Technical data download for large-diameter original internal pilot operated pressure reducing valve

Common Faults

(1) Export pressure is almost equal to import pressure, without pressure reduction

This fault phenomenon is manifested as: the inlet and outlet pressures of the pressure reducing valve are almost equal, and the outlet pressure does not change with the rotation adjustment of the pressure regulating handle. The causes and elimination methods are as follows.

① Due to burrs on the main valve core or the edge of the sunken groove in the valve body hole, or dirt stuck in the gap between the main valve core and the valve body hole, or due to excessive tolerance of the main valve core or valve hole shape, hydraulic clamping occurs, and the main valve core is stuck at the maximum opening position. Due to the large opening, the oil does not reduce pressure. At this point, methods such as deburring, cleaning, and repairing the valve hole and valve core accuracy can be adopted according to the above situation to eliminate it.

② Due to the tight fit between the main valve core and the valve hole, or the valve hole or core being pulled during assembly, the valve core may be stuck in the maximum opening position. At this time, a reasonable clearance can be selected. The clearance between J-type pressure reducing valves is generally 0 007～0. 015mm， Before fitting, the valve hole can be ground appropriately before fitting the valve core.

③ The short damping hole or valve seat hole of the main valve core is blocked, and the automatic adjustment function is lost. The spring force of the main valve pushes the main valve to the maximum opening, becoming a straight through unobstructed flow, and the inlet pressure is equal to the outlet pressure. Use a 1.0mm steel wire or blow through the damping hole with compressed air, clean and reassemble.

④ For J-type pressure reducing valves, the damping element with a damping hole is pressed into the main valve core, and may be ejected due to insufficient interference during use. After flushing out, the pressure in the inlet and outlet chambers is equal (without damping), and the force area on the valve core is equal. However, there is a spring in the outlet chamber, so the main valve core is always in the maximum opening position, making the outlet pressure equal to the inlet pressure. At this point, it is necessary to reprocess the damping component with a slightly larger outer diameter and re press it into the main valve core.

⑤ The JF type pressure reducing valve is sealed with an oil plug when it leaves the factory. When this oil plug is not unscrewed and used, it traps oil in the upper chamber (spring chamber) of the main valve core, causing the main valve core to be at its maximum opening without reducing pressure. The J-type tubular valve is the same as this. If the installation plate of the J-type plate valve is designed without connecting the L port to the oil tank, this phenomenon may also occur.

⑥ For J-type tubular valves, it is easy to install the valve cover in the wrong direction (90 ° or 180 °) during disassembly and repair, which can block the oil outlet and prevent oil discharge, resulting in the same trapped oil phenomenon as above, causing the main valve to be pushed at the maximum opening without pressure reduction. When repairing, simply install the valve cover in the correct direction.

⑦ When installing the JF type pressure reducing valve in the wrong direction of the top cover, it can cause the output oil hole to communicate with the drain hole, resulting in no pressure reduction. Attention should also be paid.

(2) The export pressure is very low, even if the pressure regulating handwheel is tightened, the pressure cannot rise

① The inlet and outlet of the pressure reducing valve are connected incorrectly: there is a design error in the installation plate for the plate valve, and there is a connection error for the tube valve. The inlet and outlet of the J-type pressure reducing valve are exactly opposite to those of the Y-shaped relief valve. Please pay attention to the steel seal markings (Pl, P2, L, etc.) near the oil port on the valve when using it, or refer to the hydraulic component product catalog. Do not make design or connection errors.

② The inlet pressure is too low, and after passing through the pressure reducing valve core and throttling port, the output pressure from the outlet is even lower. At this time, the reason for the low inlet pressure should be identified (such as a malfunction of the relief valve).

③ The downstream circuit load of the pressure reducing valve is too small, and the pressure cannot be established. At this time, it is possible to consider connecting a throttle valve in series downstream of the pressure reducing valve to solve the problem.

④ The contact between the pilot valve (cone valve) and the valve seat fitting surface is poor due to the retention of dirt, resulting in poor sealing; Or the pilot cone valve has serious scratches, and the valve seat is out of roundness and has gaps, causing the pilot valve core to not fit tightly with the valve seat hole.

⑤ During disassembly and repair, the cone valve is missing or not installed in the valve seat hole. For this, the assembly or sealing condition of the cone valve can be checked.

⑥ The long damping hole on the main valve core is blocked by dirt, as shown in Figure 3-21. The oil in chamber P2 cannot flow into the main valve spring chamber through the long damping hole e, and the feedback pressure from chamber P2 cannot be transmitted to the pilot cone valve, causing the pilot valve to lose its regulating effect on the outlet pressure of the main valve. After the damping hole is blocked, the main valve P. The chamber loses the effect of the oil pressure p3, making the main valve a linear spool valve with weak spring force (only the main valve balance spring). Therefore, when the outlet pressure is very low, the force of the balance spring can be overcome to close the throttle port of the pressure reducing valve YMIN. In this way, the inlet pressure p1 is greatly reduced to p2 through the YMIN throttle port, and the outlet pressure cannot increase. The long damping hole should be unobstructed.

⑦ The pilot valve spring (pressure regulating spring) is mistakenly installed as a soft spring, or due to spring fatigue causing deformation or breakage, the p2 pressure cannot be adjusted high and can only be adjusted to a certain low set value, which is far below the maximum regulating pressure of the pressure reducing valve.

⑧ The pressure regulator handle cannot be fully tightened due to thread strain or insufficient effective depth, resulting in the inability to adjust the pressure to the maximum.

⑨ The sealing between the valve cover and valve body is poor, resulting in severe oil leakage. The possible causes may be missing or damaged O-rings, loose clamping screws, and errors in the flatness of the end face during valve cover processing, which are generally convex on all sides and concave in the middle.

⑩ The main valve core is stuck in a small opening position due to dirt, burrs, etc., resulting in low outlet pressure. Can be cleaned and deburred.

(3) Unstable voltage, large pressure oscillation, and sometimes loud noise

According to relevant standards, the pressure swing of J-type pressure reducing valve is ± 0.1 MPa, and that of JF type is ± 0.3 MPa. Exceeding this standard is considered as large pressure swing and unstable pressure.

① The J-type and JF type pressure reducing valves are pilot operated, and the pilot valve is compatible with the relief valve. Therefore, the causes and elimination methods of large pressure oscillation can refer to the relevant parts of the relief valve.

② When the pressure reducing valve is used beyond the rated flow rate, the main valve often oscillates, causing the pressure reducing valve to become unstable. At this time, the outlet pressure undergoes a cycle of "increasing pressure and decreasing pressure again and again", so it is necessary to choose a pressure reducing valve that is suitable for the model and specifications.

③ The back pressure on the oil drain port L is high, which can also cause pressure oscillations and instability. It is recommended to return oil separately from the oil drain pipe.

④ If the spring is deformed or has poor stiffness (due to poor heat treatment), resulting in large pressure fluctuations, a qualified spring can be replaced.

(4) After setting the work pressure, the pressure at the oil outlet increases automatically

Large caliber original internal pilot operated pressure reducing valve technical data download AR825 AR925