Pneumatic quarter-turn actuators series r are used for the actuation of valves with 90°travel, such as ball valves, plug valves as well as butterfly valves. Today the quarter-turn actuators comply with the en- standards, which will supersede a large proportion of the din- standards, as well as a variety of iso-standard drafts and various factory standards used in large-scale industry. These actuators find their further areas of application in:clude functions with rotary movements of 90 or 180°. The transmission of force is accomplished by rack and pinion. On the double-acting version the valve is opened or closed by application of compressed air to the actuator. On single-acting actuators, compressed air is applied only to one direction; movement to the opposite direction is accomplished by spring force. In case of a compressed air failure tthese drives therefore automatically return to a safe position, in case of a compressed air failure. Depending on the process or the requirements the springs are used to accommodate the opening or closing function. Today the quarter-turn actuators comply with the en- standards, which will supersede a large proportion of the din- standards, as well as a variety of iso-standard drafts and various factory standards used in large-scale industry.
