Abstract

A steam generator tubesheet is serviced by end effectors mounted on a slew table cantilevered from a carriage slidable along an arm rotatable in a plane parallel to the tubesheet. In servicing a selected hole in the tubesheet, the rotatable arm and the carriage arm are driven to positions which allow the cantilevered slew table to be slewed to a predetermined angle associated with the selected hole. The arm and carriage are then driven to positions which place the end effector under the selected hole taking into account the offset of the slew table. Alternatively, a determination is first made whether the arm and carriage can be positioned within preset limits to place the end effector under the selected hole using the existing slew angle. If so, the existing slewed angle is used but, if not, the table is slewed as mentioned above.