Regarding the markings on the QEV:
P usually means Pressure (or pressure source, IE your air line)
A is for Air Cylinder (or Actuator), As Brian stated
R is for Relief or Release, as this is where the air from your cylinder is exhausted / purged.
In most commercial applications for a QEV, you have an air cylinder attached to where your chamber (or resevoir) would be connected.
To the port marked P, where your fill and pilot would be located, they normally attach an air line, which would be used to actuate the air cylinder.
To the R port, where you would connect your barrel, they would connect an exhaust silencer or muffler, to deaden the sound of the exhaust air being purged from the cylinder.
Normally, a QEV is used to speed up the actuation of an air cylinder or air ram, they put in pressure, and the cylinder extends, they pilot the valve, and the cylinder quickly retracts.
Just trying to help clarify what these valves are
supposed to be used for, lol!
