What Issues Should Be Noted When Customizing The Hydraulic System's Control Valves with Hydraulic Control Function?

What issues should be noted when customizing the hydraulic system's control valves with hydraulic control function?

①The custom hydraulic system must ensure that the hydraulic control valve has sufficient control pressure and that the control pressure does not drop. Attention should be paid to whether the control pressure meets the requirements for reverse opening. If the control of the hydraulic control valve is an independent system, then the influence of the pressure changes in the main system on the control oil circuit pressure should be analyzed to avoid incorrect operation of the hydraulic control valve.

② Based on the position of the electro-hydraulic directional valve in the customized hydraulic system or the resistance (back pressure) of the liquid flow after the reverse oil outlet, a reasonable choice should be made for the structure (simple or complex) and the oil discharge method (internal or external) of the electro-hydraulic directional valve. For the internal discharge type electro-hydraulic directional valve, when the pressure at the reverse oil outlet exceeds a certain value, the control part will lose its control effect. Therefore, the internal discharge type electro-hydraulic directional valve is generally used in situations where there is no back pressure or the back pressure is relatively small in the reverse oil outlet; while the external discharge type electro-hydraulic directional valve can be used in situations where the back pressure in the reverse oil outlet is relatively high, in order to reduce the small control pressure and save control power.

If the custom hydraulic system adopts the internal leakage type, the plunger cylinder will intermittently descend, causing vibration and noise. When the pressure in the reverse oil inlet chamber is high, a hydraulic control directional valve with a relief valve core should be used. At this time, the control oil pressure will be reduced to a fraction or several fractions of the original. If an external leakage type hydraulic control directional valve is selected, it is necessary to connect the external leakage port separately to the oil tank. Additionally, the ratio of the non-rocker chamber to the rocker chamber of the hydraulic cylinder should not be too large, otherwise the hydraulic control directional valve may fail to open.

In a hydraulic system where the hydraulic cylinder is locked using two hydraulic control check valves or a dual check valve with two-way hydraulic control, it is important to select a directional valve with Y-type or H-type neutral function. This ensures that the pressure at the control port of the hydraulic control check valve can be released immediately when the neutral position is reached, the check valve closes immediately, and the piston stops.

If the O-type or M-type function is adopted, when the directional valve is in the neutral position, since the hydraulic oil in the control chamber of the hydraulic control valve is blocked, the control oil path of the hydraulic control valve still has pressure, keeping it in an open state and preventing it from closing immediately. As a result, the piston cannot stop immediately, causing a jittering phenomenon. Only when the internal leakage of the directional valve causes the control chamber to be depressurized, can the hydraulic control valve close, which affects its locking accuracy. When using the H-type neutral function, it should be done very carefully because when the high-flow hydraulic pump passes through the oil discharge pipe, if the oil discharge pipe is long and slender or there is local blockage, or other reasons cause local friction resistance (such as the presence of a low-pressure filter, or many pipe joints, etc.), it may cause the control piston to receive a higher control pressure, resulting in the hydraulic control valve being unable to close and causing the hydraulic cylinder to malfunction. The Y-type neutral function will not have this situation.

④ The flow rate during operation should match the rated flow rate of the valve.

⑤ During installation, make sure not to confuse the main oil port, the control oil port and the drain oil port. Also, clearly identify the forward and reverse directions of the main oil port to avoid any disruption to the normal operation of the hydraulic system.