What Is a Vane Actuator?

A vane actuator is a hydraulic or pneumatic device used to supply partial turn activation motion for secondary devices such as butterfly and ball valves. In contrast to conventional cylinder and piston types, the vane actuator features a straight vane that is moved within a sealed chamber by fluid or gas pressure to supply actuation motion. The chamber, typically shaped like a clam shell, is fitted with a pair of inlet ports used to introduce fluid to one side of the vane or the other allowing the mechanism for bi-directional movement. Depending on the particular actuator design in question, the vanes may be either single- or double-sided, with some actuator types featuring several individual vanes.

Hydraulic and pneumatic actuators typically employ a cylinder and piston arrangement to translate the input power of a compressed gas or fluid to a linear working motion. When used to actuate large quarter-turn valves, such as butterfly and ball valves, a partial turn vane actuator is often employed. These actuators are designed to produce powerful rotary actuation motion with a range of a full 360° turn or less. They are capable of bi-directional motion with the inclusion of forward and reverse valves in the fluid or gas system.

Most vane actuator variants use one vane of a single- or double-sided design, although some types do utilize several vanes. Single-sided vane actuators typically consist of a clam shell-shaped pressure chamber. The working shaft used to transfer the actuator's working motion exits the chamber at the bottom of its narrow side. The vane is attached to the shaft at its one end, allowing it to turn in an arc across the wide side of the chamber. The tip of the vane opposite of the shaft point is equipped with a seal that is kept in contact with the inner surface of the chamber wall at all times during rotation.

Because the seal is constantly in contact with the chamber wall, it effectively divides the pressure chamber into two separate sections at any given point in the vane's arc movement. Two inlet ports are situated on either side of the chamber's wide section allowing pressurized fluid or gas to be introduced on one side of the vane or the other. As the fluid or gas is introduced on one side, it pushes the vane away from it to the opposite side of the chamber. To reverse the process, the fluid or gas direction is switched, allowing it to enter the opposite side of the vane, moving it back to the other side of the chamber.

As the vane is attached to the shaft, this motion is transferred to it, and, in turn, to the secondary mechanism. Double-sided vane actuator types work in the same fashion as single-sided types and have the shaft attached to the vane in the center rather than at one end. Multiple vane actuators also follow the same basic operating principle, but employ multiple sets of directionally-opposed vanes.