Common faults and solutions of overflow valves

1. Voltage regulation failure
1) Rotate the pressure regulator handle, but the pressure cannot reach the rated value.
The main reason for the pressure not reaching the rated value is due to the deformation and fracture of the pressure regulating spring; The pilot valve core has poor sealing and serious leakage; Remote control port leakage; Poor sealing between the main valve core and the main valve sleeve, severe leakage, etc.

2) After the system is pressurized, it immediately loses pressure and cannot be adjusted by turning the handle.
This fault is mostly caused by the sudden blockage of the damping hole at the rear end of the main valve body or pilot valve by dirt during use.
After the damping hole is blocked, the system oil pressure directly acts on the lower end face of the main valve core. At this time, the system is pressurized. Once the oil storage top of the upper chamber of the main valve core is pushed open, the guide cone valve is first opened, and the upper chamber is depressurized. The main valve opens, and the system is immediately depressurized.

Due to the blockage of the damping hole, the system pressure oil cannot enter the upper chamber of the main valve, and even if the system pressure drops, the main valve core cannot descend. The opening of the main valve core will not decrease, and the system pressure will continuously overflow.
In this situation, no matter how you turn the handwheel, the system cannot be pressed up. When the main valve is fully open, if the main valve core is stuck by dirt, the above phenomenon will also occur.

3) System overpressure or overpressure, overflow valve does not function.
One situation is that when the damping hole in front of the pilot valve core is blocked, even if the oil pressure is high, it cannot act and open the pilot valve core. The pressure regulating spring keeps the pilot valve core closed, and the pilot valve cannot overflow. The pressure in the upper and lower chambers of the main valve core is always equal.
Another situation is that after the damping hole in the upper chamber of the main valve core is blocked, the oil in the upper chamber of the main valve core is sealed off. In the above two situations, under the action of the main valve spring, the main valve remains closed and cannot be opened, and the overflow valve loses its pressure limiting and overflow function. The system pressure increases with the increase of load. When the actuator stops moving, the system pressure continues to rise under the action of the hydraulic pump, and even produces ultra-high pressure phenomenon. At this point, it is easy to cause malignant accidents such as bolt breakage and pump damage.

2. Unstable pressure with significant pulsation
1) The oil pollution is severe, and impurities are sometimes trapped in the guide valve seat hole.
2) The main valve core cannot move flexibly due to oil contamination.
3) There is too much air mixed in the oil.

4) The oil temperature is too high, causing the main valve core to become stuck.
5) Poor contact between valve core and valve seat.
6) The diameter of the damping hole is too large, resulting in weak damping effect.
7) Generate resonance.

3. Noise and vibration

1) Resonance occurs with other valve components. The pressure can be readjusted to slightly higher or lower than the rated pressure. It is best to replace the spring with a suitable one and adopt external oil leakage methods.
2) The pilot valve port is worn or there is air in the remote control chamber. The pilot valve should be repaired or replaced and the air in the system should be purged.
3) The diameter of the pipe fittings between the remote control port of the valve and the main valve of the overflow valve should not be too large, as excessive diameter can cause vibration. Generally, a diameter of 6mm is suitable.
4) There is dirt inside the valve body, causing the valve core to tilt to one side, resulting in unbalanced radial force, unstable performance, and vibration and noise.

The main valve core cannot move flexibly, but instead moves abnormally by sticking to one side of the internal control. When the pressure is adjusted to a certain value, it will inevitably cause vibration of the main valve core.
This vibration is not a conventional vibration that occurs during the working motion of the main valve core, but a high-frequency vibration caused by the main valve core being stuck in a certain position (at this time, the   main   valve core is also subjected to hydraulic clamping force).
This high-frequency vibration will inevitably cause strong vibration of the spring, especially the pressure   regulating spring, and produce noise and resonance.

In addition, due to the fact that high-pressure oil does not overflow through the normal overflow port,   but   instead overflows back into the oil tank through the stuck overflow port and internal drain passage, this high-pressure oil flow will emit high-frequency fluid noise.
This kind of vibration and noise is excited under the operating conditions of the system's characteristics, which is why there is no screaming sound when the pressure is below 10MPa. However, when the pressure is above 10MPa, the system emits a screaming sound like a whistle, and at this time, the pressure gauge pointer can be seen to vibrate violently.

5) Excessive traffic. It is best to use external oil drainage when replacing large-sized valves.