ML19246B715
| ML19246B715 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 06/28/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Cavanaugh W ARKANSAS POWER & LIGHT CO. |
| References | |
| NUDOCS 7907180376 | |
| Download: ML19246B715 (1) | |
Text
UNITED STATES PDR:HQ y1 pr$'s NUCLEAR REGULATORY COMMISSION
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REGION IV S
611 RYAN PLAZA DRIVE.SutTE 1000 pjg((
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%,, %# " o AR LINGTON, TEX AS 76012 June 28, 1979 Docket Nos.
50-313 50-368 Arkansas Power and Light Company ATIN:
Mr. William Cavanaugh III Vice President of Generation and Construction P. O. Box 551 Little Rock, Arkansas 72203 Gentlecen:
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,
')
Karl Y. Seyfrit/ /
Director
Enclosures:
1.
IE Circular No. 79-12 2.
- of IE Circulars Isst;ed in Last 12 Month 3 cc: James P. O'Hanlon, Plant Managt -
Arkansas Nuclear One P. O. Box 608 Russellville, Arkansas 72801 L. Alexander, QC Supervisor
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7907180376 364 124
UNITED STATES NUCLEAR REGULATORY COT!ISSION OFFICE OF INSPECfION AND ENFORCEMENT WASHINGTON, D.C.
20555 IE Circular No. 79-12 Date:
June 28, 1979 Page I of 2 POTENTIAL DIESEL GENERATOR TURBOCHARGER 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 node, 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 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 dieset 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 previons 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 actually reach operating speed, 900 RPM, established at the turbocharger thrust b,before_the_ reauired oil possyrr$<: _ _._
m of the bearing metal so that cumulative
. ; DUPLICATE DOCUMENT would result in a turbocharger failure.
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No. of pages:
6
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