United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 85-32: Recent Engine Failures of Emergency Diesel Generators

                                                         SSINS No.:  6835
                                                            IN 85-32 

                                UNITED STATES
                           WASHINGTON, D.C. 20555

                               April 22, 1985



All nuclear power reactor facilities holding an operating license (OL) or a 
construction permit (CP). 


This information notice is provided to alert recipients of potentially 
significant problems pertaining to engine failures of emergency diesel 
generators. It is expected that recipients will review the information for 
applicability to their facilities and consider actions, if appropriate, to 
preclude a similar problem occurring at their facilities. However, 
suggestions contained in this notice do not constitute NRC requirements; 
therefore, no specific action or written response is required. 

Description of Circumstances: 

During the last few months, engine failures of emergency diesel generators 
have occurred at three reactor sites. These events are significant because 
more than one diesel generator had been affected at two of the sites and 
because of the extent of damage caused by the failures. 

On January 10, 1985, the Detroit Edison Company notified the NRC of a trip 
on low lube oil pressure of the number 11 emergency diesel generator engine 
at the Enrico Fermi Atomic Power Plant Unit 2 (Fermi). Subsequent inspection
revealed damage to connecting rod bearings and main bearings on the upper 
crankshaft as well as to some pistons. The upper crankshaft was scored. The 
upper crankshaft; upper main and connecting rod bearings; upper pistons 
numbers 2, 3, and 4; and cylinder liners numbers 2, 3, and 4 were replaced. 

The other three diesel generator engines at Fermi were inspected. On the 
number 12 engine, some of the upper bearings had been damaged; all upper 
bearings were replaced. The number 13 and number 14 engines showed prelim-
inary signs of wear, but no repairs were necessary. 

At North Anna Power Station Unit 2, both diesel generators experienced 
engine failures over the last several months. On December 9, 1984, both 
diesel generators were inoperable at the same time. Inspection of the 2J 
diesel generator engine revealed that upper pistons, numbers 2 and 3, were 


                                                           IN 85-32 
                                                           April 22, 1985 
                                                           Page 2 of 4 

and the number 11 cylinder liner seal was leaking. The upper pistons, 
numbers 2, 3, and 11, and cylinder liner number 11 were replaced. The 2H 
diesel generator engine was found to have shattered rings on the number 10 
lower piston. The number 10 lower piston and rings were replaced. 

On February 2, and again on February 4, 1985, the jacket water tank for one 
of the diesel generator engines at North Anna Power Station Unit 1 was found
to be empty. On the second occasion, water leakage in the engine was observ-
ed. Subsequent inspection revealed jacket water in other cylinders and in 
the engine lube oil, severe scoring of the number 3 cylinder liner and upper 
piston, seizure of the number 3 upper piston, and three failed upper main 
bearings. The apparent cause of trouble on the engine was the failure of a 
jacket water seal, which resulted in loss of lubrication to the number 3 
cylinder and engine lube oil dilution of which, in turn, caused bearing 
damage. There appears to be a similarity between this failure and the Unit 2 
engine failures in December 1984 as well as the Unit 2 engine failure in 
June 1983. 

On March 15,1985, the 2J engine at North Anna Power Station Unit 2 tripped 
on high crankcase pressure. Subsequent inspection revealed that two cylinder
liners were leaking coolant; they were replaced. Several upper piston insert
assemblies also required replacement parts. The lower pistons of the cylin-
ders with damaged parts were inspected, but no abnormal wear was found. 

In February 1985, a diesel generator engine at William B. McGuire Nuclear 
Station Unit 2 tripped on low lube oil pressure. During subsequent testing, 
excessive engine vibration prompted plant operators to manually trip the 
diesel. Brass metal was found on the oil screens. Four of eleven main bear-
ings were damaged; all main and connection rod bearings were replaced as a 
precaution. One piston and the crankshaft also are being replaced because of
scoring. Following inspection of the other diesel engine, the licensee re-
placed all main bearings as a precaution because scoring and close 
tolerances were noted. 


Detroit Edison Company has attributed the Fermi engine failure to inadequate
lubrication during fast starts. The engines at Fermi are Fairbanks-Morse 
Model Number 38D8 1/8 of the opposed-piston design. Each engine has a keep-
warm system, a manually controlled prelube system, and a lube oil booster 
for the upper crankshaft. The booster is filled with two gallons of oil that 
is forced by starting air pressure into the upper crankline bearings. The 
booster was installed in 1982 for the number 11 and number 12 engines and in 
1983 for the other two. Detroit Edison Company discontinued manual 
prelubrication in January 1984. Engine number 11 has experienced 
approximately 100 starts without manual prelubrication. 


                                                           IN 85-32 
                                                           April 22, 1985 
                                                           Page 3 of 4 

In consultation with the engine manufacturer, Detroit Edison Company has 
made, or plans, the following changes as a result of this problem: 

1.   Revise surveillance test procedures and Technical Specifications to  

     a.   prelube all planned starts 

     b.   start engine at idle speed, run for five minutes, and then 
          increase to synchronous speed 

     c.   increase load in incremental steps 

     d.   on shutdown, decrease load in incremental steps 

2.   Inspect and replace oil filters and inspect strainers on a quarterly 

3.   Conduct bearing inspections (after 20 unplanned starts or after 18 
     months, whichever comes first) to detect any future problems. 

4.   Analyze oil samples, including an analysis for metallics on a monthly 
     basis for the next 18 months for trend determination. 

5.   Perform a spectrographic analysis of lube oil filter media and any 
     deposits that are found during the quarterly replacement. 

The engines at North Anna Units 1 and 2 were also manufactured by Fairbanks-
Morse. The cause of the water leaks have not been determined. 

The engines at McGuire Unit 2 were manufactured by Nordberg. It appears that
misalignment of the lower crankcase bed contributed to the damage at 
McGuire. In this case, it is of interest that oil samples taken some months 
ago had some metal products in them, which at the time were considered to be 
the result of normal bearing wear-in. Oil samples taken recently had higher 
levels of contaminants. 

The above identified engine problems occurred in engines that were far from 
the end of their normal design lives. While the exact causes of these pre-
mature failures have not been determined, there is reason to believe that 
the testing requirements may have aggravated existing situations. Good oper-
ating practices, coupled with careful maintenance and periodic inspections, 
therefore are important. In addition, it is apparent that minimizing stress 
and wear on the diesel generator engines by testing, in accordance with the 
manufacturer's recommendations, also is essential. As part of Generic Letter
84-15, "Proposed Staff Actions to Improve and Maintain Diesel Generator 
Reliability," the staff proposed measures to reduce the severity of engine 
starts and loadings. In responding to the generic letter, many licensees 
apparently did not elect to consider changes to fast start and fast loading 
test requirements. 


                                                           IN 85-32 
                                                           April 22, 1985 
                                                           Page 4 of 4 

In light of the above problems, licensees may want to reconsider the desir-
ability of reducing the severity of engine starts and loading by proposing 
changes to the Technical Specifications to accomplish the goals of Generic 
Letter 84-15. Furthermore, facility owners may desire to reevaluate the ade-
quacy of their maintenance, testing, and operating practices for the 
required engine service and to take steps to monitor wear on key engine 
parts such as bearings. 

No specification 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 Contacts:  E. M. McKenna, NRR 
                     (301) 492-7468 

                     R. J. Kiessel, IE 
                     (301) 492-8119 

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