Excavator select valve hydraulic safety valve 14543998 secondary relief valve

1.The overall structure of the full hydraulic excavator

          Hydraulic excavators mostly use double pump circuit constant power variable hydraulic system, most of which use constant power regulator to control two hydraulic pumps, and all working mechanisms are divided into two groups (see bottom map)
Manual mechanical operation valve or pilot system control operation valve to complete the job. In addition, in the bucket rod, bucket, boom operation, in order to improve the speed of two pumps combined flow.
Diagnose and remove common faults

2.  Overall Faults

    The failure of the whole machine is caused by the failure of the common part, at this time should focus on checking the amount of oil in the hydraulic tank, the oil suction filter, the oil suction pipe is broken; For servo-operated excavators, the pilot pressure is insufficient
It will make the operation fail, so the pilot oil circuit (pilot pump, filter element, relief valve, oil pipe, etc.) should be checked; If the whole machine has no action and the excavator has no sense of load, the power connection between the oil pump and the engine should be checked
Parts, such as splines, gears, etc.; If the action is slow, check the servo adjustment system of the oil pump.
3.When several actions controlled by a group of control valves are abnormal at the same time, there is no fault in the public part of the two groups of systems, and the fault point is in the public part of these actions.

    1) The main relief valve is faulty.
         Most of the main relief valves of modern excavators use pilot relief valves. If the pressure of the relief valve is improperly adjusted, the spool is not tightly closed, and the spring is broken, the pressure of the whole system is low and the flow is small.
Detection of pressure and component displacement can be used as diagnostic methods.
    2) Subsystem hydraulic pump regulating mechanism.
            Some excavators use a constant power variable regulation system, and each variable pump is controlled by its own constant power regulator. .
If the regulating mechanism fails, such as the valve core is stuck and the wear is serious, the oil output pressure of the oil pump does not conform to the constant power law, resulting in weak and slow action.