SRD FAQ #15b

ADVANTAGES OF NEW STYLE:
Two less moving parts. (actuator and solenoid)

Low Pressure Purge (LPP) remains on when controller is turned off. (Constant positive N2 pressure in bowl, even if controller is turned off, helps minimize particles.)

Disadvantages:
Low Pressure Purge remains on when controller is turned off. (To turn off LPP flow the N2 supply must be turned off).

The old style N2 valve assembly uses a fast acting actuator to turn the LPP on and off. The 101 and 102 controllers open the LPP actuator when power is applied to the controller.

The new style N2 valve assembly is now used by Semitool on all new SRDs .

The new style N2 assembly eliminates the LPP actuator replacing it with a fixed valve, decreasing the number of moving parts on the SRD. The new style N2 valve assembly connects to the SRD the same as the old style. All of the facility hook-ups to the SRD are the same.