ML19246B722
| ML19246B722 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 06/28/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Millen C PUBLIC SERVICE CO. OF COLORADO |
| References | |
| NUDOCS 7907180385 | |
| Download: ML19246B722 (1) | |
Text
f#""%o, CENTRAL FILES UNITED STATES pg NUCLEAR REGULATORY COMNISSION O -h.*. [o a
'y E
REGION IV
$ j'f Gli RYAN PLAZA DRIVE, SulTE 1003 gg7g v e ARLINGTON, TE X AS 7G012 g ++,,*
June 28, 1979 Docket No.
50-267 Public Service Company of Colorado ATTN:
Mr. C. K. Millen Senior Vice President P. O. Box 840 Denver, Colorado 80201 Gentlemen:
The enclosed IE Circular No. 79-12, is forwarded to you for infc,rmation.
No written response is required.
Should you have any questions related to your understanding of this matter, please contact this office.
Sincerely, C
, f,
/
~Karl V. Seyfri Director
Enclosures:
1.
IE Circular No. 79-12 2.
List of IE Circulars Issued in Last 12 Months cc:
D. W. Warenbourg, Nuclear Production Manager Fo r t S t. Vrain Uuclear Station P. O. Box 368 Platteville, Colorado 80651 L. Brey, Manager, Quality Assurance A
7907180385 364 137
UNITED STATES NUCLEAR REGULATORY C0!L'!ISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 IE Circular No. 79-12 Date:
June 28,1979 Page 1 of 2 POTENTIAL DIESEL GENERATOR TURBOCHARGER PROBLEtt Description of Circumstances:
The Electro-Motive Division (EMD) of General Motors Corporation has recently identified a potential failure mode of turbochargers used on EMD die:..ls in nuclear plant standby service.
When an engine is in the normal standby mode, the lubricating oil temperature is maintained at about 115 legrees 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 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 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 stirt 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 temperature 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 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 af ter a hot shutdown, lack of prime oil system pressure can cause engine damage.
In the worst case of a repeat fast start, the engine may actuallyreachoperatingspeed,900 RPM,beforethe,re_quirepoil_pressureis established at the turbocharger thrust bc of the hearing metal so that cumulative c
[ DUPLICATE DOCUMENT would result in a turbocharger failure.
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