What is a shuttle valve? 

It is also called a double check valve, it has two inlets and one outlet. If any of the inlets is unloaded the flow will be shut off in that direction and it will be open from the loaded one to the outlet. A shuttle valve may be installed, for example when a power unit or control unit is to be actuated from two points, which may be remote from one another. A shuttle valve is a pressure operated valve, these valves can separate the normal hydraulic system from the emergency pneumatic system. The air pressure in the lines will be removed through the vent port of the control valve if the control handle is returned to the normal position. The working of the shuttle valve is related to the OR logic function. If we supply fluid under pressure to any of the two inlet ports, then there will be a supply from the outlet port. Inside the valve body, the shuttle valve has a ball or poppet. The ball poppet closes the other inlet port if the fluid is supplied to any of the inlet ports, and the fluid will flow to the cylinder port.

Applications:

• By using it in a machine we can operate more than one switch and each switch can be placed at any suitable location. This would increase the safety and reliability of the machine. So because of this shuttle valves are used in many industrial types of machinery.
• It can be used in standby systems, so in operation, if there is a case of compressor failure then the standby tank will take over the function from the shuttle valve. Shuttle valve will only take over the standby system if the compressor pressure is re-established
• It can be used with pumps it must be used regardless of whether the speed is controlled in one direction or both. Its purpose is to pick a pressure signal from the cylinder port with the higher pressure, according to whether the cylinder is extending or retracting, and still to vent the sensing line in the valve neutral. Without the shuttle valve and the open cylinder ports on the 4-way valve, the pump cannot unload when it becomes deadhead in the neutral.