A Three-Stage Air Valve is a device with 3 orifices, one that allows air in and two that allow air out. The first outlet orifice is large to allow most of the air to be expelled quickly and the second outflow orifice is smaller to release the air more slowly and reduces air slam. The transition from the primary outflow orifice (Outflow Diameter) to the second orifice (Outflow Diameter 2) usually occurs at a specified pressure (psi or kpa) but can be modeled to switch on flow (cfs or cms) or volume (ft^3 or m^3). These devices are usually constructed so that a float controls which orifice is activated.

Disable This Surge Protection Device

If this box is checked, then the selected SPD will not be modeled in the Surge analysis.

Device Type

Type of Surge Protection Device to be used.

3-Stage Air Vacuum Valve Input

  • Inflow Diameter - The diameter (mm in SI/ inch in English) of the orifice that allows air to enter the system.

  • Outflow Diameter - The diameter of the orifice (mm in SI/ inch in English) that allows air to exit the system. (For 1 stage air valves, the Inflow and Outflow diameters will be the same).

  • Outflow Diameter 2 - The diameter of the secondary orifice (mm in SI/ inch in English) that will be utilized for outflow if the flow, pressure or air volume exceeds the corresponding switching value.

  • Initial Air Volume - This allows you to specify an air pocket volume (m3 in SI/ ft3 in English) that has accumulated at the valve at the start of the simulation. Normally this value is 0 which means that no air pocket is initially present.

  • Switching Type - This setting determines if the switch value is a Volume, Flow, or Pressure.

  • Switching Value - This is the value at which the 2nd outflow orifice will be activated. In case of Flow or Pressure as a switching type, the unit is set by the Flow and Pressure units selected in the Simulation Options. In case of Volume, the unit is m3 in SI or ft3 in English.

  • Air Valve Delay Time - Air Valve Delay Time is the time for the air valve to activate.

Purge - Use the Purge button to remove existing Data.

Create/Update - Enter new or changed data and exit the dialog box.

Cancel - Cancels any new or changed data and closes the dialog box.