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Roadheader Knowledge (Part 1)

Oct. 16, 2020

未标题-15.jpgAnalysis of several failures of hydraulic system and their treatment measures

1. Malfunction of hydraulic oil

1. The hazards of high hydraulic oil temperature

①The viscosity of hydraulic oil, volumetric efficiency and hydraulic system work efficiency are all reduced, leakage increases, and even mechanical equipment cannot work normally.

②The parts of the hydraulic system expand due to overheating, which destroys the original normal matching gap of the relative moving parts, resulting in increased frictional resistance and easy jamming of hydraulic valves. At the same time, the lubricating oil film becomes thinner and mechanical wear increases, resulting in pumps, valves, Precision mating surfaces of motors, etc., become invalid or scrapped due to premature wear.

③Accelerate the deterioration of rubber seals, shorten their lifespan, and even lose their sealing performance, making the hydraulic system unable to work normally.

Causes, consequences and solutions of the increase in oil temperature of the hydraulic system of tunneling boring machine

(1) The hydraulic system has energy loss during work, including pressure loss, volume loss and mechanical loss. These losses are converted into heat energy, which increases the oil temperature of the hydraulic system. The oil temperature of the general hydraulic system should be controlled within the range of (30-60) ℃, and the highest should not exceed (hydraulic winch 60-70) ℃. The increase in oil temperature will cause a series of undesirable consequences: (decreases the viscosity of the oil, increases leakage, reduces the volumetric efficiency, and even affects the normal movement of the working mechanism;

(2) Deteriorate oil, produce oxide impurities, block small holes or gaps in hydraulic components, and make them unable to work normally;

(3) Cause the gap between relative moving parts with different thermal expansion coefficients to become smaller, or even get stuck and unable to move;

(4) Cause thermal deformation of the machine tool or machinery and destroy the original accuracy.

Measures to ensure the normal working temperature of the hydraulic system of the roadheader for mining:

1. When the setting value of the pressure control valve is too high, the working pressure should be lowered to reduce energy loss;

2. When heat is generated due to volume loss caused by the leakage of the hydraulic pump and its connections, the connections should be tightened to strengthen the seal;

3. When the fuel tank volume is small and the heat dissipation conditions are poor, the fuel tank volume should be appropriately increased, and a cooler should be installed if necessary;

4. Due to the high viscosity of the oil, when the internal friction increases and heat is generated, hydraulic oil with low viscosity should be used;

5. When the oil pipe is too slender and bent, which increases the resistance loss of the oil along the way and the oil temperature rises, the pipe diameter should be increased, and the pipeline should be shortened to make the oil unobstructed;

6. When the oil temperature rises due to the high ambient temperature, heat insulation materials and reflectors should be used to isolate the system from the outside world;

7. When high-pressure oil returns to the oil tank from the overflow valve unnecessarily for a long time, and the oil temperature rises, the circuit design should be improved, and variable pumps or unloading measures should be adopted;





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