33AWS
Well Service Air Release and Vacuum Breaker Valve
Cla-Val 33AWS Well Service Air Valves regulate air discharge from the pump column to prevent shock and air entering the system with each start. Conversely, with each pump stop, full flow unrestricted air is allowed back into the column to avert vacuum formation (which can damage pump seals) as well as to stop the pump from restarting against a full head in the column if a vacuum condition prevented the pump column from draining.
33AWS Engineering Data Sheet – US & Metric Units