Pressure Relief Valve Fault Maintenance Common Faults (1) The outlet pressure is almost equal to the inlet pressure. The phenomenon of no decompression is manifested as follows: the pressure at the inlet and outlet of the valve is nearly equal, and the outlet pressure does not change with the rotation adjustment of the pressure regulator handle. The causes and exclusion methods are as follows. Pressure relief valve fault maintenance Poly Mailers,Poly Mailing Bags,Plain Mailing Bags,Plastic Bags Dongguan Pasike Packaging Co., Ltd. , https://www.nbdgpasike.com
1 There is burr on the main valve core or on the edge of the valve body bore sink groove or there is dirt in the gap between the main valve core and the valve body hole, or because the tolerance of the main valve core or valve hole shape position is poor, The hydraulic pressure is generated and the main spool is stuck at the maximum (max) position. Due to the large opening, the fluid is not decompressed. At this time, according to the above conditions, the method of removing the burr, cleaning and repairing the valve hole and the valve core can be separately adopted.
2 Because the main valve core and the valve hole are too tight, or when the valve hole or the valve core is pulled when assembling, the valve core is stuck at the maximum opening position, and a reasonable clearance can be selected at this time. J-type pressure relief valve with a clearance of 0. 007 ~ 0. 015mm, equipped with a suitable grinding valve hole, with the valve core.
3 The main spool has a short orifice or a seat hole that is blocked and loses its ability to automatically adjust. The main valve spring force pushes the main valve to the maximum opening and becomes straight and unobstructed. The inlet pressure is equal to the outlet pressure. The orifice can be blown with φ1. Omm wire or with compressed air and cleaned and reassembled.
4 For the J type pressure reducing valve, the damping element with orifice is pressed into the main valve core. During use, it may be flushed out due to insufficient amount of interference. After rushing out, make the pressure in the oil inlet chamber and the oil outlet chamber equal (without damping), and the upper and lower force areas of the valve core are equal, but the oil outlet chamber has a spring, so the main valve core is always in the position of maximum opening, making the outlet The pressure is equal to the inlet pressure. In this case, rework the damper with a slightly larger outer diameter and re-press the main spool.
5JF type pressure reducing valve, factory drain hole is plugged with oil plug. When the oil plug is not used for screwing out, the main valve core upper chamber (spring chamber) is trapped in oil, causing the main valve core to be at maximum opening without decompression. J-tube valve is the same as this. The J-plate valve can also cause this phenomenon if the mounting plate is not designed to connect the L-port to the oil reservoir.
6 J-type tube valve, it is easy to install the valve cover in the wrong direction (wrong 90 ° or 180 °), so that the external drain port blocked, can not drain, resulting in the same phenomenon of trapped oil, so that the main valve The maximum opening without decompression. When repairing, assemble the bonnet assembly direction.
7 For the JF type pressure reducing valve, if the direction of the top cover is wrong, the output oil hole will be in communication with the drain hole, resulting in no decompression, and care must be taken.
(2) The outlet pressure is very low. Even if the pressure regulator hand wheel is tightened, the pressure will not rise. 1 The pressure relief valve enters and exits the oil port and is reversed: the plate valve is designed with a wrong mounting plate, and the tube valve is taken over with an error. The inlet and outlet ports of the J type relief valve are just opposite to the inlet and outlet ports of the Y relief valve. When using, please pay attention to the mark (Pl, P2, L, etc.) stamped on the valve near the oil port of the valve, or consult the hydraulic component catalog. Do not design errors or errors.
2 The pressure at the inlet is too low. After the orifice of the pressure reducing valve is reduced, the pressure output from the outlet is lower. At this time, the reason for the low pressure at the inlet should be ascertained (such as the overflow valve failure).
3 Pressure relief valve downstream circuit load is too small. The pressure cannot be established. At this time, consider connecting the throttle valve downstream of the pressure reducing valve.
4 The contact between the pilot valve (valve valve) and the valve seat mating surface due to dirt retention and poor contact, not tightly sealed; or the pilot cone valve is severely scratched, the valve seat cooperates with å‘L out of round, there is a gap, causing the pilot valve core Not in close contact with valve seat hole.
5 Leaking poppet or poppet valves are not installed in the valve seat hole during the repair. In this regard, check the poppet valve assembly or sealing conditions.
6 The long orifice on the main spool is blocked by dirt. As shown in Figure 3-21, the oil in the P2 chamber cannot flow into the main valve spring chamber through the long orifice e. The feedback pressure in the outlet chamber P2 is not transmitted to the pilot cone. On the valve, the pilot valve loses its regulating effect on the outlet pressure of the main valve. After the orifice is blocked, the main valve P. The cavity loses the effect of oil pressure p3, making the main valve a direct-acting slide valve with very weak spring force (only the main valve balance spring), so when the pressure at the outlet is very low, the effect of the balance spring can be overcome. Force to make the throttle valve throttle off a small ymin, so that the inlet pressure p1 ymin throttle by a large step down to p2, so that the pressure on the outlet can not come. The long orifice should be open.
7 pilot valve spring (pressure regulating spring) is wrongly installed into a soft spring, or due to spring fatigue caused permanent deformation or broken and other reasons, resulting in p2 pressure adjustment is not high, can only be adjusted to a certain low value, this value is much lower Relief valve maximum regulation pressure.
8 The pressure regulator handle cannot be tightened to the maximum due to the strained or effective depth of the thread.
9 The seal between the valve cap and the valve body is bad and there is a serious oil leakage. The reason may be O-ring leaking or damage. When the compression screw is not tightened and the bonnet is finished, flatness error occurs. Generally, it is convex around and concave in the middle.
10 The main spool is stuck in a small opening position due to dirt, burrs, etc., which results in low outlet pressure. Can be cleaned and deburred.
(3) No regulation, large pressure swing, and sometimes large noise According to the provisions of the relevant standards, the J-type valve pressure swing is ± o. lMPa, JF is ±o. 3MPa, more than this standard for the pressure swing large, no pressure.
Type 1J and JF type pressure reducing valves are pilot type. Pilot valves and relief valves are common. Therefore, the causes of large pressure swings and the elimination methods can be referred to the relevant parts of relief valves.
2 When the pressure reducing valve is used in excess of the rated flow rate, the phenomenon of main valve oscillation often occurs, so that the pressure reducing valve is not stabilized. At this time, the pressure at the outlet pressure appears a cycle of “boost-buck step-by-step pressure step-up and step-down repeatedlyâ€. , so be sure to choose the appropriate type of pressure relief valve.
3 If the back pressure of the drain port L is large, the phenomenon of large pressure swing and non-regulation will also occur. The drain pipe should be returned to the oil alone.
4 Spring deformation or stiffness is not good (heat treatment is not good), resulting in large pressure fluctuations, you can replace the qualified spring.
(4) After the working pressure is set, the pressure at the outlet increases automatically. In some decompression control loops, the outlet pressure of the pressure reducing valve is used to control the hydraulic pressure of the electro-hydraulic reversing valve or the external controlled sequence valve. When the size of the electro-hydraulic reversing valve or the external controlled sequence valve is reversed or operated, the flow rate of the pressure relief valve discharge port becomes zero, but the pressure needs to maintain the original set pressure. In this case, because the valve outlet flow is zero, the flow through the decompression port is only the pilot flow. Since the pilot flow is very low, generally within 2L/min, the main valve decompression port is basically close to the fully-closed position (minimum opening degree), and the pilot flow is discharged from the triangular groove or tapered conical surface, if the main valve core cooperates. If it is too loose or worn too much, the leakage increases. According to the flow continuity theorem, this part of leakage must also flow from the main valve orifice, that is, the flow through the orifice is composed of two parts, the pilot flow and the leakage, and the orifice area and the spring pressure of the main valve spring chamber Unchanged (spring cavity oil pressure is determined by the pre-compression volume of the regulated pressure-regulating spring). In order to increase the flow through the orifice, the pressure in the lower cavity of the main valve will inevitably increase. Therefore, when the pressure at the outlet of the pressure reducing valve is set, if the outlet flow is zero, the outlet pressure will increase due to the main valve core fitting too loose or excessive wear.