ML17303A355

Torsional Vibration Analysis of Repaired Crankshaft KSV-20-T SN-7187 Arizona Public Svc Co,Palo Verde Nuclear Generating Station Diesel Generator III-B.

ML17303A355
Person / Time
Site:	Palo Verde
Issue date:	02/06/1987
From:	Horne J COOPER BESSEMER CORP.
To:
Shared Package
ML17303A352	List: ML17303A353 ML17303A355 ML17303A357 ML17303A361 ML17333A180
References
TAC-64398, NUDOCS 8704010595
Download: ML17303A355 (4)

Text

Cooper-Bessemer Reciprocating Products Division Cooper Industries, Inc.

Grove City., PA February 6, 1987 Torsional Vibration Analysis of Repaired Crankshaft KSV-20-T SN-7187 Arizona Public Service Company Palo Verde Nuclear Generating Station Diesel Generator III-B The number nine (9) crankpin of the crankshaft in this engine was damaged as a result of the master connecting,rod failure on 12-23-86. In order to restore the bearing surface of this crankpin to original specifications, the diameter was remachined from its original value of 11..499+0.001 inches to 11.323-+0;001 inches. This report addresses the, effect of this change on the

'tor sional vibration characteristics of'he engine, as well as the effects of off-design operation iamediately following the failure.

Off-Design eration Zamediately following the master rod failure, the engine operated for approximately 45'inutes at a speed of about 296 rpm, due to the inability to isolate the damaged engine from all potential sources of air, and fuel. There was no load on the engine during this period.

A torsiograph test was per formed on, an identical diesel generator, SN-7183, in 1978. This test indicated the engine mode natural frequency for these units, is 1430 cycles/minute, which would'lace the major 5th order critical at 286 rpm.

Calculations have been made for the crankshaft stress at, the peak of this 5th order critical under .no load conditions. 'These calculations indicate the maximum vibratory stress in the crankshaft would be -1,93 ksi. Since this value is, well below~ the normal limit of +5.0 ksi for continuous'peration there would be no damage to the crankshaft from operation, under these conditions.

Reduction in 'Pin Diameter The reduction in the diameter of the 89 crankpin from 11.499 inches to 11..323 inches is a change of 1.53 percent. The change in the torsional stiffness of this crankpin will be 5.9 percent, but this pin represents less than 10 percent of the total effective stiffness of the shaft, so the effective stiffness will only be reduced about 0.6 percent. "Ihis will alter the torsional natural frequency by less than 0.3 percent, .which is insignificant.

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The reduction in diameter will increase the torsional stress in the crankpin by 4.7 percent. From the 1978 torsiograph test results, the maximum crankshaft stress at any speed within 10 percent of rated speed was +3.75 ksi. This stress occured at the 2-1/2 order peak at 570 @K With the reduction in diameter, the stress from this cr itical will be -+3.93 ksi. This is still well below the normal limit of +5.0 ksi, so the reduction in crankpin diameter will have no adver se effect on the performance of this crankshaft..

7 Pv John . Horne, Manager Anal tical and Compressor E ngzneerzng

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