Reasons for 1. hydraulic pumps and hydraulic motors
1. The hydraulic pump and motor have been used for too long, the internal wear is serious, the leakage is large, and the volumetric efficiency is low, resulting in insufficient output flow of the hydraulic pump and low system pressure.
2. The engine speed is too low and the efficiency is insufficient, resulting in insufficient system flow and low hydraulic system pressure.
3. The hydraulic pump directional control device is in the wrong position or assembled incorrectly, the pump does not work, and the system has no pressure.
Reasons for 2. hydraulic control valve
1. During the working process, if it is found that the pressure cannot go up or down, it is likely that the reversing valve fails, resulting in continuous unloading or continuous high pressure of the system.
2. Blocking of the damping hole of the overflow valve, burrs on the main valve core, dirt between the valve core and the valve hole and gap, etc. may cause the main valve core to be stuck in the fully open position. The hydraulic oil output by the hydraulic pump directly returns to the oil tank through the overflow valve, and the pressure oil circuit and the oil return circuit are short-circuited, resulting in no pressure in the system. If burrs or dirt jam the main valve core in the closed position, there may be a phenomenon that the system pressure continues to be high and cannot drop; when the overflow valve or the valve core of the reversing valve is stuck, the valve core is not flexible, and the executive parts will have action and no action. When detecting the system pressure, the pressure is unstable.
3. There is a one-way valve system, if the direction of the one-way valve is installed, it may also cause the system pressure not to go.
4. Internal and external leakage of the system, such as serious leakage between the valve core and the valve body hole, will also cause the system pressure to go up.
3. other reasons
1. The oil level of the hydraulic oil tank is too low, the suction pipe is too thin, and the suction filter is blocked by impurities and dirt, which will cause the suction resistance of the hydraulic pump to be too large, resulting in insufficient system flow and low pressure.
2. In addition, the return pipe is on the liquid surface, the suction pipe is not well sealed and air leakage is easy to cause air in the hydraulic system, resulting in unstable system pressure.