It is good engineering practice, for vertical turbine pumps and deepwell, submersible pump applications, to install air valves prior to the pump discharge check valve. The purpose of these valves is to prevent air entry into the pipeline and to break vacuum in the vertical riser upon pump shutoff.
Operation of conventional 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 water column slams the air valve shut and/or slams into the closed discharge check valve.
The Vent-O-Mat Series RBXb 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 and controlled release of air in the vertical riser upon pump startup.
- Dampen surge pressures upon pump startup.
- Provide vacuum protection when the pump stops and the vertical column drains.
Upon pump stop, the pump discharge check valve closes. Liquid drains from the air valve and the pump’s vertical column. The negative differential created by the draining liquid causes atmospheric air to push the “Anti-Shock” Float (6) down, opening the Large Orifice (3) and rapidly displaces the draining liquid to prevent potentially damaging internal negative pressure *.
*Note: A differential pressure of less than 0.05 bar (0.7 psi) across the Large Orifice (3) is required to open the valve fully under vacuum conditions.
Air is forced through the “Anti-Shock” Orifice (8) resulting in the deceleration of the approaching water column due to the resistance of rising air pressure in the valve. This dampens transients when the air valve closes and the water column opens the pump, discharge check valve.
Liquid enters the valve Barrel Chamber (2) and the Floats (4), (5) are buoyed so that the “Anti-Shock” Orifice (8) is closed by the Floats (4), (5) the valve will then become internally pressurized. Disentrained air rises through the liquid and accumulates in the valve chamber when the volume of air is sufficient to displace the liquid, Float (4) will no longer be buoyant and will gravitate downwards thereby opening the Small Orifice (7) and allowing accumulated air to be discharged into atmosphere, as the air is discharged the liquid raises the Float (4) and reseals the Small Orifice(7)and prevents escape of liquid. .