Modern excavators generally adopt the mechatronic and hydraulic integrated control mode. The common faults are the engine speed dropping, the working speed slowing down, the inability to excavate and other faults in daily use. This paper briefly introduces the fault judgment and maintenance technology of excavator in these kinds of faults, and also introduces the daily maintenance technology of excavator to ensure the normal work of excavator.

With the progress of science and technology, modern excavators generally adopt the mechatronic hydraulic integrated control mode. When we remove some faults, we mostly solve the matching problems of engine, hydraulic pump, distribution valve and external load. In general, these aspects can not be matched in excavator operation, often manifested as: the engine speed drops, the working speed slows down, the excavation is weak and some common problems.

1、 Engine speed decrease

First of all, test the output power of the engine itself. If the output power of the engine is lower than the rated power, the causes of the failure may be poor fuel quality, low fuel pressure, incorrect valve clearance, one cylinder of the engine does not work, wrong injection timing, incorrect setting value of the fuel quantity, air leakage in the intake system, fault of the brake and its control lever, and carbon accumulation in the turbocharger. If the engine output power is normal, you need to check whether the flow of the hydraulic pump does not match the output power of the engine.

The speed of hydraulic excavator is inversely proportional to the load, that is, the product of flow rate and pump output pressure is a constant, and the output power of pump is constant or approximately constant. If the pump control system fails, the engine, pump and valve can not be optimized in different working conditions, and the excavator will not work normally. This kind of fault should start from the electrical system, then check the hydraulic system, and finally check the mechanical transmission system.

2、 Slow down

The main reason for the slow working speed of the excavator is that the engine power drops and the hydraulic system leaks due to the wear of each part of the whole machine. The hydraulic pump of excavator is plunger variable displacement pump. After working for a certain period of time, the internal hydraulic components of the pump (cylinder block, plunger, port plate, nine hole plate, turtle back, etc.) will inevitably produce excessive wear, which will cause internal leakage and inconsistent parameter data, resulting in insufficient flow, too high oil temperature and slow working speed. At this time, it is necessary to overhaul the whole machine and repair and replace the parts with excessive wear.

But if the excavator is not working for a long time and suddenly slows down, you need to check the following aspects. First check whether the circuit fuse is open or short circuited, then check whether the pilot pressure is normal, then check whether the servo control valve - servo piston is stuck and whether the distributor is in fault. Finally, dismantle the hydraulic pump for data measurement to confirm the problem of the excavator.

3、 Weak excavator

Digging powerlessness is one of the typical faults of excavators. There are two kinds of powerlessness in digging: one is powerlessness in digging, the engine does not hold the car, and the load is very light; the other is powerlessness in digging, when the boom or stick reaches to the end, the engine seriously holds the car, or even stalls.

① The digging is weak but the engine doesn't hold the car. The digging force is determined by the output pressure of the main pump. Whether the engine is stuck depends on the relationship between the absorption torque of the oil pump and the output torque of the engine. If the engine does not hold the car, it means that the absorption torque of the oil pump is small and the engine load is light. If the working speed of the excavator is not obviously abnormal, the maximum output pressure of the main pump, i.e. the system overflow pressure, shall be emphatically checked. If the measured value of the overflow pressure is lower than the specified value, it indicates that the setting value of the overload overflow valve of the hydraulic circuit of the mechanism is not correct, which leads to the premature overflow of the mechanism and the inability to work. You can adjust the machine by turning the adjustment screw.

② The digging is weak and the engine is holding the car. Engine holding indicates that the absorption torque of the oil pump is greater than the output torque of the engine, resulting in engine overload. This kind of fault should first check whether the engine speed sensing system is normal, and the inspection method is similar to the engine inspection method mentioned above. After the above detailed inspection and troubleshooting, the engine speed sensing system returns to normal function, the engine choking disappears, and the digging force will return to normal.

4、 Common faults in mining process

Some common failures often occur in the construction of excavators, such as: the running deviation of excavators, the possible cause is the damage of the traveling distribution oil seal (also known as the center rotary joint oil seal); the flow of the two hydraulic pumps is different; there is a problem in the traveling motor at the same time. If the hydraulic cylinder leaks rapidly, it may be that the safety relief valve is not tightly closed, or the cylinder oil seal is seriously damaged, etc.

5、 Daily maintenance of excavator

In order to prevent the failure of the excavator, it is necessary to pay attention to the maintenance of the excavator in the process of daily use. Daily maintenance includes inspection, cleaning or replacement of air filter element; cleaning of cooling system; inspection and tightening of track shoe bolts; inspection and adjustment of track reverse tension; inspection of air inlet heater; replacement of bucket teeth; adjustment of bucket clearance; inspection of front window cleaning fluid level; inspection and adjustment of air conditioner; cleaning of cab floor; replacement of crusher filter element (option). When cleaning the inside of the cooling system, slowly loosen the water filling cover after the engine is fully cooled, release the internal pressure of the water tank, and then drain the water; do not clean the engine when it is working, the high-speed rotating fan will cause danger; when cleaning or replacing the coolant, park the machine on the level ground.