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Information Notice No. 83-51: Diesel Generator Events
SSINS No.: 6835 IN 83-51 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C. 20555 August 5, 1983 Information Notice No. 83-51: DIESEL GENERATOR EVENTS Addressees: All nuclear power facilities holding an operating license (OL) or a construction permit (CP). Purpose: 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 frequently. 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. 8306270425 . IN 83-51 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 office. Edward L. Jordan Director Division of Emergency Preparedness and Engineering Response Office of Inspection and Enforcement Technical Contact: Wolfgang Laudan, IE 301-492-9759 Attachments: 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 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. . Attachment 1 IN 83-51 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 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 sheet. 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 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 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 affected: 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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