ML19256B431
| ML19256B431 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 06/28/1979 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Johari Moore SOUTHERN CALIFORNIA EDISON CO. |
| References | |
| NUDOCS 7907100531 | |
| Download: ML19256B431 (1) | |
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UNITED STATES r,, J. j)., (8\\,'
NUCLEAR REGULATORY COMMISSION W,,
REGION V S Ub]!!
I 1930 N. CAllF ORNI A DOULEVARD h'D 6
SUITE 202. WALNUT CHELK PLAZA
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WALNUT CREE K. CALIFORNIA 94596 June 28, 1979 Docket ilos. 50-361 50-362 50-206 Southern California Edison Company P. O. Box 800 2244 Walnut Grove Avenue Rosemead, California 91770 Attention: Mr. J. B. Moore Vice President Gentlemen:
The enclosed IE Circular fio. 79-12 is forwarded to you for information.
flo written response is required.
Should you have any questions related to your ur.derstanding of this matter, please contact this office.
Sincerely,
[TY,--g d,.-
R. H. Engelken Director
Enclosures:
1.
IE Circular fio. 79-12 2.
List of IE Circulars Issued in Last 12 Months cc w/ enclosures:
J. T. Head, SCE J. M. Curran, SCE J. H. Drake, SCE 8M 054 2007100 9 /
UNITED STATES NUCLEAR PEGui.3 TORY COMMISSION OFFICE OF INSPEC110N AND ENFORCEMENT WASHINGTON, D.C.
20555 June 28, 1979 IE Circular No. 79-12 (7906210065)
POTENTIAL DIESEL GENERATOR TURBOCHARGER PROBLEM Description of Circumstances:
The Electro-liotive 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 nornal 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 gpn. Since the total oil pump flow rate is 6 gom, 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 pr'ned to support a kst start.
If 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 and piston cooling pump will imediately 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 had 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 temperature would be at about 200 degrees F at time of thatdown.
Under these circumstances, the full 6 gpm output of the circu-lat f aa pump will flow only to the turbocharger bearings because of the lower viscosity of the hot lubrican 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 /t 'n 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 af ter a hot shutdown, lack of cause DUPLICATE DOCUMENy engine damage.
In the worst case of a actually reach operating speed, 900 RPM 0'5 Or~
established at the turbocharger thrust Entire document V-of the bearing metal so that cumulative into system under-USly entered would result in a turbocharger failure.
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