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Working principle and maintenance plan of lifting platform
The hydraulic oil forms a certain pressure by the vane pump, and enters the lower end of the cylinder through the oil filter, explosion-proof electromagnetic reversing valve, throttle valve, hydraulic control check valve, and balance valve, so that the piston of the cylinder moves upward and lifts the weight. The oil return from the upper end of the hydraulic cylinder is returned to the fuel tank through the flameproof electromagnetic reversing valve, and its rated pressure is adjusted by the overflow valve, and the reading value of the pressure gauge is observed through the pressure gauge.
The piston of the hydraulic cylinder moves downward (not only the weight drops). The hydraulic oil enters the upper end of the cylinder through the explosion-proof electromagnetic reversing valve, and the return oil from the lower end of the cylinder returns to the tank through the balance valve, hydraulic control check valve, throttle valve, and explosion-proof electromagnetic reversing valve. In order to make the heavy objects fall smoothly and the brakes are safe and reliable, a balance valve is installed on the oil return line to balance the circuit and maintain the pressure so that the descending speed will never change due to the weight. The throttle valve adjusts the flow rate and controls the lifting speed. In order to make the brake safe and reliable, and prevent accidents, a hydraulic control check valve, namely hydraulic lock, is added to ensure that it can lock itself safely when the hydraulic pipeline bursts accidentally. An overload sound-activated alarm is installed to distinguish overload or equipment failure.
For mechanized construction enterprises, the good condition of construction machinery technology is a direct factor in whether the enterprise can produce normally. As far as hydraulic transmission engineering machinery is concerned, the normal operation of the hydraulic system is a major indicator of its good technical condition. Qualified hydraulic oil is the guarantee for the reliable operation of the hydraulic system, and correct maintenance is the foundation of the reliable operation of the hydraulic system. According to work practice, the maintenance of the hydraulic system of construction machinery in the general working environment will be discussed roughly.
The hydraulic oil plays the role of transmitting pressure, lubricating, cooling, and sealing in the hydraulic system. The choice of hydraulic oil is by no means the main reason for the early failure and durability of the hydraulic system. The hydraulic oil should be selected according to the brand specified in the random "Instruction Manual". When a substitute oil is needed in special circumstances, the performance should be the same as the original brand. Different brands of hydraulic oil cannot be mixed to prevent chemical reaction and performance changes of the hydraulic oil. Dark brown, milky white, and odorous hydraulic oil is deteriorating oil and must not be used.
Prevent solid impurities from mixing into the hydraulic system
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 gaps, etc. If the intrusion of solid impurities causes strain on precision parts, hairpins, blockage of oil passages, etc., it will endanger the safe operation of the hydraulic system. Common ways for solid impurities to invade hydraulic systems include: hydraulic oil is absolutely unclean; refueling tools are absolutely unclean; refueling, repairs, and maintenance are never careful; hydraulic components are desquamated. It can prevent solid impurities from invading the system from the following aspects:
2.1 When refueling
The hydraulic oil must be filtered and refilled, and the refueling tools should be clean and reliable. Never remove the filter at the fuel tank filler opening in order to increase the fueling speed. Fueling personnel should use clean gloves and work clothes to prevent solid impurities and fiber impurities from falling into the oil.
2.2 During maintenance
Remove the hydraulic oil tank filler cap, filter cap, inspection hole, hydraulic tubing and other parts to avoid dust when the system oil passage is exposed. The disassembled parts must be thoroughly cleaned before being opened. For example, when disassembling the filler cap of a hydraulic fuel tank, first remove the dirt around the fuel tank cap. After unscrewing the fuel tank cap, remove the debris remaining in the joint (never flush with water to prevent water from leaking into the fuel tank), and then open the fuel tank cap after cleaning. For example, when you need to use wiping materials and hammers, you should choose a wiping material that does not remove fiber impurities and a special hammer with rubber attached to the striking surface. Hydraulic components and hydraulic hoses should be carefully cleaned and assembled after drying with high-pressure air. Use genuine filter elements with intact packaging (the inner packaging is damaged, although the filter element is intact, it may never be clean). In addition to cleaning the filter when changing the oil, wipe the dirt on the bottom of the filter housing before installing the filter element.
2.3 Cleaning of hydraulic system
The cleaning oil must use the same brand of hydraulic oil as the system used. The oil temperature is between 45 and 80°C. Use a large flow rate to remove impurities from the system as much as possible. The hydraulic system should be cleaned more than three times, after each cleaning, let it out of the system while the oil is hot. After cleaning, clean the filter again, replace the new filter element and add new oil.
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 be released from the oil, and the bubble burst will cause the hydraulic components to "cavitation" and generate noise. A large amount of air entering the oil will aggravate the "cavitation" phenomenon, increase the compressibility of the hydraulic oil, work instability, reduce work efficiency, and cause "crawling" of the actuator. In addition, the air will also oxidize the hydraulic oil and accelerate the deterioration of the oil. The following points should be paid attention to to prevent air intrusion:
1. After maintenance and oil change, the air in the system must be removed according to the provisions of the accompanying "Instruction Manual", and normal operation can be performed.
2. The oil suction pipe port of the hydraulic oil pump must not expose 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 there should be a "double lip" genuine oil seal, and must not be replaced by a "single lip" oil seal, because the "single lip" oil seal can only seal oil in both directions, never It has the function of sealing air. Once a Liugong ZL50 loader was overhauled in this unit, the hydraulic oil pump had continuous "cavitation" noise and the oil level of the oil tank manually increased. After checking 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 misused. Caused by "single lip" oil seal.
3.2 Prevent water intrusion into hydraulic system
Excessive moisture in the oil will cause the hydraulic components to rust, emulsify the oil, reduce the strength of the lubricating oil film, and accelerate mechanical wear. In addition to preventing moisture intrusion during maintenance, it is also important to tighten the lid when the oil storage barrel is not necessary. It is easy to put it 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 on the hot iron plate and no steam will come out. And the burning item can be raised immediately.
4.1 Machinery work should be gentle and smooth
Rough mechanical operations should be avoided, if impact load is bound to occur, mechanical failures occur frequently and the service life is greatly shortened. The impact load generated during operation, on the other hand, causes early wear, fracture, and breakage of mechanical structural parts. On the other hand, impact pressure is generated in the hydraulic system. The impact pressure will also damage the hydraulic components, the oil seal and the pressure of the high-pressure oil pipe joint and the rubber pipe. Early failure of the joint, oil leakage or pipe burst, frequent action of the overflow valve, oil temperature rise.
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