Analysis and Elimination of Common Faults of Excavators

The excavator cannot be started or is difficult to start

1.1 Electrical system failure

1.1.1 When the battery power is insufficient, it should be charged in time. Check the height of the battery liquid level and replenish the electrolyte to the specified height in a timely manner. If it is found that the battery is aged and poorly charged, it should be replaced. At the same time, pay attention to the daily maintenance of the battery and do not let it remain in a state of low power for a long time.

1.1.2 Repair or replacement of the starter for faults.

1.1.3 Generator failure repair or generator replacement.

1.1.4 Line Fault: Inspect and repair the lines.

1.2 Engine oil circuit failure

1.2.1 Low-pressure oil circuit air resistance

Under the suction effect of the fuel transfer pump or fuel injection pump, fuel is delivered from the fuel tank to the high-pressure pump through the low-pressure fuel line. If the low-pressure oil circuit is not tightly sealed or the oil level in the fuel tank is too low, and the vehicle is parked or driven at an Angle, air will take the opportunity to enter the oil circuit. If the temperature is high and the fuel evaporates, it will also form vapor lock in the low-pressure fuel line, causing unstable engine operation, automatic stalling or the engine to fail to start.

1.2.2 Oil circuit blockage

The common areas where fuel lines get clogged mainly include the oil suction pipe, filter screen, diesel filter, and vent hole of the fuel tank cap inside the fuel tank. The main problems causing fuel line blockage are the injection of diesel that does not meet the standards or the mixing of impurities during refueling. The key to prevention is to ensure the cleanliness of diesel and the sealing of the oil circuit, carry out regular maintenance of the oil circuit, strengthen the cleaning and maintenance of the diesel filter, clean or replace the filter element in time, and clean the fuel tank in a timely manner according to the working environment conditions to thoroughly remove the sludge and water at the bottom of the fuel tank.

1.2.3 Faults of the fuel injection pump

The fuel injection pump plunger and the fuel outlet valve pair are severely worn, causing difficulty in starting the engine. At this point, the plunger and the oil outlet valve pair should be replaced in a timely manner.

The excavator is weak in operation

2.1 The engine power is sufficient and operates normally, but the excavator's working speed is slow and the digging is weak.

2.1.1 The hydraulic pumps of excavators are mostly variable piston pumps. After working for a certain period of time, the internal parts of the pump inevitably wear out, causing internal leakage. The parameter data are not coordinated, resulting in insufficient flow, excessively high oil temperature, slow speed, and inability to establish high pressure. Therefore, the operation is slow and weak. For such problems, the hydraulic pump must be removed for data measurement to confirm the location of the problem. Replace the parts that can no longer be used or repair the parts that can still be used. After reassembly, put it on the calibration bench for debugging and match the parameters of each circuit (pressure, flow, power and variables, etc.).

2.1.2 An important hydraulic component on an excavator - the multi-way distribution valve - is equipped with a main safety valve, secondary valve, relief valve, oil replenishment valve, etc. If the pressure set by these valves does not reach the standard pressure, it will result in weak excavation. In addition, if the gap between the valve stem and the valve hole is too large due to wear, and the valve stem does not return to its original position completely or the reversing is not in place, a large amount of internal leakage will occur, resulting in insufficient flow and slow speed. For such issues, the multi-way distribution valves should be removed and sent to the test bench for debugging. The pressure of all valves should be reset to the standard pressure, and the gap between the valve stem and the valve hole should be eliminated.

2.1.3 The hydraulic pumps on imported excavators are all equipped with pilot gear pumps. This pump mainly participates in the variable flow of the hydraulic pump and serves as the pilot oil to open the valve stem of the multi-way distribution valve to reverse its direction. If the gear pump wears out excessively and fails to establish a certain pressure or the safety valve on the gear pump is set to a certain pressure, it will cause the hydraulic pump to always be in a low-flow state, and the valve stem cannot be fully reversed, resulting in insufficient flow, slow operation, insufficient pressure, and weak excavation. For such problems, it is only necessary to replace the pilot gear pump or reset the pilot safety valve.

When the machine is cold, everything is normal. However, when it is hot, the operation is slow and the digging is weak. The occurrence of such a problem indicates that the internal components of the hydraulic pump are severely worn. It is necessary to replace the vulnerable parts inside the pump, reassemble it, and put it on the test bench for calibration and debugging.

Another major reason for the slow and weak operation of the entire excavator is the deterioration of the hydraulic oil. Therefore, it is necessary to pay attention to monitoring the quality of the hydraulic oil (viscosity, fluidity, and whether there are suspended solids, etc.), and replace the hydraulic oil that meets the regulations on time. This can largely prevent the occurrence of such faults.

The excavator's movement deviated

3.1 There is a fault with the hydraulic pump

Under normal circumstances, excavators are usually equipped with double pumps. If the movement deviates, it is often due to a fault in one pump. The simplest way to determine this is to swap the two high-pressure oil outlet pipes of the hydraulic pump. If the originally slow one becomes faster and the originally fast one becomes slower, it indicates that one pump is faulty. Troubleshooting method: Remove the hydraulic pump, replace the damaged parts, and then debug it on the laboratory bench.

3.2 The safety valve of the walking motor is leaking oil

Oil leakage from the safety valve will cause the pressure within the system to be too low, resulting in insufficient rotational speed of the traveling motor and thus causing the movement to deviate. The troubleshooting method is: Replace the damaged safety valve of the walking motor. When making a judgment, you can safely swap the left and right walking motors to see if they deflect when moving in the opposite direction.

3.3 The excavator veered to one side

If the spring inside the main traveling valve becomes soft or breaks, or if the valve core gets stuck, it may cause a decrease in oil pressure and result in the traveling deviation. When conducting the inspection, measure the pressure in the oil circuit of the main walking valve. The normal value is 32.5Mpa. If the main valve for walking is damaged, it needs to be replaced or repaired.

Through the above analysis, we can see that 80% of excavator malfunctions are caused by untimely maintenance or improper operation. Therefore, it is necessary to do a good job in the maintenance of excavators, and at the same time improve the technical level of operators to reduce the occurrence of malfunctions and ensure the smooth progress of engineering construction.