Electrically insulating joints for high-pressure pipelines

Claim 1

An electrically insulating joint comprising two electrically conducting pipes for conveying a liquid at high pressure and which in use are at different electrical potentials, said pipes having end portions of enlarged external diameter, a rigid pressure-resistant and electrically-insulating spacer sleeve between the enlarged ends of the pipes, a pair of collars separate from the pipes each interposed between the end of a respective pipe and the adjacent end of the spacer sleeve, and a clamping sleeve surrounding the enlarged ends of the two pipes and electrically insulated from at least one of the pipes, said clamping sleeve including at one end a portion of reduced internal diameter, said joint further comprising a clamping nut at the other end of said clamping sleeve for urging the two enlarged end portions inwards to press the pipes against the collars and the collars against the spacer sleeve in a liquidtight manner to form the joint, at least the one of said collars which is anodic with respect to the other in use of the arrangement being in contact with the liquid and being of a metal which forms under electrolytic action a protective skin which is highly resistant to the flow of electric current, thereby reducing the rate of galvanic corrosion.