Release Valves are essential pipe valves. No pipeline design can be
completed without the use of Air Release Valves. The basic function of
air release valve is to release air pockets. Air pockets collect at each
high point of a full pressured pipeline. These buildups cause flow
capacities to be reduced by 5-15% of designed flow. These reduced
capacities are usually not noticed because air is invisible culprit.
These accumulation of air pockets increase energy consumption. This is
because pumping operation will be at higher heads to overcome air
constricted flow. The use of air release valves open against internal
pressure. The internal lever mechanism multiplies the float force which
is greater than the internal pressure. This force helps in opening the
orifice whenever air pockets collect in the valve. For pipeline
efficiency and water hammer protection, air release valves are thus very
Some factors to consider are as follows:
- Working Pressure
- Test pressure
- Working temperature
- Body and Cover Materials
- End Connection
- End Usage
- Minimal Closing Pressure
- Cost Efficient
- Corrosion Resistant
Types of Air Release Valves:
- Stainless Steel
- Carbon Steel
- Cast iron
- Plastic etc.
Air release valves are divided into two types:
How does an Air Release Valve works?
- Single Air Release Valve
- Double Air Release Valve
An air release valve is a normally-open valve. This valve will remain
open till your system is pressurized. Air is already present. As
pressure increases within the system, unwanted air reaches the highest
point in the system. When pressure inside the system exceeds the regular
atmospheric pressure, air is expelled. As the flow rises, the poppet
becomes buoyant and eventually closes. When pressure and liquid level
drop, the air release valve will automatically re-open.
How to install an Air Release Valve?
air release valve should be installed at the highest possible point in a
piping system. It must be oriented upright. In some cases, residual
liquid/ air in the valve is expelled from the outlet port just prior to
valve shut-off. Therefore, it is suggested to pipe the outlet port to a
safe area for hazardous liquids, or rather use a standpipe for
Uses of Air Release Valves:
- They are an inexpensive and positive method of preventing the
formation of air pockets in pipelines because air pockets are a
major cause of pressure surges and water hammer in pipelines.
- They are essential components for complete pipeline design.
- Air Release Valves are economical.
- They improve pipeline efficiency.
- Air Release Valves are the low cost insurance to protect
expensive Pipelines and Pump Stations.
- They are automatic and kinetic for irrigation and commercial
- Air release valves provide protection from pipeline collapse due
- They provide air bound pump protection.
- They are used for vacuum protection (pipe joints,gaskets,packing,