A hydraulic valve is an automatic component operated by pressure oil. It is controlled by the pressure oil of a pressure regulating valve. It is usually used in combination with an electromagnetic pressure regulating valve and can be used to remotely control the on/off of the oil, gas, and water pipeline systems of a hydropower station. It is often used for clamping, controlling, lubricating, and other oil circuits. There are direct-acting and pilot-operated types, and the pilot type is mostly used.
Direction control
According to the purpose, it is divided into a one-way valve and a reversing valve. A one-way valve: only allows the fluid to be connected in one direction in the pipeline, and the reverse direction is cut off. Reversing valve: changes the on/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-way, three-way, etc.; according to the number of channels controlled, it is divided into two-way, three-way, four-way, five-way, etc.; according to the valve core drive mode, it is divided into manual, motorized, electric, hydraulic, etc. In the late 1960s, an electro-hydraulic proportional control valve was developed based on the above-mentioned hydraulic control valves. Its output (pressure, flow) can change continuously with the input electrical signal. Electro-hydraulic proportional control valves are divided into electro-hydraulic proportional pressure control valves, electro-hydraulic proportional flow control valves and electro-hydraulic proportional directional control valves according to their functions.
Pressure control
According to their uses, they are divided into overflow valves, pressure reducing valves and sequence valves. (1) Overflow valve: It can control the hydraulic system to maintain a constant state when the set pressure is reached. The overflow valve used for overload protection is called a safety valve. When a system failure occurs 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 fixed value pressure reducing valves (the output pressure is a constant value), fixed differential pressure reducing valves (the input and output pressure difference is a fixed value) and fixed ratio pressure reducing valves (the input and output pressures maintain a certain ratio). (3) Sequence valve: It can make one actuator (such as a hydraulic cylinder, hydraulic motor, etc.) actuate, and then make other actuators actuate in sequence.
Flow control
The flow rate is adjusted by adjusting the throttle area between the valve core and the valve body and the local resistance it produces, thereby controlling the movement speed of the actuator. Flow control valves are divided into five categories according to their uses. (1) Throttle valve: After adjusting the throttle area, the movement speed of the actuator with little load pressure change and low movement uniformity requirements can be basically kept stable. (2) Speed control valve: When the load pressure changes, the inlet and outlet pressure difference of the throttle valve can be kept constant. In this way, after the throttle area is adjusted, no matter how the load pressure changes, the speed control valve can keep the flow through the throttle valve unchanged, thereby stabilizing the movement speed of the actuator. (3) Diverter valve: Regardless of the load size, the equal flow diverter valve or synchronous valve can make two actuators with the same oil source get equal flow; the proportional diverter valve can get proportional flow. (4) Combining valve: The function is opposite to that of the diverter valve, so that the flow flowing into the combining valve is proportionally distributed. (5) Diverter and combining valve: It has both the functions of a diverter valve and a combining valve.
