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Selection and application of hydraulic oil
Source: China Bearing Network Time: 2013-06-25
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1. Selection of hydraulic oil (1) Hydraulic parts. Different hydraulic components have a minimum equipment requirement for the hydraulic oil used; therefore, when selecting hydraulic oil, attention should be paid to the type of hydraulic components and the materials and seals used. The compatibility of paints or paints with hydraulic oils; ensuring that each movement pair is smooth and outstanding; allowing the components to reach the life of the drawing; satisfactory use of the function.
The hydraulic pump is one of the most sensitive components for the viscosity and viscosity of the hydraulic oil; therefore, the demand for hydraulic oil in the system is often used as an important basis for selecting hydraulic oil (the system with servo valve is outside).
(2) System working conditions. If the demand for execution organization speed, system pressure and organizational measures accuracy is higher, the demand for hydraulic oil wear resistance and bearing capacity is higher.
According to the operating temperature of the system; the working time of the continuous operation and the cleaning condition of the working environment; the oil must be focused on the viscosity, high temperature function and thermal stability of the oil; to reduce the composition and accumulation of sludge.
(3) The size of the fuel tank. The smaller the fuel tank, the higher the demand for oil oxidation stability, extreme pressure wear resistance, air release and filtration.
(4) Ambient temperature. Aligned in underground, water, indoor, outdoor, cold, or cold areas with temperature changes; and ambient temperature characteristics such as high temperature heat source or open flame; reasonable selection of hydraulic oil. Open flame; operating temperature below 60 ° C; when the load is light; the usual hydraulic oil can be used; if the equipment must be started at a very low temperature; low-condensation hydraulic oil must be used.
In summary; if the quality of the hydraulic oil is qualified; the speed of the system execution is high; the flow rate of the oil is also high; the hydraulic loss is increased; and the leakage is relatively reduced; therefore, the oil with lower viscosity should be selected, and vice versa. When the flow rate of the oil is low; the amount of leakage is relatively increased; it will affect the moving speed of the working tissue; this is to select the oil with higher viscosity. Usually; when the working pressure is high; the hydraulic oil with high viscosity should be selected; The problem of leakage in dealing with high pressure should be given priority over the resistance of the oil. When the operating pressure is low, the oil with low viscosity should be used. When the ambient temperature is high, the oil with higher viscosity should be used; otherwise, the viscosity should be lower. oil.
(5) Final determination of hydraulic oil. After the start of hydraulic oil is selected; it must also pay attention to the nuclear source, viscosity, quality, application characteristics, scope of application; and compatibility of system and component data; Can be completely satisfied with the needs.
(6) Economics. It is necessary to summarize the price of hydraulic oil, the lifespan, the hydraulic system and the protection, safe operation cycle, etc.; focus on the brand with good economic efficiency.
2, the economic analysis of the selection of hydraulic oil when selecting hydraulic oil; can not only focus on oil prices; but ignore the type, quality, protection and regeneration; such as; high temperature, high temperature and fine hydraulic system in the vicinity of high temperature heat source and open flame; Phosphate ester liquid anti-combustion hydraulic oil is used; it can't be replaced by cheap water-containing anti-burning liquid because it is expensive; this will cause premature wear of hydraulic pump; reduce system accuracy, and; for example, in high-pressure hydraulic system; Grinding hydraulic oil; if cheap mechanical oil or anti-rust and anti-oxygen hydraulic oil is used, the life of hydraulic pump will be shortened. For example, L-HH and L-HM oils with ISO viscosity of VG46 are used as examples; The same YB-D25 vane pump (pressure is 12. 5MPa, temperature is 65 °C; speed is 1500r/min); the wear amount is measured after 250h operation; the wear of the pump is L-HH oil. 63 times when HM oil. Thus; in medium and high pressure systems; L-HH or L-HL oil should not be used; L-HM anti-wear hydraulic oil should be used.
The high-pressure system for cold room and severe cold room operation; the temperature is low; the ambient temperature changes greatly; the low-temperature hydraulic oil with high viscosity index should be selected; so that the low-temperature oil liquidity of the system is good; the cold start is simple; The system is common with oil in winter and summer; it is not replaced frequently.
High-quality anti-wear hydraulic oil; high thermal stability; good hydrolytical stability; strong emulsification; short air release time; long service life; improved system operation; therefore; high-performance hydraulic system should be high Quality hydraulic oil.
High-quality hydraulic oil is used; although the oil price is relatively expensive, the service life of the oil is long; the hydraulic components wear less; the system protection is simple; the production efficiency is high; therefore, the total economic benefit is still cost-effective.
Second, the rational use of hydraulic oil
1. Factors affecting the quality of hydraulic oil (1) Water. The water content of water in oil is in accordance with the national standard GB/T1118. 1-94. The quality target should not exceed the trace. If the water in the oil exceeds the excess, it is necessary to replace it; otherwise, it will not only damage the bearing, but also rust the steel, which will cause the hydraulic oil to emulsifie, mutate and form sediment; hinder the heat conduction of the cooler; affect the operation of the valve; The oil filter has a useful working area; it increases the abrasive effect of the oil.
(2) Oxidation. The operating temperature of mechanical hydraulic oil is usually 30-80 °C; the life of hydraulic oil is closely related to its operating temperature; experience is notified; when the working oil temperature exceeds 60 °C; every 8 °C is added; the use of oil The life expectancy will be halved; that is, the life of the oil at 90 °C is about 10% of the oil at 60 ° C; the reason is that the oil is oxidized. The oxygen in the oil and the oil reacts; the oil gradually oxidizes, the color becomes dark, and the viscosity rises. Finally, the oxide can not be dissolved in the oil; the brown mucus layer is deposited somewhere in the system; it is easy to block the control oil passage in the component; the wear of the ball bearing, the valve core, the piston of the hydraulic pump, etc. is aggravated; The system works normally. Oxidation also causes corrosion of acid solution. The oxidation process begins gradually; when it reaches a certain period, the oxidation rate will accelerate rapidly; the viscosity will rise with the increase; the result will increase the working oil temperature; the oxidation process will be faster. Accumulated deposits and acid will be more; eventually the oil can no longer be used.
(3) Impurities. Impurities can not only wear the moving parts; but once they are stuck in the valve core or other moving pairs; it will affect the normal operation of the whole system; cause machine problems.
(4) Air. If the hydraulic oil circuit is rich in gas; when the air bubbles overflow, the impact on the pipe wall and components will constitute cavitation; the system will not work properly; the time will be longer and the component will be damaged.
(5) Physical and chemical reaction. Clean the paint in the fuel tank; it will cause the chemical properties of the oil to change.
2, oil viewing and protection of water content: release 2-3cm3 oil into a test tube; let stand for a few minutes to make the bubbles disappear; then heat the oil; (such as with a lighter); together at the top of the test tube to pay attention to listen A subtle "squeaky" sound of water vapor; if any; it is stated that the oil is rich in water.
There is usually no condition to check the water content of the system oil; the simplest method is to wait for the whole machine to stand overnight; turn the oil plug on the bottom of the fuel tank; release a small amount of oil into a container; investigate the oil in the field. Can it be rich in moisture?
Odor and appearance: a mixture of virgin oil and used oil; a comparison of the same temperature and glassware; if the color of the oil is very different or has a special odor; The oil has been metamorphosed; it needs to be replaced. If the color and odor of the two oil samples are not significantly different; the two oil samples can be placed together for one night; if the bottom of the container with used oil is deposited, the system It is necessary for the oil to be filtered through a fine oil filter; and the fuel tank is removed.
Others; should also pay attention to the following oil matters:
(1) Check the oil level before starting the machine; check if the opening of each oil circuit is in the correct standby condition.
(2) The machine idles for about 5 minutes; check whether there is air bubble in the level gauge oil; if the new car or the new hydraulic oil is changed; the bubble in the oil mark is normal when idling; the air bubble is not visible before the machine is allowed to work.
(3) Pay close attention to the temperature of the oil. When the machine is working for a period of time; if the oil temperature is high, the best can stop; after the oil temperature is normal, then work from scratch; to extend the system and the life of the oil.
(4) It should be paid attention to whether the values ​​of various parameters of the hydraulic system can be normal; it is also necessary to pay attention to the external characteristics of the system - static and dynamic. If the intake, water or oil path in the system is not smooth, etc.; abnormal noise will be announced. Shaking the appearance value is not normal; at this moment should stop and check in time.
(5) Timing filter hydraulic oil. The impurity particles in the oil are controlled within the regular range.
(6) Timely replacement of hydraulic oil. Change the oil regularly according to the requirements of the machine clarification book; replace the oil filter together; conditionally test; determine whether it can change oil according to the results, and can also according to the mechanical application site and system requirements. Formulate the oil change cycle; and classify the oil change period into the equipment technical file.
Pay attention to oil change: the new oil and the old oil should be the same standard of the same trademark; before the oil change; the old oil should be completely discharged and washed clean; the valve body, hydraulic cylinder, etc. can not be discharged and can not be washed locally; The oil return pipe can be dismantled and put into a temporary oil drum; after participating in the new oil; use the method of jogging the engine; make the new oil replace the old oil; the criterion is to write the new oil to be no less than the system filter Accurate oil filter filtration; if the construction site is indeed unconditional; should replace the oil filter in the system after participating in the new oil operation for about 1h, after the machine is replaced by new oil idling; should check the oil level again; if necessary, continue to add new oil .
(7) When the car wash or machine period is not used; the fuel tank cover should be placed.
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