How to use superimposed hydraulically controlled check valve

The use of superimposed hydraulically controlled check valves requires attention to controlling pressure, choosing a suitable structure and oil drainage method, and reasonably matching the reversing valve. The specific details are as follows:

Ensure control of pressure

Control pressure requirements: The superimposed hydraulically controlled check valve must be guaranteed to have sufficient control pressure and the control pressure is not allowed to lose pressure. Pay special attention to whether the control pressure meets the requirements of reverse opening. If the control of the hydraulically controlled check valve is directed from the main system, the impact of the change in the main system pressure on the control oil circuit pressure should be analyzed to avoid malfunction of the hydraulically controlled check valve.

Reasonable selection of structure and oil drainage method

Select according to the fluid flow resistance (back pressure) after the reverse oil outlet chamber: For the internal leakage superimposed hydraulic control check valve, when the reverse oil outlet pressure exceeds a certain value, the hydraulic control part will lose its control effect. Therefore, the internal leakage hydraulic control check valve is generally used in situations where there is no back pressure or a small back pressure in the reverse oil outlet chamber; while the external leakage hydraulic control check valve can be used in situations where the reverse oil outlet chamber has a higher back pressure in order to reduce the minimum control pressure and save control power. If the system adopts an internal disassembly, the plunger cylinder will drop intermittently to cause vibration and noise.

Reasonably match the reversing valve

Ensure that the hydraulic lock pressure can be released immediately when the hydraulic cylinder is in the middle: When using a superimposed hydraulic controlled check valve to achieve the function of locking the hydraulic cylinder, pay attention to choosing a suitable reversing valve (such as H or Y) to ensure that the hydraulic lock pressure can be released immediately when the hydraulic lock pressure is in the middle. Close the check valve immediately and stop the piston movement. If an M-type or O-type reversing valve is used, the reversing valve will close the pressure oil in the control chamber under the action of hydraulic lock, causing the hydraulic lock to remain pressure, and the check valve cannot be closed in time, and the piston will continue to move, resulting in a squirting phenomenon.

Precautions for hydraulic system design

Analyze the relationship between control pressure and main system pressure: If the superimposed hydraulic control check valve is the main system control, the relationship between control pressure and main system pressure should be analyzed to avoid hydraulic locking malfunction.

Set up safety valve: In the cylinder closed circuit, if the external load changes sharply and greatly, the pressure of oil in the blocked circuit will rise abnormally, which will be risky of damaging the pipeline system and equipment. For systems with this possibility, a safety valve with small capacity and small internal leakage is required in the cylinder two-chamber pipeline.

Considering the impact of delay time: In the system configuration of some hydraulic machinery, the oil cylinder installation position is relatively high, and when the reversing valve is in the intermediate channel position, the second chamber pipeline of the oil cylinder and the return chamber are connected, and all the oil in the pipeline returns to the oil tank. When switching the reversing valve to make the cylinder work, pressure must be established before opening the pilot check valve. In systems where cylinder operation switching takes time, the impact of this delay time needs to be considered. In addition, since there is no oil in the pipeline, it is possible to enter air. If switched to refueling, it will also cause impact and vibration of the system pipeline. Therefore, please set a check valve with appropriate valve opening pressure in the return oil circuit to keep the pipeline filled with oil.