BOP control system
BOP functions are controlled using several methods such as direct, piloted, electro hydraulic, and MUX. One method employs piloted hydraulic controls. In this case, a hydraulic signal is transmitted from the surface control station to the subsea BOP. A hydraulic pilot valve receives the signal triggering the actuation of the subsea function. Because the hydraulic signal travels slowly, this type of control is best suited for use in shallower water depths. Another type of control uses electro-hydraulic technology. Systems in deeper water depths use multiplexed electrical or fiber optic signals sent from the surface to the pods to actuate the function on the subsea BOP.
Source: API RP 96, Deepwater Well Design and Construction, First Edition, March 2013. Global Standards