Abstract: A torque restraint system for a top drive unit in a drilling rig, in which rigid torque arms rotate about a horizontal axis to transmit reactive force from the power swivel to the mast to prevent rotation of the power swivel about a vertical axis. The rotatability of the torque arms also allows lateral displacement of the motor from an operating position to a parked position behind the vertical axis of the well bore. The torque restraint system can be utilized in conjunction with an inclined mast.

Abstract: An annular blowout preventer control system which provides a closing hydraulic pressure to the preventer in proportion to the well-bore pressure with an additive offset equal to the pressure required to energize the preventer. The control system utilizes an annular-type blowout preventer, a hydraulic pressure regulator valve, a pneumatic pressure regulating valve, and necessary controls, all mounted above a standard blowout preventer assembly on a well casing during drilling operations, or on the existing well head during workover operations. The regulator valve includes a diaphragm which operates to establish the initial closing pressure needed to seal the annular blowout preventer. After activation, changes in pressure in the well bore are sensed by the hydraulic pressure regulator valve, which delivers regulated closing pressure to the annular blowout preventer. The regulated closing pressure is proportional to the pressure encountered in the well bore.