A device that breaks electrical continuity between pipe sections: either a factory-made monolithic joint or an insulating flange kit of non-conductive gasket, bolt sleeves and washers. Insulators separate a protected pipeline from stations, plants, customer piping and foreign lines. They are checked with an isolation tester or by comparing potentials on each side; a shorted kit can drain protective current away and starve an entire line.
Potentials are identical both sides of the insulating joint at the meter set, the flange kit is shorted.
Keep welding heat and spatter away from insulating flange kits. Carbonized sleeves and gaskets short the kit and nobody notices until the next survey.
Also heard as
- isolation joint
- insulating flange kit
- IJ
- monolithic joint
Related terms
Bond
Wire or cable connection that ties two metal structures together electrically, often to control CP current.
Decoupler
Solid-state device that blocks DC but passes AC and fault current, grounding a pipeline without losing CP.
Shorted casing
Road or rail crossing casing pipe that has made metal contact with the carrier pipe and steals CP current.
Galvanic corrosion
Accelerated corrosion of the more active metal when two dissimilar metals touch in a shared electrolyte.