Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
SSINS No.: 6835
IN 84-92
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
December 17, 1984
Information Notice No. 84-92: CRACKING OF FLYWHEELS ON CUMMINS FIRE
PUMP DIESEL ENGINES
Addressees:
All nuclear power reactor facilities holding an operating license (OL) or
construction permit (CP), research and test reactors, and fuel facilities.
Purpose:
This information notice is to alert recipients of a potentially significant
problem of cracking flywheels on certain models of Cummins fire pump diesel
engines. This cracking apparently becomes noticeable only after it has
propagated through the thickness of the flywheel and appears on its outer
surface. It is expected that recipients will review the information for
applicability to their facilities and consider actions, if appropriate, to
preclude similar problems occurring at their facilities. However,
suggestions contained in this information notice do not constitute NRC
requirements; therefore, no specific action or written response is required.
Description of Circumstances
Since December 12, 1983, LaSalle County Station has experienced repeated
fatigue cracking of flywheels on both of its Peerless Pump Co. fire pump
diesel engines, Cummins Model No. NT-855-F2 equipped with flywheel Part No.
3453 (assembly no. 3023676). The cracks appear to initiate on the engine
side (blind side) of the flywheel at a circumferential groove which
intersects each crank shaft attachment bolt hole. Cracks have been found to
initiate after as little as 34 hours of operation, but can only be detected
with the use of a liquid penetrant. The initial development of these cracks
is fast, but subsequent growth is slower and there have been no catastrophic
failures to date. The cracking is believed to be related to the response of
the flywheel to inherent engine and gearbox vibration and it appears to be
generic to the flywheel design.
This problem was first discovered when a flywheel on an engine with 850
hours of operation had cracked through its thickness over 360 of the
circumferential groove. A second unit with approximately 1500 hours of
operation was found to have had its flywheel cracked through its thickness
over approximately 270 of the circumferential groove. Both flywheels
were replaced and a 6-month inspection program was established. At the end
of the first 6-month period, a surface penetrant test was used and cracks
were discovered on the engine side of the flywheels on both units (one unit
with 34 hours of operation and the other with 50 hours). At this point it
was decided to establish a program to inspect the flywheels after 50 hours
of operation.
8412120541
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IN 84-92
December 17, 1984
Page 2 of 2
Cummins has discontinued the use of this flywheel and is currently using
their standard truck engine flywheel (Part No. 2965) on the NT 855 F4 fire
pump diesel. They have been running comparison tests on these two flywheels
(Parts No. 2965 and No. 3453) and are considering recommending use of the
truck engine flywheel as a replacement for the flywheel that has the
cracking problem. The retrofit of the new flywheel (Part No. 2965) would
require some modification because of size differences in the stub shafts.
The following Cummins diesel fire pump engines that are equipped with
flywheel Part No. 3453 are:
NH 220 IF
N 855 F
NT 855 F1
NT 855 F2
No specific action or written response is required by this information
notice. If you have any questions about this matter, please contact the
Regional Administrator of the appropriate NRC regional office or this
office.
Edward L. Jordan, Director
Division of Emergency Preparedness
and Engineering Response
Office of Inspection and Enforcement
Technical Contact: Chauncey Gould
(301) 492-8597
Attachment: List of Recently Issued IE Information Notices
