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.
8503220444
.
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.
.
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, March 09, 2021