Generally, directional valves are used in hydraulic and pneumatic systems. These control valves have a spool, piston, diaphragm and a plug inside. On the application of a actuating force, the spool will shift from a fully open position to a closed position. On removal of the actuating force, the spool returns to its normal working position.
There are many types of directional valves. Some of these include hydraulic, pneumatic, ball and butterfly valves. They can be operated manually or electronically. Most are rated for pressures between 26” Hg and 150 psi. These valves are typically compact in size. Depending on the type of system and application, these valves are available in multiple sizes and can be custom-made to suit any need.
For pneumatic directional control valves, the operating pressure is usually around 26” Hg. They can also be rated for higher pressures. However, their size and viscosity should be inspected to make sure they can work in your specific application. For example, a high-pressure valve will not perform properly if it is too small for your application.
Some directional valves are actuated by manual means. These valves use levers or wheels to apply force to the flow-directing element. Some valves also use a spring to return the spool to its original position. Some use push buttons or detented toggles to operate them.
These types of valves have two basic positions: the open position, which allows fluid to flow through, and the closed position, which prevents the flow. They are normally used in pneumatic systems, though they can be found in other applications as well. The directional valve is typically found in water, gas, oil or fuel. They are also used in wastewater.
For hydraulic directional control valves, the operating pressure may be as high as 400 bar. They are made from metal, composite materials, or plastic. They can be as small as a pencil tip and as large as a bowling ball. They are designed to be robust and precise. They are used in applications such as wastewater treatment and process control.
Some of the common valve types are pilot operated, manual, and pneumatic. The pilot operated type is used in applications where the spool will shift if the force required to do so exceeds the practical limits of the solenoid. Some of these are also rated for potentially explosive atmospheres.
The manual version uses a spring or a lever to close and a paddle or a lever to open. These are subject to wear and tear and need a force to open and close. These are ideal for remote actuation. The manual valve is sometimes used to reverse the motion of a cylinder. Some manual valves use a lever to return the spool to its original open position.
The majority of directional-control valves for industrial applications are three-position or two-position. There are four-way and five-way valves, and some manufacturers specialize in center-position configurations for certain applications. The spool of a two-port, two-position directional valve will have two ports, and the spool of a four-port, four-position directional valve will have four ports.