Air Valve


Double Orifice, Isolation Valve

Fig 764 Air Valve

This design of air valve is for use in water systems incorporates both small and large orifices, and is complete with an integral screw-down isolating valve to allow regular inspection and maintenance without the need to de-water the pipeline. The small orifice is for automatic release of accumulated air during normal operations.

Air can enter a pipeline in a number of ways, through pump glands, leaking joints and is even contained in solution in the water itself. This air accumulates at the high points of the system, and unless the flow of water is fast enough to purge the line, large pockets of air form to seriously impede the flow, a condition known as “air binding”. By locating these air valves at specific points in the system, ventilation of these air pockets is achieved, increasing pumping efficiencies and flow capabilities of the pipeline. The large orifice is to allow automatic ventilation of the pipeline during filling and emptying.

When filling, air is exhausted at a sufficiently high capacity to prevent restriction of the filling rate due to built up back pressure. When emptying, air is admitted to the pipeline at a rate sufficient to prevent high vacuum pressures developing.

Item Details
Body Material
Spheroidal Graphite Ductile Iron
Body Coating
Rubber - Cedar Core, EPDM, EPDM (PN21 on Request), EPDM (NBR on Request), Butyl, Gunmetal
Pressure Range
Size Range
Flange Connection
AS4087 / AS2129 Table E & F / ANSI
End Connection
Epoxy Coating
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Fig 764 Air Valve