ML19225A104
| ML19225A104 | |
| Person / Time | |
|---|---|
| Site: | 05000484 |
| Issue date: | 06/28/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Dienhart A NORTHERN STATES POWER CO. |
| References | |
| NUDOCS 7907180423 | |
| Download: ML19225A104 (1) | |
Text
[pn Mooq(o PDR UNITED STATES
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NUCLEAR REGULATORY COMMISSION
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J REGION 111 g,
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GLEN ELLYN, ILLINOls 60137 S
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JUN 2 81979 Docket No. 50-484 Northern States Power Company ATTN:
Mr. A. V. Dienhart Vice President - Tyrone Energy Park 100 North Barstow Street Eau Claire, WI 54701 Gentlemen:
The enclosed IE CirLular No. 79-12, is forwarded to you for infor-mation. No written response is require Should you have any questions related to your understanding of this matter, please contact this office.
Sincerely, f ^o^h%
James G. Ke,ppIer Director
Enclosure:
IE Circular No. 79-12 cc w/ enc 1:
Central Files Director, NRR/DPM Dicector, NRR/ DOR PLR Lacal PDR NSIC TIC Regions I & IV
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7907180423 s
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U.S. NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT REGION III 7
$6 -
June 28, 1979 IE Circular No. 79-12 (7906210065)
POTENTIAL DIESEL GENERATOR TUR3OCHARGER 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 temperat're 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 pu=p flow rate is 6 gpo, 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 pri=ed 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 i==ediately receive oil from the primed lube oil filter-cooler system thus providing a rapid buildup of engine lube oil pres;ure throughout the engine bearing and turbocharger systems.
A potential problem occurs, however, if the diesel engine receives a repeat rapid start within a mini =um of 15 -inutes and a maximu= 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 te=perature.
If, for exa=ple, 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 shutdown. Under these circumstances, the full 6 gpm output of the circu-lating pu=p will flow only to the turbocharger bearinga because of the lower viscosity of the hot lubricant. At this temperature, the circulating pu=p pressure will not reach 30 psi. Until the lube oil cools to about 160 degrees I, 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 su=p via the lube oil scavenging pu=p, and some of the oil from the strainer box will be drawn into the cooler by the pvstem.vacuu= that develops. The result is that when a repeat fast start occui time frame sfeer a het shutdown, lacF DUPLICATE DOCUMENT engine damage. In the worst case of actually reach operating, speed, 900 F Entire document previously entered established at the turbocharger thrus into system under:
of the bearing =etal so that cumulatJ i
hh hh 1
would result in a turbocharger failu:
ANO No. of pages:
e l'29 O$