Created on:2021-06-24 14:01

Tractor hydraulic failure -- hose burst and system leakage

Tractor hydraulic failure -- hose burst and system leakage

1、 Hose burst

In the separate hydraulic system of Dongfanghong-75, tieniu-55 and dongfanghong-28 tractors, there is a rubber hose in the pipeline connecting the distributor and the hydraulic cylinder. When repairing the hydraulic system of these vehicles, it is often found that these hydraulic hoses burst. Hydraulic hose burst, hydraulic oil leakage, affect the normal work of the hydraulic system.

(1) Causes of hydraulic hose burst

① When the distributor control handle is in the neutral position, the oil holes leading to the front and rear cavities of the oil cylinder are closed, and the oil can neither enter into the hydraulic cylinder nor flow out of the hydraulic cylinder, so that the farm tools, the suspension mechanism and the piston of the hydraulic cylinder are integrated. When the tractor is working on farmland, if the control handle is always in the neutral position, the piston will be forced to move up and down due to the uneven ground, resulting in a sharp increase in the oil pressure in the hydraulic hose and the hydraulic hose will be squeezed out. Therefore, when ploughing, the handle should be placed in the "floating" position.

② When the suspension system lifts the farm tools to the transportation position, the distributor handle will automatically jump to the neutral position. When driving at high speed on uneven road, the high-pressure hose has to bear the impact load several times larger than the original pressure, and the safety valve of the distributor can not be opened in time, resulting in the rupture of the high-pressure hose. Therefore, the tractor should drive at a low speed on uneven roads. In the transportation state, when hanging farm tools, the positioning valve of the hydraulic cylinder should be pressed down.

③ When the farm implements are in the transportation position, if the sealing between the piston and cylinder barrel of the hydraulic cylinder is not tight, and the piston leaks oil, the farm implements will settle, and the oil in the lower chamber of the hydraulic cylinder will flow into the upper chamber until the pressure in the upper and lower chambers is equal. At this time, if the tractor bumps on the uneven road, the farm tools will continue to drop, and the push rod entering the hydraulic cylinder will squeeze the oil to the oil pipe with great pressure, causing the hydraulic hose to be broken.

④ Improper use of high-pressure hose, hydraulic hose aging, extrusion, long-term excessive bending and twisting state, reduce the bearing pressure, even under normal working pressure, the hose will burst.

(2) Prevention of hydraulic hose burst

① When the hydraulic system suspends the farm tools with depth adjustment device, the distributor control handle must be placed in the floating position, not in the neutral position.

② The tractor should be driven at low speed when hanging farm tools on uneven road or crossing ditches.

③ When maintaining the hydraulic system, pay attention to check the tightness of the hydraulic cylinder, and replace the piston or piston oil seal in time if it is unqualified.

④ For the hydraulic hose in use, a thin iron wire with a diameter of 1-1.5mm can be used to properly wrap a layer on its outer surface to improve the pressure resistance. When the tractor is parked for a long time, the hydraulic hose should be removed and stored in a dry and clean place to avoid sun exposure.

2、 System leakage

The hydraulic linkage of a zhongyuan-180 small four-wheel tractor can't be lifted. After inspection, the hydraulic oil level is only 10 mm high, indicating that the hydraulic oil is insufficient. So full of hydraulic oil test, hydraulic take-off and landing normal.

But after starting, just a few steps to test the hydraulic pressure, still the same as before, can't rise.

Once checked, there was no hydraulic oil, so it was suspected that the bottom plate of the hydraulic oil tank was broken or the sealing gasket was broken, and the hydraulic oil leaked into the gearbox, but the results of disassembly inspection showed no above phenomenon. Then the next way of oil leakage is the gear pump. When the gear pump is removed, it turns out that the pump shaft seal is not installed in place.

Replaced a new oil seal, filled with hydraulic oil, test again, everything is normal. But after stopping for a while, the linkage still couldn't lift and the hydraulic oil was gone.

People judged that the fault must still be in the gear pump, so they removed the gear pump for inspection, and found that the new seal was washed out again. When the gear pump was disassembled, the sealing blocks at both ends of the gear of the pump were wrongly installed, which could not play the role of sealing at all. The hydraulic oil flowed into the gear box through this. Later, the sealing block was installed in the right direction, and everything returned to normal.

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