The main manifestations of abnormal flow in the hydraulic system are as follows:

(l) due to filter blockage and other reasons, the hydraulic pump oil supply is insufficient, the hydraulic system is short of oil, resulting in slow or no movement of the working mechanism, resulting in movement failure of the actuator or even out of control.

(2) the leakage of hydraulic pump, hydraulic cylinder, hydraulic valve or pressure pipeline will not only increase the consumption of oil for nothing, but also cause the work pressure can not go up, making the output force of the working mechanism is insufficient, and even form pressure when the leakage is serious.

(3) frequent fluctuation of flow rate aggravates the vibration and noise of the system, and at the same time greatly reduces the filtration performance of the filter. As a result, the pollution degree of oil cannot be controlled within the predetermined level, which seriously threatens the normal operation of the hydraulic system. When the flow pulsation is large, will cause hydraulic impact, which is the main reason for the damage of some hydraulic equipment.

(4) when the leakage of some components in the hydraulic system is too large, the pressure of the hydraulic oil can be converted into heat energy. If the heat dissipation device capacity is limited or poor heat dissipation, then the equilibrium temperature of hydraulic oil rises, resulting in a short period of oil temperature is too high, oil viscosity drops, further increase the leakage, leading to a significant reduction in the volume efficiency and the efficiency of the entire system, and cause rubber seals, hoses and other early aging, loss of function. The movement speed of the actuator in the hydraulic system should meet the specified speed range, which requires no crawling at low speed and no hydraulic impact at high speed. Speed switch when smooth, in the case of variable load speed change to be small and so on.

According to the actual use of hydraulic equipment in the field statistics, the hydraulic system of the actuator often appear fault phenomenon is: no movement, movement instability, movement direction is not correct, the speed of movement does not meet the requirements, the order of action disorder, force output instability, crawling and other forms. These fault forms are closely related to abnormal flow. Therefore, when the hydraulic actuator cannot work normally, it is often possible to find the cause of the fault by the working parameter of flow rate and eliminate it.

Hydraulic system flow abnormal refers to no flow into the actuator, the supply actuator flow is insufficient, the oil pump output flow is unstable and the flow into the actuator is too large these four situations.