United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 86-26: Potential Problems in Generators Manufactured by Electrical Products Incorporated

                                                            SSINS No: 6835 
                                                            IN 86-26        

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

                               April 17, 1986

INFORMATION NOTICE NO 86-26:      POTENTIAL PROBLEMS IN GENERATORS 
                                   MANUFACTURED BY ELECTRICAL PRODUCTS 
                                   INCORPORATED 

Addressees: 

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

Purpose: 

This notice is to alert recipients to a potentially significant problem 
involving the failure of Electrical Products Incorporated (EPI) diesel 
generators without prior warning during an emergency demand Actions taken 
by licensees to prevent recurrence also are discussed It is expected that 
recipients will review this 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 information notice do not constitute NRC requirements; therefore, no 
specific action or written response is required 

Description of Circumstances: 

Washington Public Power Supply System (WPPSS) Unit 2 

On July 21, 1983, emergency diesel generator (DG) 1A had high vibration 
level readings accompanied by sparks from the rotor shaft bearing area Upon
disassembly it was determined that a shim, required to maintain clearance at
the thrust bearing, was missing Inspection of DG 1B showed that the same 
shim was missing The two generators were returned to EPI (Cleveland, Ohio) 
where the missing shim was installed and the damaged areas refurbished The 
original design, which placed electrical insulation between the rotor shaft 
and the slip-ring end bearing inner race, was maintained 

On July 9, 1984, during monthly surveillance testing, a high vibration alarm
was observed on emergency DG 1B Investigation after completion of the 
4-hour test revealed that the slip-ring end bearing had turned on the shaft 
insulation destroying the insulation The reduction in insulation cross 
sectional thickness allowed the rotor shaft to drop slightly and rub on the 
bearing housing The corrective action employed after this failure was a 
design modification The insulation between the bearing and the shaft was 
removed and the bearing was mounted directly on the shaft The bearing 
housing was insulated to provide the required electrical insulation No 
failure has been reported since the reported test failure in July 1984 

8604150542 


                                                             IN 86-26      
                                                             April 17, 1986 
                                                             Page 2 of 3   

Grand Gulf Unit 1 

At Grand Gulf Unit 1, the high pressure core spray pump is powered by a 
dedicated DG On July 13, 1985, during surveillance testing, the generator 
failed and was observed to be emitting sparks Power Systems Division (PSD) 
of Morrison Knudsen, the supplier of the DG unit, determined that the 
electrical insulation between the inner race of the cylindrical roller 
bearing at the slip-ring end and the rotor shaft had degraded The 
degradation allowed the shaft to drop down and rub the inner and outer oil 
seals causing the sparks EPI and PSD have developed a procedure to 
implement the same design modification at Grand Gulf as used previously at 
WPPSS 

Watts Bar Unit 2 

On June 10, 1983, during the performance of a test, the generator shaft was 
observed to be rubbing against the inner and outer oil seals at the 
slip-ring end Examination after disassembly revealed that the thickness of 
the oil thrower was less than specified, causing a mismatch between the 
inner and outer races of the slip-ring end bearing that resulted in the 
inner race breaking loose and turning on the underlying electrical 
insulation 

The repairs at a Tennessee Valley Authority (TVA) workshop consisted of 
rebuilding oil seals, polishing the shaft under the oil seals, replacing the
insulation material under the bearing, machining the bearing housing cap to 
correct the alignment, adding a shim to restrain the outer race, and 
installing new bearings TVA inspected four other generators and made 
similar modifications 

Background: 

The failures occurred in electrical generators manufactured at EPI located 
in Cleveland, Ohio EPI was a division of Portec from 1969-1979 In 1979, 
Portec sold EPI to Northern Electrical Industries-Parsons Peebles 
(NEI-Peebles) of Great Britain The manufacturing operations at Cleveland 
ceased in the Fall of 1984 Currently, EPI furnishes spare parts and 
modifications to existing units 

Discussion: 

The failures described above have all occurred at the slip-ring end of the 
tandem diesel engine configurations Installation of the insulation between 
the rotor shaft and the bearing also is used for single engine applications 
and in some cases it is installed under the shaft bearing at the other end 
of the generator as well The purpose of the insulation (3M Scotchply brand,
type 1009, glass/epoxy composite tape) is to prevent circulating currents 
through the generator shaft This insulation method was limited by EPI to 
8-pole 900-rpm machines The initiating failure mechanism of the insulation 
has been attributed by various sources to insulation creep fatigue, 
misalignment of the engines, poor insulation workmanship, or inadequate 
original design The first WPPSS and the Watts Bar failures appear to be 
isolated cases of improperly machined pieces; however, the failures manifest
themselves in a similar manner and may be discovered during the checks for 
insulation damage 


                                                             IN 86-26      
                                                             April 17, 1986 
                                                             Page 3 of 3    

PSD has stated that a procedure to monitor shaft movement will have to be 
specific for each plant because of design differences that impact the 
allowable movement and the jacking force Jacking the shaft up and down and 
recording the movement will determine the vertical play between the shaft 
and bearing housing, but care should be taken to use a load cell or circle 
force gauge between the jack and the generator shaft to prevent damage 

Other suppliers that have used EPI generators include Stewart & Stevenson, 
Alco and Bruce GM (EMD) See Attachment 1 for a list of facilities 
identified by EPI and PSD as recipients of the subject generators Some of 
the generators have been resold from the original customer or user and some 
have been cancelled; therefore specific plant applications may be different 
than originally supplied 

No specific action or written response is required by this notice If you 
have any questions regarding this notice, 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:  James C Stewart, IE
                    (301) 492-9061

                    K R Naidu, IE
                    (301) 492-4179

Attachments:
1   List of EPI 900 RPM Generators 
2   List of Recently Issued IE Information Notices


                                                             Attachment 1  
                                                             IN 86-26      
                                                             April 17, 1986 
                                                             Page 1 of 1   

                      Domestic EPI 900 RPM Generators

Customer/Site                      No Units                D/G Supplier 

Arkansas P&L/Nuclear 1                  2                Stewart & Stevenson
Boston Edison/Pilgrim 1                 2                ALCO
Duke Power/Oconee                       1                PSD
Florida P&L/St Lucie                   2                PSD
Houston L&P/Allens Creek                1 (See Note 1)   PSD
Jersey Central P&L/Oyster Creek         2 (See Note 1)   PSD
Mississippi P&L/Grand Gulf              2                PSD 
Mississippi P&L/Grand Gulf              2                Bruce GM (EMD)
New York State Power                    4                Bruce GM (EMD)
Authority/FitzPatrick 
Pacific G&E/Diablo Canyon               5                ALCO
Portland G&E/Trojan                     2                PSD
Public Service of Oklahoma/Black Fox    2 (See Note 3)   PSD
Puget Sound/Skaggit                     1                PSD
SMUD/Rancho Seco                        2                Bruce GM (EMD)
TVA/Hartsville, Phipps Bend             6 (See Note 4)   PSD 
TVA/Sequayah                            4                Bruce GM (EMD)
TVA/Sequayah                            1                PSD 
TVA/Watts Bar                           6                PSD
Vepco/North Anna                        4                Stewart & Stevenson
WPPSS/Hanford                           2                Stewart & Stevenson


Notes:    1   Generator returned to PSD
          2   Obtained from TVA
          3   One unit sent to foreign plant, one unit spare 
          4   Two units to Oyster Creek, three units sent to foreign 
               plants, one unit sent to NASA

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