For mechanized construction enterprises, whether the technology condition of construction machinery is good or not is a direct factor for the normal production of enterprises. For the hydraulic transmission engineering machinery, the normal operation of the hydraulic system is a main sign of its good technical condition. Qualified hydraulic oil is the guarantee for reliable operation of the hydraulic system, and proper maintenance is the basis for reliable operation of the hydraulic system. For this reason, I make a rough discussion on the maintenance of hydraulic system of construction machinery in general working environment according to the work practice.
1 select the suitable hydraulic oil
Hydraulic oil plays the role of transmitting pressure, lubrication, cooling and sealing in the hydraulic system. The improper selection of hydraulic oil is the main reason for the early failure of the hydraulic system and the decline of the durability. Hydraulic oil should be selected according to the number of the random "instructions". When special oil is used in special case, the performance of the oil should be the same as that of the original brand. Different grades of hydraulic oil can not be mixed to prevent chemical reactions and performance changes of hydraulic fluids.
Maintenance methods and measures for hydraulic systems of common construction machinery
Dark brown, milky white, and odorous hydraulic oil is a metamorphic oil that can not be used.
2 prevent solid impurity into hydraulic system
The clean hydraulic oil is the life of the hydraulic system. There are many precision parts in the hydraulic system, some have damping holes, some have cracks. If the solid impurity invasion will cause the precision parts to be pulled, hairpin and oil passage blockage, it will endanger the safe operation of the hydraulic system. General solid impurities into the hydraulic system through: hydraulic oil dirty; dirty refueling tools; refueling and maintenance, careless maintenance; hydraulic components, such as chip removal. The solid impurity invasion system can be prevented from the following aspects:
2.1 refueling time
The hydraulic oil must be filtered and filled, and the refueling tools should be reliable and clean. It is not possible to remove the filter at the fuel tank outlet in order to improve the speed of refueling. Refueling personnel should use clean gloves and work clothes to prevent solid impurities and fiber impurities from falling into the oil.
2.2 maintenance
Disassemble the refueling cover of the hydraulic oil tank, the cover of the filter, the testing hole, the hydraulic tubing and so on. It is necessary to avoid the dust when the system oil channel is exposed, and the disassembly part should be thoroughly cleaned before it can be opened. If the oil tank is dismantled, the soil around the tank cover is removed, the cover of the oil tank is loosened, the residue remaining in the joint is cleared (and the water can not be rinsed into the tank), and the oil tank cover can be opened after cleaning. When wiping materials and hammers are needed, wiping materials that do not remove fiber impurities and special hammers with rubber attached to the hitting surface should be selected. Hydraulic components and hydraulic hoses should be carefully washed and assembled after high pressure air drying. It is necessary to select the intact filter cartridge (damaged in the inner packing), even though the filter core is intact, it may be unclean. While cleaning the filter while changing the oil, wipe the material before installing the filter element and carefully clean the bottom dirt in the filter shell.
2.3 cleaning of hydraulic system
Cleaning oil must use the same brand of hydraulic oil as the system, the oil temperature is between 45 80 C, with a large flow as far as possible to remove impurities from the system. The hydraulic system should be cleaned more than three times. After each cleaning, it will be discharged from the system when the oil is hot. After cleaning, clean the filter, replace the new filter element and add the new oil.
3 prevent air and water intrusion hydraulic system
3.1 air intrusion prevention hydraulic system
In the normal pressure and normal temperature, the hydraulic oil contains 6 to 8% of the air. When the pressure is reduced, the gas will come out from the oil, and the bubbles break up to make the hydraulic element "cavitation" and produce noise. A large amount of air entering oil will aggravate the phenomenon of "cavitation", the compressibility of hydraulic oil increases, the work is unstable, the working efficiency is reduced, and the execution of the work "crawling" and so on. In addition, the air will also oxidize the hydraulic oil and accelerate the deterioration of the oil. To prevent air invasion, the following points should be paid attention to:
1, after repair and oil change, it is necessary to exclude the air in the system according to the random instruction manual, so that it can operate normally.
2, the oil suction pipe mouth of the hydraulic oil pump must not expose the oil surface, and the oil suction pipeline must be well sealed.
3, oil pump driving shaft seal should be good, should pay attention to replace the oil seal should use "double lip" positive oil seal, can not use "single lip" oil seal instead, because the "single lip" oil seal can only seal one one oil, do not have the function of sealing gas. After a heavy repair of the ZL50 loader in this unit, the hydraulic oil pump has continuous "cavitation" noise, and the oil tank oil level rises automatically. After inquiring the repair process of the hydraulic oil pump, it is found that the oil seal of the hydraulic oil pump drive shaft is misused as the "single lip" oil seal.
3.2 water intrusion prevention hydraulic system
Excessive moisture in oil will cause corrosion of hydraulic components, oil emulsion deterioration, lubricant film strength reduction, and accelerate mechanical wear.
In addition to maintenance and maintenance to prevent water invasion, but also to pay attention to the oil storage bucket should not be used, tighten the lid, the best inverted placement; the oil with large amount of water should be filtered many times, each filter once replaced by a drying filter paper, in the absence of special instrument testing, the oil can be dripped to the hot iron plate, no steam emerge side by side. That is, the burning side can be added to the injection.
Precautions in 4 assignments
4.1 the mechanical work should be smooth and smooth
Mechanical operation should avoid rough, otherwise it will produce impact load, which will cause frequent mechanical failures and shorten the service life greatly. The impact load produced during the operation, on the one hand, causes the early wear, fracture and breakage of the mechanical structure parts. On the one hand, the impact pressure is produced in the hydraulic system. The impact pressure will cause the damage of the hydraulic components, the oil seal and the premature failure of the oil seal and the joint of the high pressure tubing joint and the hose, and the oil temperature rise frequently. My unit has bought a new UH171 shovel excavator, in the operation every 4~6 days the Doumen oil pipe will leak or burst, the tubing is a random import of the pure positive products, there are no quality problems. Through field observation, it was found that the opening and closing of Doumen caused strong impact on the block and doorframe. To avoid the impact load effectively: the operation rules must be strictly enforced; the hydraulic valves are open and closed not too fast; avoid the strong impact of the movement of the working device components to the limit position; the hydraulic equipment without the impact function can not use the working device (such as the shovel of the excavator) to hit the operating object violently to achieve a broken goal. Yes. There is another notable problem: the operator should be stable. Because there are certain differences in the free clearance of each equipment control system, the wear degree of the connecting parts is different and the gap is different, the size of the engine and hydraulic system is different, and these factors give the personality of the equipment. Only with the operator of the equipment, the manipulating action of the equipment can be corrected to adapt to the personality of the equipment. After a long period of operation, a good habit of operating the personality of the equipment can be formed. The general machinery industry insists on the fixed machine system, which is also one of the factors.
4.2 attention should be paid to cavitation and overflow noise
In the operation, we should pay attention to the sound of the hydraulic pump and the overflow valve. If the hydraulic pump has "cavitation" noise, it can not be eliminated after the exhaust. It is necessary to find out the reasons and eliminate the failure. If an actuator is slow in action without load and accompanied by overflow valve, it should be shut down for maintenance immediately.
4.3 strictly enforce the handover class system
When the driver shifts to stop the machine, he must ensure the safety of the driver during the inspection and check the accurate oil level. Whether the leakage of the system, the connection is loose, the bump of the piston rod and the hydraulic hose, the reliability of the connection of the low pressure inlet pipe of the hydraulic pump and the correct oil level of the tank, are the key points for the successor driver to check the hydraulic system. The normal pressure tank should also check and clean the air hole of the tank to keep it unblocked, in order to prevent the gas hole from blocking the tank vacuum, causing the hydraulic oil pump to suck the oil hard and damage.
4.4 maintain a suitable oil temperature
The working temperature of the hydraulic system is generally controlled between 30~80 degrees (the dangerous temperature is more than 100 degrees Celsius). The high oil temperature of the hydraulic system will lead to the decrease of oil viscosity, the leakage of oil, the decrease of efficiency, the decrease of the strength of the lubricating oil film, the acceleration of the wear of the machinery, the formation of carbide and silt, the oxidation of oil to accelerate the deterioration of the oil quality, and the premature aging of the oil seal and the high pressure hose. In order to avoid excessive temperature: do not overload for a long time; pay attention to the radiator radiator not to be contaminated by oil, to influence the effect of heat dissipation by adhering to dust soil; keep enough oil to help the circulating heat of the oil; do not work all day in the hot summer and avoid the high temperature at noon. When the oil temperature is too low, the viscosity of the oil is large, the fluidity is poor, the resistance is large and the working efficiency is low. When the oil temperature is below 20 C, the hydraulic motor, valve, pipe and so on are easily damaged. At this time, it is necessary to carry out the warm machine operation, start the engine, the idle idle running 3 ~ 5min, increase the engine speed with the medium speed throttle, control the handle to make any action of the working device (such as the excavator Zhang Dou) to the limit position, and keep the hydraulic oil to raise the temperature by 3 to the overflow. If the oil temperature is lower, it is necessary to increase the running time of the warmer properly.
4.5 control of pressure and oil amount of hydraulic oil tank
Pressure type fuel tank should pay attention to the pressure of the fuel tank at any time during work, and the pressure must be kept within the range stipulated in the random "instructions for use". Low pressure, insufficient oil pump suction easy to damage, too high pressure, will make the hydraulic system oil leakage, easy to cause low-pressure oil pipeline burst. For the equipment after maintenance and oil transfer, after exhausting the air in the system, it is necessary to check the oil level state according to the random "instructions" and stop the machine in the flat place. After the engine is flameout 15min, the oil level will be rechecked. If necessary, it should be supplemented.
4.6 other matters of attention
In operation, we should prevent falling rocks from hitting hydraulic cylinders, piston rods, hydraulic tubing and other components. If there is a small clicking injury on the piston rod, it should be used in time to grinded the edge edge of the small point with oil stone, in order to prevent the sealing device of the piston rod, and can continue to use in the case of no oil leakage. Equipment that has been shut down for more than 24h will be injected into the hydraulic pump before starting, so as to prevent damage caused by dry grinding of the hydraulic pump.
5 precautions for regular maintenance
At present, some engineering machinery hydraulic systems have set up an intelligent device. This device has some warning functions for some hidden troubles in the hydraulic system, but the range and extent of its monitoring are limited, so the inspection and maintenance of the hydraulic system should be combined with the monitoring results of the intelligent device and the regular inspection and maintenance.
5.1 250h inspection and maintenance
Checking the attachments on the filter screen, such as too much metal powder, often marks the oil pump wear or cylinder cylinder, which must be confirmed and take appropriate measures to open the machine. If it is found that the filter screen is damaged and the dirt is accumulated, it is necessary to replace it in time and replace the oil at the same time if necessary.
5.2 500h inspection and maintenance
The filter core should be replaced regardless of the filter core condition, because it is difficult to detect the small damage of the filter core by the naked eye, and the filter core should be replaced in advance if the high temperature operation is long.
5.3 1000h inspection and maintenance
Clean the filter, replace the filter element, clean the hydraulic oil tank, and replace the hydraulic oil. The long term high temperature operation time should be advanced in advance. Of course, it is the most economical to guide oil exchange through oil testing and analysis, but should pay attention to prolong the use of oil, every 100h should be detected once, in order to find and replace the oil in time.
5.4 7000h and 10000h inspection maintenance
The hydraulic system must be checked by professional personnel for necessary adjustment and maintenance. According to practice, the imported hydraulic pump and hydraulic motor must be overhauled after working 10000h, otherwise the hydraulic pump and motor may be damaged because of the loss of repair, and the hydraulic system is destructive to the hydraulic system.
