Abstract: The clamp mounts a cable and service lines in spaced relationship to a tubing string used in producing a well, and formed of lengths of tubing joined by a coupling. The clamp comprises first and second clamping elements for clamping around the tubing string and hinged on a first pin. A cover is hinged to the first element by a second pin. The first element and the inner surface of the cover are provided with formations which ensure that the cable and service lines are firmly held when the cover is closed against the first element by a captive bolt, which also clamps the first and second elements firmly around the coupling. A single hinge pin version clamps to the tubing string on each side of a coupling.

Abstract: A pressure-actuated head for detonating a gun for perforating a well bore is suspended on a tubing string for lowering down the well. The head includes a detonator pin biased towards a detonator but restrained until detonation is required. Detonation is effected by causing or allowing a pressure differential to develop across a piston. Fluid communication between chambers on respective sides of the piston is via a pressure control system which allows the pressure differential to develop over a period of time.