Measures to reduce the failure of the integrated multi-way valve 1, the valve stem leaking oil valve leakage accounted for about half of the valve failure, so the focus of the analysis. 1.1 Causes (1) The 46 × 3.5 O-rings (4 in total) installed at both ends of the stem are the key parts of the oil seal. The material of the sealing ring is nitrile rubber, which is resistant to high temperature and hard to be aged. 2-3 months after testing the use of elasticity on the decline, hair hard deformation, resulting in oil spills. (2) 46 × 3.5O-ring seals installed at both ends of the body groove size control is not strict, at the same time seal the assembly adjustment process is not perfect. When fitted with seals, pressure pad and dust ring, if the height is significantly lower than the groove depth, the seal is not compressed, in a floating state, the valve high pressure oil will leak along the stem, while sealing Circle with the stem movement, easy to damage due to friction and squeeze deformation, reducing oil seal effect. Due to the gap, dust easily enters, thus reducing the service life of the valve. When fitted with seals, pressure pad and dust ring, if the height is significantly higher than the groove depth, the seal is subject to great pressure, over-pressure condition, the larger deformation occurs, so that the ring and the stem Greatly increased friction between the use of a period of time, the ring wear and tear, loss of sealing function, leading to high pressure oil valve along the stem to the outside leakage. (3) The thickness of the back cover plate should be slightly higher than the height of the back cover, the actual thickness of the plate was found to be lower than the height of the back cover, so the plate does not compress the seal. 1.2 Measures (1) to change the O-ring material, the oil resistance is good, not easy to aging, long life fluorine rubber O-ring. (2) reduce the groove depth groove size 0.5-1mm and strictly control the groove depth size, its tolerance should be controlled at 0.005-0.01mm, so that the ring by a reasonable pre-pressure, to ensure that the sealing effect. If the groove depth is too large, the assembly should take measures, such as the use of adjustable cushion to ensure that the compaction of the seal ring; if the groove depth is too shallow, the depth of the groove re-processed to the required size range to ensure Its seal oil effect. (3) Strictly control the height of the back cover, to ensure that the thickness of the back cover plate is higher than the height of the back cover. 2, relief valve and overload valve leakage 2.1 reasons (1) the valve sleeve installed 30 × 3.1O-ring groove and the valve back to the oil return road too close to easily punching, causing the system pressure drop, or even no pressure. (2) 24 × 2.4 O-ring seals installed on the main valve plug and pilot valve seat are vulnerable to oil leakage. 2.2 Measures (1) The overall length of the valve sleeve changed from 79mm to 81mm, so that the spool sealing groove position forward 2mm, in order to avoid the spool seal groove and back to the oil passage, so that the ring was punching. (2) strictly control the position and depth of the seal groove size, and these two kinds of O-ring material is also changed to fluorine rubber material. 3, Relief valve and overload valve The main spool back to the ineffective or stuck 3.1 Causes (1) valve body and valve clearance is too small. (2) spring flexibility down. (3) O-ring groove size is too shallow, can also cause friction between the O-ring and the valve body increases. 3.2 Measures (1) The spool and the valve sleeve with a suitable gap between the appropriate amplification, with the gap adjusted to 0.025-0.035mm. (2) increase the spring stiffness, improve the spring quality. (3) Strict control of the seal groove position and depth dimensions. 4, relief valve and overload valve spring is easy to deform or break (1) the reason. Some of the spring material is defective or not tempered. (2) measures. Strict control of spring raw materials and heat treatment process quality. 5, multi-way valve stem valve inflexible operation 5.1 Causes (1) the valve stem ends facing the center of the stem hole vertical error error. (2) body, stem with the gap is too small. (3) the back cover hole and return spring clearance is too small or back cover hole and the section perpendicularity error, resulting in back cover hole and the return spring friction, so the main valve stem inflexible operation, Shen. (4) back cover plate parallelism deviation between the two ends is too large (0.03mm). 5.2 Measures (1) Note that the valve body when processing the valve hole and both ends of the vertical error within the specified tolerance. (2) body, stem with the gap set at a reasonable range. (3) Body back cover and return spring movement gap can be properly enlarged, the spring assembly to remove burrs sharp angle, the back cover plate to ensure that the parallelism of both ends of the deviation within 0.015mm. Note: During the test, if found to be manipulated, it is not allowed to use loose-back screws or padding because it can reduce the occurrence of heavy oil leakage. 6, multi-way valve leakage or valve stem card issuance 6.1 reason The leakage and the valve body, the valve stem with the cubic proportional to the gap, as with the gap is too small, although the internal leakage is small, but the valve in the use of a Time will produce about 80-100 ℃ high temperature, due to the valve stem (carbon steel) thermal expansion coefficient greater than the body (cast iron), resulting in thermal expansion, coupled with the decline in oil cleanliness, it is very easy to produce the operation is not flexible, Sinking or burning phenomenon. 6.2 Measures Through a large number of practices, proved that the leakage will be set at 80-170ml / min, the corresponding gap between 0.014-0.018mm more reasonable. 7, filling valve leakage 7.1 The main reason for the multi-way valve is to prevent the upper chamber of the boom cylinder cavitation erosion due to the rapid lowering of the boom occurs vacuum. After the measured comparison, we found that the free-fall time of the boom is about 7s which is much larger than the boom-down time of 4.8s at the rated speed of the engine. That is, the charge valve is not opened during the free-fall of the boom, Arm free fall process ineffective, and at a certain speed to supply boom cylinder oil is sufficient, and the boom stem has a one-way valve can form a certain back pressure, it is difficult to vacuum.
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