Vane actuators consist of a shaft mounted in a cylindrical housing, with one or more vanes attached to the shaft. Applying fluid pressure to the vanes produces shaft rotation. An internal barrier between housing OD and shaft divides interior volume into two chambers. For this reason, single-vane actuators are normally limited to about 280° of rotation, and double-vane actuators to about 100°. Torque is directly proportional to vane area and effective fluid pressure. Vane actuators have torque outputs as high as 500000 lb-in.