Analysis of walking weakness of EX400 excavator

A EX400 excavator has been used for about 10 years, and its working device and slewing gear are all working properly. The system has obvious power shortage, but it does not walk too far.

Based on the analysis of the hydraulic system, the cause of lack of power running system may be: hydraulic pump and its control system failure; the main unloading valve disorder or being locked; walking control system (such as the pilot valve control circuit, etc.) failure; centerswivel joint failure, such as channeling oil or because wear and leakage; valve malfunction and walking motor group.

Because of the working device and rotary system is normal, it can determine the pump and its control system and the main unloading valve is normal; in the range of pilot oil control valve of the pressure detecting 6MPa, regardless of engine speed is high or low, pilot oil pressure is always in the standard value (3.0~3.2MPa) range, indicating that the pilot circuit normal; remove the running system of the control valve, the valve core and valve seat wear, found no clamping stagnation, indicates that the control valve is normal; with iron fixed track, don't let it turn, and then use the gauge detection range for 60MPa walk into motor oil pressure, the pressure is only 20MPa, far below the standard pressure value (36MPa).

Therefore, the cause of the machine failure is that the central swivel joint is seriously leaking; the motor is seriously leaking; the running motor safety valve is out of order.

Then, with a self-made rotary joint (install pressure gauge) installed in two. The competent Road a walking motor, then the joystick to make another walking motor, the pressure gauge value does not change, indicating the centerswivel joint normal; and the fixed track block can not be rotated, with a range of 60MPa pressure gauge put into the oil system of the walking motor and make it work, the system pressure is 20MPa, re adjust this safety valve, working pressure in the system from 20MPa to 36MPa. It is known that the running motor is normal and the fault is caused by the misalignment of the safety valve.