Hydraulic valves are automated components which controlled the pressure, flow and direction of a liquid, which is actuated. There are different categories to classify hydraulic valves, and different types of hydraulic valves use different types of hydraulic solenoids as their actuators. Based on the control methods, there are manual hydraulic valves, electrical control hydraulic valves, pilot-operated hydraulic valves. Based on different functions, there are hydraulic flow valves (such as throttle valves, flow control valves, diverter valves), hydraulic pressure valves (relief valves, pressure reducing valves, sequence valves, unloading valves), hydraulic directional valves (solenoid directional valves, manual directional valves, check valves, pilot operated check valves). Based on the installation ways, there are plate valves, tube valves, sandwich plate valves, threaded cartridge valves, cover valves.Sometimes, you may find some hydraulic valves with similar shapes, but based on its mode of actions, they may have different functions. In the following articles, we will introduce several different types of hydraulic valves.
Electromagnetic Directional ValveElectromagnetic directional valve is actuated. The force of on-off solenoid can push the valve spool so that the valve can control the direction of the fluid flow.
There are two typical structures of solenoid directional valve, hydraulic directional slide valve, and hydraulic directional ball valve. Normally, when we say solenoid directional valve, it means the hydraulic directional slide valve, hydraulic directional ball valves are normally called as directional seated valve. There are many different types of Electromagnetic directional valves. Based on the numbers of valve service tapping position and NG, there are 2-way NG3 directional valve, 2-way NG4 directional valve, 3-way NG4 directional valve, etc. Based on the structure of the solenoid the valve used, there are wet valve and dry pipe valve.Manual Directional ValveManual directional valve is the valve that can switch the directions by hand lever. It has been widely applied in hydraulic systems to control the direction shift, cut-off of the oil fluid. The most common manual directional valve structure is the 3-way NG4 directional valve.Hydraulic Proportional ValveElectro-hydraulic proportional valve is actuated by the installed.
According to the input voltage signal, proportional solenoids will respond appropriate actions, which cause the displacement of the valve spool. Therefore, the opening size of hydraulic proportional valve changes and the rated output flow can be controlled.
Also, the feedback of proportional valve spool displacement can be realized in the form of mechanical, hydraulic, electrical, etc. Electro-hydraulic proportional valve has been widely used in different hydraulic systems as it holds the advantages of various species, easy assembly, high control accuracy, strong antipollution ability, etc.Hydraulic Servo ValveHydraulic servo valve mainly refers to electro-hydraulic servo valve, which is the core controller of electro-hydraulic servo system.
After the servo valve receives electrical analog signals, the corresponding flow and pressure have been exported. It is not only an electric and hydraulic transform component, but also a power amplifier, which turns the low power electrical signal into high volume hydraulic energy (flow and pressure). In electro-hydraulic servo systems, it connects the electrical part and hydraulic part realizes the transformation between the electrical signal and hydraulic signal, and the amplification of hydraulic.Hydraulic Relief ValveHydraulic relief valve is also known as hydraulic overflow valve. When a hydraulic relief valve is working, it controls and adjusts the pressure of hydraulic oil by the pressure of the spring. When the pressure of hydraulic oil is lower than operating pressure, valve spool is pressed to the hydraulic oil inlet by the spring. When the pressure of hydraulic oil is higher than operating pressure, valve spool is pushed away by hydraulic oil, and hydraulic oil flows in the valve.
It is obvious that as the pressure of hydraulic oil increases, the valve spool will be pushed further, therefore, more hydraulic oil can flow back to the oil box through the relief valve. If the hydraulic oil pressure is lower than the spring pressure, valve spool can seal the hydraulic oil inlet.
Manual Pneumatic Directional Control Valves
As the pressure of hydraulic oil from the oil pump is stable, but the pressure of hydraulic oil in the operating oil box must be lower than the oil pump hydraulic oil pressure.