What Are the Functions of the Hydraulic Valve?

Hydraulic valves are a vital part of hydraulic systems, which consist of hydraulic pumps, oil reservoirs, hydraulic motors and hydraulic cylinders. Hydraulic valves regulate the flow of hydraulic oil to hydraulic motors and cylinders. Hydraulic valves can be actuated by equipment operators or by automated actuators such as solenoids or pneumatic signals from control systems or computers.

Construction

Hydraulic valves are most often constructed of steel or stainless steel because of the high pressure of hydraulics. High grades of billet aluminum are also commonly used. Valve-sealing surfaces might be elastomeric or plastic. O-ring seals and gaskets are common because of the pressure.

Valve Action Types

As with all valve classes, hydraulic valves are available in a number of valving types from simple on-off to throttling, to crossover valves where two hydraulic signals can be cross-exchanged and to selector valves where a single output can be sourced from any of a number of inputs at one at a time. Many of these actions are made possible with multiple port spool valves, which can be configured or connected in a number of ways to achieve the desired valve action.

Valve Use

As implied by their designations, valves are designed to perform specific functions within hydraulic systems, the simplest of which is performing on-off functions, which either blocks or allows the passage of hydraulic oil to the cylinder or motor. Throttling valves are variants that allow regulation of the flow of oil to either speed up or slow down the motor or cylinder. Reversing or crossover valves essentially exchange the two signals, either extending or retracting a cylinder rod or reversing a the circular motion of a rotating motor. Check valves are usually spring-loaded and biased valves allow flow in one direction only. Biasing means that the oil pressure must exceed a preset value before the valve will allow flow in the correct direction. Relief valves relieve hydraulic pressure.

Levers and Knobs

Many advances have been made in the area of ergonomics--making it easier for humans to optimally operate machinery safely and efficiently. Watching an expert hydraulic excavator operator dig a foundation with his power shovel is a marvel of precision movements as both hand and foot operated valves are actuated in precise unison.

Automated Valves

Automated valves mimic human motion with hydraulics, but as the part of an automated program that is controlled by a machine's programmable control system or manufacturing computer system.

References

• valves
• hydraulic valves