United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 86-07: Lack of Detailed Instruction and Inadequate Observance of Precautions during Maintenance and Testing of Diesel Generator Woodward Governors

                                                            SSINS No: 6835 
                                                            IN 86-07       

                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF INSPECTION AND ENFORCEMENT
                           WASHINGTON, DC 20555

                              February 3, 1986

Information Notice No. NO 86-07:   LACK OF DETAILED INSTRUCTION AND 
                                   INADEQUATE OBSERVANCE OF PRECAUTIONS 
                                   DURING MAINTENANCE AND TESTING OF DIESEL 
                                   GENERATOR WOODWARD GOVERNORS 

Addressees: 

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

Purpose: 

This notice is provided to alert recipients of a potentially significant 
problem with the maintenance of Woodward Governors used on standby diesel 
generators Loss of engine speed control has resulted from inadequate oil 
inventory following maintenance on the governor This notice is also 
provided to make recipients aware of the importance of starting the engines 
in a highly controlled manner, especially following maintenance activities, 
to preclude excessive engine speed while confirming proper operation 

It is expected that recipients will review this information for 
applicability to their facilities and consider actions, if appropriate, to 
preclude a similar problem from occurring However, suggestions contained in 
this information notice do not constitute NRC requirements; therefore, no 
specific action or written response is required 

Description of Circumstances: 

During startup of a standby diesel generator at Grand Gulf Unit 1, the 
diesel engine oversped for about 15 seconds This startup was the first 
following preventive maintenance on the governor The overspeed damaged 
numerous engine components, including connecting rods, rod bearings, main 
bearings, link pin bushings, wrist pin bushings, and the engine base It is 
not known whether the manual trip, the overspeed trip, or excessive 
vibration terminated the overspeed 

Because the governor was suspected as the cause of the overspeed, it was 
removed without modification and returned to the manufacturer, Woodward 
Governor, for testing Those tests demonstrated that the governor was 
ineffective in controlling speed because of an inadequate inventory of oil 
It is postulated that inadequate filling and venting by licensee personnel 
following the maintenance work resulted in the low oil level 


8601290059 


                                                           IN 86-07        
                                                           February 3, 1986 
                                                           Page 2 of 3     

Based on Information available; the inadequate venting after refilling with 
oil has been attributed to use of an outdated technical manual, oil capacity
figures for the governor and associated components not being available, no 
detailed procedure for filling and venting, and inexperienced or 
insufficiently trained personnel 

During normal operation, the governor is actuated by an electrical signal 
from the generator and a mechanical signal from the engine However, both 
signals depend on the same hydraulic actuator and a common oil supply to 
control engine speed In this case, the electrical signal was deactivated 
because the generator field had no excitation, as was required by the 
licensee's procedure Because the remaining mechanical governor is 
relatively slow-acting (in comparison to the electric governor), a reduction 
in the governor control setting is usually made during initial startup after
maintenance to limit engine speed overshoot At Grand Gulf the governor 
control reduction had been omitted from the procedure With the governor oil
level low, the licensee concluded that a lower governor control setting 
would not have prevented the overspeed 

In addition to the above, the engine has an overspeed trip device that uses 
engine lube oil as its actuating fluid, thus making it independent of the 
hydraulic governor This trip was ineffective in preventing engine overspeed
because it was found by the licensee to be relatively slow acting in 
relation to the engine acceleration experienced during the overspeed A 
design change to reduce the overspeed trip response time is being considered 
by Transamerica Delaval 

Discussion: 

The corrective action taken at Grand Gulf in response to the overspeed event
included development of: (1) detailed procedures for venting trapped air 
from hydraulic governors and associated components during oil refilling 
operations and (2) detailed procedures that establish highly controlled 
conditions for initial startup following such maintenance activities Highly 
controlled conditions included "air rolling" the engine, exercising direct 
manual control of the engine, reducing the governor control and overspeed 
trip settings, and limiting fuel rack travel 

Licensees are reminded that every reasonable effort, as detailed in Generic 
Letter 83-28, "Required Actions Based on Generic Implications of Salem ATWS 
Events," dated July 8, 1983, should be made to ensure the most recent 
technical information is available at plant sites for proper guidance of all
equipment maintenance and testing activities Utilities that use Woodward 
Governors on their diesel engines are encouraged to contact Woodward 
Governor to ensure they have the latest technical information applicable to 
their equipment 


                                                           IN 86-07        
                                                           February 3, 1986 
                                                           Page 3 of 3     

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 regional office or this office 


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


Technical Contact:  W P Haass, IE
                    (301) 492-9041

Attachment: List of Recently Issued IE Information Notices 

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