US Patent 8240371 Multi-function sub for use with casing running string

A multi-function sub is connected between a top drive of a drilling rig and a casing gripper. The sub has telescoping upper and lower members that rotate with each other. A sleeve is mounted to one of the members. That sleeve is prevented from rotation with the upper and lower members by an anti-rotation device. A piston is located on the other member and reciprocally carried within the sleeve. An external pump is connected to the sleeve for supplying pressurized fluid into the sleeve to act against the piston. This fluid provides compensation for thread makeup when a new joint of casing is being secured to a string of casing.