Information Notice No. 83-51: Diesel Generator Events
SSINS No.: 6835
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
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.
August 5, 1983
Page 2 of 2
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
August 5, 1983
Page 1 of 4
SELECTED EXAMPLES OF LICENSEE EVENT REPORTS AND VENDOR REPORTS
RELATED TO EMERGENCY DIESEL GENERATORS
QUAD-CITIES 2, OCTOBER 6, 1982
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.
SEQUOYAH 2, OCTOBER 20, 1982
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.
SUSQUEHANNA, OCTOBER 27, 1982
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.
BRUNSWICK 1, NOVEMBER 5, 1982
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.
DRESDEN 3, NOVEMBER 9, 1982
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.
August 5, 1983
Page 2 of 4
CALVERT CLIFFS, APRIL 7, 1983
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
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.
August 5, 1983
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LOUIS ALLIS REPORTED TWO DIFFERENT POTENTIAL PROBLEMS, MAY 20, 1983
(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.
TRANSAMERICA DELAVAL - 1981 TO 1983
The manufacturer reported the following turbocharger thrust bearing
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.
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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