1. Choose the right hydraulic oil

Hydraulic oil plays the role of transmitting pressure, lubricating, cooling and sealing in the hydraulic system. Improper selection of hydraulic oil is the main reason for the early failure and durability decline of the hydraulic system. Hydraulic oil should be selected according to the grade specified in the random “Instruction for Use”. When a substitute oil is used in special circumstances, its performance should be the same as that of the original grade. Different grades of hydraulic oil cannot be mixed to prevent chemical reaction and performance change of hydraulic oil. Dark brown, milky white, odorous hydraulic oil is deteriorating oil and cannot be used.

2. Prevent solid impurities from mixing into the hydraulic system

Clean hydraulic oil is the life of a hydraulic system. There are many precision parts in the hydraulic system, some have damping holes, some have gaps and so on. If the solid impurities invade, it will cause the precision coupler to be pulled, the card is issued, the oil passage is blocked, etc., and the safe operation of the hydraulic system will be endangered. The general ways for solid impurities to invade the hydraulic system are: unclean hydraulic oil; unclean refueling tools; careless refueling and repair and maintenance; hydraulic components desquamation, etc. The intrusion of solid impurities into the system can be prevented from the following aspects:

2.1 When refueling

Hydraulic oil must be filtered and filled, and the filling tool should be clean and reliable. Do not remove the filter at the filler neck of the fuel tank in order to increase the rate of refueling. Refueling personnel should use clean gloves and overalls to prevent solid and fibrous impurities from falling into the oil.

2.2 During maintenance

Remove the hydraulic oil tank filler cap, filter cover, inspection hole, hydraulic oil pipe and other parts, so as to avoid dust when the oil passage of the system is exposed, and the disassembled parts must be thoroughly cleaned before opening. For example, 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 remove the debris remaining in the joint (do not rinse with water to prevent water from infiltrating the oil tank), and open the oil tank cap after confirming that it is clean. When wiping materials and hammers need to be used, wiping materials that do not remove fiber impurities and special hammers with rubber attached to the striking surface should be selected. Hydraulic components and hydraulic hoses should be carefully cleaned and dried with high pressure air before assembly. Choose a well-packaged genuine filter element (the inner package is damaged, although the filter element is intact, it may be unclean). When changing the oil, clean the filter at the same time. Before installing the filter element, use a wiping material to carefully clean the dirt at the bottom of the filter housing.

2.3 Cleaning of the hydraulic system

The cleaning oil must use the same grade of hydraulic oil used in the system, the oil temperature is between 45 and 80 °C, and the impurities in the system should be taken away as much as possible with a large flow rate. The hydraulic system should be repeatedly cleaned more than three times. After each cleaning, all the oil should be released from the system while the oil is hot. After cleaning, clean the filter, replace the new filter element and add new oil.

3. Prevent air and water from invading the hydraulic system

3.1 Prevent air from invading the hydraulic system

Under normal pressure and normal temperature, the hydraulic oil contains air with a volume ratio of 6 to 8%. When the pressure is reduced, the air will be freed from the oil, and the bubble burst will cause the hydraulic components to “cavitate” and generate noise. A large amount of air entering the oil will aggravate the “cavitation” phenomenon, increase the compressibility of the hydraulic oil, make the work unstable, reduce the work efficiency, and the executive components will have adverse consequences such as work “crawling”. In addition, the 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 must be removed in accordance with the provisions of the random “Instruction Manual” before normal operation.

2. The oil suction pipe port of the hydraulic oil pump shall not be exposed to the oil surface, and the oil suction pipe must be well sealed.

3. The seal of the drive shaft of the oil pump should be good. 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 in one direction and does not have Air sealing function. After the overhaul of a Liugong ZL50 loader, the hydraulic oil pump had continuous “cavitation” noise, the oil level of the oil tank automatically increased and other faults. After checking the repair process of the hydraulic oil pump, it was found that the oil seal of the driving shaft of the hydraulic oil pump was misused” Single lip” oil seal.

3.2 Prevent water from invading the hydraulic system Oil contains excess water, which will cause corrosion of hydraulic components, emulsification and deterioration of oil, decrease in strength of lubricating oil film, and accelerate mechanical wear. , Tighten the cover, preferably upside down; oil with high water content should be filtered many times, and the dried filter paper should be replaced every time it is filtered. When there is no special instrument for testing, the oil can be dropped onto the hot iron , no vapour emerges and burns immediately before refilling.

4. Matters needing attention in the work

4.1 The mechanical operation should be gentle and smooth

Rough mechanical operations should be avoided, otherwise shock loads will inevitably occur, causing frequent mechanical failures and greatly shortening the service life. The impact load generated during operation, on the one hand, causes early wear, fracture, and fragmentation of mechanical structural parts; Premature failure, oil leakage or pipe burst, frequent action of relief valve, oil temperature rise.