For mechanized construction enterprises, whether the technical condition of construction machinery is good or not is the direct factor of normal production. The normal operation of hydraulic system is a main sign of good technical condition of hydraulic transmission construction machinery. Qualified hydraulic oil is the guarantee of reliable operation of hydraulic system, and correct maintenance is the fundamental of reliable operation of hydraulic system.

1. Select the appropriate hydraulic oil

Hydraulic oil plays the role of pressure transfer, lubrication, cooling and sealing in hydraulic system. Improper selection of hydraulic oil is the main reason for early failure and durability decline of hydraulic system. The hydraulic oil should be selected according to the brand specified in the manual. When the substitute oil is used in special circumstances, its performance should be the same as the original brand. Different grades of hydraulic oil can not be mixed to prevent chemical reactions and performance changes of hydraulic oil.

Dark brown, milky white, smelly hydraulic oil is metamorphic oil, can not be used.

2. Prevent solid impurities from mixing with the hydraulic system

Clean hydraulic oil is the life of hydraulic system. There are many precision parts in the hydraulic system, some have damping holes, some have gaps, etc. The intrusion of solid impurities will cause strain of precision couplings, hairpin, blockage of oil channel, and endanger the safe operation of the hydraulic system. General solid impurities invade the hydraulic system in the following ways: hydraulic oil dirty; The oil tool is unclean; Careless refueling, repair and maintenance; Hydraulic components, such as chip removal. Solid impurities can be prevented from invading the system in the following ways:

2.1 when refueling

The hydraulic oil must be filtered and filled, and the refueling tool should be reliable and clean. Do not remove the filter at the tank filling port to increase the filling speed. Refueling personnel should use clean gloves and overalls to prevent solid and fibrous impurities from falling into the oil.

2.2 maintenance

Remove the refueling cover, filter cover, test hole, hydraulic oil pipe and other parts of the hydraulic tank, resulting in the exposure of the system oil channel to avoid dust, the disassembly part should be thoroughly cleaned before opening. When removing the hydraulic tank cover, remove the soil around the tank cover first, loosen the tank cover, remove the debris remaining in the joint (can not be washed with water to avoid water infiltration into the tank), and confirm the cleaning before opening the tank cover. If you need to use the wiping material and hammer, should not remove the fiber impurities of the wiping material and the hitting surface of the rubber attached to the special hammer. Hydraulic components, hydraulic hose should be carefully cleaned, with high pressure wind dry after assembly. Select the authentic filter element with intact packaging (the inner packaging is damaged, although the filter element is intact, it may also be dirty). When changing the oil, clean the filter at the same time. Before installing the filter element, wipe the material carefully to clean the dirt at the bottom of the filter shell.

2.3 Cleaning of hydraulic system

The cleaning oil must be the same as the brand of hydraulic oil used in the system. The oil temperature is between 45 ℃ and 80℃. The impurities in the system should be taken away with a large flow rate as far as possible. The hydraulic system should be cleaned repeatedly more than three times, and after each cleaning, the oil should be released into the system when it is hot. After cleaning, clean the filter, replace the new filter element and add new oil.

da (1)

3 Prevent air and water from invading the hydraulic system

3.1 Prevent air from invading the hydraulic system

At normal pressure and room temperature, the hydraulic oil contains a volume ratio of 6 ~ 8% air. When the pressure is reduced, the air will be free from the oil, and the bubble rupture will make the hydraulic components “cavitation” and produce noise. A large amount of air into the oil will aggravate the phenomenon of “cavitation”, increase the compressibility of hydraulic oil, work instability, reduce the work efficiency, the implementation of the element work “crawling” and other adverse consequences. In addition, the air will make the hydraulic oil oxidation, accelerate the deterioration of the oil. The following points should be paid attention to to prevent air invasion:

1. After maintenance and oil change, the air in the system should be excluded according to the provisions of the random Manual for normal operation.

2. The suction pipe mouth of the hydraulic oil pump shall not expose the oil surface, and the suction pipe line must be well sealed.

da (2)

3, the oil pump drive shaft seal should be good, pay attention to the replacement of the oil seal should use the “double lip” genuine oil seal, can not be replaced by the “single lip” oil seal, because the “single lip” oil seal can only seal oil one-way, does not have the function of sealing gas. After the overhaul of a LIugong ZL50 loader in our unit, the hydraulic oil pump appeared continuous “cavitation” noise and the oil level of the oil tank automatically increased, etc. After inquiring the repair process of the hydraulic oil pump, it was found that it was caused by the misuse of “single lip” oil seal for the driving shaft of the hydraulic oil pump.

3.2 Prevent water from invading the hydraulic system

Oil contains excessive water, will make hydraulic components rust, oil emulsion deterioration, lubricating film strength reduction, accelerate mechanical wear.

In addition to maintenance to prevent moisture invasion, but also pay attention to the oil storage bucket is not used, to tighten the lid, the best inverted placement; The oil with large water content should be filtered several times, and the dried filter paper should be replaced every time it is filtered. When there is no special instrument to detect it, the oil can be dropped onto the hot iron plate, and no steam can be emitted and burned immediately before filling.

4 Points for attention in homework

4.1 Mechanical operation should be soft and smooth

Mechanical operation should avoid rough, otherwise it will inevitably produce impact load, make mechanical failure frequent, greatly shorten the service life. The impact load produced during operation, on the one hand, causes early wear, fracture and breakage of mechanical structural parts, on the other hand, produces impact pressure in the hydraulic system, and impact pressure will damage hydraulic components, premature failure of oil seal and high-pressure tubing joint and rubber hose, oil leakage or pipe explosion, and frequent action of relief valve oil temperature rise. My unit has purchased a new UH171 shovel excavator, the operation every 4 ~ 6 days the door oil pipe will leak or burst, the oil pipe is random import of pure products, no quality problems after testing. Through field observation, it is found that the gate is caused by strong impact on the limit block and door frame when opening and closing. To effectively avoid the impact load: must strictly implement the operating procedures; Hydraulic valve opening, closing can not be too fast; Avoid the working device component movement to the limit position to produce strong impact; Hydraulic equipment without impact function can not be used to violently impact the working object with working devices (such as the bucket of excavator) to achieve the purpose of crushing. There is one other issue worth paying attention to: the operator should maintain a steady hand. Because the free clearance of the control system of each device is different, the wear degree of the connection part is different and the clearance is different, and the output size of the engine and hydraulic system is not the same, these factors give the personality of the device. Only operators using the equipment carefully explore and modify their manipulation actions to adapt to the personality of the equipment, after a long period of operation, can develop good operating habits in line with the personality of the equipment. General mechanical industry adhere to the fixed mechanism, which is one of the factors.

4.2 Pay attention to cavitation and overflow noise

During the operation, we should always pay attention to the sound of the hydraulic pump and the relief valve. If the cavitation noise of the hydraulic pump can not be eliminated after exhaust, the cause should be found out and the fault can not be used. If an executive component is slow when there is no load, and accompanied by the overflow valve overflow sound, it should be immediately shut down for maintenance.

da (3)

4.3 Strictly implement the shift handover system

When the shift driver parks the machinery, it is necessary to ensure the safety and check the exact oil level when the shift driver checks. Whether the system leakage, whether the connection is loose, whether the piston rod and the hydraulic hose is injured, whether the low pressure inlet pipe connection of the hydraulic pump is reliable, whether the oil level of the tank is correct, etc., is the focus of the succession driver to check the hydraulic system. Atmospheric oil tank should also check and clean the gas tank vent, keep it unblocked, in order to prevent the gas tank vacuum caused by pore blockage, resulting in the hydraulic oil pump oil absorption difficulty and damage.

4.4 Maintain appropriate oil temperature

The working temperature of the hydraulic system is generally controlled between 30 and 80℃ (dangerous temperature ≥100℃). The high oil temperature of the hydraulic system will lead to: the viscosity of the oil is reduced, easy to cause leakage, and the efficiency is decreased; The strength of lubricating oil film is reduced and the wear of machinery is accelerated; Forming carbides and ballast; Oxidation of oil accelerates deterioration of oil quality; Oil seal, high pressure hose premature aging. To avoid excessive temperature: do not overload for a long time; Pay attention to the radiator radiator not to be polluted by oil, to prevent dust attachment affect the heat dissipation effect; Maintain enough oil to facilitate the circulation of oil heat dissipation; Do not work all day in hot summer, to avoid the high temperature time at noon. When the oil temperature is too low, the oil viscosity is large, the fluidity is poor, the resistance is large, the working efficiency is low; When the oil temperature is lower than 20℃, the sharp turn is easy to damage the hydraulic motor, valve, pipeline, etc. At this time, it is necessary to carry out hydraulic pump repair and warm-up machine operation, start the engine, and after no-load idle operation for 3-5 minutes, increase the engine speed with medium speed throttle, manipulate the handle to make any action of the working device (such as the excavator bucket) to the limit position, and keep the hydraulic oil rising through the overflow for 3-5 minutes. If the oil temperature is lower, it is necessary to increase the running time of the warm machine appropriately.

4.5 Control of pressure and oil quantity of hydraulic tank

In the work of pressure tank, pay attention to the pressure of the tank at any time, and the pressure must be kept within the range specified in the Manual. If the pressure is too low and the oil pump is not enough to absorb oil, it is easy to damage. If the pressure is too high, the hydraulic system will leak oil and it is easy to cause the low-pressure oil pipeline to burst. For the equipment after maintenance and oil change, after exhausting the air in the system, it is necessary to check the oil level state according to the provisions of the random Operation manual, stop the machine in a flat place, check the oil level again after engine flout for 15min, and supplement if necessary.

4.6 Other Precautions

During the operation, it is necessary to prevent falling stones from hitting hydraulic cylinders, piston rods, hydraulic tubing and other components. If there is a small point on the piston rod, it is necessary to use the whetstone to grind the edge around the small point in time to prevent the destruction of the piston rod sealing device, in the case of no oil leakage can continue to use. For the equipment that has been continuously shut down for more than 24 hours, oil should be injected into the hydraulic pump before starting to prevent the hydraulic pump from dry grinding and damage.

5. Precautions for regular maintenance

At present, some hydraulic systems of construction machinery are equipped with intelligent devices, which have the function of warning some hidden dangers of the hydraulic system, but its monitoring scope and degree have certain limitations, so the inspection and maintenance of the hydraulic system should combine the monitoring results of intelligent devices with regular inspection and maintenance.

5.1 250h Inspection and maintenance

Check the attachment on the filter screen, such as too much metal powder, often marks the oil pump wear or cylinder pulling, for this, hydraulic pump maintenance must be diagnosed and take corresponding measures before starting. If it is found that the filter is damaged and dirt accumulates, it is necessary to replace it in time, and change the oil when necessary.

5.2 500h inspection and maintenance

No matter how the condition of the filter element should be replaced, because it is difficult to detect the small damage of the filter element by the naked eye. If the operation at high temperature for a long time, the filter element should be replaced appropriately in advance.

5.3 1000h Inspection and maintenance

Clean the filter, replace the filter element, clean the hydraulic tank, and replace the hydraulic oil. The oil change time of long-term high temperature operation should be appropriately advanced. Of course, it is most economical to guide oil change through oil quality detection and analysis, but attention should be paid to the extended use of oil, every 100h should be tested, in order to find and replace the deteriorated oil in time.

5.4 7000h and 10000H Check and maintain

The hydraulic system needs to be tested by professional personnel for necessary adjustment and maintenance. According to practice, the imported hydraulic pump and hydraulic motor must be overrepaired after working for 10,000 hours, otherwise the hydraulic pump and motor may be damaged due to disrepair, which is the ultimate destruction of the hydraulic system.