Type 759 Integral Positioner Air-To-Close Actuator

The Type 755 actuator with integral, top-mounted positioner is a pneumatically operated, spring opposed diaphragm actuator designed specifically to fit the RESEARCH Control Valve body-bonnet assembly. The unit is available in two sizes: one to fit the 1/4" valve and a larger version to fit the 1/2" through 1" valves. The unit, when equipped with the model TLDA positioner, functions as an air-to-close actuator extending the stem and closing the valve on an increasing instrument signal. The unit is designed to retract the stem, opening the valve, on a decreasing or loss of instrument signal. A force-balance system is incorporated utilizing the full force of the air supply to position the stem precisely and with a high degree of repeatability. This type of actuator should be used when the application calls for high positioning accuracy or when greater force is required over the standard actuator such as in the case of high shutoff pressures or excess packing friction.