A directional control valve is a device capable of controlling the flow of air or fluid. A very simple example is a check valve, a design that allows material to move in one direction through the valve without permitting back flow. Directional control valves are used on a wide variety of systems and equipment and they are particularly important for hydraulics. Their designs can be quite complex.
There are two important characteristics to a directional control valve. One is the number of ports. A single valve can receive input from a number of sources, not just one; a four port valve, for example, has four inlets. The other is the number of positions the valve can be placed in, determining how many different ways it can route the materials it controls. The more ports and positions, the more functionality available to the valve as it is opened or closed.
Hydraulic directional control valves are designed to handle fluids, including water, as well as more viscous materials. Pneumatic directional control valves work with air. The designs in both cases are similar, with the valve having seals to keep the contents contained and under control. Using a directional control valve, it is possible to create a pressurized system, to route materials through a facility without physically handling them, and to perform a wide variety of other tasks.
Control systems for these devices are highly variable. Some can be manually operated, allowing people to open and close ports and change position. Others are remotely operated using mechanical settings or computer control systems. A directional control valve can be controlled from a distance in settings where it might be dangerous to be in the same room as the device, and remote control systems can also be designed for automation, allowing the system to manipulate valves as needed. In an emergency, the system can quickly open or close valves to address a safety situation.
The directional control valve can be a weak point in a system, as it contains moving parts and these can wear with time, eventually creating leaks or freezing up. Valves have to be regularly inspected and maintained and may require periodic oiling or greasing, along with replacement of components like seals as they wear down. Failure of a valve could cause a catastrophe and the goal of regular inspections is to identify problem valves and service or replace them before they become an issue.