Valve Orifice Sizing - Liquid Pipeline Gravity Draining
A power failure or line break may result in a sudden change in the flow velocity, potentially causing column separation from the resulting gravity flow. The gravity flow may create excessive vacuum conditions at the adjacent high points. Appropriate air valves should be provided at all high points with the orifice sized to allow the required inflow of air to replace the liquid in the pipe. This tool was developed using AWWA M51 method for sizing vacuum valve orifice under full gravity flow conditions (worst-case scenario).
Consult the available orifice sizes from suppliers and select the valve that meets both the capacity and pressure requirements of the application.