It is good engineering practice to install a sewage air valve prior to the pump discharge check valve, on vertical turbine pumps and deepwell submersible pump applications. The purpose of these valves is to prevent air/gas entry into the pipeline on initial pump start up and to break vacuum in the vertical riser upon pump shutoff.
Operation of conventional sewage air valves in this application is such that the air in the vertical riser is released very rapidly upon pump startup, resulting in very high pressure transients when the liquid column slams the sewage air valve shut and/or slams into the closed discharge check valve.
The Vent-O-Mat Series RGXb valve has specifically been developed for use on deep well submersible pump and vertical turbine pump applications where they are installed prior to the pump discharge check valve to fulfill the following functions:
- Provide effective release of air/gas in the vertical riser upon pump startup.
- Dampen surge pressures upon startup.
- Provide vacuum protection when the pump stops and the vertical column drains.
Upon pump stop, the discharge check valve closes. Sewage/effluent drains from the sewage air valve and the pump’s vertical column. The negative differential created by the draining liquid causes atmospheric air to push the “Anti-Surge” Float down, opening the Large Orifice and allows air to displace the draining liquid to prevent potentialy damaging internal negative pressure*.
The hollow smooth side float design, discourages the adherence of solids and viscous substances which, therefore tend to withdraw from the valve into the pipeline when draining occurs, for this reason NO FLUSHING CONNECTIONS ARE NECESSARY
Air/gas is forced through the “Anti-Surge” Orifice resulting in the deceleration of the approaching liquid column due to the resistance of rising air pressure in the valve.
This dampens transients when the sewage air valve closes and the liquid column opens the discharge check valve.
Sewage/effluent has entered the valve chamber and buoyed the floats to close both the “Anti-Surge” orifice and the small orifice. The design’s compression/volume relationship prevents the media from ever exceeding the maximum surge level indicated in diagram 3. The resultant sewage/effluent free area protects against the fouling of the orifice seals by solids or high viscous substances – for this reason NO FLUSHING CONNECTIONS ARE NECESSARY.
The volume of disentrained air/gas increases in the valve and displaces the sewage/effluent level to the lower, normal operating level (small orifice control float buoyancy level ) Any additional lowering of the sewage/effluent level, as would occur when more air/gas enters the valve, will result in the control float dropping away from the small orifice through which pressurized air/gas is then being discharged to atmosphere. The control float will close the small orifice when sufficient air/gas has been released to restore the sewage/effluent level to the normal operating level. The considerable sewage/effluent free are obviates the possibility of leaks that could otherwise be caused by solids entering the sealing areas – for this reason NO FLUSHING CONNECTIONS ARE NECESSARY
*Note: A differential pressure of less than 0.05 bar (0.7 psi) across the large orifice is required to open the valve fully under vacuum conditions.