What are the differences between the directional valve and the flow control valve?

Directional Control Valves

Directional control valves have been commonly referred to as switching valves because they simply direct or “switch” fluid passing through the valve from the source of flow to one of a selection of available cylinder ports. The flow control variety of valve generally selects an orifice which only allows a specified volume of flow to pass. The specified volume controls the speed of a cylinder or hydraulic motor. Likewise, the pressure control type is used to select a particular pressure setting.

Changing direction, flow or pressure during machine operation with these valves would require a separate individual valve for each direction, flow or pressure desired. The hydraulic circuit would become quite complex very quickly!

How does the directional control valve work

Discrete hydraulic Directional control valves are a simple form of binary valves, passing and blocking the fluid flow. Using a ball, plunger, or poppet, a check valve shuts the system if fluid attempts to flow in the opposite way.

Multiple gates may be present in hydraulic directional control valves with more complex characteristics since these valves can switch fluid between various ports according to the device they are supplying hydraulic fluid to. As a result, established numbering systems that have two values, such as 4/3 or 2/2, discriminate against them. The first number represents the number of valve ports, while the second one represents the number of valve positions that the apparatus is capable of.

Proportional Valves

The technological solution to these more complex circuits has been the development of proportional valves. These revolutionary valves allow infinite positioning of spools, thus providing infinitely adjustable flow volumes. Either stroke-controlled or force-controlled solenoids are used to achieve the infinite positioning of spools.

This variable positioning allows spools to be designed with metering notches to provide flow/speed control as well as directional control functions all in one valve, instead of requiring separate valves for direction and speed. The other major benefit is when the circuit requires more than one speed. The various speeds are achieved by changing the electrical signal level to deliver the flow/speed required. No additional hydraulic components are required! These proportional directional valves are controlled by DC power.

How does the hydraulic pressure control valve work

The majority of fluid systems are created to function at a specific range of pressures. These valves are essential in stopping pressure increases that could cause hydraulic fluid leaks or the bursting of pipes and tubes. Additionally, they are put in place so that certain areas of a hydraulic circuit have the desired pressure.

Hydraulic systems frequently use reduction valves, relief valves, sequence valves, counterbalance valves, and unloading valves among other pressure control valve types.