ISOLATION RING ON GAP SUB

摘要

A gap sub comprises at least one, and in a preferred embodiment, two electrically isolating threaded joints in a conductive tubular collar. The threads of the joints are isolated by a non-conductive coating in accordance with the prior art. The shoulders of the joints are separated by an isolating ring. Annular faces on the ring make contact with the shoulders in the joints. The ring is made of conductive material with a non-conductive coating deployed on (1) at least one, and advantageously both, of the ring's annular faces, and (2) the interior surface of the ring. An annular recess in the collar prevents electrical contact between collar sections nearby the ring either side of each threaded joint.