How Does an Air Valve Work?

The functions of a combination air valve

A combination air valve is typically used in water networks or irrigation schemes for the following functions:

1. To relieve all the air during pipeline filling for effective operation.
2. To ensure that any entrained air in the water system is automatically released to maximize the system’s performance. Entrained air pockets in pipes can cause excessive head loss and flow reductions if the air is not effectively released. It’s also designed to automatically release any entrained air that accumulates at the high spots during water transfer, maximizing pipeline efficiency.
3. To protect the pipeline from vacuum conditions. The air valve is used during pipe drainage to maximize water outflow in case of a burst, preventing vacuum conditions.
4. Finally, air valves have the potential to generate water hammer during excessive filling of the pipe or column separation conditions. Valves fitted with Surge Protection (SP) ensure that the pipe cannot be filled at an uncontrolled rate that induces water hammer.

What are the main components of an air release valve?

• Valve body
  The unique straight flow body with a nominal (equal) inlet and outlet enables higher than usual flow rates. It is compact and houses the float and the surge protection (SP) mechanism. The body is designed so that the inlet is completely free of float’s guides, to maximize air flow capacity. Each body has a lower 316SS grade drain valve, enabling the valve to be drained and tested quickly and safely.
• Upper seat
  The 316S grade stainless steel seat cleverly houses the seal that makes the seal between the seat and float.
• Inner float assembly
  The parts of the float and the Surge Protection (SP) Disc are all manufactured from bar stock polypropylene which ensures they cannot ever change in their mass or shape. These parts are guided and aligned to the body by the four guide ribs on the valve body, ensuring they cannot get blown offset to the side. Low pressure sealing is 0.1 bar; 1.5 psi.
• Automatic orifice rod
  The automatic orifice rod provides an innovative and patented 2‑step function, automatic air release, which minimizes water spraying during air release. This will also contribute to extending the operational period in the field without maintenance.
• Surge Protection (SP) disc
  During pipeline filling with high velocity or a pressure surge, the surge protection disc lifts and partially closes the kinetic orifice, allowing controlled air relief. The surge protection feature ensures a smoother operation and prevents damage to the air valve or system.
• Mushroom (circular surround) or down outlet
  The valve outlet has a stainless-steel mesh that prevents any possibility of external contamination of the inner floats and keeps vermin and spiders away from the underside of the outlet. The ductile iron outlet is robust and keeps any direct sunlight away from the floats and is strong enough to be stood on if fitted inside a valve pit.

How does a combination air valve operate?

The following animation highlights the features and operation of the Combination Air Valve functions described above.

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