Abstract: A pressure regulator for a BOP stack includes a housing having an input port, an output port, and a pilot port and a regulator piston axially movable through the housing between an open position and a closed position. The regulator piston has an internal passage formed through its first axial end. When the regulator piston is in the open position, the internal passage is in fluid communication with the input and output ports. When the regulator piston is in the closed position, the internal passage is in fluid communication with the output port and fluidly isolated from the input port. A space with regulator fluid is also provided within the housing adjacent a second axial end of the regulator piston, opposite the first axial end, wherein the space is fluidly isolated from the input port and the output port in both the open position and the closed position.

Abstract: A subsea blowout preventer control system has horizontally oriented solenoid valve housings. Solenoid valves mounted within each of the solenoid valve housings are electrically controlled to selectively provide a hydraulic pilot signal to a hydraulic valve. A vertically extending central chamber contains a dielectric liquid and extends alongside the solenoid valve housings. A communication tube for each solenoid valve housing has an open upper end within the central chamber adjacent an upper end of the central chamber. Each of the communication tubes has an open lower end extending into one of the solenoid valve housings for communicating dielectric liquid in the central chamber with an interior of each of the solenoid valve housings. A separate drain line mounted to each of the solenoid valve housings enables draining of one of the solenoid valve housings for maintenance without requiring draining of other of the solenoid valve housings.