regarding A Diesel Generator Valid Failure on November 28. 1989 Pursuant to the South Texas Project Electric Generating Station Technical Specifications 4.8,1,1.3 and 6.9.2, Houston Lighting & Power submits the attached Interim Special Report regarding a diesel generator valid failure which occurred on November 28, 1989.

If you should have any questions on this matter, please contact Mr. C. A..Ayala at (512) 972-8628 or myself at (512) 972-7921.

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. . Vaugh Vice President Nuclear Operatio s GEV/BEM/n1

Attachment:

Interim Special Report Regarding a Diesel Generator Valid Failure on November 28, 1989 9001040040 891227 // k

,PDR .ADOCK 05000499 S PDC

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$/*E' ST HLoAE 3326 Houston Lighting & Power Company File No.: C02 South Texas Project Electric Generating Station -Page 2

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Regional Administrator, Region IV -Rufus-S. Scott Nuclear Regulatory Commission Associate General Counsel ,

611 Ryan Plaza Drive, Suite 1000 Houston Lighting & Power Comparty Arlington, TX 76011 P. O. Box 61867 i Houston, TX 77208 George Dick, Project Manager U.S. Nuclear Regulatory Commission INPO Washington, DC 20555 Records Center l

.1100 Circle 75 Parkway '

J..I. Tapia Atlanta, CA 30339-3064 l Senior Resident Inspector I c/o U. S. Nuclear Regulatory Dr. Joseph M. Hendrie l Commission 50 Be11 port Lane P. O. Box 910 Be11 port, NY 11713 Bay City, TX 77414 D. K. Lacker J. R. Newman, Esquire Bureau of Radiation Control Newman & Holtzinger, P.C. Texas Department of Health 1615 L Street, N.W. 1100 West 49th Street Washington, DC 20036 Austin, TX 78704 D. E. Ward /R. P.-Verret Central Power & Light Company P. O. Box 2121-Corpus Christi, TX 78403 I J. C. Lanier Director of Generation l City of Austin Electric Utility L

721 Barton Springs Road I Austin, TX 78704 ,

R.,J. Costello/M T. Hardt City Public Service Board P. O. Box 1771 San Antonio, TX 78296 Revised 12/15/89 L4/NRC/

y, tj i? li .g Attachment ST-HL AE-3326 Page 1 of 3 -i South Texas Project Electric Generating Station Unit 2 Docket No. STN 50-499 Int'erim Special Report Regarding A Diesel Generator Valid Failure On November 28. 1989 Description of Event:

On November 28, 1989 Unit 2 was in Mode 5 for a maintsnance outage. The Technical Specification required twenty-four hour load test was being performed on Standby Diesel Generator (SDG) 22. At 0957 hours0.0111 days <br />0.266 hours <br />0.00158 weeks <br />3.641385e-4 months <br />, approximately ten hours into the test, a loud knocking noise was heard by two maintenance technicians. The technicians immediately evacuated the area. The #4 master connecting rod subsequently failed and the engine tripped. No indication of

-the trip was received by the control room. Immediate inspection of SDG 22 revealed that the #4 articulated rod, both #4 pistons and other debris had been ejected through the right centerframe door. The #4 crankcase overpressure relief valves.were pushed off the centerframe doors on both sides of the engine and the right sido centerframe door was driven into the adjacent starting air dryer. The master rod, cap and counterweights were in the engine base.

Investigation and recovery teams were formed to evaluate the failure and implement corrective actions. A. thorough inspection of the engine was performed. The following was observed:

The master connecting rod was broken into two pieces through the oil passage between the crankpin bore and the articulated rod pin bore and through the upper end of the balls.

The left side connecting rod cap bolts were broken and the right side bolts bent.

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All four cap nuts had been stripped from the studs.

- There was evidence of significant heating of the articulated rod pin, its bushing, and the rod on both the bail and load sides of the articulated pin.

The centerframe sustained minor damage including several cracks and l~ impact damage.

- The #4 crankpin was gouged at several locations The crankshaft runout was 0.003"

- There were numerous superficial gouges on the crankwebs and crankpin thrust faces.

- The piston pins had slight impact damage.

The inlet valves were slightly bent on both heads, the rocker arms were cracked and the push rods were bent.

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Attachment ST-HL-AE 3326 Page 2 of 3 Cause of Event:

The master rod was subjected to both macroscopic and scanning electron microscope examination. It was determined that a fatigue failure was initiated at an improperly drilled oil passage on the master rod (see Figures I and 2). In an attempt to repair the improperly drilled passage, the vendor  ;

threaded and plugged it (see Figure 3. Case A) which left stress risers sufficient to form a fatigue crack initiation site. The cracking proceeded by high cycle fatigue to the transverse oil passage followed by failure of the rod balls and cap studs. Loss of lubrication to the articulated rod pin or l ingested debris caused overheating of the pin, bushing, connecting rod bore and connecting rod bails in the final stages of the fatigue failure. l Cooper Energy Services has identified that the repair of the master  ;

connecting rod which failed was documented and dispositioned in accordance i with Cooper Energy Services procedures at the time of manufacture. This was the only master rod repaired in this manner. Laboratory analysis of the material composition and mechanical properties of the failed connecting rod j indicated that it met specification requirements.

l Other master connecting rods were inspected which exhibited similar, I though less severe, manufacturing defects (see Figure 3, Cases B and C) .

Therefore, it can be concluded that a less than adequate manufacturing process was in effect at Cooper Energy Services at the time of fabrication of the #4 l connecting rod. In this case, it is clear that an inappropriate repair  !

disposition was approved by Cooper Energy Services engineering on the #4 master connecting rod. As licensee, HL&P was responsible for ensuring that i the vendor's quality program was properly implemented. An evaluation of the i HL&P vendor control program in effect at the time of SDG manufacture is being conducted to assure that any potential programmatic weaknesses have been  !

identified and resolved to ensure that our present program is effective. This evaluation will be discussed in the final report of this valid failure, j Corrective Action:

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Remedial actions are in progress to restore SDG 22 to operability.

These activities include:

1 Crankshaft straightening to within the specified runout of .002".

- Remachining of the crankshaf t rod journal Repair of the engine centerframe Repair of support equipment and instrumentation Reassembly and testing The current scheduled date for completion of these activities and return of SDG 22 to service is January 2,1990.

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Attachment ST HL-AE 3326  ;

Page 3 of 3 Corrective Action Cont'd.

In order to determine if other incorrectly drilled or repaired connecting rods had been supplied, HL&P inspected two spare master rods. The-oil passage on one had been drilled all the way through and chamfered. The oil passage on the other rod had been drilled past the transverse oil passage.

These configurations are illustrated in Figure 3, Cases B and C, respectively.

Oil passages in the remaining master rods on SDG 22 were subsequently measured. Most were found to be partially drilled as shown in Figure 3, Case C. One was not overdrilled. None had been drilled through and repaired.

An evaluation of the as-found condition was performed to justify continued operation of Unit 1 and to justify restart of Unit 2 once repairs to SDG 22 are complete. Based on the unique nature of the rod failure, a qualitative analysis of operational data and industry experience, interim operation has been justified. Outside consultants are currently performing a finite element analysis of the effect of overdrilled oil passages on master rod integrity. This analysis will be used to confirm that safe operation of the SDC's may continue indefinitely.

Upon completion of the recovery effort and recurn of SDG 22 to operation, a final special report will be issued detailing the remaining corrective actions. This report is currently scheduled to be completed by March 15, 1990.

Additional Information:

Per the criteria of Regulation Guide 1.108, the failure described in this report has been classified as a valid failure. This is the third valid failure in the last twenty starts. The test interval is currently once per seven days due to the second valid failure which occurred on November 21, 1989. Due to the extensive rework associated with the failure described in this report, HL&P plans to secure certification that SDG 22 has been restored to like-new condition. If this certification is obtained, the test interval will be changed to once per thirty-one days.

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