For the mechanized construction enterprises, whether the construction machinery technology is good or not is the direct factor for the normal production of the enterprises. As far as the construction machinery with hydraulic transmission is concerned, the normal operation of the hydraulic system is a main sign of its good technical condition. Qualified hydraulic oil is the guarantee of reliable operation of hydraulic system, and correct maintenance is the basis of reliable operation of hydraulic system. According to the working practice, the maintenance of the hydraulic system of construction machinery in the general working environment is discussed.
The hydraulic oil plays a role of transmitting pressure, lubricating, cooling and sealing in the hydraulic system. The improper selection of hydraulic oil is the main reason for the early failure and durability decline of the hydraulic system. The hydraulic oil shall be selected according to the brand specified in the attached operation manual. When the substitute oil is needed in special circumstances, the performance shall be the same as that of the original brand. Different brands of hydraulic oil can not be mixed to prevent chemical reaction and performance change of hydraulic oil. The dark brown, milky white and peculiar smell hydraulic oil is metamorphic oil and cannot be used.
Prevent solid impurities from mixing into hydraulic system
Clean hydraulic oil is the life of hydraulic system. There are many precise coupling parts in the hydraulic system, some have damping holes, some have gaps, etc. If the solid impurities intrude, it will cause the precise couple to be pulled, stuck and the oil passage to be blocked, endangering the safe operation of the hydraulic system. Generally, the ways of solid impurities invading the hydraulic system are: unclean hydraulic oil; unclean refueling tools; careless refueling and maintenance; hydraulic components desquamation, etc. Solid impurities can be prevented from invading the system from the following aspects:
2.1 when refueling
The hydraulic oil must be filtered and filled, and the filling tools shall be reliable and clean. Do not remove the filter at the oil filler of the oil tank in order to improve the oil filling speed. Refueling personnel shall use clean gloves and work clothes to prevent solid and fiber impurities from falling into the oil.
Remove the oil filling cover, filter cover, inspection hole, hydraulic oil pipe and other parts of the hydraulic oil tank, so as to avoid dust when the system oil channel is exposed. The removed parts shall be cleaned thoroughly before opening. For example, when removing the oil filler cap of the hydraulic oil tank, remove the mud around the cap, loosen the cap, remove the sundries left at the joint (do not wash with water to prevent water from seeping into the tank), and open the cap after cleaning. If it is necessary to use the wiping materials and hammers, it is necessary to select the wiping materials that do not remove the fiber impurities and the special hammers with rubber attached to the striking surface. Hydraulic components and hydraulic rubber pipes shall be cleaned carefully and assembled after being dried by high-pressure air. Select the genuine filter element with good package (the inner package is damaged, although the filter element is intact, it may not be clean). When changing oil, clean the filter at the same time. Before installing the filter element, carefully clean the dirt at the bottom of the filter housing with wiping materials.
2.3 cleaning of hydraulic system
The cleaning oil must be hydraulic oil with the same brand as the system. The oil temperature is between 45 ℃ and 80 ℃, and the impurities in the system shall be removed as much as possible with large flow. The hydraulic system shall be cleaned repeatedly for more than three times. After each cleaning, the system shall be fully discharged when the oil is hot. After cleaning, clean the filter, replace the filter element and fill in new oil.
Prevent air and water from entering the hydraulic system
3.1 prevent air intrusion into hydraulic system
Under normal pressure and normal temperature, the hydraulic oil contains air with a volume ratio of 6-8%. When the pressure is reduced, the air will come out of the oil, and the air bubble will burst, causing "cavitation" of the hydraulic components, resulting in noise.
A large amount of air entering into the oil will aggravate the phenomenon of "cavitation", increase the compressibility of the hydraulic oil, make the work unstable, reduce the work efficiency, and cause the "crawling" of the actuator. In addition, air will oxidize the hydraulic oil and accelerate the deterioration of the oil. To prevent air intrusion, the following points should be noted:
1. After maintenance and oil change, the air in the system shall be removed according to the provisions of the attached operation manual, so as to operate normally.
2. The oil suction pipe orifice of the hydraulic oil pump shall not be exposed to the oil surface, and the oil suction pipe must be well sealed.
3. The drive shaft of the oil pump should be well sealed. It should be noted that when replacing the oil seal, the "double lip" genuine oil seal should be used instead of the "single lip" oil seal, because the "single lip" oil seal can only seal oil unidirectionally and does not have the function of sealing gas. After the overhaul of a Liugong ZL50 loader, the hydraulic oil pump had continuous "cavitation" noise and the oil level of the oil tank increased automatically. After querying the repair process of the hydraulic oil pump, it was found that the oil seal of the drive shaft of the hydraulic oil pump was caused by the misuse of the "single lip" oil seal.
3.2 prevention of water intrusion into the hydraulic system
Excessive moisture in the oil will make the hydraulic components rusted, the oil emulsion deteriorated, the strength of the lubricating oil film reduced, and the mechanical wear accelerated. In addition to preventing moisture intrusion during maintenance, it is also necessary to tighten the cover when the oil storage barrel is not in use, and it is better to place it upside down; the oil with large moisture content shall be filtered for many times, Replace the dried filter paper every time for filtration. When there is no special instrument for detection, drop the oil onto the hot iron plate. Fill the filter paper only after no steam emerges and burns immediately.
4.1 soft and smooth mechanical operation
Rough operation shall be avoided in mechanical operation, otherwise impact load will inevitably occur, which will cause frequent mechanical failure and greatly shorten service life. The impact load generated during operation, on the one hand, causes early wear, fracture and breakage of mechanical structure parts, on the other hand, causes impact pressure in the hydraulic system, and the impact pressure will cause damage of hydraulic components, premature failure of oil seal and high-pressure oil pipe joint and rubber pipe joint, oil leakage or pipe burst, frequent action of overflow valve and oil temperature rise.