ML19246B718
| ML19246B718 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 06/28/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Pilant J NEBRASKA PUBLIC POWER DISTRICT |
| References | |
| NUDOCS 7907180379 | |
| Download: ML19246B718 (1) | |
Text
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UNITED STATES PDR:HQ
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ARLINGTON, TEX AS 76012 June 28, 1979 Docket No.
50-298 Nebraska Public Power District NfTN:
J. M. P11 ant, Director Licensing & Quality Assurance Post Office Box 499 Columbus, Nebraska 68601 Centlemen:
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 your understanding of this catter, please contact this office.
Sincerely, w*
Kar V Seyf i Director
Enclosures:
1.
IE Circular No. 79-12 2.
List of IE Circulars Issued in Last 12 Months cc:
L. C. Lessor, Superintendent Cooper Nuclear Station Post Office Box 98 Brownville, Nebraska 68321
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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 GENF.RATOR TURBOCHARGER 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 diese.'s 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 ratt is 6 gpm, 4 gpm is also circulated, via a 30 psi relief valve, through the lube oil filter and coolet 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 e gine has reached full operating temperature.
If, for example, the engine had been operated for about I hour at full load, the lube oil temperature would be at about 200 degrees F at time of shutdoun.
Under these circumstances, the full 6 gpm output of the circu-lating pump will flow only to 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 wor ' case of a repeat fast start, the engine may actually reach operating d, 900 RPM, before the required _ oil _pressute js _.
established at the turbocharger thrust be.
__.m of the bearing metal so that cumulative d.
DUPLICATE DOCUMENT could result in a turbocharger failure.
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