PNEUMATIC ACTUATOR - SPRING RETURN (FAIL SAFE)
Sizing example of spring return actuator:
Valve torque 60N.m plus 30% safety factor = 78N.m. Minimum operating pressure: 6bar(87psig). The spring return actuator selected is HTS-105-12. The HTS-105-12 has the following output torques:
1. air torque 0°(valve close) = 124N.m > 78N.m
2. air torque 90°(valve open) = 84N.m > 78N.m
3. spring torque 90゜(valve open) = 120N.m > 78N.m
4. spring torque 0°(valve close) = 80N.m > 78N.m
The operating principle of single acting spring return actuator
|Air to port A forces the pistons outwards,
causing the springs to compress. The pinion
turns counter-clockwise while air is being
exhausted through port B.
|Loss of air pressure through port A allows the
stored energy in the springs to force the
pistons inwards. The pinion turns clockwise
while air is being exhausted through port A.