Elephant Fluid Power Co., Ltd.
Elephant Fluid Power Co., Ltd.

Comparison of Directional Control Valves and Proportional Valves

Understanding the technologies available in fluid power is essential in order to design the most efficient, cost-effective, and energy-efficient systems. Traditional hydraulic equipment designs use almost exclusively directional control valves.


1. Comparison of directional control valve and proportional valve


These directional valves are sometimes called "switches" and can be used to control flow direction, flow rate, and fluid pressure. These valves can be operated from AC or DC power.


Directional Control Valves: Directional control valves are often referred to as switching valves because they simply direct or "switch" fluid through the valve from the flow source to one of the selected available cylinder ports. The flow control variety of the valve generally selects the orifice that only allows a specific volume flow through. The specified volume controls the speed of the cylinder or hydraulic motor. Likewise, the pressure control type is used to select a specific pressure setting. Changing direction, flow or pressure during machine operation using these directional control valves would require a separate separate valve for each direction, flow or pressure required. Hydraulic circuits can quickly become quite complex.


Proportional Valves: Proportional valves allow infinite positioning of the spool, thus providing infinitely adjustable flow. Either stroke control solenoids or force control solenoids can be used to achieve infinite positioning of the spool.


This variable positioning allows the spool to be designed with metering notches to provide flow/speed control as well as directional control in one valve without requiring separate valves to control direction and speed. Another major benefit is when the circuit requires more than one speed. Various speeds are achieved by varying electrical signal levels to provide the desired flow/speed. No additional hydraulic components required! These proportional directional valves are controlled by DC power.


Proportional controls are used with their associated electronic controls and also add the required acceleration and deceleration functions. This provides a variety of machine cycles to operate safely at higher speeds with controlled start and stop characteristics. Adjusted acceleration and deceleration increase the overall cycle time and productivity of the machine.


2. Matters to consider when choosing a directional control valve


The type of directional control valve should be selected according to the requirements of the work. For example, if the oil flow is required to flow in only one direction, and not in the opposite direction, a check valve should be used; When the working cycle of "stop" or frequent movement back and forth, the reversing valve should be used to change the direction of oil flow and turn on or off the oil circuit; if the actuator is required to complete the forward-backward-stop working cycle, three three-position should be selected. Reversing valve; if only two working states are completed, namely feeding and retracting, a two-position reversing valve should be used.


The directional control valve can also be selected according to the working state of the system and the characteristics of the valve. For example, the quality of the moving parts is small, the reversing accuracy is not high, and when the flow rate is less than 63L/min, the electromagnetic reversing valve should be selected, because this kind of valve reversing impact If the mass of the moving parts is large, the speed change range is large, and the commutation is required to be stable, when the flow rate is greater than 63L/min, the electro-hydraulic with stable commutation and no impact should be selected. Reversing valve; if there is a locking circuit in the system, a hydraulically controlled check valve with good sealing performance should be selected instead of a reversing valve with poor sealing performance.