An air valve is a hydro-mechanical device designed to automatically discharge air and wastewater gases or permit air during the filling, draining, or normal operation of water or sewage piping systems. The safety and efficiency of a piping system depend on the proper release of air and wastewater gases from the piping system.
Water contains approximately 2% dissolved air or gas at typical conditions (1 bar) however it can contain even more, depending on the water pressure and temperature in the piping system. Wastewater systems tend to have more dissolved air and gases due to its nature. Dissolved air and sewage gases tend to come out of solutions in the pipeline system where turbulence, hydraulic changes, and other pressure variation phenomena take place, like pumps, meters, bends, and so on. Once out of liquid, air and sewage gases will not immediately dissolve and will gradually accumulate in pockets at high points within the piping system.
As air pockets accumulate at high points, it reduces the effective cross-section of the piping system in that location, which decreases the liquid flow, and increases energy required to pump water through, which in turn, reduces the overall system efficiency. Also, air bubbles and soluted air can trigger cavitation- the formation of vacuous cavities which subsequently erode and wear the pump and/or pipe components. The movement of these air pockets tends to cause pressure surges and pipeline ruptures. Aside from the fact that trapped air can promote corrosion in the pipe internal surface, damage water meters, malfunction valves and increase vibration in the system.
On the other hand, while draining a piping system or having a transient, it is crucial to admit air into the piping system in order to occupy the volume of drained or moving liquid in order to avoid negative pressure (vacuum) in the pipeline which in turn can lead to buckling. Thus, air valve helps preventing vacuum conditions when, for example, the pump trip (as in power failures) which in turn prevent column separation phenomena.
Air valves are mounted vertically on top of the pipe. They contain a float, made of plastic or metal, which settles by either gravity when the pipe is empty or vacuum when pressure is negative. Once water enters the valve, the float float rises and seals off the orifice. As the pipeline is pressurised, the valve cannot reopen to release air that may gradually accumulate. When the pressure becomes negative as a result of a pressure transient or draining the pipeline, the float drops and allow air into the pipeline. Automatic-combination air valves, which are now the common type in the industry, contain smaller orifice and is intended to release small quantities of air that gradually accumulate at high points within the pipeline. The small orifice is controlled by a plunger activates by the float. As air accumulates in the air valve body, the float settles and opens the small orifice. Once the air is expelled, the rises again and seals off the small orifice.
As air pockets accumulations at pipeline high points, reduce the effective cross-section of the pipeline in that location, which decreases the water flow, and increases energy required to pump water through. Thus, reducing the overall system efficiency. Furthermore, air bubbles and saluted air can trigger cavitation – the formation of vacuous cavities which subsequently erode and wear the pump and/or pipe components. The movement of these air pockets tend to cause pressure surges and pipeline ruptures. Aside from the fact that trapped air can also promote corrosion in the pipe internal surface, damage water meters, malfunction of valves and promote vibration in the system. Also, while draining a pipeline or having a transient is crucial to admit air into the pipeline in order to occupy the volume of drained or moving water in order to avoid negative pressure (vacuum) in the pipeline which in turn can lead to collapse. Thus, air valve prevents vacuum conditions when, for example, the pump trip (as in power failures) which in turn prevent column separation phenomena. Laminar Air Valves offers the most reliable air valve design to overcome challenges associated in pipeline systems. Our air valves are designed for efficient discharge and admit of air in water pipelines and other places where trapped air could harm the system’s operation and efficiency.