The forklift multi-way valve, also known as the forklift multi-way reversing valve, is an important part of the diesel forklift truck hydraulic system. When a fault occurs, it will directly affect the normal operation of the forklift. If it is not eliminated in time, it will cause adverse consequences. The specific fault diagnosis and maintenance methods are shared as follows:
The forklift multi-way valve is leaking. The fault phenomenon is that when an internal leakage occurs, the working oil passage is connected with the oil return passage or the oil spill passage, and the hydraulic oil flows directly back to the oil tank, and the required action cannot be completed, resulting in inability or inability to lift, the fork sliding down and the door. The rack tilts forward by itself, etc.
The fault diagnosis is as follows:
1. The wear gap between the valve stem and the valve body of the forklift multi-way valve is too large to cause internal leakage. If the wear clearance of the forklift multi-way valve is too large, the oil in the working oil passage will communicate with the oil in the return oil passage or the oil overflow passage, and automatically return to the oil tank.
Troubleshooting method: The forklift multi-way valve distribution valve has been used for too long or the oil is not clean, which will accelerate the wear of the valve stem and the valve body, destroy the matching sealing surface and cause oil leakage. If the valve stem is severely worn, it needs to be replaced.
2. Oil leaks between valve bodies. Since the working oil passage, return oil passage and oil spill passage of the forklift multi-way valve run through between the four single-piece valve bodies, the sealing performance between the valve bodies is very high. Each valve body must be firmly connected with bolts, and an O-ring seal must be installed between the valve body and the oil passage of the valve body. If the tightening torque of each bolt is different, it may cause the valve body to warp and the seal ring to fail, resulting in internal leakage; if the accuracy of the valve body surface is damaged during installation, or the O-ring seal is aged or damaged, the gap between the valve bodies may be damaged. It is also prone to internal leakage.
Troubleshooting method: If the valve body of the forklift multi-way valve is damaged, it is necessary to grind, replace the O-ring seal, and tighten the bolts according to the sequence and torque requirements.
3. Internal leakage caused by the failure of the spring of the safety valve of the forklift multi-way valve. The safety valve of the forklift multi-way valve is used to adjust the working pressure of the system, keep the pressure within a certain range, and prevent the hydraulic cylinder piston from reaching the limit position due to overloading of the forklift, or various parts of the hydraulic system caused by other reasons. damage. The switch of the forklift safety valve is mainly determined by the elastic force of the spring. If the safety valve spring fails, the hydraulic oil can force the steel ball to leave the valve seat and flow into the oil spill under the pressure lower than the system specified, causing internal dripping and making System failure.
Troubleshooting method: The spring must be replaced, and then use the adjusting screw to adjust the spring pressure to the specified value (14MPa). When adjusting, load 7.5t (adjusted according to the requirement of 25% overload of the forklift) according to the requirement at a distance of 600mm between the load center Adjust the pressure to 14MPa.
4. The valve stem of the forklift multi-way valve cannot be reset and causes internal leakage. The valve stem return spring is installed at the lower end of the valve stem. No matter when the valve stem is working in the upper or lower position, the valve stem can compress the spring. Under no external force, the spring force can quickly restore the valve stem to its original position. If the valve stem cannot be reset, the groove of the valve stem is connected with the oil passage, and internal leakage will occur.
Troubleshooting method: due to the deformation or damage of the valve stem return spring of the forklift multi-way valve, the valve stem cannot be returned to its original position due to the reduction of the elastic force, and the spring can be replaced during maintenance; the valve body and the valve stem are not clean, resulting in greater resistance , it is difficult to reset the valve stem, just clean the multi-way valve.
5. The conical valve is worn and causes internal leakage. Diagnostic methods, check the cone valve, the cone valve is used to prevent the backflow of oil. If the cone valve is worn, the oil passage will not be closed tightly, the hydraulic oil will return, and the system function will fail.
Troubleshooting method: It should be ground or replaced to eliminate the phenomenon of adding flow.
2. The valve body of the forklift multi-way valve is leaking. The valve body of the forklift multi-way valve affects the operation of the system, making it difficult for the forklift to lift and tilt. Fault inspection, the O-ring between the valve stem and the valve body is aging or damaged, under the action of the system oil pressure, the oil will flow out along the valve stem, causing the valve body to leak oil.
Troubleshooting method: replace the O-ring of the forklift multi-way valve.