Actuator, Pneumatic (Type 754)

The Type 754 actuator 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 in. valve and a larger version to fit the
1/2…1 in. valves. It provides smooth linear retraction of the valve stem upon an increasing instrument signal. A decrease in instrument signal causes the stem to extend and close the valve. Downward closing force is generated by the spring, bearing on the diaphragm plate. An increasing pressure in the diaphragm cavity opposes the force of the spring and retracts the stem, opening the
valve. The unit is designed to extend the stem, closing the valve,
should the instrument signal fail. The actuator has an integrated
up-travel stop.

FUNCTION

The 1/4 in. size 754 actuator normally operates in response to a 3…15 psi (0.21…1.03 bar) change in instrument signal, or a
12 psi (0.8 bar) range. This signal range causes the valve to stroke a distance of approximately 7/16 in. (11 mm). The standard spring
has a deflection rate of 25 pounds (11.3 kg) per 1/8 in. (3.2 mm) and operates against an effective diaphragm area of approximately
7.3 in.2 (4709.6 mm2). The 1/2 in. size 754 actuator also normally operates in response to a 3…15 psi (0.21…1.03 bar) change in instrument signal, or a 12 psi (0.8 bar) range. This signal range causes the valve to stroke a distance of approximately 9/16 in. (14.4 mm). The standard spring in the 1/2 in. unit has a deflection rate of 30 pounds (13.6 kg) per 1/8 in. (3.2 mm) and operates against an effective diaphragm area of approximately 11.25 in.2 (7258 mm2).

STANDARD FEATURES

Compact lightweight design
1/4 in. unit = 2.05 lb (0.9 kg)
(excluding handwheel and body-bonnet assembly)
1/2 in. unit = 3.76 lb (1.7 kg)
(excluding handwheel and body-bonnet assembly)
Stainless steel external hardware
Powder coated for increased corrosion resistance
Integrated up-travel stop
Simple design for easy maintenance

OPTIONAL FEATURES

Choice of other signal ranges: 3…27#, 6…30#
All stainless steel housing (1/2 in. unit only, refer to the actuator
Type 891)
Manual handwheel for operation without air; can also be used
as a down-travel stop
Manual handwheel for use as an up-travel stop
Side mounted positioner (for top mounted positioner, refer to
Type 766)