ML20077F632

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Special Rept:On 910516 & 18,diesel Generator 1B Invalid Failures Occurred During Maint Testing of Engine.Caused by Control Air Pressure Dropping Below Shutdown Setpoint & Control Devices Not Charging.Reversed Tubing Reinstalled
ML20077F632
Person / Time
Site: Catawba Duke Energy icon.png
Issue date: 06/12/1991
From: Tuckman M
DUKE POWER CO.
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9106200039
Download: ML20077F632 (3)


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f ; ~, -;$,j DUKE POWER June 12, IW1 U. S, Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555

Subject:

Catawba Nuclear Station, Unit 1 Docket No. 50~413 Special Report Invalid Failures of Diesel Generator IB Pursuant to Technical Specification 4.8.1.1.3 and 6.9.2, find attached a Special Report concerning four invalid failures on Diesel Generator IB. Two of these failures occurred on hfay 16,1991 and the other two occurred on hfay 18, 1991.

Very truly yours, f

N b hChA hl S. Tuckman CRUSR61291 Attachment xc: S. D. Ebneter Regional Administrator, Region II R. E. hfartin, ONRR W. T. Orders Senior Resident Inspector i

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SPECIAL REPORT CATAWBA NUCLEAR STATION DIESEL GENERATOR IB INVALID FAILURES DURING MAINTENANCE TESTING OF Tile ENGINE Four invalid failures occurred on 15sel Generator (D/G) IB during May,1991. At the time of the invalid failures, Unit I was in hiode 5 during outage number 5 (IEOC5).

Catawha Technical SpeciGcations require nat mly one D/G be OPERABLE in Mode 5.

Since the 1 A D/G was OPERABLE, the.1 D/G was not required during this time.

Therefore, there is no unavailability time associated with these invalid failures. Two invalid failures (start No's 934 and 935) of D/G IB occurred on May 16,1991. The third and fourth invalid failures occurred on May 18,1991 (start No's 941 and 942). All of the

- invalid failures occurred during the Maintenance testing Breakin procedure. D/G 1B was on a monthly operability test schedule at the time of these invalid failures. There have been 0 valid failures in the past 20 valid starts and 2 valid failures in the past 100 valid starts for D/G 1B. The D/G remains on a 31 day operability schedule per Technical Specification 4.8.1.1.2, Table 4.8-1.

The first invalid failure occurred during the first start of the Maintenance Testing Breakin Run, Procedure MP/0/A/7400/13. The start of the D/G appeared normal in all respects.

Approximately 2 minutes into the start, the D/G shutdown when control air pressure dropped below the shutdown set point.

A second start (start #935) for testing was conducted with IAE observing the pneumatic instrumentation. Approximately 2 minutes into the start, the D/G shutdown when control air pressure dropped below the shutdown set point. The test indicated that the pneumatic control devices were not charging.

IAE inspected and tested the pneumatic shutdown sensors in search of a possible fault that would have caused the engine to shutdown. They found the instrument tubing to the turbocharger high vibration sensor reversed at the sensor. This reversal prevented the system from pressurizing because it was continually venting. No other abnormal system configurations were found.

The reversed tubing was reinstalled in the correct configuration. To prevent reoccurrence, metal identification / positioning tags have been installed in place of paper tags in this area.

Metal tags are now on all engines in this arer.

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e 2 of 2 The D/G was restarted and successfully completed all loaded runs of the Modified Breakin procedure. The final step of the procedure requires a start and idle run to collect cold compression data. The governor was set to achieve a slow start. The slow start is used to minimize the high starting stresses on the engine during all maintenance starts. During the slow start, (start # 9415/18/91) the start timer ran out causing a fail to start signal which shut down the engine. The slow start time slightly overlapped into the start timer tolerance causing the shutdown.

The governor slow start time was reset and D/G start # 942 was attempted. The engine rolled on air, the fuel racks were full open, but the cylinders were nct getting sufficient fuel to support the start. Procedures were drawn to inspect and clean or change, as necessary, both fuel strainer elements.

Inspection of the in service fuel strainer proved it to be nearly clogged. The off service strainer as expected, was clean and showed no debris. The in service fuel filter was then l-examined and found to be clean with no evidence of any debris.

The fouled strainer was replaced with a new one from spares and the D/G was successfully restarted. The final step of the breakin procedure, cold compression data collection, was performed and the DIG shut down.

Both IB fuel storage tanks and the day tank had been cleaned this outage. The only area that was not cleaned was the piping from the storage tanks to the day tank. The day tank had been drained and refilled twice following its cleaning. The refilling flow rate is much greater when the tank is empty than when in a normal full condition. The two fast refills flushed existing debris from the piping into the day tank. No time was allowed for settling, and, therefore, the debris was carried into the strainer.

Performance then conducted their required after maintenance testing without incident.

The D/G was started, fully loaded and commenced its 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> run that carried out to approximately 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />. The in servive strainer was then removed and inspected. The in service strainer had only normally appearing deposits present. The strainer was cleaned and reinstalled.

l Total time accumulated on the strainer at the time of this inspection was in excess of 40 hours4.62963e-4 days <br />0.0111 hours <br />6.613757e-5 weeks <br />1.522e-5 months <br />. These hours include approximately 10 fast starts which require a high fuel demand versus a steady state smaller fuel consumption.

Operations then performed the Operability PT and declared the D/G " Operable".

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