I. Introduction Pressure reducing valve is a valve outlet pressure (secondary oil pressure) is lower than (a oil pressure) pressure regulating valve. Use a hydraulic system of two or more different pressure of the branch, used in the system of clamping oil and other control circuit. According to its working principle and structure can be divided into direct-acting and pilot-type two categories, direct acting in the differential pressure relief valve (such as used in speed control valve) and the ratio of pressure reducing valve, etc. pilot There are fixed value output pressure reducing valve (commonly known as the pressure reducing valve) and one-way valve. Second, the failure analysis and exclusion (A) the outlet pressure is almost equal to the inlet pressure, not decompression This failure phenomenon is that the pressure near the inlet and outlet of the pressure regulator is nearly equal, the outlet pressure does not change with the pressure regulator handle rotation ①due to the main valve Burrs on the core or on the edge of the cutting hole of the valve body hole or dirt in the gap between the main valve body and the valve body hole or a hydraulic pressure card due to over tolerance of the valve core or the valve hole shape Tight, the main spool stuck in the position of the maximum opening degree, due to the large opening, the oil is not decompression. ② due to the main spool and the valve hole with tight, or pull the valve hole or valve spool assembly, the valve core stuck in the maximum opening position, this time can be equipped with reasonable clearance. ③ The main spool short hole or seat orifice clogging, loss of automatic adjustment function, the main valve spring force will push the main valve to the maximum opening, into a straight through, the inlet pressure equal to the outlet pressure. (B) the outlet pressure P2 is very low, even tighten the pressure regulating hand wheel, the pressure does not rise up ①reverse the inlet and outlet of the pressure reducing valve; ② inlet pressure is too low, after the relief valve spool orifice, The output pressure from the oil outlet is lower, this time should identify the cause of the inlet pressure is low; ③ valve downstream loop load is too small, the pressure can not be established at this time can be considered in the downstream of the valve series Flow valve to solve; ④ pilot valve (cone valve) and valve seat with the surface due to the retention of dirt and poor contact, do not meet; or pilot cone valve has a serious scratch, the valve seat hole with a circle, a gap, Resulting in pilot valve and valve seat hole is not in close contact; ⑤ disassembly, missing taper valve or cone valve is not installed in the valve seat hole; ⑥ the main spool on the long damping orifice is blocked by dirt; ⑦ pilot valve spring Pressure spring) wrongly installed as a soft spring, or due to spring fatigue permanent deformation or breakage and other reasons, resulting in P2 pressure is not high, can only be transferred to a certain low value, the value is far below the maximum pressure reducing valve Adjust the pressure; ⑧ regulator handle due to thread tension or effective depth is not enough In the end of the pressure can not be adjusted to the maximum; poor sealing between the valve cover and the valve body ⑨, excessive oil leakage; ⑩ main valve by dirt, burrs or the like stuck in the position of the small opening, the low-pressure outlet. (C) instability, the pressure vibration large, and sometimes large noise JB2146-77 provisions, J-type pressure relief valve pressure swing ± 0.1Mpa, JF-type ± 0.3Mpa, more than this standard pressure swing large, Unstable (D) work pressure After setting the pressure rise of the oil outlet in some decompression control loop, the relief valve outlet pressure is used to control the electro-hydraulic valve or external control sequence valve control oil pressure Size, when the electro-hydraulic valve or external control sequence valve to change or work, the valve outlet flow becomes zero, but the pressure still need to maintain the original set pressure. In this case, because the valve outlet flow is zero, the flow through the pressure relief port has only pilot flow. As the pilot flow is very small, so the main valve pressure relief port is basically close to the full close position (opening degree is very small), the pilot flow from the triangular groove or inclined cone at the outflow, if the main spool with loose or excessive wear, then Leakage increases. Therefore, when the relief valve outlet pressure is set, if the outlet flow is zero, the outlet pressure will increase due to the main spool with loose or excessive wear and tear. (E) a serious leak
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