Should the pressure at the output, for any reason, rise above that of the input then the valve would open regardless of the state of the solenoid and pilot valve.
22.
The pressure at which the control pilot relieves at is the functional set pressure of the PORV . When the pilot valve reaches set pressure it opens and releases the pressure from the dome.
23.
With no material or weight limit, it could be powered by a piston driven by high pressure compressed air, with a pilot valve manually triggered which opens the large main air valve very quickly.
24.
Diaphragm valves can be controlled by various types of actuators e . g . manual, pneumatic, hydraulic, electric etc . The most common diaphragm valves use pneumatic actuators; in this type of valve, air pressure is applied through a pilot valve into the actuator which in turn raises the diaphragm and opens the valve.
