A typical fluid power system consists of a hydraulic pump, line relief valves, proportional direction control valves, and actuators. Because the advantages of fluid power systems have more than other control systems, they have widely used in space, industrial and mobile equipment.

These advantages include a high power-to-weight ratio, having the ability to stop, be reversed, or operate intermittently, and have the ability for rapid response and acceleration. The fluid power system also offers reliable operation and long life.

In a hydraulic system, most of the liquid used must be incompressible, or very solid. For a variety of applications, utilizing the liquid to drive an engine is more desirable than drier methods. Using liquid will not cause the same type of wear on the system, nor will it require many moving parts. In addition, the movement is more precise and the equipment will run much more smoothly than by mechanical means.

Hydraulic control valves is used to control pressure in the hydraulic fluid power system. This valve controls the pressure, flow rate, and flow direction. Hydraulic valves can be defined in various ways.

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Often, a given valve will be given a different name when used in different applications. Hydraulic valves allow fluid to enter or leave certain spaces throughout the hydraulic system. Generally, hydraulic valves are used with hydraulic pumps and cylinders to control fluid flow.

In general, hydraulic valves are classified by function, including pressure, flow, and directional control valves; or based on the control mechanism, such as, on / off, servo and proportional electro-hydraulic valves. Hydraulic valves can also be classified based on their structure, such as spools, poppets, and needle valves. The hydraulic valve controls the fluid power system by opening and closing the valve flow area.