United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 85-24: Failures of Protective Coatings in Pipes and Heat Exchangers

                                                     SSINS No.:  6835 
                                                       IN 85-24 

                               UNITED STATES 
                       NUCLEAR REGULATORY COMMISSION 
                    OFFICE OF INSPECTION AND ENFORCEMENT 
                           WASHINGTON, D.C. 20555 

                               March 26, 1985 

Information Notice No. 85-24:  FAILURES OF PROTECTIVE COATINGS IN PIPES 
                                  AND HEAT EXCHANGERS 

Addressees: 

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

Purpose: 

This information notice is provided to alert recipients of a potentially, 
significant problem pertaining to the selection and application of protec-
tive coatings for safety-related use, especially painting interior surfaces 
of pipes and tubing. It is expected that recipients will review the informa-
tion for applicability to their facilities and consider actions, if appro-
priate, 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: 

1.   Spray Pond Piping  

     While making minor repairs to the spray pond piping system in 1982, 
     Palo Verde Nuclear Generation Station Unit 1 personnel discovered 
     delamination and peeling of the interior epoxy lining in three 
     24-inch-diameter 90 elbows. Examination of the remainder of the 
     piping system showed similar lining failures in other elbows, such as 
     3-inch blisters that contained solvent, poor adhesion, soft film, and 
     excessive film thickness. The spray pond is the ultimate heat sink for 
     the Palo Verde Station. During a shutdown where the ultimate heat sink 
     was needed, separation of the epoxy lining from the elbows could 
     potentially cause a flow restriction in the piping system. 

     The epoxy coating specified was Plasite 7122-H, a product of Wisconsin 
     Protective Coatings Company. This material is formulated to be applied 
     by mechanical spraying equipment in layers 2-1/2 to 4 mils thick with 
     sufficient time allowed for each layer to cure. The use of mechanical 
     spray equipment provides a uniform and controlled coating film 
     thickness. The straight sections of the piping system were coated in 
     this manner. The multilayer mechanical deposition and curing of 12-15 
     mils of coating in the straight sections of pipe took 7 days, and no 
     discrepancies similar to those in the elbows were found. 


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                                                           IN 85-24 
                                                           March 26, 1985 
                                                           Page 2 of 3 

     However, the elbows were coated in two layers using a hand-held gun. 
     The lining was uneven with the coating up to 25 mils thick. Coating 
     took only 3 days in December of 1980; this reduction in curing time can 
     be critical, especially in the winter when chemical curing and solvent 
     evaporation tends to be retarded. In addition, the elbows were capped 
     after the final coating application and there was insufficient air 
     necessary for curing. 

     A hand-held gun was used to spray the coating because of the shape of 
     the elbow. There are other methods of applying epoxy coatings that are 
     more controllable and use less solvent. Electrostatic spray uses less 
     epoxy and solvent for the same coating thickness. Electrodeposition in 
     a water solution provides the most uniform coating and does not use 
     solvents. The fluidized bed method will provide the thickest epoxy 
     deposit. Whatever application method is selected, epoxies are thermo-
     setting materials and are normally cured by oven baking or infrared 
     heating. Heating reduces curing time from several days to several 
     hours. 

     The elbows were repaired by removing the deficient lining, preparing 
     the surface by grit blasting, and recoating with Plasite 9009-IT. The 
     repairs were acceptable and a final report was issued in January 1984. 

2.   Diesel Generator Heat Exchangers While operating train A of the spray 
     pond piping system in May 1984, Palo Verde Nuclear Generation Station 
     Unit 2 personnel discovered an accumulation of epoxy material. The 
     jacket water cooler, air after-coolers, and lube oil coolers of all the
     train A and train B diesel generator heat exchangers had extensive 
     failure of the epoxy coating and resulted in complete blockage of the 
     governor oil coolers. 

     The failures of the epoxy coating included severe blistering, moisture 
     entrapment between layers of the coating, delamination, peeling, and 
     widespread rusting. The epoxy coating specified was Plasite 7155-H. It 
     is formulated to be deposited in thin layers using mechanical spraying 
     equipment. 

     An evaluation of the deficiencies showed the presence of cutting oils 
     on the heat exchanger surface before the coating was applied. It is a 
     basic requirement to have a dry, oil-free surface before applying 
     coatings. In addition, the surface was too smooth for the epoxy coating
     to adhere. Epoxy coatings are applied directly to the metal without a 
     primer and it is necessary to slightly roughen the metal surface. 
     Finally, the heat exchangers were sealed after spraying and there was 
     insufficient air to complete the curing process. Repairs were success-
     fully made with Plasite 9009-IT and a final report was issued in Sep-
     tember 1984. 

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                                                           IN 85-24  
                                                           March 26, 1985 
                                                           Page 3 of 3 

It should be noted that this information notice is not intended to imply 
that Plasite materials produced by Wisconsin Protective Coatings Company are
unacceptable. Other applications using appropriately selected materials and 
application techniques have been successful. 

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:  P. Cortland, IE 
                    (301) 492-4175 

Attachment:  List of Recently Issued IE Information Notices 
Page Last Reviewed/Updated Tuesday, November 12, 2013