A shuttle valve is a type of

valve A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fitting ...

which allows fluid to flow through it from one of two sources. Generally a shuttle valve is used in

pneumatic Pneumatics (from Greek ‘wind, breath’) is a branch of engineering that makes use of gas or pressurized air. Pneumatic systems used in industry are commonly powered by compressed air or compressed inert gases. A centrally located and ...

systems, although sometimes it will be found in hydraulic systems.

Structure and function

The basic structure of a shuttle valve is like a tube with three openings; one on each end, and one in the middle. A ball or other blocking valve element moves freely within the tube. When

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country a ...

from a fluid is exerted through an opening on one end it pushes the ball towards the opposite end. This prevents the fluid from traveling through that opening, but allows it to flow through the middle opening. In this way two different sources can provide pressure without the threat of back flow from one source to the other. In pneumatic logic a shuttle-valve works as an OR gate.

Applications

A shuttle valve has several applications including: # The use of more switches on one machine: by using the shuttle valve, more than one switch can be operated on a single machine for safety, and each switch can be placed at any suitable location. This application is normally used with heavy industrial machinery. #Winch brake circuit: a shuttle valve provides

brake A brake is a mechanical device that inhibits motion by absorbing energy from a moving system. It is used for slowing or stopping a moving vehicle, wheel, axle, or to prevent its motion, most often accomplished by means of friction. Backgroun ...

control in pneumatic

winch A winch is a mechanical device that is used to pull in (wind up) or let out (wind out) or otherwise adjust the tension of a rope or wire rope (also called "cable" or "wire cable"). In its simplest form, it consists of a spool (or drum) attach ...

applications. When the compressor is operated the shuttle valves direct air to open the brake shoes. When the control valve is centered, the brake

cylinder A cylinder (from ) has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base. A cylinder may also be defined as an ...

is vented through the shuttle valve, and the brake shoes are allowed to close. #Air pilot control: converting from air to oil results in locking of the cylinder. Shifting the four-way valve to either extreme position applies the air pilot through the shuttle valve, holding the two air-operated valves open and applying oil under

air pressure Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1013.25 millibars ...

to the corresponding side of the cylinder. Positioning a manual valve to neutral exhausts the air pilot pressure, closing the two-way valves, and trapping oil on both sides of the cylinder to lock it in position. #Standby and emergency systems:

compressor A compressor is a mechanical device that increases the pressure of a gas by reducing its volume. An air compressor is a specific type of gas compressor. Compressors are similar to pumps: both increase the pressure on a fluid and both can tr ...

systems requiring standby or purge gases capability are pressure controlled by the shuttle valve. This is used for instrumentation, pressure cables, or any system requiring continuous pneumatic input. If the compressor fails, the standby tank—regulated to slightly under the compressor supply—will shift the shuttle valve and take over the function. When the compressor pressure is re-established, the shuttle valve shifts back and seals off the standby system until needed again.

References

{{reflist Control devices Valves