When purged with compressed air, liquid within the downpipe is displaced by air pressure equal to the hydrostatic force of liquid in the tank. If carefully regulated at a low rate of flow, air pressure will constantly maintain equilibrium against the force of the liquid. Output is proportional to liquid depth and can be transmitted as an electronic 4-20 mA signal or pneumatically as a direct 1:1 pressure signal.
788 D/P Purge Control is a differential pressure regulator and air flow control. It generates a constant flow of compressed air to purge a downpipe. Its integral differential pressure transmitter provides 4-20 mAdc output proportional to liquid level.
APPLICATION NOTE: Available in all-pneumatic configurations for hazardous area service.