The use of a shuttle valve is most commonly found in hydraulic systems, which use liquid under pressure, or pneumatic systems, which use gas or air under pressure. A pneumatic shuttle valve is used exclusively in systems with air or gas under pressure and is a highly effective way to control flow from one or two different inlets.
The design of the pneumatic shuttle valve is not complicated, but it is highly effective. It uses a ball or a similar type of blocking object that is found in the middle of the convergence of three tubes. The two tubes meet in a straight line, with the third at 90 degrees to this line.
When there is pressure from one of the tube inlets, the ball or blocking element moves to the other end, allowing the fluid or, in this case, the air or gas, to move the ball to block the opposite end. By blocking the opposite end, the gas or air is required to flow through the middle tube and on through the system.
The flow of the gas or air can be reversed, which moves the blocking element to the other end, allowing the air or gas from the open inlet to flow down the middle tube. In this way, two different gases or air and gas can be moved through the same valve without any risk of mixing or creating flow through the other inlet.
One of the most common uses of a pneumatic shuttle valve is in an air compressor system that is on standby or emergency. This is often essential in industrial applications but also in instrumentation applications. The loss of pressure from the primary compressor causes the blocking element to shift, causing the backup or standby system to engage automatically. When the primary air compressor is back on the reverse happens, and the systems switch automatically with no loss of performance.