Created on:2021-07-01 09:21

Tractor hydraulic failure of farm tools lifting is weak or slow

Tractor hydraulic failure of farm tools lifting is weak or slow

(1) Farm tools cannot be improved

The lifting capacity of farm tools is not enough, that is, they can not reach the technical capacity (the lifting force per kilowatt traction power should not be less than 300N). The reasons are as follows.

① The serious wear of gear pump is mainly caused by long-term overload or dirty hydraulic oil.

② The reasons for the low pressure or oil leakage of the safety valve are: A. improper pressure adjustment; b. The lock nut is loose, which causes the safety valve sleeve to be loose; c. The compression spring has plastic deformation, which makes the elastic force decrease; d. Valve and seat wear, strain or dirt stuck. Carefully dismantle and inspect the parts of the safety valve. If the parts are damaged or deformed, they must be repaired. If they can't be repaired, they must be replaced. Then clean it, assemble and adjust it carefully to ensure the opening pressure is about 15.7mpa.

③ The main control valve sleeve is seriously worn. Replace the main control valve sleeve and grind it with the main control valve to ensure the fit clearance of 0.006 ~ 0.012mm.

④ The piston sealing ring of hydraulic cylinder is damaged. Replace the piston sealing ring.

⑤ The sealing rings at both ends of the shaft sleeve are damaged. Replace the sealing rings.

⑥ The seal ring of lowering speed regulating valve or block valve is damaged and replaced.

(2) Slow improvement of farm tools

When the hydraulic system is equipped with different farm tools, the required lifting speed is also different. For the hanging plow, the lifting time from cultivation to transportation is less than 2S for medium and small tractors and less than 3So for large tractors. The main reasons for the slow lifting are as follows.

① Air is drawn into the oil inlet pipe. This is because the sealing between the inlet pipe and the hydraulic pump and fuel tank is not strict. The damage of the oil pipe or the oil seal of the driving gear will cause the air to enter the oil passage, causing air and oil to form foam and produce emulsification. The volume of compressed gas shrinks and the working pressure decreases, resulting in the slow lifting of farm tools. Carefully check the pipeline and O-ring, tighten the nut and replace the O-ring if necessary. If air hole is found, it must be welded again. If there is insufficient work pressure and foam in the fuel tank, the air in the hydraulic system should be immediately removed. The elimination method is to operate the distributor handle and lift it continuously for several times, then loosen the vent plug of upper and lower cavities of the hydraulic cylinder, and then tighten it after the air is exhausted. The air in the pipeline is generally caused by the loosening of the nuts and screws of the pipeline joint, or the aging and damage of the O-ring and the welding air hole.

② The oil return valve in the distributor is stuck in the guide sleeve and cannot close the oil return passage. The oil from the hydraulic pump flows back to the oil tank from the oil return valve, which makes the pressure of the hydraulic cylinder too low.

③ If the oil temperature of the hydraulic system is too high or too low, the lifting of farm tools will be slow. When the temperature is too high, the viscosity of the oil decreases, the leakage increases and the pressure loss increases. The oil temperature is too low, the viscosity of oil is high, the filter of oil tank is slow, the flow performance of hydraulic oil is poor, it is not easy to flow into the suction pipe of hydraulic pump, which is easy to appear in winter. Therefore, before winter operation, preheating should be carried out in the way of oil circulation of the hydraulic system itself to keep the oil temperature at normal working temperature.

④ The serious internal leakage of the hydraulic pump reduces the flow of the pump, resulting in the slow lifting of farm tools. This is due to the hydraulic pump due to long-term use and wear, or due to the hydraulic pump seal ring failure, seal is not tight, causing leakage. If the seal is aged or damaged, replace it with a new one; If the shaft sleeve and gear pair wear, generally do not do repair, need to replace a new pump.

⑤ The poor contact between the distributor return valve and the valve seat makes the seal not tight, and also causes the slow lifting of farm tools. The valve and valve seat can be cleaned with diesel oil and put back to the original position. If the hydraulic oil is too dirty, the hydraulic oil should be replaced.

⑥ The pressure of distributor safety valve is low, and it opens in advance when working, so the hydraulic pressure in the hydraulic system is reduced, and the lifting of farm tools is slow. Solution: adjust the opening pressure of the safety valve and replace the spring of the safety valve.

⑦ The oil filter is blocked. Clean the oil filter, pipeline and lifter housing, and change the hydraulic oil.

⑧ The hydraulic oil level is too low. Enough hydraulic oil should be filled.

(3) Farm tools cannot be kept in transportation

① If the sinking of piston rod is more than 8 mm within 30 minutes, it may be due to the wear of piston seal or the wear between slide valve and hole in distributor. The distributor handle can be placed in the lifting position, and the positioning valve on the hydraulic cylinder can be lifted and pressed to check. If the settlement stops and shrinks after the positioning valve is depressed, it means that the slide valve of distributor is worn, otherwise, the piston seal is worn. This fault needs to be repaired and replaced with a new one.

② Oil leakage from the connection between the piston rod and the piston in the hydraulic cylinder will also cause the farm tools can not be kept in the transportation position. This fault can be eliminated by tightening the nut on the piston rod.

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