Actuators with hydraulic speed control are used where very slow operating times are required or where sudden changes in load need to be restrained. For instance to prevent the slam sut effect when closing a butterfly valve with a high rate of flow across the disk.

An extra hydraulic damping cylinder is incorporation in a standart double acting pneumatic actuator. A control valve, mounted in the by pass at the side of the actuator, provides a very fine speed adjustment by restricting the oil flow one to the other side of the piston.