Information Notice No. 83-51: Diesel Generator Events

                                                            SSINS No.: 6835 
                                                            IN 83-51       

                                UNITED STATES
                           WASHINGTON, D.C. 20555
                               August 5, 1983

Information Notice No. 83-51: DIESEL GENERATOR EVENTS 


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


This information notice is provided to bring to the attention of licensees 
and construction permit holders some events and experience of generic diesel
generator problems and corrective action taken. It is expected that 
recipients will review the information for applicability to their 
facilities. No other action or response is required. 

Description of Circumstances: 

In its continuing review of licensee event reports (LERs), NRC has 
identified during the past five months more than 100 LERs pertaining to 
diesel generator problems. Most of these appear to be material, equipment, 
or component failures . No single common trend can be identified. 

NRC is concerned about the large number of diesel generator events. During 
discussions with diesel manufacturers and licensees, it appears that many of
these events could have been eliminated or prevented by implementation of a 
conscientious maintenance and inspection program as well as monitoring 
equipment through a plant's trend program. Some licensees have instituted 
such a program to determine the underlying cause of the failures (see IE 
Information Notice 82-10) and to prevent their recurrence. Components or 
materials that have experienced failures are monitored or inspected more 
frequently. Many affected items are repaired or replaced before actual 
breakdown. For example, cooling water heat exchangers that were found to be 
ineffective after a certain period of time because of tube fouling were 
replaced. Cooling jacket circulating water pump bearings are inspected for 
wear and replaced in certain intervals. Pressure switches and timers have 
been found with drifting setpoints and were recalibrated or replaced 

Because of the large number of diesel generator events it is not feasible to
describe all the events reported. However, Attachment 1 to this information 
notice gives several representative examples and corrective actions taken. 


                                                             IN 83-51      
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If there are any questions regarding this material please contact the 
Regional Administrator of the appropriate NRC Regional Office, or this 

                                   Edward L. Jordan Director 
                                   Division of Emergency Preparedness 
                                     and Engineering Response 
                                   Office of Inspection and Enforcement 

Technical Contact:  Wolfgang Laudan, IE

1.   Selected Examples of Licensee Event Reports
       Related to Emergency Diesel Generators
2.   List of Recently Issued IE Information Notices 

                                                             Attachment 1  
                                                             IN 83-51      
                                                             August 5, 1983 
                                                             Page 1 of 4   



During the monthly preventive maintenance testing of Unit 2 diesel 
generator, the diesel tripped on high temperature 10 minutes after loading. 
The cause was determined to be fouling in the cooling water heat exchanger. 
The heat exchanger was replaced and the diesel testing was satisfactorily 
completed. The licensee placed the heat exchanger on a preventive 
maintenance schedule for cleaning. 


During a performance test of diesel generator 2B-B, the cooling jacket 
circulating water pump on the diesel generator was found to be inoperable as
a result of a ball bearing failure in the pump. The bearing was replaced and
the diesel generator was returned to service. 


During a performance test of a diesel generator, the diesel generator 
tripped on high vibration. It was postulated that a vibration switch and a 
pressure regulator were both involved in the trip. Both were repaired and 
the diesel generator was returned to service. The equipment will be 
monitored through the plant's trend program. 


During a quick start testing program of diesel generator No. 4, the diesel 
generator tripped on "low lube oil pressure." The same problem occurred 2 
days later on the same unit. Both events resulted from intermittent failures
of the "low lube oil pressure start time relay" (STR). The relay timed out 
before actual pressure was above the low trip setpoint. The relay was 
replaced and the diesel testing was satisfactorily completed. 


During a Unit 3 diesel generator surveillance test, the diesel generator 
tripped on low cooling water pressure. A defective low cooling water 
pressure switch caused this event. The switch was replaced and the testing 
was satisfactorily completed. 

RANCHO SECO, MAY 25, 1983 

During startup testing, the diesel generator would not reach full operating 
speed. The Woodward governor speed adjustment on the unit stopped at about 
650 rpm. It was found that the pointer disk was hanging up behind the dial 
plate. The manufacturer recommended filing about 1/16-inch off the pointer 
disk to allow free movement. 
                                                             Attachment 1  
                                                             IN 83-51      
                                                             August 5, 1983 
                                                             Page 2 of 4   


During a routine inspection of the intake air check valve of No. 11 diesel 
generator, the licensee found a check valve holding pin sheared and the 
check valve loose. The same valve on two other diesel generators at Calvert 
Cliffs had been found to be cracked when inspected during 1982. The disk of 
one of these valves was found broken in two pieces. The engines in question 
are Fairbanks Morse Model 38TD81/8. 

Because these failures did not render the diesel generators inoperable, as 
evidenced by successful completion of weekly operational tests, no LER was 
issued. The licensee pointed out that there were internal baffles between 
the check valves and the diesel turbocharger which made it unlikely to have 
a piece of the check valve enter the diesel's turbocharger. The check valve 
in question diverts air between the diesel turbocharger and integral 
air-blower. Failure of the check valve would result in air being available 
through the turbocharger at low loads and would affect the load control. 

SHOREHAM, OCTOBER 15, 1982; APRIL 15, 1983; APRIL 20, 1983; MAY 4, 1983 

During preoperational testing of Shoreham's three Transamerica Delaval, Inc.
emergency diesel generators, the following mechanical problems were 
identified in the past 9 months and reported by the licensee under 10 CFR 
50.55 (e): 

October 15, 1982    - The jacket waterpump shaft failed. 
April 15, 1983      - The engine head cracked. 
April 20, 1983      - The fuel injection line failed. 
May 4, 1983         - The rocker arm bolt failed. 

Approximately 2 years before these problems occurred, the licensee 
discovered the following: 

1.   Loose hardware in cam gears during initial onsite inspection. 
2.   Multiple broken cylinder head exhaust bolts resulting from insufficient 
     pipe guide clearances in the exhaust manifold. 
3.   Cracks in the fuel oil ejector that connects to the fuel oil drip line. 
4.   Absence of a drilled passageway for the relief valve on one lube oil 
     pump line as required by design. 
5.   Leaky lube oil cooler tubes resulting from improper rolling in the tube 
6.   Cracks in rocker arm push rod socket (or cup). 
7.   Cam gear fitted bolts not installed at the factory as required. 

The problems were corrected under the surveillance of vendor 
representatives. Nuclear sites with Transamerica Delaval diesel generators 
are listed on page 4 of this attachment. 
                                                             Attachment 1  
                                                             IN 83-51      
                                                             August 5, 1983 
                                                             Page 3 of 4   


(Louis Allis is the successor to Belouit Power Systems, Inc., and to Colt-
Fairbanks Engine Division) 

1.   At the diesel generator in the Clinton Nuclear Plant, a three-phase 
     rectifier assembly in the exciter was not connected in parallel, which 
     could cause field winding insulation to deteriorate. Louis Allis field 
     service took corrective action by making the necessary connections. 

2.   Detroit Edison experienced high vibration on its diesel generator. The 
     cause was loose pole wedges. Louis Allis performed a detailed 
     engineering evaluation of this problem and found that in 1976 a 
     material change from HRS 1020 steel to 1045 steel was made. This means 
     that diesel generators manufactured before this change may experience 
     the same loose pole wedge problem. The affected plants are Fermi, 
     Millstone Unit 2, and Hatch . These plants were notified by copy of the 
     Part 21 report dated May 20, 1983. 


The manufacturer reported the following turbocharger thrust bearing 
lubrication problem: 

The design of the lubricating oil system permits the oil flow to the 
turbocharger bearing only when the diesel generator is running. When the 
diesel generator is in the standby mode, the turbocharger bearing lube oil 
system is bypassed to prevent a possible fire hazard should pressurized oil 
leak around the bearing seals onto hot impellers. Therefore, during startup,
a sufficient amount of oil would not be available to adequately lubricate 
the turbocharger bearing. Because diesels are started once a month and run 
for a short length of time, premature bearing wear was experienced because 
of insufficient lubrication. 

At San Onofre, the wear rate for this condition after 100 hours of operation
was equivalent to 15,000 to 20,000 hours of continuous operation. 

To ensure proper lubrication during startup, a design modification in the 
form of a lubrication oil drip system causing the lubricating oil to drip on
the bearings through an orifice at a given rate was proposed, installed, and
tested. An alternate method to this design modification is a change in the 
operating procedure. Before a monthly start, an operator would manually run 
the auxiliary lube oil pump for 30 to 60 seconds and confirm lube oil 
pressure. In the event of an emergency start, the bearings will function 
until oil pressure is developed. 

                                                             Attachment 1  
                                                             IN 83-51      
                                                             August 5, 1983 
                                                             Page 4 of 4   

Transamerica Delaval reported that the following nuclear sites were 

Shoreham                      Perry                    WPPSS 4 
Grand Gulf                    Bellefonte               Midland 1 & 2
Catawba                       WPPSS 1                  Hartsville 
San Onofre                    Comanche Peak 1 & 2      Phipps Bend 

The licensees of the above plants were notified by copy of Transamerica 
Delaval Part 21 report dated September 19, 1980. 

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