Air Rams: What are Shuttle Valves?

pressure gauges and valves
For air rams, pressure valves, and other pneumatic tools, be sure to call us at MasterMac 2000.

Oil unloader

This is a specialised shuttle valve that is mounted on the front of the pump assembly housing. This valve in an oil unloader allows air pressure to flow to the power unit. During a power exhaust stroke, when airflow is reversed and the shuttle valve is lifted from its seat, any oil inside the line in the power unit and oil unloader valve is discharged into the atmosphere.

What are Shuttle Valves?

Shuttle valves or pressure control valves (also called air rams) are considered simple components but are much more versatile than ever imagined. For pressurised air or fluid power, shuttle valves are the least-complex components that perform the simple function of allowing flow from an outlet port from either two inlet ports while blocking flow to another. Another function is to allow flow into a third port while blocking flow from both inlets.

Shuttle valve function

Shuttle valves can have two inlet ports and a single outlet port, or a single inlet to two outlets. Flow direction is controlled by fluid pressure. Whenever a higher pressure flows through an inlet port to the outlet port, the flow is blocked from the other inlet port. All shuttle valves incorporate a spring that acts against an inlet pressure at any port. 

As mentioned earlier, shuttle valves also allow for reverse flow (outlet port open becomes inlet port, but only one inlet port open to become an outlet). This is important as this distinguishes the difference between shuttle valves and check valves. When input pressure drops, shuttle valves must be able to relieve the system pressure, particularly with brake and pilot circuits.

For standby or emergency systems

Aside from air pilot controls, motor fluid crossovers, brakes, and power inputs, shuttle valves are used for pressure controls of multiple compressors that are required for standby or purge gas capability. Should the compressor fail, the standby tank (with a lower compressor supply) will shift to the shuttle valve and take over the function. The shuttle valve will close off the main compressor inlet port until compressor pressure is re-established there, in which the shuttle valve shifts and closes the standby system.

Get your shuttle valves from MasterMac 2000

Whether you’re looking for shuttle valves, air rams, and process valves or pneumatic components, MasterMac 2000 is one of Australia’s largest privately-owned distributors that can provide you with all these, and more. Get quality brands like Mack, Univer, and Tolomatic. Call us on 07 3344 4711 or visit

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