Introduction And Classification Of Hydraulic Valves

Hydraulic valve is an automatic component operated by pressure oil. It is controlled by pressure oil of pressure distribution valve. It is usually used in combination with electromagnetic pressure sensor distribution valve and can be used to remotely control the on-off of oil, gas and water pipeline systems in hydro power stations. Commonly used for clamping, control, lubrication and other oil circuits. There are direct-acting type and pilot type, and the pilot type is mostly used. Components used in hydraulic transmission to control the pressure, flow and direction of liquids. The one that controls the pressure is called the pressure control valve, the one that controls the flow is called the flow control valve, and the one that controls the opening, closing and flow direction is called the directional control valve.

Hydraulic valve classification

Classification by control method: manual, electronic control, hydraulic control.

Classified by function: flow valve (throttle valve, speed regulating valve, diverting and collecting valve), pressure valve (overflow valve, pressure reducing valve, sequence valve, unloading valve), directional valve (electromagnetic reversing valve, manual change valve, check valve, hydraulic control check valve).

According to the installation method: plate valve, pipe valve, stack valve, threaded cartridge valve, cover valve.

According to the operation mode: manual valve, motorized valve, electric valve, hydraulic valve, electro-hydraulic valve, etc.

1. Direction control

According to the purpose, it is divided into one-way valve and reversing valve. One-way valve: Only allow the fluid to be connected in one direction in the pipeline, and the reverse is cut off. Reversing valve: Change the on and off relationship between different pipelines. According to the number of working positions of the valve core in the valve body, it is divided into two, three, etc.; according to the number of controlled channels, it is divided into two-way, three-way, four-way, five-way, etc.; according to the driving mode of the valve core, it is divided into manual, motorized, electric , hydraulic etc. In the late 1960s, an electro-hydraulic proportional control valve was developed on the basis of the above-mentioned hydraulic control valves. Its output (pressure, flow) can change continuously with the input electrical signal. Electro-hydraulic proportional control valve is divided into electro-hydraulic proportional pressure control valve, electro-hydraulic proportional flow control valve and electro-hydraulic proportional directional control valve according to different functions.

2. Pressure control

According to the purpose, it is divided into relief valve, pressure reducing valve and sequence valve.

(1) Relief valve: It can control the hydraulic system to maintain a constant state when the set pressure is reached. The relief valve used for overload protection is called a safety valve. When the system fails and the pressure rises to a limit value that may cause damage, the valve port will open and overflow to ensure the safety of the system.

(2) Pressure reducing valve: It can control the branch circuit to obtain a stable pressure lower than the main circuit oil pressure. According to the different pressure functions it controls, the pressure reducing valve can be divided into a fixed value pressure reducing valve (the output pressure is a constant value), a fixed difference pressure reducing valve (the difference between the input and output pressure is a fixed value) and a fixed ratio pressure reducing valve. (Maintain a certain ratio between input and output pressure).

(3) Sequence valve: After making one actuator (such as hydraulic cylinder, hydraulic motor, etc.) act, other actuators act in sequence.

3. Flow Control

The flow is adjusted by the throttle area between the regulating valve core and the valve body and the local resistance it produces, thereby controlling the movement speed of the actuator. There are 5 types of flow control valves according to their application.

(1) Throttle valve: After adjusting the area of ​​the orifice, the movement speed of the actuator with little change in load pressure and low requirement for uniformity of movement can be basically kept stable.

(2) Speed regulating valve: when the load pressure changes, the pressure difference between the inlet and outlet of the throttle valve can be kept as a constant value. In this way, after the orifice area is adjusted, no matter how the load pressure changes, the speed regulating valve can keep the flow rate through the throttle valve unchanged, so that the movement speed of the actuator is stable.

(3) Diverter valve: Regardless of the size of the load, the one that can enable the two actuators of the same oil pump source to obtain the same flow is an equal-amount diverter valve or a synchronous valve; the one that obtains a proportional flow distribution is a proportional diverter valve.

(4) Collector valve: The function is opposite to that of the diverter valve, so that the flow into the collector valve is proportionally distributed.

(5) Diverting and collecting valve: It has both functions of diverting valve and collecting valve.