For the failure of the hydraulic system of the construction machinery on site, according to the working principle of the hydraulic system, according to the sequence of power components-control components and actuators, the cause of the failure can be analyzed in a positive way on the system diagram. According to the analysis, it is generally caused by a drop in oil pressure or a decrease in flow rate. From the system diagram, the possible factors causing the pressure drop are: ①The oil tank, such as lack of oil, blockage of the oil suction filter, and unblocked air vent; ②Leakage of the hydraulic pump , For example, the matching gap of the hydraulic pump plunger pair is large; ③The pressure adjustment of the main valve on the control valve is too low, and the configuration of 30 is analyzed, and related problems are explained.

For the belt conveyors mainly used for horizontal and upward transportation, the main problem is to solve the driving problem, while for the belt conveyors mainly used for the following transportation, the main problem is to solve the braking problem. Because when the down conveyor is running with load, the load drags the motor to run, and the motor is in the state of power generation braking. Once the motor loses power and is not equipped with a suitable braking system, the speed of the down conveyor will become faster and faster, causing a runaway ACCIDENT. The driving system and braking system of the large belt conveyor are discussed separately below.

1. The drive system of large belt conveyors For horizontal or upward belt conveyors, the drive system generally consists of an electric motor, a hydraulic coupling and a reducer. Due to the torque-limiting fluid or serious internal leakage; ④ The setting pressure of the overload valve of the boom hydraulic cylinder is too low or the internal leakage is serious, ⑤ The oil return line is not smooth, etc. Consider these reasons, and then eliminate certain factors according to the existing inspection results, narrow the scope of the fault until the fault point is found and eliminated.

In the fault diagnosis of the hydraulic system of construction machinery during on-site construction, according to the working principle of the hydraulic system, it is necessary to master some rules and common sense, and to analyze whether the fault is premature or gradual. If it is premature, it is mostly due to improper adjustment. If it is gradual, it is often caused by component wear, corrosion, fatigue, and aging; secondly, it is necessary to analyze whether it is a wearing part or a non-wearing part. If it is under high frequency and heavy load The moving parts are the hydraulic components that are prone to failure, such as the plunger pair of the hydraulic pump, the oil distribution plate pair, the variable servo and the hydraulic cylinder, etc., while the components at low frequency, light load or basically relatively static are not prone to failure. Such as reversing valve, sequence valve, slide valve, etc., after mastering these laws, it can play a positive role in quickly judging the fault location.