1. Export pressure is almost equal to the import pressure, no pressure
The failure phenomenon: valve inlet and outlet pressure are nearly the same and the outlet pressure with the pressure handle turn adjusting and change. Causes and elimination methods are as follows.
1) Because of the main spool or the valve bore sink groove cutting edge edge have burrs, or the main valve and the valve hole between the gap ricca dirt, or because of the main spool or valve hole shape position tolerance ultra poor, hydraulic clamping, the main valve core card dead in the largest opening (max) position, because of the opening, fluid pressure. At this time can be taken according to the above situation to burr, cleaning and repair valve hole and valve core accuracy of the method to be ruled out.
2). Due to the main valve spool and valve hole with the tight, assembly or galling valve hole or spool, spool stuck on the maximum opening position, at this point, reasonable selection of the gap. J type pressure relief valve with the gap is generally 0.007 ~ 0.015mm, equipped with the appropriate grinding valve hole, and then with the spool.
3).Short damping hole or the main spool valve seat hole plug, lost the automatic adjustment function, the main valve spring force to push the main valve to the maximum opening, into a straight without resistance, the import pressure is equal to the outlet pressure. The compressed air blowing through the damping hole diameter 1.Omm steel wire or available, and then cleaning assembly.
4). In J type pressure reducing valve, with damping hole of the damping piece is pressed white core, using a may be due to the amount of interference is not out. Out after the oil inlet chamber and the oil cavity pressure equal (without damping), and spool up and down by force equal area, but oil cavity is provided with a spring, so the main spool is always in the maximum opening position, the outlet pressure is equal to the inlet pressure. At this point need to re processing of the outer diameter of a slightly larger damping parts and re pressure into the spool.
5). The JF type valve factory, oil drain plug is blocked with oil alone L. When the oil plug is not screwed out and used, the main valve core cavity (the spring cavity) trapped oil, resulting in the main valve core is in the maximum opening and no pressure relief. J type tube valve with the same. J type plate valve if the design and installation of the board did not connect the L port oil pool will also appear this phenomenon.
6). The J type pipe valve type, overhaul when it is easy to valve cover installed in a wrong direction, wrong 90 DEG or 180 DEG), the leakage oil port blocked and unable to drain, ibid caused by the phenomenon of trapped oil, the main valve top opening on the maximum without decompression. When the valve cover assembly direction can be installed in the repair.
7).The JF type valve cover, install the wrong direction, will make the output of the oil hole and the oil drain hole is caused by pressure, also must pay attention to.
2. The export pressure is very low, even if the tightening adjustment hand wheel, the pressure can not rise up
1).The import and export of oil and gas pressure valve: the plate valve for the installation of the board design is wrong, the tube valve is to take over the mistake. J type pressure relief valve inlet and outlet with the Y type overflow valve of the import and export of oil is just the opposite. Users please pay attention to the valve oil near the mouth of the dozen of Stamp Marking (P1, P2, l words), or refer to the hydraulic component catalogue, no fault and fault connection.
2).The inlet pressure is too low, after the pressure relief valve, the pressure from the output port is lower, at this time should identify the reasons for the low inlet pressure (such as relief valve failure).
3).The downstream loop load is too small. Pressure can not be established, at this time can be considered in the lower reaches of the valve to solve the throttle valve.
4). Pilot valve (poppet valve and valve seat with the surface between the dirt retention and poor contact, not close together; or pilot cone valve has serious scratch. The seat with the larvae l roundness, gap, caused by pilot valve core and the valve seat hole is not closed, as shown in Figure 3-20.
5).The overhaul, leak valve or cone poppet valve is not installed in the valve seat hole. In this regard, can check the assembly of the cone valve or close.
6).The main spool on long damping hole is blocked by dirt, as shown in Figure 3-21. P2 cavity of the oil liquid can't through long damping hole e into the main valve spring chamber, oil chamber P2 pressure feedback transfer to pilot cone valve, pilot valve lost to the main valve outlet pressure regulation. After the damping hole is blocked, the main valve is P. Cavity lost oil pressure P3, the main valve into a spring force is very weak (only the balance valve main spring) direct acting valve type, so in the oil outlet pressure is very low, to overcome the force of the spring balance and the pressure reducing valve throttle off a small Ymin, into the oil inlet pressure P1 through the Ymin orifice large amplitude step-down to P2, resorted to the oil outlet pressure on not to. Long damping hole should be made.
7).The pilot valve spring (pressure regulating spring) wrong loaded into soft spring, or permanent deformation or fracture reason produced by spring fatigue, resulting in P2 pressure adjustment is not high, can only be transferred to a low value, this value is far lower than the valve the maximum regulating pressure.
8).The pressure adjusting handle by screw thread strain or effective depth is not enough, can not be screwed in the end which cannot be transferred to the maximum pressure.
9).Poor sealing between the valve cover and the valve to the serious oil spill. The cause may be O - shaped ring leakage or damage, the compression screw is not tightened and the valve cover when the surface flatness error occurs, generally around the convex, concave convex.
10).The main spool due to dirt, burrs stuck in the small opening position, the outlet pressure is low. Can be cleaned and de burr.
