The manual forklift has been used for a while, but the hydraulic pressure suddenly stopped rising today, which made Mr. Xu, a customer of Hangzhou forklift, feel very depressed. The electric pallet truck
manufacturer will answer for you: if the hydraulic pressure of the manual forklift is not high, it must be a problem! Reason 1: When the internal leakage of the multi-way reversing valve occurs, the working oil passage is connected to the oil return passage or the oil overflow passage, and the hydraulic oil flows directly back to the oil tank. The operation cannot be completed, causing the lifting hydraulic cylinder to be weak or unable to lift. Failures such as the forks sliding down and the mast tilting forward. Causes of internal leakage and troubleshooting methods: 1. The wear gap between the valve stem and the valve body is too large. There are three grooves on the lifting and tilting valve stems of the directional valve. The groove and the oil passage can be connected or cut off. Oil circuit, change the way of working. The gap between the valve stem and the valve body of a good distribution valve is very small, and there is very little oil leakage, so the hydraulic cylinder drops or tilts very little, and does not affect the work. However, when the wear gap is too large, the hydraulic oil under the pressure generated by the working pump will cause the oil in the working oil passage to communicate with the oil return passage or the oil spill passage and automatically return to the oil tank. The main reason is that the long-term use of the distribution valve or the unclean oil has accelerated the wear of the valve stem and the valve body, damaged the mating sealing surface, and caused oil leakage. If the valve stem is lightly worn during repair, the valve stem can be chrome-plated and polished; if the valve stem is severely worn, it needs to be replaced. 2. Oil leakage between valve bodies. Since the working oil passage, oil return passage and oil spill passage run through the three single-piece valve bodies, the tightness requirements between the valve bodies are very high. After installing the O-ring seal in between, connect the valve body with bolts to achieve the purpose of sealing. If the tightening torque of the bolts is different, it may cause the valve body to warp. If the sealing ring fails, internal leakage occurs; if the valve body is damaged or the O-ring is aging or damaged during installation, internal leakage between the valve bodies is also prone to occur under the action of oil pressure. When repairing, if the valve body is damaged, it is necessary to grind, replace the O-ring seal, and tighten the bolts according to the sequence and torque requirements. 3. Safety valve spring failure The safety valve is used to adjust the working pressure of the system to keep the pressure within a certain range to prevent damage to the hydraulic system components due to overload, hydraulic cylinder piston reaching the limit position or other reasons. The safety valve is mainly pressed by the spring force to press the steel ball on the valve position to achieve the purpose of opening and closing. When the oil pressure output by the hydraulic pump exceeds the specified value, the pressure of the high-pressure oil overcomes part of the high-pressure oil and returns to the oil tank through the safety valve spillway. When the oil pressure reaches the specified value, the spring will press the steel ball against the valve position under the action of its own pre-tightening force, and the safety valve will be closed. If the safety valve spring fails, the hydraulic oil can force the steel ball to leave the valve position and flow into the spillway at a pressure lower than the system's specified pressure, causing internal leakage and causing system failure. The spring must be replaced when repairing, and then use the adjusting screw to adjust the spring pressure to the specified 14 Mpa. During adjustment, load 7.5t cargo according to the demand at 600mm from the load center. When the cargo appears to be lifted, use the lock nut to lock it. The pressure at this time is the pressure that needs to be adjusted. 4. The multi-way reversing valve stem cannot be reset. The valve stem return spring is installed at the lower end of the valve stem. The spring can be compressed regardless of whether the valve stem is in the upper position or in the lower position. When there is no external force, the valve stem is caused by the elastic force of the spring. Quickly restore to the original position. If the valve stem cannot be reset and the groove communicates with the oil passage, internal leakage will occur. One is that the return spring of the valve stem is deformed or damaged, and the spring force is reduced and the valve stem cannot be returned to its original position. The spring must be replaced when repairing; the other is that the valve body and the valve stem are not clean, resulting in greater resistance, which makes the valve stem It is difficult to reset, and the inside of the multi-way reversing valve must be cleaned during repair to eliminate resistance. 5. The cone valve wears the cone valve to prevent the oil from flowing back. If the poppet valve is worn and the oil passage is not tightly closed, the hydraulic oil will flow back and the system will fail. When repairing, it should be ground or replaced. Eliminate backflow. Reason two: the valve body leaks oil. The seal between the valve stem and the valve body is achieved by the O-ring seal. If the seal ring is aging or damaged, the hydraulic oil will flow out along the valve stem under the action of the system pressure, causing oil leakage in the valve body . It is only necessary to replace the O-ring to eliminate this fault. In fact, there are many other reasons why the hydraulic pressure of the forklift hand pallet truck
is not high. For details, please consult the customer service of the forklift headquarters in South China! If you usually pay attention to forklift maintenance, there must be few forklift problems!
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