Hydraulic Directional Control Valves Explained

One of the most fundamental and important components of any fluid power system is the directional-control valve. As the name suggests, directional control valves are used to direct the flow of fluid through the system. Directional control valves control when and where the fluid in the system flows. These valves serve to direct fluid flow in a system.

How Directional Control Valves Work

Directional control valves are selected to handle the pressure in a system. Valves will shift from fully open to closed or proportionally. This occurs instantly, causing fluid to rapidly accelerate and decelerate, or in the case of a proportional valve, it is modulated to ramp acceleration and deceleration of actuators. This is done either manually or automatically with settings to cycle valves. Directional control valves keep fluid in a standby mode which prevents its flow from within the system until it’s needed to move and perform its designed function. When called into action, directional control valves shift to perform the operation and then shift back to the neutral position when completed. This action occurs instantaneously, causing fluid to accelerate and decelerate.

The simplest directional control valve is a 2-way valve. These simply stop flow or allow flow. As the name suggests, a 2-way valve has two ports called the inlet and the outlet. A water faucet is an excellent illustration of a 2-way valve and its simplicity. A water faucet allows flow or stops flow by its manual control.

When selecting a DCV, the designer is looking for two primary characteristics; fluid ports and the number of positions. Valve ports provide a passageway for hydraulic fluid to flow to or from other components. The number of positions refers to the number of distinct flow paths a valve can provide. IE: Forward – Neutral – Reverse

Selecting a Directional Control Valve

Directional control valves are classified according to their various characteristics such as the max flow rate, max rated working pressure, the number of ports, number of positions, actuating method used, the fluid path, leakage rates and so on as follows:

• Max Flow Rate/Max Rated Working Pressure: Maximum pressure to perform the work in the process
• Fluid Path: Check valves are an example of 2-way 2-position valve, actuated by line pressure to free flow fluid in one direction or blocking flow in the opposite direction. Shuttle valves is an example of 3-way 2-position allowing switching from two ports into a one common circuit
• Positions: There are typically two or three positions – Forward – Neutral – Reverse
• Ports: The number of flow paths through which fluid can flow into and out of the valve.
• Actuation: How the valve is cycled

Every hydraulic system is different. Choosing the right types of valves is vital to building and maintaining an efficient hydraulic system. PHC maintains an inventory of over $3 million in our distribution centers to provide our customers with quality products when they need them. We stock quality brands like Hawe, Butech, and Haskel. Contact PHC your hydraulic experts for help choosing the right valves and components for your applications.