ML20079L970
| ML20079L970 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 02/14/1983 |
| From: | Schroeder C COMMONWEALTH EDISON CO. |
| To: | Schwencer A Office of Nuclear Reactor Regulation |
| References | |
| 5988N, NUDOCS 8302230518 | |
| Download: ML20079L970 (7) | |
Text
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Commonwealth Edison
( O '] Address Reply to: Post Office Box 767 0
One First National Plaza. Chicago, lilinois
\\
/ Chicago Illinois 60690 February 14, 1983 Director of Nuclear Reactor Regulation Attention:
Mr. A. Schwencer, Chief Licensing Branch No. 2
' Division of Licensing U. S. Nuclear Regulatory Commission Washington, DC 20555
Subject:
LaSalle County Station Units 1 and 2 Diesel Generator Prelube Oil Pump Modification Operating' License NPF-11, Condition 2.C.21.b NRC Docket Nos. 50-373-and 50-374 Reference (a):
October 6, 1982 letter from C.
W.
Schroeder to A. Schwencer:
Dear Sir:
During a telecon with the NRC on November 10, 1982, we discussed our proposal to meet the requirements of LaSalle Unit 1 Operating License Condition 2.C.21.b.
This license condition requires us to install a prelube pump or an alternative that is acceptable to the NRC to preclude dry-starting of the diesel engines.
In our letter of October 6, 1982 to Mr. A. Schwencer, we had proposed to modify the engine lubrication system per EMD Maintenance Instruction 9644, which is the only lube oil modification that is recommended by EMD, the diesel manufacturer, and Stewart and Stevenson, the equipment supplier.
During the November 10, 1982 telecon, the NRC expressed doubts that our proposed change would fulfill the requirements of the license condition because it does not prelubricate the upper engine parcs, which include the valve rocker arm assemblies and camshaft.
The NRC requested additional information before they could consider the EMD MI 9644 as an acceptable alternative.
Since this telecon, EMD and Stewart and Stevenson have furnished additional information on the EMD MI 9644 modification and engine prelubrication requirements.
In a letter dated January 24, 1983, EMD strongly recommended against prelubrication of the upper deck because it is not necessary and it would degrade the reliability of the diesel engine.
Oil could enter the cylinders from the lash adjusters through the valve guides and cause a hydraulic oil lock.
If an engine is started with substantial oil in a cylinder, it can be severely damaged.
Even if oil could not flow into the cylinders, prelubricating the camshaft and rocker arm bearings will not increase their reliability or improve their performance.
The oil does not completely drain dry from the bearing cavities during periods of inactivity, and this oil film will allow them to operate satisfactorily without pressurized oil for the short period of 8302230518 830214
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-Director of. NRR February 14, 1983 time following startup.- LaSalle Station has inspected several diesel generators immediately prior to conducting the 30-day surveillance test run and has' verified that a oil film will remain on the upper deck components for at least a month.
These bearings also require less lubrication during startup because they are lightly loaded during this period.
This has been verified by operating experience.
In engines that were not equipped with the immersion heater system, the upper deck bearings have not been damaged during startup even when the oil system was not fully charged (prelubricated).
In engines equipped with the EMD MI 9644 011 system, operating oil pressure is reached within a few revolutions of the engine following startup because the main oil gallery and other large volumes in the oil system such as the external accessories are maintained in a fully charged condition.
The only unfulfilled volume is in the camshaft (1/2 to 1 gellon), and it is filled within the first ten revolutions of the engine.
After the engine lube oil pump develops oil pressure, which requires four or five revolutions, the oil pumps that are installed on the LaSalle diesel engines will deliver about 1/4 gallon per engine revolution..The EMD January 24, 1983 letter is attached for your information.
The additional information provided by EMD supports our position that the EMD MI 9466 modification will meet the requirements of License Condition 2.C.21.b in lieu of a prelube pump, because neither EMD nor Stewart and Stevenson recommend a prelube pump, a prelube pump will increase the probability of a malfunction of equipment important to sa fety, and a prelube pump will not improve bearing life.
Commonwealth Edison Company requests that the NRC consider the EMD MI 9466 modification, which is recommended by both manufacturer and supplier, as an acceptable alternative.
Enclosed for your use are one (1) signed original and thirty-nine (39) copies of this letter and the enclosures.
If there are any further questions in this matter, please contact this office.
Very truly yours, CMLL llu/s3 c.
C.
W.
Schroeder Nuclear Licensing Administrator im Enclosures cc:
NRC Resident Inspector - LSCS
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STEWART & STEVENSON SERVICES, INC.
P.O. BOX 1637
- HOUSTON TEXAS 77001. (713) 923-2161 TWX: 910-8811755
- TELEX 762301
- CABLE:"STEWSTEVE" f'
1 January 27, 1983 Commonwealth Edison Co.
P.O. Box 767 - SNED 35 FNW Chicago, IL 60690 ATTENTION:
E. L. Seckinger
SUBJECT:
LaSalle County Station Prelube Requirements on DGS
Dear Ed:
Enclosed is a copy of Mr. John G. Hayden's (Assistant General Service Manager, EMD) letter and " position" paper dated January 24, 1983, in regard to prelubrication requirements.
Please let us know if there are any questions.
Very truly yours, STEWART & STEVENSON SERVICES, INC.
k L-H.M. Arbuckle Nuclear Contracts HMA/kh cc: Tom Boyce l
FAMOUS FOR SERVICE AROUND THE WORLD A ISON D ESE
ELECTRO-MOTIVE eE-Dectro-Motive DMslon General Motors CorporaUon LaGrange, Illinois 60525 (312) 387-6000 January 24, 1983 FILE: 9180 Mr. Tom Boyce STEWART & STEVENSON SERVICES 4516 Harrisburg Boulevard P.O. Box 1637 Houston, TX 77001
Dear Tom:
The attached memorandum is in response to your request for a " position" paper on top deck prelubrication. A Pointers article will be published in the near future.
Very truly yours, 0f
~
f John G. Hayden, Assistant General Service Manager Marine & Industrial JGH/jr Enclosure cc:
M. Arbuckle (S&S)
M. J. Fleckenstein i
G. A. Klippel K. J. Williams
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no s c2 A l
E Inter-organization To:
Memorandum oste: January 24, 1983 Frorn:
J. G. Hayden subject:
ENGINE PRELUBRICATION REQUIREMENTS Years of experience in many different applications have demonstrated that EMD engines are reliably capable of successful start-ups with-out the benefit of prelubrication,provided running time without oil pressure is not excessive or significant increases in engine speed and load do not occur before pressurized oil is supplied. This ability is primarily due to several important factors described below:
1.
Sensitive bearings are supplied with lube oil during start-up.
Of all bearings in the engine, the turbocharger thrust bearing has exhibited the least tolerance to abnormally long delays in oil supply following start-up. The tapered ramps on the thrust face use bearing rotation to develop oil wedges which separate the bearing surfaces with hydraulic pressure. This hydro-dynamic geometric configuration is very vulnerable to severe wear and wiping damage if oil pressure delays are extensive.
Turbocharger drive gears rotate the compressor wheel approximately 18 times engine speed, which exposes the turbocharger bearings to significant loads and speed even at idle. These bearings are lubricated during start-up with an external electrically drivenoil pump to help compensate for their distant location from the engine oil pump.
2.
The oil wetted surfaces of the various bearing cavities do not completely drain dry during periods of inactivity, which allows them to operate successfully without pressurized oil for the relatively short periods of time that normally occur during the starting phase. The primary purpose of prelubrication is to fill the voids in the lube system rather than to lubricate or wet the bearings. Except for turbocharger bearings, which are externally lubricated during start-up, the other engine bearings have demonstrated an ability to operate satisfactorily during the relatively short start-up interval.
3.
The time periods without pressurized oil following start-up are generally relatively short because of the favorable ratio between the lube oil pump delivery rate and the engine lube system volume, where very little time elapses before the entire engine is pressurized following crank-up.
The engine lube oil pump will develop engine oil pressure only after the oil system is fully Bectro-Motive DMslon General Motors Corporation LaGrange,Imnois 60525
ed.,ou I-Memorandum January 24, 1983 recharged. The engine oil system consists of 011 ;a53 ages within the engine in addition to the oil filters, oil cooler, and external piping having substantial volume.
Inasmuch as engine speeds should not significantly exceed idle until after oil p essure is developed, the lubrication delay at start-up is If a lube oil primarily a function of voids in the oil system.
system is allowed to drain extensively during periods of inactivity, considerable time may elapse before pressurized oil is generated at start-up.
4.
Longer lubrication delays which can lead to bearing distress can be experienced if the oil system had been allowed to drain prior to.s tart-up. This condition should be avoided. Generally we surmise that the lube oil system has drained dangerously, too low to attempt start-up, if an engine has been inactive for more than 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />. Starting should not be attempted without recharging the oil system unless the oil system is constantly replenished by an immersion heater system. When necessary, recharging is most easily accomplished with the prelubrication procedure. EMD maintenance instructions recommend prelubrication for recharging the oil system for engines that have been inoperative for more than 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />. Charging the oil system prior to start-up greatly reduces the interval during which the lube oil pump is filling the passages with oil.
Emergency and standby power plants and other applications that are likely to have long periods of inactivity and where prelubrication is not feasible before every start, must be equipped with immersion heaters. The immersion heater system performs three important functions.
The lube oil is heated, reducing its viscosity, allowing it to be readily pumped by the engine oil pumps. The immersion heater lube oil circulating pump keeps the external oil system accessories fully charged thereby enabling prompt oil supply. The circulating pump also lubricates the turbocharger bearings which exhibit sensitivity to marginal lubrication at start-up.
As described in MI 9544, EMD's original immersion heater system performs these functions satisfactorily except that the external oil system accessories are not maintained at a fully charged level for a period of about three hours following shutdown. Oil flow to the accessories is resumed when the oil viscosity increases as the oil cools. No difficulty is expected if routine fast start-ups are avoided during this three-hour period.
A more desirable alternative is to apply the improved immersion heater system as outlined in Modernization Recommendation MI 9644 which continually replenishes the oil cooler and filters to the full level regardless of oil temperature and viscosity. Oil systems modified in accordancewith MI 9644 also provide a constant oil supply to the main oil gallery in the engine (which feeds the engine crankshaft bearings) i Dectro-Motive DMsion General Motors Corporation LaGrange. Imnois 60525
c~dsa f Memorandum January 24, 1983 in addition to supplying oil to the turbocharger. Although oil flows through the crankshaft bearings, the standby oil level in the engine is intentionally kept below the camshafts and valve rocker arm assemblies. The durability of camshaft and rocker arm bearings is well documented. Years of experience have demonstrated that bearings at the camshaft and rocker arms are lightly loaded and do not experience damage or distress at start-up even when the oil system is not fully charged or immersion heaters are not utilized.
In an engine equipped with ar. MI 9644 immersion heater, the small remaining unfilled volume of the camshaft oil system (1/2 to 1 gallon depending on engine size) is rapidly filled during the first few revolutions of the engine by the engine lube oil pump uich delivers 1/10 to 1/4 gallon per engine revolution depending on engine size. Engines equipped with MI 9644 inmersion heater systems very rapidly approach operating oil pressures following start-up because.the ;nain o.il gallery and other large volumes'in the' oil system are fully charged.
The pump initially develops oil pressure during the first four or five revolutions of the engine.
There have been some persuasions to further improve the system by raising the oil level to the camshafts. We strongly recommend that
'hese attempts be rejected as not only unnecessary, but prejudicial t,' the reliability of the engine because of the danger of oil entering tl e cylinders from lash adjusters through valve guides. Any attempts to start an engine having substantial lube oil in the cylinder is likely to cause severe engine damage. The start-up reliability of the bearings in the top deck leaves no room for further improvement.
The immersion heater system described in MI 9644 provides optimal prelubrication for all fast start emergency and standby power plants.
'.b f-
"~
John G. Hayden, Assistant General Service Manager Marine & Industrial JGH/jr cc:
M. Arbuckle (S&S)
T. Boyce (SSS)
D. W. Chirikos H. W. Falter (PSD)
M. J. Fleckenstein
~
G. A. Klippel D. l.. Schroder K. J. Williams -- please use this as a basis for a Power Pointers.
T. G. Winfield Electro-Motive DMslon Geners! Motors corporation LaGrange,Imnois 60525