When the driver is working, he often finds that the forklift can't always lift to the highest position, which makes the progress of the operation daunting. Later, the investigation was that the oil leaked below, which prevented it from rising to the highest point.
Oil leakage is the most common problem with multiple directional valves. When encountering such doubts, don't worry, analyze the factors:
1. Internal leakage
When the multi-way directional valve has an internal leakage, the working oil channel is connected to the oil return channel or the oil overflow channel, and the hydraulic oil directly flows back to the oil tank. Some problems, such as sliding down and leaning forward. The factors of internal leakage and the elimination methods are:
(1) The wear gap between the valve stem and the valve body is too large
There are three grooves on the lifting and tilting stems of the multi-way reversing valve. The groove and the oil passage cooperate to connect or block the oil passage and change the operation mode. The gap between the 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, which does not affect the operation. However, when the wear gap is too large, the hydraulic oil will form the oil in the working oil channel to communicate with the oil return channel or the oil overflow channel under the pressure of the operation pump, and actively return to the oil tank. The main reason is that due to the long-term use of the distribution valve or the unclean oil, the valve stem and the valve body are worn away immediately, which destroys the cooperative sealing surface and causes oil leakage.
If the valve stem is lightly worn during the correction, 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
Because the working oil passage, the return oil passage, and the oil overflow passage penetrate between the three single-piece valve bodies, the tightness between the valve bodies is very demanding. After installing an O-ring seal between the valve body and the valve body oil passage, Bolt the valve body 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 shows damage or the O-ring is aging or damaged during the installation, under the effect of oil pressure, internal leakage is easy to occur between the valve bodies. When repairing, if the valve body is damaged, it is necessary to grind, replace the O-ring, and tighten the bolts according to the order and torque requirements.
(3) The safety valve tension spring fails
The safety valve is used to adjust the operating pressure of the system to keep the pressure within a certain range to avoid damage to various components of the hydraulic system due to overload, the piston of the hydraulic cylinder to the extreme orientation, or other factors. The safety valve mainly uses the elastic force of the tension spring to press the steel ball against the valve position to reach 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 part of the 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 against the valve position under the effect of its own pretension 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 regular pressure of the system, forming an internal leakage and invalidating the system. When repairing, it is necessary to replace the tension spring, and then use the adjustment screw to adjust the tension spring pressure to a regular 14 Mpa. During the adjustment, load 7.5t of goods at the distance of 600mm from the load base. When the goods seem to start and stop, lock them with lock nuts. The pressure at this moment is the pressure to be adjusted.
(4) The multi-way reversing valve stem cannot be reset
The valve stem reset spring device is located at the lower end of the valve stem, whether the valve stem is in the upper position or in the lower position, the spring can be contracted. Orientation. If the valve stem cannot be reset and the groove communicates with the oil passage, an internal leakage will occur. One is that the spring of the valve stem is deformed or damaged, and the spring force of the spring is reduced, so that the valve stem cannot be returned to its original position. The spring must be replaced when repairing; It is difficult to reset the valve stem. When repairing, the inside of the multi-way directional valve must be cleaned to eliminate resistance.
(5) Worn cone valve
The poppet valve is used to avoid backflow of oil. If the cone valve is worn and the oil passage is not tightly closed, the hydraulic oil will return and the system will fail. When repairing, it should be ground or replaced. Eliminate backflow.
2. Valve body oil leakage
The sealing of the valve stem and the valve body is completed by an O-ring. If the sealing ring is aged or damaged, hydraulic oil will flow out of the valve stem under the effect of the system pressure, causing the valve body to leak oil. To eliminate this problem, just replace the O-ring seal.
