When the driver is working, he often finds that the lifting fork of the forklift cannot be raised to the highest position, resulting in poor progress of the operation. Later, it was found that there was an oil leak below, which prevented it from rising to the top.
Oil leakage is the most common problem of multi-channel directional valve. In case of such a question, don't worry, but analyze the following factors:
1. Internal leakage
In case of internal leakage of the multi-way directional valve, the operating oil passage is connected with the oil return passage or the oil overflow passage, and the hydraulic oil directly flows back to the oil tank. The operation cannot be completed, resulting in problems such as weak lifting or unable lifting of the lifting hydraulic cylinder, automatic sliding of the fork and automatic forward tilting of the gantry. Internal leakage factors and elimination methods:
(1) Excessive wear clearance between valve rod and valve body
There are three grooves on the lifting and tilting valve stems of the multi-channel directional valve. The groove and the oil passage cooperate to connect or block the oil circuit and change the operation mode. The clearance between the valve rod and the valve body of a good distribution valve is very small, and there is very little oil leakage, so the drop or inclination of the hydraulic cylinder is very small, which will not affect the operation. However, when the wear clearance is too large, the hydraulic oil will form a connection between the oil in the operation oil passage and the oil return passage or overflow passage under the pressure of the operation pump, and return to the oil tank actively. The main cause is that the valve stem and valve body are worn due to long-term use of the distribution valve or unclean oil, which destroys the cooperative sealing surface and causes oil leakage. If the valve rod is slightly worn during correction, the valve rod can be chrome plated and polished; If the valve stem is severely worn, it needs to be replaced.
(2) Oil leakage between valve bodies
Because the operating oil passage, oil return passage and oil overflow passage run through the three single-piece valve bodies, the sealing between valve bodies is very important. After installing O-ring between valve body and oil passage of valve body, the valve body is bolted to achieve the purpose of sealing.
If the consolidation torque of bolts is different, the valve body may be warped. The sealing ring fails and internal leakage occurs; If the valve body is damaged or the O-ring is aged or damaged during the installation, internal leakage is also easy to occur between the valve bodies under the oil pressure effect. During repair, if the valve body is damaged, grind it, replace the O-ring, and tighten the bolts according to the sequence and torque requirements.
(3) Safety valve tension spring failure
The safety valve is used to regulate the operating pressure of the system to keep the pressure within a certain range, so as to avoid the damage of various parts of the hydraulic system caused by overload, the piston of the hydraulic cylinder reaching the limit position or other factors. The safety valve mainly presses the steel ball on the valve position by the tension spring to achieve the intention of opening and closing. When the oil pressure output by the hydraulic pump exceeds the regular value, the pressure of the high-pressure oil overcomes the pressure of some high-pressure oil and returns to the oil tank through the overflow passage of the safety valve. When the oil pressure reaches the regular value, the tension spring presses the steel ball on the valve position under the effect of its own pre tightening force, and the safety valve is closed.
If the tension spring of the safety valve fails, the hydraulic oil can force the steel ball to leave the valve position and flow into the oil overflow channel under the pressure lower than the system rule, forming internal leakage and invalidating the system. It is necessary to replace the tension spring during repair, and then use the adjusting screw to adjust the tension spring pressure to the regular 14 MPa. During adjustment, 7.5t goods shall be loaded according to the requirements 600mm away from the load base. When the goods seem to start or not, they shall be locked with lock nuts. The pressure at this moment is the pressure to be adjusted.
(4) Multi way reversing valve rod cannot be reset
The valve rod reset tension spring device is at the lower end of the valve rod. The tension spring can be compressed when the valve rod is at the upper or lower position. When there is no external force effect, the spring force of the tension spring can quickly recover the valve rod to its original position. If the valve rod cannot be reset and the groove is connected with the oil passage, internal leakage will occur. First, because the reset tension spring of the valve rod is deformed or damaged, and the tension spring fails to return the valve rod to its original position due to the decrease of the tension spring, the tension spring must be replaced during repair; Second, the valve body and valve rod are not clean, resulting in large resistance, making it difficult to reset the valve rod. During repair, the interior of the multi-channel directional valve must be cleaned to eliminate resistance.
(5) Wear of cone valve
The cone valve is used to avoid oil backflow. If the cone 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 shall be ground or replaced. Eliminate backflow.
2. Oil leakage of valve body
The sealing between the valve rod and the valve body is completed by the O-ring. If the sealing ring is aged or damaged, the hydraulic oil will flow out along the valve rod under the effect of system pressure, resulting in oil leakage of the valve body. To eliminate this problem, only replace the O-ring.
