Prevention method of cavitation failure of hydraul

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Prevention methods for cavitation failure of hydraulic cylinder of construction machinery

prevention methods for cavitation failure of hydraulic cylinder of construction machinery

China Construction machinery information

the harm of cavitation in hydraulic cylinder is quite large, which will lead to the blackening of mating surface, and even the scorching of support ring and seal ring, resulting in internal leakage of hydraulic cylinder. When cavitation and other types of corrosion work together, it will accelerate the corrosion rate of the main parts of the hydraulic cylinder several times or even dozens of times, which will seriously affect the normal use of construction machinery. Therefore, it is necessary to prevent the cavitation of hydraulic cylinder

1. The main causes of cavitation

⑴ the essential analysis of cavitation

cavitation is mainly caused by a certain amount of air mixed in the oil between the piston and the guide sleeve during the working process of the hydraulic cylinder. With the gradual increase of pressure, the gas in the oil will become bubbles. When the pressure rises to a certain limit value, these bubbles will break under the action of high pressure, which will quickly act on the surface of parts with high temperature and high pressure, resulting in gas corrosion of hydraulic cylinders and corrosive damage of parts

⑵ cavitation caused by unqualified hydraulic oil quality

ensuring the quality of hydraulic oil is an important factor to prevent cavitation. If the foam resistance of the oil is poor, it is easy to produce foam, resulting in cavitation. Secondly, the change frequency of oil pressure is too fast and too high, which will also directly cause the formation of bubbles and accelerate the rupture speed of bubbles. The test shows that the speed of cavitation will be accelerated in the parts with high pressure change frequency. For example, at the inlet and return ports of the hydraulic cylinder, due to the relatively high frequency of pressure changes, the degree of cavitation is also relatively higher than other parts. In addition, overheating of oil will also increase the probability of cavitation

⑶ cavitation caused by improper manufacturing and maintenance

because the hydraulic system is not fully vented during assembly or maintenance, there is gas in the system, which can produce cavitation under the action of high temperature and high pressure

⑷ there is a problem with the quality of the coolant, leading to cavitation erosion

when the coolant contains corrosive media, such as various acid radical ions, oxidants, etc., it is prone to chemical and electrochemical corrosion, etc. under their combined action, it will also accelerate the speed of cavitation erosion; If the cooling system is well maintained, cavitation can be prevented. For example, if the pressure cap of the radiator of the cooling system is well maintained, the coolant pressure of the radiator can always be higher than the vapor pressure, so as to prevent cavitation. Another example is the thermostat of the cooling system; A thermostat with good performance can keep the coolant within the appropriate temperature range and reduce the energy released when bubbles burst

2. Measures to prevent cavitation erosion

although the causes of cavitation erosion are various, cavitation erosion can be avoided as long as necessary measures are taken to actively prevent it. The following is about the preventive measures that should be taken in view of the causes of cavitation

⑴ strictly turn off the selection of hydraulic oil

select hydraulic oil in strict accordance with the oil standard. Selecting high-quality hydraulic oil can effectively prevent bubbles in the working process of the hydraulic system. When selecting oil, you should choose according to the lowest temperature in different regions, fill hydraulic oil according to the dipstick standard, and keep the hydraulic system clean, which is conducive to the continuous growth of high-performance composite materials in the fields of aerospace and national defense utilization (when filling hydraulic oil, you should prevent moisture and other impurities from being brought in), and often check the oil quality, oil level and oil color of hydraulic oil. If bubbles and foam are found in hydraulic oil, Or when the oil turns milky white, carefully find the source of air in the oil and eliminate it in time

⑵ to prevent the oil temperature from being too high in fact and reduce the hydraulic shock

the key to keep the hydraulic oil temperature normal is to reasonably design the heat dissipation system and prevent the oil temperature from being too high. In case of abnormality, find out the cause and eliminate it in time. When operating the hydraulic control lever and distribution valve, we should strive to be stable, not too fast, too fierce, and not frequently increase the engine throttle, so as to minimize the impact of hydraulic oil on hydraulic components. At the same time, the cooling system should be maintained in time to keep the temperature of the cooling system within an appropriate range, so as to reduce the energy released when bubbles burst. Without affecting the normal circulation of coolant, a certain amount of anti-corrosion additives can be appropriately added to inhibit corrosion

⑶ maintain the normal clearance of the joint surface of each hydraulic element

when manufacturing or repairing the main parts of the hydraulic cylinder (such as cylinder block, piston rod, etc.), it should be assembled according to the tolerance lower limit of the assembly dimension. Practice has proved that this can well reduce the occurrence of cavitation. If cavitation has occurred to hydraulic components, only metallographic sandpaper polishing technology can be used to remove cavitation pitting and surface carbon deposition, and general fine sandpaper cannot be used for polishing

⑷ pay attention to exhaust during maintenance

after the maintenance of the hydraulic cylinder, the hydraulic system should run smoothly for a certain time, so that the hydraulic oil in the hydraulic system can be fully circulated; If necessary, disassemble the oil inlet pipe (or oil return pipe) of the hydraulic cylinder to overflow the hydraulic oil, so as to achieve the effect of exhaust of a single hydraulic cylinder

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