A shuttle valve is a plumbing device that allows two separate fluid inputs to flow to a single output. These valves may be used to mix, or alternate between, two separate materials in a manufacturing or industrial process. A shuttle valve may also be used to supply backup fluids during an emergency situation if the first input source fails. While shuttle valves often transport liquids, they are most commonly associated with hydraulic fluid or compressed air used in a pneumatic system.
Each shuttle valve consists of a square or rectangle with two inputs and one output. During normal operation, the valve blocks one of these inputs so that no fluid or air can enter the valve from this location. In this scenario, materials can freely enter the valve from the other input and exit through the output. If the first input fails or becomes blocked, pressure changes within the valve displace an internal shuttle, which cuts off the first input and opens up the second. With only one input valve open at a time, there is little to no risk of backflow into the source.
Different types of shuttle valves can be identified by their internal mechanisms. The most common units feature a cylindrical plunger, or shuttle, which slides back and force to close off one of the inputs. Other models may use a piston or ball that operates using spring power. No matter which of these devices is used, the plunger or piston must fit precisely within the shuttle in order to block the input completely.
Buyers must consider a number of additional factors when choosing a shuttle valve in order to ensure the valve will function as intended. The overall valve size, including inputs and outputs, must be able to fit within the available space for each application. Installers should also determine the pressure and temperature capabilities of each valve to confirm that they meet the needs of the project. It's also helpful to compare different types of input and output fittings to find one that is compatible with those used in the surrounding plumbing system.
The shuttle valve can be found in a variety of applications, including automotive and manufacturing facilities. In a car or truck, a shuttle valve controls the fluid within the power braking or transmission system. If this system should fail, the shuttle valve automatically supplied fluid from a secondary source to maintain safe operation. These valves can be used in the same manor in large equipment or machinery, where they often serve as part of an emergency braking system.