For mechanical construction enterprises, whether the technical condition of construction machinery is good or not is the direct factor for the normal production of enterprises. Nowadays, most construction machinery adopts electromechanical hydraulic integration, and the normal operation of hydraulic system is a main sign of its good technical condition. Qualified hydraulic oil is the guarantee of reliable operation of hydraulic system. Correct maintenance is the foundation of reliable operation of hydraulic system. Xiaobian specially summarized some precautions for the maintenance of hydraulic system.
Only when the hydraulic system is well maintained can the giant of second-hand construction machinery move freely.
Hydraulic transmission technology has almost penetrated into all modern engineering fields. Compared with mechanical transmission and electric transmission, hydraulic transmission has unique advantages: (1) under the same volume, the power generated by hydraulic transmission device is greater than that generated by electrical device; (2) under the condition of the same power, the hydraulic transmission device has small volume, light weight and compact structure; (3) Hydraulic transmission has stable quality, high mechanical efficiency and good low-speed load characteristics.
Due to friction loss and leakage loss, the energy loss of hydraulic transmission system is large; The cleanliness of the oil is required to be high, and it is required to replace it regularly; The change of oil temperature will affect the control of running speed and noise. In addition, construction machinery often works outdoors, often in soil, sand and dust, wind, frost, snow and rain. The working load is often changeable and accompanied by vibration, and the working speed is often in transient transformation with inertial impact. Therefore, the hydraulic system of construction machinery should have special requirements: it should have good environmental adaptability and reliable sealing; It shall have higher working reliability and sensitive real-time response ability; It shall have better mobility to make the system closed and can make various changes. For these reasons, when using the hydraulic system, we should operate according to the relevant regulations.
1. Select the appropriate hydraulic oil
Hydraulic oil plays the role of transmitting pressure, lubrication, cooling and sealing in the hydraulic oil 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 it is necessary to use alternative oil under special circumstances, its performance shall be the same as that of the original brand. Hydraulic oils of different brands cannot be mixed to prevent chemical reaction and performance change of hydraulic oil. Dark brown, milky white and smelly hydraulic oil is deteriorated oil and cannot be used.
2. Precautions for regular maintenance
At present, some hydraulic systems of construction machinery are equipped with intelligent devices, which have warning functions for some hidden dangers of the hydraulic system, but their monitoring scope and accuracy have certain limitations. Therefore, the inspection and maintenance of the hydraulic system should combine the monitoring results of intelligent devices with regular inspection and maintenance.
250h inspection and maintenance
Check the attachments on the filter screen. If there is too much metal powder, it often indicates that the oil pump is worn or the oil cylinder is pulled. In this regard, it must be diagnosed and corresponding measures must be taken before starting the machine. If the filter screen is damaged and dirt accumulates, replace it in time, and replace the hydraulic oil if necessary.
500h inspection and maintenance
After 500h operation of construction machinery, the filter element shall be replaced regardless of its condition, because it is difficult to detect the small damage of the filter element with the naked eye. If it is operated at high temperature for a long time, the filter element shall be replaced in advance.
1000h inspection and maintenance
At this time, the filter should be cleaned, the hydraulic oil tank should be cleaned, the filter element and hydraulic oil should be replaced, and the oil change time for long-term high-temperature operation should be properly advanced. It is the most economical to guide the oil change through oil quality detection and analysis, but it should be noted that the hydraulic oil used for extension should be tested every 100h, so as to find and replace the deteriorated hydraulic oil in time.
7000h and 10000h inspection and maintenance
At this time, the hydraulic system of construction machinery needs to be tested by professionals for necessary adjustment and maintenance. Hydraulic pump and hydraulic motor may be damaged fatally after overhaul.
3. Prevent solid impurities from mixing into the hydraulic system
Clean hydraulic oil is the life of the hydraulic system. There are many precision coupling parts in the hydraulic system, some of which are equipped with damping holes or gaps. If solid impurities invade, it will cause strain of precision coupling parts, hairpin, oil duct blockage, etc., which will endanger the safe operation of hydraulic system. The invasion ways of general solid substances are: unclean hydraulic oil; Dirty refueling tools; Careless refueling, repair and maintenance; Desquamation of hydraulic components, etc. Solid impurities can be prevented from invading the system from the following aspects:
(1) During refueling, the hydraulic oil must be filtered, and the refueling tools should be reliable and clean. The filter at the oil filler of the hydraulic oil tank cannot be removed in order to improve the oil filling speed. Refueling personnel shall use clean gloves and work clothes.
(2) During maintenance, remove the oil filler cover, filter cover, detection hole, hydraulic oil pipe and other parts of the hydraulic oil tank. Avoid dust when the oil passage of the hydraulic system is exposed. The disassembled parts must be thoroughly cleaned before opening. When removing the oil filler cap of the hydraulic oil tank, first remove the soil around the oil tank cap, unscrew the oil tank cap, and then remove the sundries left at the joint (do not flush with water to prevent water from penetrating into the oil tank). Open the oil tank cap only after confirming that it is clean. If it is necessary to use wiping materials and hammers, the wiping materials without fiber impurities and special hammers with rubber attached to the striking surface shall be selected. Hydraulic components and hydraulic hoses shall be carefully cleaned and assembled after drying with high-pressure air. Select genuine filter element with intact package (if the package is damaged, although the filter element is intact, it may also be unclean). Clean the filter while changing the oil. Before installing the filter element, carefully remove the dirt inside the filter housing with wiping material.
(3) The cleaning oil of the hydraulic system must use the hydraulic oil with the same brand as that used in the system. The oil temperature is between 45 ~ 80 ℃. Use large flow to take away the impurities in the system as much as possible. The hydraulic system shall be cleaned repeatedly for more than three times. After each cleaning, all the oil shall be discharged from the system when the oil is hot. Clean the filter after cleaning, and add new oil after replacing the filter element.
4. Prevent air and water from invading the hydraulic system
Prevent air from invading the 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 dissociate from the oil, and the bubble will burst, causing "cavitation" of hydraulic components and noise. A large amount of air entering the oil will aggravate the phenomenon of "cavitation", increase the compressibility of hydraulic oil, work instability, reduce work efficiency, and "crawling" of actuator. In addition, air will oxidize the hydraulic oil and accelerate its deterioration. The following points should be noted to prevent air intrusion:
1) After maintenance and oil change, remove the air in the system according to the provisions of the attached operation manual.
2) The oil suction pipe orifice of the hydraulic oil pump shall not expose the oil surface, and the oil suction pipeline must be well sealed.
3) The seal of the oil pump drive shaft shall be good. When replacing the oil seal, the "double lip" genuine oil seal shall be used instead of the "single lip" oil seal, because the "single lip" oil seal can only seal oil in one direction and does not have the function of air sealing. After the overhaul of a Liugong ZL50 loader, the hydraulic oil pump had continuous "cavitation" noise and the automatic rise of oil level in the oil tank. After querying the repair process of the hydraulic oil pump, it was found that it was caused by the misuse of "single lip" oil seal in the oil seal of the drive shaft of the hydraulic oil pump.
