2.4.17
Electrically Isolating Pipe Joints
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NOTE: The cathodic protection system will fail
unless full consideration is given to specifications
for electrically isolating pipe joints, electrically
conductive pipe joints, and casing cradles and
seals. Mechanical and electrical specifications
should reference this paragraph and paragraph
"Electrically Conductive Couplings."
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Electrically isolating pipe joints for above or below ground use shall be
[flexible, mechanical pipe couplings of an electrically isolating type
consisting of bolted or compression design provided with electrically
isolating joint harness if required to provide pull-out strength]
[flexible, integral electrically isolating pipe couplings designed for
field installation by means of a swaging system and providing pull-out
strength with a factor of safety] [nonflexible flanged type electrically
isolating pipe joints to be field assembled] [nonflexible factory assembled
electrically isolating pipe joints designed with stub ends for installation
by welding and providing pull-out strength with a factor of safety].
2.4.17.1
Threaded Fittings
Threaded type electrically isolating pipe joints shall have molded plastic
screw threads and be used above ground only. Machined plastic screw
threads shall not be used.
2.4.17.2
Electrically Isolating Pipe Joints
Electrically isolating pipe joints shall be of a type that is in regular
factory production.
2.4.18
Electrically Conductive Couplings
Electrically conductive couplings shall be of a type that has a published
maximum electrical resistance rating given in the manufacturer's
literature. Cradles and seals shall be of a type that is in regular
factory production made for the purpose of electrically isolating the
carrier pipe from the casing and preventing the incursion of water into the
annular space.
2.4.19
Joint and Continuity Bonds
Bonds shall be provided across joints or any electrically discontinuous
connections in the piping, and other pipes and structures with other than
welded or threaded joints included in this cathodic protection system.
Unless otherwise specified, bonds between structures and across joints in
pipe with other than welded or threaded joints shall be with No. 4 AWG
stranded copper cable with polyethylene insulation. Bonds between
structures shall contain sufficient slack for any anticipated movement
between structures. Bonds across pipe joints shall contain a minimum of
100 mm 4 inches of slack to allow for pipe movement and soil stress. Bonds
shall be attached by exothermic welding. Exothermic weld areas shall be
insulated with coating compound and approved by the Contracting Officer.
Continuity bonds shall be installed as necessary to reduce stray current
interference. Additional joint bonding shall be done where determined
during construction or testing or as directed. Joint bonding shall include
SECTION 13112A
Page 23
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