Causes and solutions for abnormal pressure in Hydraulic systems

Working pressure is one of the most fundamental parameters of a hydraulic system. It largely determines the quality of the working performance of the hydraulic system. The magnitude of the working pressure depends on the size of the load. Abnormal working pressure is manifested as: when adjusting the hydraulic system, the pressure regulating valve fails, the system pressure cannot be established (insufficient pressure), or there is no pressure at all, or the pressure cannot be adjusted down, or it rises and then drops, as well as unstable pressure, etc.

The influence of abnormal pressure on the working performance of hydraulic systems

1) The hydraulic system cannot achieve the correct working cycle, especially in the sequential action circuit of pressure control.

2) If the actuating component remains in its original position and does not move, the hydraulic equipment cannot function at all.

3) Noise occurs, the speed of the moving parts is significantly reduced, and even crawling may happen.

2. Causes of abnormal stress

1) No flow output or insufficient output flow is caused by the oil pump. The oil pump is turning in the wrong direction, and there is no pressure oil output at all. The system pressure does not rise at all. Due to the motor's excessively low speed and insufficient power, or the internal wear of the oil pump after long-term use, resulting in significant internal leakage and low volumetric efficiency, the output flow of the oil pump is insufficient, and the system pressure is inadequate. If the oil inlet and outlet ports of the oil pump are installed in reverse and the pump is a non-reversible pump, not only will oil not be supplied, but the oil seal will also be damaged. If the suction pipe of the pump is too small, the sealing of the suction pipe is not good and air leakage occurs, the viscosity of the oil is too high, and the filter is clogged with impurities and dirt, it will also cause high suction resistance of the pump and result in suction emptiness, making the output flow of the pump insufficient and the system pressure unable to rise.

2) Faults in pressure regulating valves such as relief valves. The core of the relief valve is stuck at the large opening position. The pressure oil output by the oil pump flows back to the oil tank through the relief valve, short-circuitating the pressure oil with the return oil circuit. The damping hole of the pressure control valve is blocked, or the pressure regulating spring is broken, etc., causing the system to have no pressure. When the core of the relief valve is stuck at the position of the closed valve port, the system pressure cannot be reduced.

3) If during operation, it is found that the pressure cannot be raised or lowered, it is very likely that the directional control valve has malfunctioned, causing the system to unload and close, or it could be due to severe internal leakage between the valve core and the valve body hole.

4) The unloading valve is stuck at the unloading position, and the system is under total unloading, with the pressure not rising.

5) Leakage inside and outside the system.

3. Elimination methods for abnormal stress

1) Replace the motor wiring, correct the rotation direction of the oil pump, and replace it with a motor of matching power.

2) Correct the positions of the oil pump's inlet and outlet, especially for pumps that cannot be reversed.

3) Troubleshoot the situation where the pressure of the pressure valve cannot be raised or lowered.

4) Appropriately thicken the size of the pump suction pipe, enhance the sealing at the suction pipe joint, and clean the oil filter port

5) Eliminate the faults of the directional valve as required. If an unloading valve is installed, the faults of the unloading valve should also be eliminated.

6) Identify the specific locations where internal and external leaks occur and eliminate them.