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Home >> News >> The Basics of Control Valves in a Hydraulic System

The Basics of Control Valves in a Hydraulic System

A typical fluid power system is made up of a hydraulic pump, a line relief valve, a proportional direction control value, and an actuator. Because of the advantages fluid power systems have over other control systems, they are widely used on aerospace, industrial and mobile equipment. These advantages include high power-to-weight ratio, having the capability of being stalled, reversed, or operated intermittently, as well as having the capability for fast response and acceleration. Fluid power systems also offer reliable operation and a long service life.

In hydraulic systems, the liquid used must be mostly incompressible, or very dense. For a variety of applications, utilizing a liquid to move machinery is more desirable than drier methods. Using a liquid will not cause the same type of wear on the system, and also will not require as many moving parts. Additionally, motion is more precise and the equipment will run much smoother than it would with more mechanic means.

Hydraulic control valves are used to control pressure in a hydraulic fluid power system. These valves control the pressure, flow rate and direction of the flow. Hydraulic valves can be defined in many different ways. Oftentimes, a given valve will be named differently when it is used in different applications. Hydraulic valves permit liquid to enter or leave specific spaces throughout the hydraulic system. Commonly, hydraulic valves are used with hydraulic pumps and cylinders to control the flow of the liquid.

Generally, hydraulic valves are classified based on their functions, including pressure, flow and directional control vales; or based on their control mechanisms, such as, on/off, servo, and proportional electrohydraulic valves. Hydraulic valves can also be classified based on their structures, such as spool, poppet, and needle valves. A hydraulic valve controls a fluid power system by opening and closing the flow-passing area of the valve.

Fluid power systems are adaptable in a variety of applications depending the on the working environment and task. For example, in industrial applications, a major concern is the noise level. Typically, a noise level below 70dB is desirable. Industrial fluid power systems commonly operate in the low (below 7 MPa or 1000 psi) to moderate (below 21 MPa or 3000 psi) pressure range and operate at a low noise level.

On the other hand, with mobile applications, the primary concern is size. Mobile hydraulic systems commonly operate between 14 and 35 MPa (2000-5000 psi). Also, their allowable temperature operating range is usually higher than in industrial applications, making them ideal for mobile applications.

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