The specifications and models of various hydraulic control valves can be based on the maximum pressure of the system and the actual flow through the valve and take into account the control characteristics of the valve, the stability and the size of the oil port, the size of the shape, the way of installation and connection, the mode of manipulation, etc., from the sample or catalogue of the product. The selection of various hydraulic control valves in the hydraulic system of Jinze hydraulic production is as follows:

1. Actual flow of hydraulic valves

The actual flow of the hydraulic valve is related to the series and parallel of the oil road: the flow of the series is equal to each other; at the same time the flow of the parallel oil road is equal to the sum of the oil flow. In addition, for the system using a single piston rod hydraulic cylinder, it is necessary to pay attention to the difference in the flow rate of the piston when the piston is extended and within the internal shrinkage: the ratio of the flow rate to the oil in the rod cavity is equal when the inner shrinkage is reduced and the ratio of the two cavity area is equal.

2, rated pressure and rated flow of hydraulic valves

The rated pressure and rated flow of each hydraulic control valve should be close to the pressure and flow rate. For systems with higher reliability requirements, the rated pressure of valves should be higher than that of their valves. If the rated pressure and rated flow is less than the use of pressure and flow, it is easy to cause hydraulic clamping and hydraulic power and have a bad effect on the working quality of the valve; for the sequence valve and pressure relief valve in the system, the flow rate should not be far less than the rated flow rate, otherwise vibration or other instability will occur easily. For flow valves, the minimum steady flow should be noted.

3, the installation and connection mode of the hydraulic valve

Because the installation and connection mode of the valve has a decisive influence on the structure type of the later designed hydraulic device, the hydraulic control valve should be counted in the way of integrating the hydraulic control device. For example, the plate type connecting hydraulic valve can be installed on the oil road board or the oil road block. On the one hand, it is convenient for the system integration and the rationalization of the hydraulic device design. On the other hand, the replacement of the hydraulic valve does not need to disassemble the tubing and the installation and maintenance is more convenient. If the Superposition valve is used, the series of superposition valves need to be studied according to the pressure and flow. Type selection, and so on.

4. Selection of directional control valve

For simple unidirectional valves with simple structure, we should pay attention to the rational selection of the opening pressure: lower opening pressure can reduce the resistance loss of the liquid flow through the one-way valve; however, for the one-way valve used as a back pressure valve, the opening pressure is higher to ensure enough back pressure. For the liquid controlled one-way valve, in addition to the relevant notes in the reversing valve, in order to avoid the abnormal vibration and noise of the system, we should also pay attention to the reasonable selection of its pressure relief mode: when the outlet of the liquid controlled one-way valve has back pressure, it is appropriate to choose the outlet type, and the other conditions are optional.

For the commutation valve, we should pay attention to the reasonable selection of the control type from the manual, mechanical, electromagnetic, electrohydraulic and other types from the requirements of the system to meet the requirements of the automation and operation cycle. Correctly select the middle position function of the spool valve and grasp its transition quasi state function. For the system using hydraulic lock (double liquid controlled one-way valve) locking hydraulic actuator, "H" and "Y" shape function valve type reversing valve should be selected to make the middle of the valve position, the control chamber of two hydraulic control unidirectional valves are all connected to the oil tank, so as to ensure the reliable reset of the hydraulic control one-way valve and the good locking state of the hydraulic actuator. The middle function of the selected valve type reversing valve in the transition position should not be completely blocked by the oil path, otherwise it will lead to the instantaneous pressure of the system and cause the accident of the pipe blasting.

5. Selection of pressure control valve

When the system needs to be unloaded, attention should be paid to the difference between unloading relief valve and external control sequence valve. The unloading overflow valve is mainly used in the hydraulic circuit equipped with accumulator. If the general external control sequence valve is selected, the pressure of the hydraulic pump will be high and low when the outlet pressure of the hydraulic pump is used, and the system work is abnormal. The leakage of the pilot pressure relief valve is larger than that of the other hydraulic valves, and the leakage always exists as long as the valve is in the working state. This point should be fully paid attention to when selecting the capacity of the hydraulic pump. At the same time, we should also pay attention to the minimum regulating pressure of the pressure reducing valve, so as to ensure that the pressure difference between the inlet and outlet of the pressure reducing valve is 0.3-1Mpa.

6. Selection of flow control valve

The minimum steady flow of throttle valve and speed regulating valve should meet the minimum working speed requirement of actuators. In order to ensure the control accuracy of the speed control valve, a certain differential pressure should be guaranteed. A temperature compensated speed control valve should be selected for larger temperature changes.

7. Effect of electro-hydraulic control valve

The electro-hydraulic control valve has electro hydraulic servo valve, proportional valve and digital valve, etc., and is used for controlling occasions with high performance requirements. It can be selected according to the control content, control accuracy, response characteristics and stability of the actuator.