3.4
PROTECTION AGAINST CORROSION (FIELD APPLIED)
3.4.1
Corrosion Protection Systems
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NOTE: A preliminary field survey of the area in
which the gas distribution system is to be installed
shall be made to determine the requirement for a
cathodic protection system for metal gas piping and
to obtain data on which to base the type and design
of a cathodic protection system if required. The
survey shall be accomplished as outlined in MIL-HDBK
1004/10, "Cathodic Protection," and shall be
reviewed by the EFD cathodic protection specialist
for verification of the results and recommendations.
When existing piping is abandoned, removed, or
replaced with plastic pipe, indicate modifications
required to the existing cathodic protection system
and specify testing to ensure continuity of the
system.
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Buried metallic gas pipe, fittings, and accessories installed on gas
distribution systems shall be shop coated as specified [and cathodically
protected as specified in Section [13110N CATHODIC PROTECTION BY GALVANIC
ANODES] [13111N CATHODIC PROTECTION BY IMPRESSED CURRENT]]. Valves and
other metallic components installed on buried plastic piping shall also be
shop coated [and cathodically protected]. Paint metallic piping, fittings,
and accessories aboveground and in vaults. Electrically isolate metallic
pipe from other underground metallic structures, including metallic
casings. After completing pressure tests, wrap joints and damaged areas of
shop coatings with plastic tape as specified in paragraph entitled
"Application of Plastic Tape," or coat using material and procedures
recommended by the manufacturer of the pipe shop-coating.
3.4.2
Application of Plastic Tape
Apply plastic tape in the field to pipe joints and damaged areas of
coatings. The joint area to be taped shall be clean and free of burrs and
rust. Smooth down or cut away damaged coating if not firmly bonded to the
pipe. Wrap spirally with a two-layer wrapping system, overlapping the
coating surface at least 76 mm 3 inches. Initially stretch the tape
sufficiently to conform to the surface to which it is applied, using one
layer half-lapped for tape 50 mm 2 inches or less in width, or one layer
lapped at least 25 mm one inch for tape more than 50 mm 2 inches wide.
Apply a second layer lapped as above, with a tension as it comes off the
roll, and press to conform to the shape of the component.
3.4.3
Coal Tar Base Coating
Apply in accordance with the manufacturer's written instructions.
3.4.4
Painting
Exposed metal gas piping, valves, and other accessories not specified as
being shop coated or otherwise finished shall be cleaned in accordance with
SSPC SP 3, painted as specified in Section 09900 PAINTS AND COATINGS.
Touch up damaged shop coatings as required to restore them to original
finish.
SECTION 02551N
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