1.1 The working pressure of the hydraulic system is abnormal, and the pressure does not go up. The working pressure is one of the basic parameters of the hydraulic system. Whether the working pressure is normal or not will greatly affect the working performance of the hydraulic system. The abnormal working pressure of the hydraulic system is often manifested in the failure of the pressure regulating valve when the pressure is adjusted, the system pressure cannot be established, there is no pressure at all, the high pressure is continuously maintained, the pressure rises and then falls, and the pressure is unstable.
Once the pressure is abnormal, it will be difficult for the actuators of the hydraulic system to perform a normal working cycle. It may always be in the original position and not work, the action speed will be significantly reduced, and the relevant control valve group often makes harsh noises during action, etc., resulting in the machine being in an abnormal state. status, which affects the performance of the whole machine.
1.1.1 Causes of abnormal pressure
1. Reasons for hydraulic pumps and motors:
a. 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.
b. The engine speed is too low and the power is insufficient, resulting in insufficient system flow and low hydraulic system.
c. The position of the hydraulic pump directional control device is wrong or the assembly is wrong, the pump does not work, and the system has no pressure.
2. Reasons for the hydraulic control valve: 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.
Blockage of the damping hole of the relief valve, burrs on the main spool, dirt in the spool and the valve hole and in the gap may cause the main spool to be stuck in the fully open position, and the hydraulic oil output by the hydraulic pump will overflow through the overflow valve. The valve directly returns to the oil tank, that is, the pressure oil circuit and the oil return circuit are short-circuited, resulting in no pressure in the system; if the above-mentioned burrs or dirt blocks the main spool in the closed position, the system pressure may continue to be high and cannot be lowered. Phenomenon; when the spool of the relief valve or the reversing valve is stuck, the spool of the hydraulic equipment factory is inflexible, and the executive components are prone to the phenomenon of sometimes moving and sometimes not moving. When the system pressure is detected, it is expressed as pressure unstable.
In a system with a one-way valve, if the direction of the one-way valve is reversed, the pressure may not rise. Leakage inside and outside the system, such as serious leakage between the valve core and the valve body hole, will also cause the system pressure to fail.
3. Other reasons: the oil level of the hydraulic oil tank is too low, the oil suction pipe is too thin, and the oil suction filter is blocked by impurities and dirt, which will cause the hydraulic pump to have too much oil suction resistance (when the hydraulic pump is empty, it is often accompanied by harsh noise), This results in insufficient system flow and low pressure. In addition, the oil return pipe is on the liquid surface (foaming occurs when the oil returns to the oil in the tank, causing a large amount of oil in the tank to be mixed with air). Stablize.
1.1.2 Method of eliminating pressure abnormality
Assemble in strict accordance with the correct assembly method of the hydraulic pump, and check whether the wiring of its control device is correct.
Increase the height of the hydraulic oil tank relative to the hydraulic pump, appropriately increase the diameter of the oil suction pipe, replace the filter element of the oil filter, and clear the pipeline. Viscosity hydraulic oil to avoid difficulty in pumping oil due to excessively high oil viscosity when the machine is at a lower ambient temperature.
The treatment method for the hydraulic control valve is mainly to check whether the unloading or directional valve is on and off, clean the valve core, clear the damping hole, check whether the direction of the one-way valve is correct, replace the clean oil (refill the hydraulic pressure) When refueling, it is recommended to use a refueling truck equipped with a filter device) and so on.
The oil return pipe in the oil tank is submerged below the liquid level, and the sealing of the oil suction pipe joint is strengthened, which can effectively prevent air from mixing in the system and avoid system pressure instability.
Post time: Aug-09-2022