Carter excavator is slow and incapable of servicing       

Fault: Excavator full load lifting weakness, slow, temperature. In this regard, can be detected and the investigation according to the following steps.

1. in the hydraulic system connected to the pressure gauge, measured pressure is 18MPa, reached the specified system rated pressure value, so ruled out the possibility of failure of the safety valve. Preliminary judgment, the problem may be in the boom cylinder or hydraulic pump.

2. because it is troublesome to disassemble the hydraulic cylinder, so it is necessary to test and judge whether the hydraulic cylinder is normal before disassembly. In full load, the boom will be lifted to the maximum height (attention to safety), and then the engine will be closed so that the main valve of multi way valve is in the middle locking state, and the boom cylinder will continue to sink obviously. The reason for this phenomenon is that:

(1) the pressure of boom overload valve is low. According to the requirement, the setting pressure of the boom overload valve is 20MPa. When the full load lifting boom, the pressure indicator system pressure is 18MPa, indicating that the setting pressure of the overload valve is not less than 18MPa. Therefore, you can exclude the possibility of low pressure overload valve arm. Can also be a safety valve and valve system overload position to determine accurately the swap.

(2) leakage of main valve of multiway valve. Generally speaking, under normal pressure, the normal leakage of the main valve in the middle position is very small, which is not enough to cause obvious hydraulic cylinder subsidence. At the same time, taking into account the use of this machine is not long, so it can basically eliminate the possibility of multi valve main valve leakage.

(3) damage of piston ring seal in boom cylinder. Through the above analysis, the maximum likelihood. Therefore, the hydraulic cylinder was removed and it was found that the piston rings of the two boom cylinders had been seriously damaged, which confirmed the prior judgment.

However, there is a problem puzzling: even if the piston sealing ring damage, so that the hydraulic cylinder on the lower and the lower chamber interlinked, because the spool in the middle of the lock, hydraulic oil nowhere to go, why will cause hydraulic cylinder subsidence? Through the analysis to understand this truth.

The hydraulic cylinder piston rod diameter D=80mm, diameter d=45mm, load F0 normal, F=P1 * A1, pressure P1=18MPa, A1 piston area. Because of the damage of the piston seal ring, the hydraulic cylinder is communicated with the lower chamber, the pressure is P2, A2 is the piston rod area, so F=P2 x A2, namely P1 x A1=P2 * A2, P2= P1 * A1/ A2. P2=3.16 P1 can be obtained by substituting the numerical value. That is to say, when the piston seal fails, the pressure at this time is 3 times more than the original pressure, greatly exceeding the opening pressure of the overload valve, so the overload valve unloading. If the valve is completely locked without overload valve, this will be very dangerous, and it will seriously damage the hydraulic cylinder and other hydraulic components.

After the replacement of the new sealing ring with the boom cylinder, it is found that the situation is better than the original one, but the lifting speed is much slower than the normal one. The judge has also undergone a severe wear of hydraulic pump. The replacement of the double pump after the new test proved that the system has returned to normal.

Because the hydraulic pump premature wear, therefore, we also examined the hydraulic oil and hydraulic oil tank, because in use do not pay attention to the cleanliness of hydraulic oil caused by impurities into the system, there are a lot of impurity particles in the tank, the return oil filter is blocked, the bypass valve return oil filter at the lower part of the open, lost the filtration capacity. The replacement of hydraulic oil and oil filter element after the new machine returned to normal.

There is evidence that the hydraulic system 70 above fault and hydraulic oil related. In this case, because of impurities into the system caused by oil pollution, the hydraulic pump premature wear and leakage increases, volumetric efficiency decreases, the temperature; the temperature in turn makes leakage increased. This vicious cycle not only caused premature retirement of the hydraulic pump, but also caused the seal failure of the hydraulic cylinder and the instability of the system. Therefore, in the process of using the machine, be sure to maintain the cleanliness of hydraulic oil, regular inspection and replacement of filter elements. This must cause enough attention to users.