A manually or automatically controlled valve enabling the isolation of a device powered or supplied with compressed air from the compressed air network.
- At the compressor outlet, shutoff valves stop compressed air flow, preventing it from entering the downstream system or air receiver tank.
- In distribution lines, shutoff valves can shut off specific sections or equipment for maintenance or repairs without interrupting the system.
- Shutoff valves at the air receiver tank’s inlet and outlet connections allow operators to isolate the tank from the system, controlling the flow of compressed air in and out of the tank as needed.
As per their construction, they are classified as:
- ball valves
- wafer valves
- butterfly valves
- plug valves
- globe valves
- gate valves
However, a caution for the ‘pressure drop’ across them should be exercised in using such valves for ‘shut off’ application considering that most of the time, they would be open for air flow to the applications.
There are a number of globe and gate valves installed in compressed air services and they should be the last choice for shut-off valves in the piping system. There are a number of drawbacks to globe and gate valves. They have the highest pressure drop of any valve for line service. In addition, they cost two to three times as much as the other valve types. They are heavy and difficult to install. They are remarkably difficult to remove and service and tend to leak more often than other available valves for the same service.
Plug valves have minimum pressure drop for shut off service, but usually cost more than ball, butterfly, or wafer valves. They are not as easy to work with and cost more than ball, wafer, and butterfly valves.
Ball type, wafer, and butterfly valves are superior for inline shut off service in compressed air piping systems.
Use full bore (full flow) ball valves for 1/2-inch to 2-inch piping.
In larger piping, use either a compression-type wafer valve or a butterfly valve. The butterfly valve bolt pattern mates to the adjacent flanges. The wafer valve usually has a grooved ring seat in the valve body for an O-ring that is compressed to form a seal between the mating flanges when bolted together.
Valves in compressed air service are either fully opened or fully closed. There is usually no service in between. It is difficult to tell if stem type valves are fully open even if they have rising stems. This can add to an already high pressure drop while in service.
Consider the types of contaminants present and select appropriate components. Pay particular attention to stem valve packing, seals, and internal valve components. Some lubricants can be very aggressive with rubber components such as low nitrile Buna N. Viton is a common material compatible with most compressed air contaminants.