US Patent 11629570 Blowout preventer with reduced fluid volume

A system for operating a blowout preventer (BOP) includes a front piston positioned at least partially in a front chamber. The front chamber includes a front volume on a front side of the front piston, and a back volume on a back side of the front piston. The system also includes a back piston connected to the front piston. The back piston is positioned at least partially in a back chamber. The back chamber includes a front volume on a front side of the back piston, and a back volume on a back side of the back piston. The system also includes a first valve configured to permit fluid flow into the front chamber during a free closing stroke of the BOP. The system also includes a second valve configured to permit fluid flow between the front and back volumes of the back chamber during the free closing stroke.