Technical requirements for throttling control valves of single column hydraulic press

If the valve core is radially stuck, all parts should be disassembled, cleaned, dirt removed, and all faults causing the jamming eliminated. When the one-way throttle valve is connected reversely, the flow rate through the valve will not change after adjusting the handwheel, so it only functions as a one-way valve. The unstable flow of throttle valves and one-way throttle valves mainly occurs at the minimum stable flow rate. The main reasons are loosening of the locking device, partial blockage of the throttle port, increase in oil temperature, and changes in load pressure. Due to mechanical vibration, the adjusted throttle locking device will loosen, and the flow area of the throttle will change, which will cause changes in flow rate. Dirt in the oil accumulates and adheres to the orifice, reducing the flow area and causing a decrease in flow rate. Sometimes after the pressure oil washes away the dirt, the orifice returns to its original flow area and the flow rate increases to its original value. Changes in oil temperature cause changes in oil viscosity, and the flow rate at the flow path throttle valve port becomes unstable. When the flow rate entering the actuator changes, the speed at which the actuator pushes the load becomes unstable. Therefore, efforts should be made to prevent flow instability. The main measures include: preventing the choke port from being clogged, strengthening oil temperature control, and preventing the choke port locking device from loosening, etc.
② In hydraulic systems where the flow adjustment of the speed control valve fails or is unstable, the speed control valve is generally used as the speed control valve in hydraulic systems where the external load changes greatly, because the speed control valve can stabilize the speed of the actuator under the condition of changes in the external load. . If speed instability occurs, it is usually caused by a malfunction of the speed regulator. There are two aspects to the speed instability condition. First, when adjusting the throttle handwheel of the speed control valve, the outlet flow does not change, which is the so-called flow adjustment failure. The main reason for this phenomenon is that the valve core is stuck or the throttling part fails. If the pressure reducing valve spool or throttle valve spool is stuck in the closed position, there will be no flow at the oil outlet; if it is stuck in the fully open position or the throttle valve setting position, adjust the throttle valve handwheel to allow the oil to flow. Oral flow also does not change. Another situation is that after the throttle of the speed control valve is adjusted and locked, the oil outlet flow rate becomes unstable. This situation is more likely to occur at minimum stable flow. This is caused by the loose locking device, partial blockage of the throttle port, increased oil temperature, and low hydraulic pressure difference between the inlet and outlet oil.
When the oil flow of the QF type speed control valve is reversed, the pressure reducing valve does not have a pressure compensation effect on the throttle valve, so that the speed control valve only functions as a throttle valve. When the oil pressure difference through the valve changes, the Traffic also changes. Therefore, reverse connection should be avoided when using this kind of valve.