Patent ID: 7004444

Claim:
A rotary blowout preventer having a stationary body and a rotating body within the stationary body, the rotating body including a packer assembly mounted within the stationary body, comprising: a first fluid circuit defined into and out of the stationary body and between the stationary body and the rotating body; a second fluid circuit physically independent from the first fluid circuit defined into and out of the stationary body and between the stationary body and the rotating body; a pressure control device for controlling the pressure of a fluid in the second fluid circuit in response to the pressure of a fluid in the first fluid circuit; and a control system including a means for detecting an increase in pressure in the second fluid circuit connected to the second fluid circuit; wherein the pressure control device comprises: a pump connected by a first conduit to the stationary body into the second fluid circuit; and an adjustable orifice connected by a second conduit to the stationary body out of the second fluid circuit; a second pump connected by a third conduit to the stationary body into the first fluid circuit; and a second adjustable orifice connected by a fourth conduit to the stationary body out of the first fluid circuit.