Key points of pressure reducing valve
Key points of pressure reducing valve
1. Application of pressure reducing valve
The pressure reducing valve is mainly used to reduce, regulate and stabilize the pressure of an oil circuit in the hydraulic system.
(1) Form a pressure reducing circuit. Pressure reducing valve is widely used in clamping oil circuit, control oil circuit and lubricating oil circuit. Figure 62 is the schematic diagram of the pressure reducing valve used to clamp the oil circuit. In addition to supplying the pressure oil of the main oil circuit, it also provides the clamping cylinder with stable pressure oil lower than the pump oil pressure through the pressure reducing valve on the branch circuit. The clamping force is adjusted and controlled by the pressure reducing valve.
(2) Form a voltage stabilizing circuit. As shown in Figure 63, when the system pressure fluctuates greatly and it is necessary for hydraulic cylinder 2 to have a relatively stable output pressure, a pressure reducing valve is connected in series on the oil inlet circuit of hydraulic cylinder 2. When the pressure reducing valve is in working state, the pressure of hydraulic cylinder 2 can not be affected by the pressure fluctuation of overflow valve.
(3) Form a one-way pressure reducing circuit. When the forward and reverse directions of the actuator are different, the unidirectional pressure reducing circuit shown in Fig. 64 can be used. The one-way pressure reducing valve played by the double dotted line frame in the figure is a combined valve with the functions of one-way valve and pressure reducing valve.
(4) Form a multistage pressure reducing circuit. The remote control pressure reducing valve is externally connected to the remote control pressure reducing valve by using the remote control port of the pilot pressure reducing valve, which can form two-stage, three-stage and other pressure reducing circuits. For example, FIG. 65 shows a two-stage pressure reducing circuit, and the maximum pressure of hydraulic pump 6 is set by overflow valve 5. Whether the function of the remote pressure regulating valve 2 is controlled by the two position two-way directional valve 3 to obtain the secondary pressure in the circuit. However, during pressure regulation, the adjusted pressure of valve 2 and pilot pressure reducing valve 1 must meet P1 ＜ P2. The fixed restrictor 4 is used for pressure change when pressure shock occurs.
Multistage pressure reduction can also be realized by connecting several pressure reducing valves in parallel at the hydraulic source. For example, in the three-stage pressure reducing circuit shown in Figure 66, the maximum pressure of hydraulic pump 5 is set by overflow valve 4, and three pressure reducing valves 1, 2 and 3 with different pressure regulating values are connected at the hydraulic source to obtain three independent pressure reducing circuits.
(5) It forms a composite valve with the throttle valve. Using the pressure differential effect of the constant differential pressure reducing valve on the inlet and outlet pressure, it can be combined with the throttle valve to form a speed regulating valve, so as to realize the pressure difference compensation at both ends of the throttle and the stability of the output flow.
2. Precautions for use of pressure reducing valve
(1) The type of pressure reducing valve shall be selected according to the working conditions and specific requirements of the hydraulic system, and it shall be noted that the change trend of the opening and closing characteristics of the pressure reducing valve is opposite to that of the overflow valve (that is, the secondary pressure decreases when the flow through the pressure reducing valve increases). In addition, it should be noted that the oil discharge of the pressure reducing valve is more than that of other control valves, and oil always flows out of the pilot valve (sometimes more than 1lmin), which affects the selection of hydraulic pump capacity.
(2) Correctly use the connection mode of the pressure reducing valve, correctly select the connector (install the base plate or pipe joint), and pay attention to the sealing of the connection; Each oil port of the valve shall be correctly connected to the system, and the external oil drain port must be directly connected back to the oil tank.
(3) The rated pressure and flow (diameter) specification of the pressure reducing valve shall be reasonably selected according to the working pressure and flow of the system.
(4) The secondary pressure shall be determined and adjusted according to the purpose and function of the pressure reducing valve in the system. Attention must be paid to the relationship between the set pressure of the pressure reducing valve and the load pressure of the actuator. The set value of the secondary pressure of the main pressure reducing valve shall be higher than the set pressure of the remote pressure regulating valve. The adjustment range of the secondary pressure depends on the passing flow of the acting pressure regulating spring and valve. The minimum regulating pressure shall ensure that the difference between primary and secondary pressure is 0.3 ~ 1MPa.
(5) During pressure regulation, the pressure regulating mechanism shall be adjusted in the correct rotation direction, and the lock nut shall be fixed at the end of pressure regulation.
(6) If it is necessary to carry out multi-stage pressure reduction control on the system through the remote control port of the pilot pressure reducing valve, unscrew the screw plug of the remote control port and connect it to the control oil circuit; Otherwise, the remote control port shall be tightly sealed and blocked.
(7) The oil return circuit of the unloading overflow valve shall be directly connected to the oil tank to reduce the back pressure.
(8) In case of pressure regulating failure or high noise of the pressure reducing valve, the following methods can be used for diagnosis and troubleshooting. The disassembled and washed parts of the overflow valve group shall be installed correctly, and attention shall be paid to prevent secondary pollution.