Home > Exhibition > Content

What is the reason that the loader has a slow arm?

Aug 29, 2018

When a XG958 loader is loaded, its lifting arm is slow. It takes about 12 s to lift the arm at the rated speed at full load, about 5 s more than the normal lifting.


The machine hydraulic system as shown in the appended drawings, work mainly by the pilot pump, selecting valve, pilot operated valve, pump operation, first unloading valve, distributing valve (including movable arm valve, turning valve, safety valve, turn rodless cavity overflow valve, turn fights the overflow valve rod chamber, turning a bar cavity filling oil valve, floating valve), turning and moving arm cylinder, etc.


Since the speed of the actuator's hydraulic system depends on the flow rate, the main reason for the slow lifting of the XG958 loading manipulator arm is the insufficient flow of pressure oil. The reasons for the insufficient flow may include: serious leakage of system components and connecting pipes; Hydraulic oil deterioration; Blockage, aging or air intake system of suction pipeline filter net, resulting in insufficient oil absorption of hydraulic pump; Insufficient oil supply caused by leakage in the working pump; Hydraulic cylinder leakage; The gap between the valve core and valve body of distribution valve is too large; The pilot pressure is too low; Preferential unloading valve pressure is too low or poor sealing, resulting in insufficient confluence oil; The diesel engine runs at a low speed.


Firstly, check oil leakage and deterioration problems. Start the loader, increase the accelerator and hold the bucket for a while after receiving the limit position, check the hydraulic system components and connecting pipes without any external leakage. There is no problem in checking the quality of hydraulic oil.


Next, check the hydraulic pump and feed filter. Step up the throttle will be the bucket received limit position, carefully distinguish the work pump sound. Check that the hydraulic oil level is normal and there is no blockage in the feed filter screen. Observe no foam in oil. Touch the working pump by hand without overheating.


Again, check the arm cylinder and distribution valve for leakage. Lift the movable arm to the limit position, take protective measures to prevent the movable arm from falling, then remove the tubing with the rod cavity of any movable arm cylinder, remove the protective measures to observe the oil production, the result does not find the hydraulic oil flow out phenomenon, thereby determining that the movable arm cylinder has no internal leakage. Disassemble the distribution valve, check the valve core, valve body and other abnormal conditions.


Then, check the pilot pressure and unloading pressure. Control the pilot handle to lift the arm to the highest position, and at the same time increase the pressure of the accelerator to measure the pilot system. As a result, the pilot pressure measured is higher than 2.5mpa, which is a normal range.


Finally, in the case of full load idling, the lifting arm measured the load-discharging pressure of the loader only 8 MPa, lower than the normal unloading pressure 13 MPa. It is concluded from this analysis that due to the low unloading pressure of the loader, the oil of the steering pump cannot fully merge with the oil of the working pump, resulting in slow lifting of the loading motor arm.


After the unloading pressure was adjusted to the normal value, the testing machine was tested. At the rated speed at full load, the lifting time of the moving arm was 6.5s, and the lifting failure of the moving arm disappeared slowly.