Cause analysis and troubleshooting methods of 4 types of failures such as overflow valve noise and pressure regulation failure（2）

Cause analysis and troubleshooting methods of 4 types of failures such as overflow valve noise and pressure regulation failure（2）

2 Pressure regulation failure

The pressure relief valve sometimes fails to regulate pressure during use. There are two situations in which the pilot pressure relief valve fails to adjust pressure: one is that the pressure cannot be built up by adjusting the pressure adjusting hand wheel, or the pressure does not reach the rated value; the other is that the pressure of the adjusting hand wheel does not drop or even continuously increases. In the case of pressure regulation failure, in addition to the radial clamping of the spool due to various reasons, there are also the following reasons:

 

(1) The damper of the main valve body is blocked

If the oil pressure is not transmitted to the upper cavity of the main valve and the front cavity of the pilot valve, the pilot valve loses its regulating effect on the pressure of the main valve. Because there is no oil pressure in the upper cavity of the main valve and the spring force is very small, the main valve becomes a direct-acting relief valve with very small spring force. When the pressure in the oil inlet cavity is very low, the main valve opens to overflow. Flow, the system cannot build up pressure. The reason for the pressure not reaching the rated value is that the pressure regulating spring is deformed or selected incorrectly, the compression stroke of the pressure regulating spring is not enough, the internal leakage of the valve is too large, or the cone valve of the pilot valve is excessively worn.

 

(2) The damping hole on the cone valve seat is blocked

 

If the oil pressure is not transmitted to the poppet valve, the pilot valve loses the adjustment function of the main valve pressure. After the damper (small hole) is blocked, the poppet valve will not open the overflow oil under any pressure, and there is no oil flow in the valve. The pressure in the upper and lower chambers of the main valve is always equal, because the upper ring pressure area of the main valve core is greater than The annular pressure-bearing area at the lower end, so the main valve is always closed without overflow, and the pressure of the main valve rises as the load increases. When the actuator stops working, the system pressure will increase indefinitely. In addition to these reasons, it is still necessary to check whether the external control port is blocked, whether the poppet valve is installed well, etc.

 

（3） The spool is clamped radially

 

 

 

Due to the influence of machining accuracy, the main valve core is clamped radially, so that the main valve cannot be opened and the pressure is not increased or the main valve is closed without pressure relief. In addition, the radial clamping is caused by pollution.

 

（4）Other faults

 

 

 

During the assembly or use of the overflow valve, due to the damage of the O-ring, the combination of the sealing ring, or the loosening of the installation screws and pipe joints, it may cause unnecessary external leakage. If the poppet valve or the main valve core is worn too much, or the sealing surface is in poor contact, it will also cause excessive internal leakage and even affect normal operation.

 

Common faults of electromagnetic relief valve include pilot solenoid valve malfunction, main valve pressure regulation malfunction and impact noise during unloading. The latter can be reduced or eliminated by adjusting the added buffer. If there is no buffer, a back pressure valve can be added to the overflow port of the main valve. (The pressure is generally adjusted to about 5kgf/cm³, that is, 0.5MPa).