A system for rotating an element inside a pressure containing housing. In some embodiments, the mechanism includes a pressure containing housing having an opening through a wall of the housing into an internal chamber in which, in use, the element to be rotated is located, a bushing located within the opening, and a worm gear rotatably mounted in the bushing. The worm gear is offset from the axial center of the bushing such that rotation of the bushing moves the worm gear between an extended position, wherein the thread of the worm gear engages an element in the chamber, and a retracted position, wherein the thread is disengaged from the element in the chamber.