ML20002D912
| ML20002D912 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 04/21/1971 |
| From: | Walke G CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Morris P, Skovholt D US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 8101230392 | |
| Download: ML20002D912 (4) | |
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Dr. Peter A. Morris Re: Docket 50-155 Division of Reactor Licensing License No DPR-6 United States Atomic Energy Commission Washington, DC 20545
Dear Dr. Morris:
Attention: Mr. D. J. Skovholt Consumers Power Company reported to the AEC, by letter dated October 8, 1970, the failure of the emergency generator diesel engine to start in the " automatic mode."
This failure was originally attributed to the loss of prime to the injection system. We also reported that further investigation was being conducted to determine and correct the cause of this failure.
The investigation has been completed and corrective action taken. The investigation revealed the cause of the failure was due to the method utilized to shut down the engine. Prior to the failure of the diesel engine to start on November 30, 1968 (reported to the Division of Reactor Licensing by letter dated February 4,1969), the diesel engine was shut down by the manual control of the governor (as recommended by the manufacturer). The cause of this 1968 failure was traced to a pin in the governor linkage that had slipped out of place.
Further investigation revealed that the pin could slip out of place during a manual shutdown of the engine if the operator's hand were to slip off the control suddenly or if the control was quickly released prior to the engine stopping. This malfunction was described to the manufacturer. The manufacturer indicated no previous history or ex-planation of this type of failure. Because of this incident with the governor linkage pin, operating instructions were revised to change to an electric shutdown mode for the diesel engine. The manufacturer was consulted prior to this change and agreed that it would not affect the starting characteristics of the diesel engine.
Since the change to electric shutdown was instituted, the automatic starting characteristics of the diesel engine was elightly slower and somewhat erratic, but the engine had always started as programmed until October 1, 1970. After this failure of the engine to start automatically, an extensive investigation was conducted.
All possible ways that the engine could lose its prire were investi-gated with no possible cause for the failure uncoverad. A program of test starting the engine following electrical and manual shutdowns Y] oN( 0 h
2 Dr. Peter A. Morris April 21, 1971 revealed that the engine started more quickly and less erratically following a manual shutdown. A study of the operating principles of
- tF2 governer revealed tnat during an electrical shutdown, the governor attempts.to maintain engine speed by applying governor oil pressure to hold open the fuel rack via mechanical linkages. The supply of oil to the governor is provided by an engine driven lube oil pump to a reservoir in the governor. As the engine coasts down to a halt, the
- oil supply to the governor is lost. However, the governor remains in-the vide open position until governor oil pressure decays to a point that spring tension returns the governor and fuel racks to the closed position. At the next attempt to start the engine, it is necessary to crank long enough for the lube oil system to provide a supply of oil to the governor. When this supply is available, the governor then actuates the fuel rack and the engine starts inmediately.
A manual shutdown traps the governor oil supply such that it is immediately available during the next attempt to start the. engine.
This results in the engine starting more quickly upon initiation of the automatic start cycle.
As a result of these investigations, the diesel engine failure to start was attributed to a statistical variation of the erratic starting experienced following electri: shutdowns. To pre-clude a recurrence of this type failure, the following corrective actions have been instituted:
1.
Operating instructions have been changed such that the engine will be shut down by manual control of the governor. These op-eratin~ instructions provide instructions to the operators on how to properl, manipulate the manual governor control lever. These revised operating instructions will be posted at the emergency diesel control panel.
2.
A slightly oversized pin has been installed in place of i
the original pin thus eliminating the possibility of the pin slipping out of place under circumstances similar to those that caused the 1968 failure.
f In our February 4,1969 letter, we agreed to install an arm position indicator at the control panel. Such an indicator will not be installed because it is impossible to install one such that it gives meaningful information.
Based on the above-described investigations, Consumers Power Company has concluded that the emergency generator diesel engine mal-function was not of a significant nature to effect normal overall plant and systems operations and did not impair plant safety. The changes m.
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.t Dr. Pettr A.: Morris'
- -3' April 21, 1971 described above should improve the already good reliability record -
of this diesel engine.
Yours very truly,
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Gerald J. Walke RBS/dmb
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