Abstract: A controller for an apparatus for installing a mechanical tube plug includes a controller having a controller console remote from the tube installation site and a solenoid assembly located proximate to that site. The console includes switches and indicators for providing a rotation control signal to the apparatus. The solenoid assembly includes a circuit for receiving a torque indication signal from the apparatus and an alarm circuit for setting the torque at a predetermined upper limit in response to a signal input at said controller console. The circuit operates to terminate rotation control and disable the apparatus when said limit is reached. Other features of the controller are also disclosed.

Abstract: An electron discharge machining (E.D.M.) tool combination is useful for removal of an installed nuclear steam generator tube plug of conductive material. A conductive wand shaft connected to an E.D.M. voltage source is movably mounted in a housing and insulated from the housing. An inlet adapter is mounted on the wand end and connected to a source of deionized and demineralized water to provide a dielectric fluid and removed material carrier. A hollow electrode is mounted on a hollow extension beyond the end of the wand and inlet adapter in fluid communication with the adapter for movement with the wand relative to the housing. A drive plate is moved by means of a ball nut along a roller ball shaft which is rotationally driven by a motor in the housing. The drive plate reciprocates the wand and electrode for E.D.M. operation. The wand position can be monitored remotely by a signal from a potentiometer with a tap movable with the wand.