ML19256B439
| ML19256B439 | |
| Person / Time | |
|---|---|
| Site: | Sterling |
| Issue date: | 06/28/1979 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Arthur J ROCHESTER GAS & ELECTRIC CORP. |
| References | |
| NUDOCS 7907110039 | |
| Download: ML19256B439 (1) | |
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UNITED STATES y yN,.c (g(,g NUCLEAR REGULATORY COMMISSION d/
REGION I
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,d KING OF PRUSSIA, PENNSYLVANI A 19406 June 28, 1979 Docket No. 50-485 Rochester Gas & Electric Corporation ATTN:
Mr. J. E. Arthur Chief Engineer 89 East Avenue Rochester, New York 14649 Gentlemen:
The enclosed IE Circular No. 79-12, is forwarded to you for information.
No written response is required.
Should you have any questions related to ycur understanding of this matter, please contact this office.
Sincerely, affk yce H. Grier irector
Enclosures:
1.
IE Circular No. 79-12 2.
List of IE Circulars Issued in Last Twelve Months cc w/encis:
C. R. Anderson, Manager, QA Lex K. Larson, Esquire N. A. Petrick, Executive Director, SNUPPS Ge~ild Charnoff, Esquire 836 117~
7907140D39 7
ENCLOSURE 1 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 IE Circular No. 79-12 Date:
June 28, 1979 Page 1 of 2 POTENTIAL DIESEL GENERATOR TURB0 CHARGER PROBLEM Description of Circumstances:
The Electro-Motive Division (EMD) of General Motors Corporation has recently identified a potential failure mode of turbochargers used on EMD diesels in nuclear plant standby service.
When an engine is in the normal standby mode, the lubricating oil temperature is maintained at about 115 degrees F and the circulating oil pump supplies warm oil to the turbocharger bearings at a flow rate of about 2 gpm.
Since the total oil pump flow rate is 6 gpm, 4 gpm is also circulated, via a 30 psi relief valve, through the lube oil filter and cooler which serves to keep the entire accessory lubricating oil system primed to support a fast start.
If a power outage occurs, the oil circulating pump may stop 5 to 10 seconds before the engine receives a start signal; but the main bearing and piston cooling pump will immediately receive oil from the primed lube oil filter-cooler system thus providing a rapid buildup of engine lube oil pressure throughout the engine bearing and turbocharger systems.
A potential problem occurs, however, if the diesel engine receives a repeat rapid start within a minimum of 15 minutes and a maximum of 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> after a shutdown from a previous run in which the engine has reached full operating temperature.
If, for example, the engine nad been operated for about 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> at full load, the lube oil ter mature would be at about 200 degrees F at time of shutdown.
Under these r
...istances, the full 6 gpm output of the circu-lating pump will flow only.o the turbocharger bearings because of the lower viscosity of the hot lubricant.
At this temperature, the circulating pump pressure will not reach 30 psi.
Until the lube oil cools to about 160 degrees F, no oil will be supplied via the relief valve to the equipment rack for the first 2 to 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> after engine shutdown.
During this cooling period some of the oil contained in the cooler and filter will drain back to the engine sump via the lube oil scavenging pump, and some of the oil from the strainer box will be drawn into the cooler by the system vacuum that develops.
The result is that when a repeat fast start occurs within the above 15 minute to 3 hour3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> time frame after a hot shutdown, lack of prime oil system pressure can cause engine damage.
In the worst case of actually reach operating speed, 900 R established at the turbocharger thrus DUPLICATE DOCUMENT r
O of the bearing metal so that cumulati would result in a turbocharger failur Entire document previously entered into system under:
f ANO No. of pages:
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