Created on:2021-09-25 14:30

Construction machinery_ Construction and construction machinery_ Roller hydraulic system failure

Construction machinery_ Construction and construction machinery_ Roller hydraulic system failure

According to the needs of railway electrification speed-up transformation, a company purchased y226c roller at the end of 2003, and several hydraulic system faults occurred in the process of use.

(1) Driving system fault

① Fault phenomenon in railway construction, there is the phenomenon of weak driving. In case of steep slope or steel wheel falling into wet pit, it can't get rid of it. Generally, it should be dragged by other machinery.

② Inspection results

a. The display of electrical system is normal and the action of electrical components is accurate.

b. The oil make-up pressure P1 = 1.2 ~ 1.6Mpa, sometimes lower, changing irregularly.

c. When the engine is running at the rated speed, push the roller as far as possible, and the measured cut-off pressure is 18 ~ 30MPa, which is in an unstable state.

d. Remove the traveling pump housing for inspection. The oil is thin, the color is dark and there are many metal powders.

③ Cause analysis

a. The machine has not changed the oil. Poor oil quality and viscosity drop are one of the causes of the fault.

b. The internal wear of pump and motor leads to the increase of internal leakage and affects the working pressure.

c. The plastic deformation of the regulating spring of the make-up pressure and cut-off pressure leads to the decrease of the set pressure. The low make-up pressure makes the thrust of the swashplate control cylinder of the travel pump insufficient, and the swashplate cannot deflect accurately, resulting in the decrease of the pump output flow.

④ Treatment method

a. Replace all oil in the system.

b. Operate at idle speed for 20min, increase the speed to the rated speed, and adjust the oil make-up pressure P1 to 2.5 ~ 2.6MPa.

c. After the oil make-up pressure is normal, set the cut-off pressure at P2 = 38Mpa.

After treatment, the system returns to normal.

(2) Vibration system fault

① Fault phenomenon: the roller suddenly loses its vibration function during pressing operation, disconnects the vibration motor from the eccentric shaft, and the starting vibration function is still invalid.

② Inspection results

a. The electrical system is normal, Y3 and Y4 can be powered off accurately and have sufficient suction.

b. Oil makeup pressure P1 = 2.5MPa, vibration pressure P2 = 2.5MPa.

C. oil temperature T = 62 ℃, oil quality is normal.

③ Cause analysis it can be seen from figure s that the possible causes of the fault are the failure of the reversing valve, the failure of the vibration pump and the failure of the vibration motor.

S.jpg

a. The change-over valve cannot change direction normally, the swashplate control hydraulic cylinder of the vibration pump does not act, and there is no flow output.

b. Failure of the pressure block valve in the vibration pump or failure of the shuttle valve in the block valve will also make it impossible to establish the system pressure.

c. If the rotating part in is stuck, the system pressure will be constant at the cut-off pressure; If the motor oil distribution plate fails, the oil inlet and outlet will be directly connected, and the hydraulic motor cannot work.

④ Treatment method

a. Check the change-over valve, put the engine at idle speed and use two M12 × 1.5 the threaded pressure measuring joint is connected with the zero measuring ports X1 and X2 on the vibration pump, and the 0 ~ 4MPa pressure gauge is connected respectively to start the vibration function. Under normal conditions, if PX1 = 2.5MPa, PX2 = 0; If PX1 = 0, PX2 = 2.5MPa; If PX1 = PX2 = 0, the directional valve is stuck. Therefore, it can be judged whether the directional valve is normal or not.

b. If the reversing valve is normal, the oil inlet and outlet of the vibration motor shall be blocked with a clean and flat steel plate with a thickness of 4mm (it can be directly fastened with screws at the butt joint between the two oil pipes and the two oil ports of the vibration motor). At this time, increase the engine speed to the rated speed and start the vibration function. If the vibration pressure P2 is about 35MPa and the oil make-up pressure P1 is about 2.5MPa, the vibration pump is normal and it can be judged that the vibration motor is faulty. If the vibration pressure P2 is equal to or close to the oil make-up pressure, which is about 2.5MPa, it can be judged that the vibration pump is faulty.

Therefore, it can be accurately judged whether the system fault comes from the control valve, hydraulic pump or hydraulic motor, and then the relevant components can be further processed. The inspection result was that the hydraulic motor failed. After the motor was replaced, the roller returned to normal operation.

When dealing with hydraulic system faults, it is inevitable to adjust relevant parameters, such as travel pump cut-off pressure, vibration pump cut-off pressure, oil make-up pressure, hydraulic zero position, vibration frequency, etc. The following two points must be noted during operation.

① Mark the original position of the adjusting element before work. If the purpose is not achieved after adjustment, the adjusting screw must be turned back to the initial state.

② Tighten the lock nut after adjustment, otherwise the hydraulic oil will leak at this point, and even the adjustment parameters will change, affecting the normal operation of the system.

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