ML19256B425
| ML19256B425 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 06/28/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Jeffery Grant TOLEDO EDISON CO. |
| References | |
| NUDOCS 7907100523 | |
| Download: ML19256B425 (1) | |
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o UNITED STATES 5 j ) '",s,, /*j NUCLEAR REGULATORY COMMISSION
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REGION 111
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GLEN ELLYN, ILLINOls 60137 5
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Docket No. 50-346 C..
Toledo Edison Company ATTN:
Mr. James S. Grant Vice President - Energy Supply Edison Plav.
300 Madison Avenue Toledo, OH 43652 Gentlemen:
The enclosed IE Circular No. 79-12, is forwarded to you for infor-mation. No written response is required.
Should you have any questions related to your understanding of this matter, please contact this office.
Sincerely,
%.h N
(/ James G. Kepp er Director
Enclosure:
IE Circular No. 79-12 cc w/ encl:
Mr. T. Murray, Station Superintendent Central Files Director, NRR/DPM Director, NRR/ DOR PDR Local PDR NSIC TIC Harold W. Kohn, Power Siting Commission Helen W. Evans, State of Ohio 835 042 ecc -
gas
U.S. NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT REGION III e-G.
June 28, 1979 IE Circular No. 79-12 (7906210065)
POTENTIAL DIESEL GENERATOR TURBOCHARGER PROBLEM Description of Circumstances:
The Electro-Motive Division (EMD/ of General Motors Corporation has recently Mentified a potential failure mode of turbochargers used on EMD diesels in ncelear plant standby service.
Aute an engine is in the normal standby mode, the lubricating oil temperature la 0.v?ntained 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 punp 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 pu=p 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 r.:pid 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 had been operated for about I hour at full load, the lube oil tempera ure would be at about 200 degrees F at time of shutdown. 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 1ressure will not reach 30 psi. Until the lube oil cools to about 160 degreec F, no oil vill 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 minu time frane after a hot shutdown, lack of DUPLICATE DOCUMENT g } } M_ 7 engine damage.
In the worst case of a re actually reach operating speed, 900 RPM, established at the turbocharger thrust b ntire document previbusly entered of tl e bearing taetal so that cumulative d Into system under:
vould result in a turbocharger failure.
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