Trouble removal of DH220 excavator

A Daewoo DH220 excavator, in the course of work, suddenly appeared moving arm lifting slowly, unable to walk, steering and walking weakness and other failures.

After the test machine, engine, hydraulic pump of excavator are no exception, no-load operation, in addition to walking can not be turned out, other speed is acceptable, but when the mining boom, not only slow, other movements are slow and weak. Obviously, this should be in the hydraulic system "speed but weak" or "flow sufficient, but the pressure is insufficient" fault. Taking into account all the action is slow, it may be the main relief valve pressure is low, the fault may be the main relief valve, so the test pressure of the main relief valve with pressure, that pressure is only 18MPa (standard overflow pressure 33MPa), test results consistent with the judgment, should be dismantling the main relief valve. Remove the check and found the main relief valve has many internal flake and mud paint substances, after cleaning and dredging the damping holes on the assembly, after installation to the main body, and then start the machine, and slowly increase the pressure of the hydraulic system, the main relief valve pressure setting in 33MPa, the the restoration of the original performance of excavator.

The root cause of this failure is that the hydraulic oil is too dirty, and the large particles of impurities in the oil tank cause the main valve damping hole of the overflow valve to be blocked or stuck to the main valve core, the pilot valve core and the valve seat. To avoid further trouble, check the hydraulic oil quality and find the hydraulic oil return to the oil filter screen with impurities, because there is no regular replacement of hydraulic oil. Replace the hydraulic oil and hydraulic oil filter, everything returned to normal.