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Working principle of hydraulic control valve
- Apr 17, 2018 -

Used to control fluid pressure, flow and direction in hydraulic drives, one of the components that control pressure is called a pressure control valve. The control flow is called a flow control valve. The control of the opening, closing, and flow direction is called a directional control valve.

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Working principle: According to the working principle and structure, the valve is divided into two types: direct-acting type and pilot type; according to the pressure control mode, the sequence valve has internal control and external control. A check valve is installed in the sequence valve, and a compound valve that can pass the reverse flow is called a one-way sequence valve. In general, this type of valve is used quite often.    
Function and Application: The basic function of the sequence valve is to control the sequence of multiple actuators. According to their different functions, they are called sequence valve, back pressure valve, unloading valve and balancing valve. The performance of the sequence valve is basically the same as that of the relief valve, but due to the different functions, there are special requirements for the sequence valve:
  

(1) In order to enable the actuators to accurately perform sequential operations, the pressure regulating accuracy of the sequence valve is required to be high and the deviation is small;

(2) In order to ensure the accuracy of the sequential operation, the amount of internal leakage when the valve is closed is required;

(3) For one-way sequence valves, the reverse pressure loss and forward pressure loss should be small.

The main functions of the sequence valve are:

(1) Control the sequential operation of multiple components;

(2) For pressure-maintaining circuits;

(3) To prevent the free fall of the cylinder piston due to its own weight and to use it as a balancing valve;

(4) Use an externally controlled sequence valve as an unloading valve to unload the pump;

(5) Use internal control sequence valve as back pressure valve.

Selection of sequence valve: The sequence valve can realize different loop functions such as overflow valve, sequence valve and balance valve according to different assembly structure.

If the opening and closing characteristics of the sequence valve are too bad, the primary pressure is too high when the flow rate is large, and the loop efficiency is reduced. The opening and closing characteristics are hysteresis, and the opening pressure is lower than the closing pressure. Attention should be paid when the load flow rate changes. Open the valve with low pressure, and then leak before the pressure is lower than the set pressure, causing the actuator to malfunction. When the flow through the valve is much smaller than the rated flow, vibration or other instability occurs. At this point, take measures on the re-loop.