Hayward offers four versions of their pneumatic valve actuators:
PC, a four piston rack and pinion design which is compact, light weight and suitable for valves up to 18"
PM, a two piston rack and pinion design having a light weight thermoplastic housing and used for valves as large as 3"
PMD4, the corrosion resistant version of the PM having anodized aluminum two-piston rack and 303 SS pinion within a GFPP housing for valves up to 6"
PMD6, a larger and heavier-duty version of the PMD4 for valves up to 24"
are available with either direct acting (requiring air to open and close) or spring return versions (fail safe)
have ISO 5211 compatible for easy attachment to ball and butterfly valves.
the solenoid connections are namur-style and the travel stops are adjustable
can be manually operated
have a high visibility position indicator
are available with cycle speed control, positioner and auxiliary limit switches
PC pneumatic actuators a have four-piston rack and pinion design with a light weight epoxy coated aluminum housing. It is an extremely compact design and has a plated steel shaft which is suitable for most applications (the shafts are upgraded to 303 SS for the PMD4 and PMD6 versions). The direct acting versions output up 15,856 in-lbs of shaft torque for ball and butterfly valves as large as 18"; if your valve is larger or you require more torque refer to the PMD6. The spring return model is limited to ball and butterfly valves up to 10" in size given the maximum amount of shaft torque created is 2,857 in-lbs.
PM pneumatic actuators all have a two-piston rack and pinion design, thus they do not output as much torque and are limited to smaller valves up to 3" in size. The larger PMD6 actuators provide a maximum of 31,500 lbs torque. The PM model is offered in three configurations, the PMD, PMD4 and PMD6. The PMD valve actuator has a nickel plated carbon steel shaft whereas the PMD4/PMD6 have a 303 SS shaft for enhanced corrosion resistance. You would generally upgrade from a PMD to a PMD4 for enhanced corrosion resistance and utilize the PMD6 design for enhanced corrosion resistance for valves >6" or for non-corrosive applications requiring valves >18". All of the housings are thermoplastic except for the PMD6 which is made from thick aluminum. Each one can be supplied in either double-acting or spring return configurations.