Created on:2022-03-29 10:31

Fault analysis and troubleshooting of multi way directional valve

Fault analysis and troubleshooting of multi way directional valve

Multi way directional valve is a combination valve of centralized manual control directional valve. Multi way directional valve is widely used in hoisting, transportation, mining, metallurgy, light industry, agriculture and other machinery to centrally control multiple actuators. The combination modes of multi-channel directional valve include parallel type, series type and sequential single acting type. The symbols are shown in Figure 31.

Multi way directional valve can be divided into integral type and multi piece type according to the structural form of valve body. The integral multi-way directional valve is a combination of directional valves and some auxiliary valves. Figure 32 shows the integral multi-way directional valve of a construction machinery. Multi piece multi-way directional valve is to make one piece of each directional valve and then connect it with bolts. Figure 33 shows the typical structure of ZFS multi-way directional valve, which is equipped with safety overflow valve and one-way valve group.

31

32.33

1. The action of slide valve is inflexible and the control force is large

(1) Cause analysis.

1) The return spring or bounce spring is damaged.

2) The circlip for the shaft is damaged.

3) The fitting clearance between the valve core and the valve body hole is inappropriate, or the taper is out of roundness due to the poor geometric accuracy of the valve core and the valve body}l; Or there are burrs between the groove edge of the valve core and the sharp edge of the valve hole, or dirt is stuck in the matching gap, resulting in inflexible movement of the valve core and large manipulation force.

4) The dust-proof sealing ring at the protruding end of the valve core has excessive clamping force due to the wrong size of the installation groove.

(2) Troubleshooting.

1) Replace the spring.

2) It should be replaced.

3) Ensure that there is a reasonable assembly gap between the valve core and the valve hole. Grind the valve hole and the valve core when necessary. Carefully remove the burrs and carefully clean it during assembly.

4) The size of the sealing groove shall be checked and trimmed, or a suitable one shall be replaced.

2. Leakage of multi-piece multi-way directional valve

(1) Cause analysis.

1) The wear clearance between the valve stem and the valve body is too large, resulting in internal leakage. Due to the long-term use of the distribution valve or unclean oil, the wear of the valve stem and valve body is accelerated, the mating sealing surface is damaged, resulting in oil leakage.

2) Oil leakage between valve bodies. Since the working oil passage, oil return passage and oil overflow passage run through the three single valve bodies, the sealing requirements between the bodies are very. After installing the O-ring seal between the valve body and the valve body oil passage, the valve body is connected with bolts to achieve the purpose of sealing. If the firm torque of the bolts is different, the valve body may be warped. The sealing ring fails, resulting in internal leakage; If the valve body is damaged or the O-ring is aged or damaged during installation, internal leakage is also easy to occur between the valve bodies under the action of oil pressure.

3) Safety valve spring failure. If the safety valve spring fails, the hydraulic oil can force the steel ball to leave the valve position and flow into the oil overflow passage when it is lower than the specified pressure of the system, resulting in internal leakage and system failure.

4) The multi-way reversing valve rod cannot be reset. The return spring of the valve rod is installed at the lower end of the valve rod. No matter whether the valve rod is in the upper or lower position, the spring can be compressed. When there is no external force, the valve rod will quickly return to the original position due to the elastic force of the spring. If the valve stem cannot be reset and the groove is connected with the oil passage, internal leakage will occur.

5) The cone valve is worn. The cone valve is used to prevent oil backflow. If the cone valve is worn and the oil passage is not tightly closed, the hydraulic oil will return and the system will fail.

6) Leak outward from the valve body. The sealing between the valve rod and the valve body is realized by the O-ring. If the sealing ring is aged or damaged, the hydraulic oil will flow out along the valve rod under the action of system pressure, resulting in oil leakage of the valve body.

(2) Troubleshooting.

1) It shall be repaired in time. When repairing, if the wear of the valve rod is light, the valve rod can be chrome plated and polished; If the valve stem is seriously worn, it needs to be replaced.

2) It shall be repaired in time. 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) The spring must be replaced during repair, and then use the adjusting screw to adjust the spring pressure to the specified pressure.

4) During repair, measures shall be taken according to the situation. First, due to the deformation or damage of the return spring of the valve stem, the spring force decreases and the valve stem cannot return to the original position. The spring must be replaced during repair; Second, the uncleanness between the valve body and the valve stem produces great resistance, which makes it difficult to reset the valve stem. During repair, the interior of the multi-way directional valve must be cleaned to eliminate the resistance.

5) When repairing, grind or replace it. Eliminate backflow.

6) Replace the O-ring seal.

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