Precautions for use of Manifold Block hydraulic control check valve
In front of the introduction of the “application of the hydraulic control check valve” and “detailed explanation of the working principle of the hydraulic control check valve”, next we introduce the precautions for the use of the hydraulic control check valve. Field practice has proved that the hydraulic control check valve is prone to problems in the use of the process, the following are precautions.
(1) Must ensure that the hydraulic control check valve has enough control pressure, absolutely do not allow the control pressure loss. Attention should be paid to whether the control pressure meets the requirements of reverse opening. If the control of the hydraulic check valve leads to the autonomous system, it is necessary to analyze the influence of the change of the pressure of the main system on the control of the oil pressure, so as to avoid the misoperation of the hydraulic check valve.
(2) According to the position of the hydraulically controlled check valve in the hydraulic system or the liquid flow resistance (back pressure) after the reverse oil outlet cavity, the structure (simple or compound) and the drainage mode (internal leakage or leakage) of the hydraulically controlled check valve are reasonably selected. For the internal leakage type hydraulic control check valve, when the reverse oil outlet pressure exceeds a certain value, the hydraulic control part will lose its control function, so the internal leakage type hydraulic control check valve is generally used for the reverse oil outlet chamber without back pressure or small back pressure occasions; And the leakage type hydraulic control check valve can be used for reverse oil outlet chamber back pressure is high occasions, in order to reduce the minimum control pressure, save control power. When the reverse oil inlet chamber pressure is higher, the hydraulic control one-way valve with unloading spool is used, and the control oil pressure is reduced to a fraction of the original to one tenth of the original. If a leaky hydraulically controlled check valve is selected, care should be taken to connect the leaky outlet to the tank separately. In addition, the ratio of the rodless cavity and the rod cavity of the hydraulic cylinder can not be too large, otherwise it will cause the hydraulic control one-way valve can not be opened. Hydraulic cylinder on the ratio of the inferior vena effect area is greater than the control of the hydraulic controlled check valve cavity and one-way valve core effect on the ratio of the area, if the inferior vena role of hydraulic cylinder area ratio of 4:1, and the role of hydraulic controlled check valve to control the piston area and the upper check valve core area than the average of (2.6 ~ 3.5) : 1, the hydraulic controlled check valve will never open. At this time, the hydraulic cylinder will be like a supercharger, the lower cavity of the hydraulic cylinder is seriously pressurized, the pressure is several times of the phase working pressure, resulting in an accident. Therefore, the ratio of the rod cavity acting area of the general industrial hydraulic cylinder to the rodless cavity acting area is usually 3:7 ~ 9:10.
(3) In the hydraulic system with two hydraulic control check valves or a double hydraulic control check valve to realize the hydraulic cylinder locking, attention should be paid to the selection of Y-type or H-type middle function of the reversing valve, to ensure that the pressure of the control port of the hydraulic control check valve can be released immediately, the check valve is closed immediately, and the piston stops. If the o-type or M-type function is used, when the reversing valve is changed to the middle position, the control chamber pressure oil of the hydraulic control check valve is closed, and the control oil circuit of the hydraulic control check valve still has pressure, so that the hydraulic control check valve is still in the open state. But cannot make it close immediately, the piston also cannot stop immediately, produce the phenomenon of movement. The hydraulic control check valve can not be closed until the control chamber is relieved by the internal leakage of the reversing valve, affecting its locking accuracy. But choose H the median function should be very careful, because when big traffic flows through the oil drain pump, if the discharge of oil pipeline slender or local jam or other reasons caused by the local friction resistance (such as with a low pressure oil filter or pipe joint, etc.), may make the control piston control of high pressure, the hydraulic controlled check valve cannot be closed and result in false operation of hydraulic cylinder. This is not the case with the y-type median function.
(4) the flow rate at work should be matched with the rated flow rate of the valve.
(5) When installing, do not confuse the main oil port, the control oil port and the oil discharge port and recognize the positive and reverse direction of the main oil port, so as not to affect the normal work of the hydraulic system.
(6) the hydraulic control one-way valve with unloading spool is only applicable to the reverse oil flow is a closed chamber, such as a chamber of the hydraulic cylinder or accumulator, etc. The pressure in this closed chamber is relieved by the release of only a small amount of flow. The reverse flow is generally not connected to a continuous hydraulic source. This is because the flow area is very small and the oil velocity is very high when the unloading valve core is opened, and the pressure loss is very large. In addition, at this time, the hydraulic source keeps supplying oil, which will lead to the reverse pressure cannot drop down, and it needs a lot of hydraulic control pressure to make the main valve core of the hydraulic control one-way valve open. If the oil pressure of the control pipeline is small at this time, there will be a failure to open the hydraulic control check valve.
(7) system can hydraulic controlled check valve is used to balance loop alone, otherwise the piston down, because of the moving parts of driving the piston down the weight faster than the speed of are set in the input, the hydraulic cylinder cavity vacuum, on the control of the hydraulic controlled check valve oil pressure is too low, check valve closed, the piston movement to stop, until the cavity pressure on the hydraulic cylinder to build up, The check valve is opened again and the piston begins to drop again. This repetition produces crawling or shaking phenomenon, vibration and noise. A one-way throttle valve is connected in series between the rodless cavity oil port and the hydraulic control one-way valve, and the system forms the oil return throttle speed control circuit. This will not be due to the weight of the piston and fall too fast, and ensure that there is enough pressure in the oil, so that the hydraulic control one-way valve to keep open, the piston smoothly drop. The reversing valve should use H or Y type function, if the M type function (or O type function), because the liquid control check valve control oil can not be timely pressure relief, the loop is locked, so that the working mechanism is not allowed to stop, produce channeling phenomenon.