ML19256B429
| ML19256B429 | |
| Person / Time | |
|---|---|
| Site: | Humboldt Bay, Diablo Canyon |
| Issue date: | 06/28/1979 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Crane R PACIFIC GAS & ELECTRIC CO. |
| References | |
| NUDOCS 7907100529 | |
| Download: ML19256B429 (1) | |
Text
'o UNITED STATES l b.
E j' y
'g NUCLEAR REGULATORY COMMISSION
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REGION V D Ypi,
[8 1990 N. Calf f 0RNIA BOULEVARD s
w-6 SUITE 202, WALNUT CREEK PLAZA 9 **,,*
WALNUT CREEK, CAllFORNIA 94596 June 28, 1979 Docket Nos. 50-133 50-275 50-323 Pacific Gas and Electric Company 77 Beale Street San Francisco, California 94106 Attention:
Mr. Philip A. Crane, Jr.
Assistant General Counsel 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 your understanding of this matter, please contact this office.
Sincerely, (N61.....,,.(C_.-
R. H Engelken Director
Enclosures:
1.
IE Circular No. 79-12 2.
List of IE Circulars Issued in Last 12 Months cc w/ enclosures:
W. A. Raymond, PG&E J. D. Ucrthington, PG&E R. Ramsay, Diablo Canyon, PG&E W. Barr, PG&E g}$ QSQ E. Weeks, Humboldt Bay, PG&E 7 9071006M r
UflITED STATES flUCLEAR REGULATORY COMMISSIO:1 0FFICE OF INSP' ' ION AND ENFORCEMENT WASHINGT;4, D.C.
20555 June 28, 1979 IE Circular No. 79-12 (7906210065)
POTENTIAL DIESEL GENERATOR TURBOCHARGER PROCLEM Description of Circunstances:
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 rode, 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 cpn. 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 systen primed to support a fast start.
I' a power outage occurs, the oil circulating pump nay stop 5 to 10 seconds before the engine receives a start signal; but the main bearing snd piston cooling pump will irmediately receive oil from the primed lube 01. filter-cooler system thus providing a rapid buildup of engine lube oil pressure throughrut 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 naximum 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 temperature would be at about 200 degrees F at tire 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:
lating pump pressure will not reach 30 psi. Until the lube oil cools to osout 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 /> tire frame after a hot shutdown, lack M
- nl w m m sure can cause engine damage.
In the worst case of a r actually reach operating speed, 900 RPM DUPLICATE DOCUMENT h 3.3 (j$ )
established 2t the turbocharger thrust t of the bearing netal so that cumulative Entire document previously entered would result in a turbocharger failure.
Into system under:
ANO 7 6%OOGT No. of pages:
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