Treatment of sudden weakness of CAT320 excavator

A CAT320 type excavator has been working in the field of about 15000h, when walking, when suddenly the engine black smoke, and the hydraulic system to work; if it continues to work, engine flameout, namely ultra super load.

After understanding, the machine works well before the transit, and this fault is a sudden fault. After inquiring about the driver and doing the whole machine inspection, we know that there is no damage to the parts and no oil leakage. All kinds of oil surfaces are normal. Test engine, if the engine is no load, it is normal work; small load work or open the hydraulic system, the engine black smoke serious, slightly larger action, the engine will stall. This indicates that the cause of the failure is not in the engine, but in the electrical control and hydraulic system of the machine. But the electrical part of the machine was detected and no fault was found. This further indicated that the electrical part of the machine had not been found. The trouble is in the hydraulic system.

The hydraulic system of this machine belongs to constant power control system. When the load is constant, the system pressure P should be a constant, while the flow Q is adjusted by the hydraulic pump regulator. Once the system for flow regulation caused by improper PxQ the product is greater than the power of W system, the pump and the engine is mechanically connected by the spline, this will cause the engine load, thus the emergence of the phenomenon of engine black smoke. Therefore, we will P, Q two indicators as the focus of investigation object. After testing, the outlet pressure of the pump is about 27.6MPa; the pilot pressure is 3.5WPa. By comparison, the pilot system pressure is normal, the main pump outlet pressure is slightly lower, but the machine in small load work should not appear overload phenomenon. Therefore, we believe that the failure is due to inadequate flow regulation.

Adjust the adjusting screws at both ends of the pump regulator first, and find that the fault has been improved, but still can not work properly. Inspection found that the main pump regulator at one end of the large, spring has broken into sections. The little spring at the other end is gone. When the new machine is tested, the trouble has been eliminated.