Isolation Joints and Cathodic Protection Performance
How monolithic isolation joints protect cathodic protection systems and what to verify before installation.
20 November 2025
Purpose
A monolithic isolation joint electrically separates two sections of pipeline so that cathodic protection current stays where it is intended and stray current does not migrate into adjacent structures.
Because the joint is welded into the line, it cannot be maintained; its quality has to be established before installation.
Verification
Require factory records for hydrostatic testing, electrical resistance testing and, where specified, dielectric strength testing.
Internal coating condition matters in wet service, since a conductive electrolyte path across the insulating section defeats the isolation.
Installation details
Supply matching pipe pups of the same grade and wall thickness so field welding does not require a transition piece.
Confirm the maximum permissible welding heat input to avoid damaging the internal insulating assembly.
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