Reversing valve for pneumatic system failure

The faults of the reversing valve include: the valve cannot be reversed or the reversing action is slow, the gas leaks, the solenoid pilot valve has faults, etc.

(1) The reversing valve can not be reversed or the reversing action is slow, which is generally caused by poor lubrication, spring stuck or damaged, oil or impurities stuck in the sliding part, etc. In this regard, it is necessary to check whether the operation of the oil mist eliminator is normal and whether the viscosity of the lubricating oil is appropriate. If necessary, replace the lubricating oil, clean the sliding part of the reversing valve, or replace the spring and reversing valve.

(2) After being used for a long time, the reversing valve is prone to wear of valve core seal ring and damage of valve stem and valve seat, resulting in gas leakage in the valve, slow action of the valve or failure of normal reversing. At this time, the sealing ring, stem and valve seat should be replaced, or the change-over valve should be replaced.

(3) If the inlet and exhaust holes of the solenoid pilot valve are blocked by sludge and other sundries, the sealing is not tight, the movable iron core is blocked, and the circuit is faulty, etc., the reversing valve can not be reversed normally. For the first three cases, clean the sludge and impurities on the pilot valve and movable iron core. The circuit fault is generally divided into control circuit fault and electromagnetic coil fault. Before checking the circuit fault, turn the manual knob of the reversing valve for several times to see whether the reversing valve can change direction normally under the rated air pressure. If it can change direction normally, the circuit is faulty. During the inspection, the voltage of the solenoid coil can be measured by the instrument to see if the rated voltage is reached. If the voltage is too low, further check the power supply in the control circuit and the associated travel switch circuit. If the change-over valve cannot change direction normally under rated voltage, check whether the connector (plug) of the solenoid coil is loose or the contact is not solid. The method is to unplug the plug and measure the resistance value of the coil (generally between several hundred ohms and several thousand ohms). If the resistance value is too large or too small, it means that the solenoid is damaged and should be replaced.