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How to Choose Grease for Smart Industry

The choice of grease, the first should be clear the purpose of the use of grease. According to the main role played by grease, grease can be roughly divided into anti-friction, protection, sealing three categories. Look at the need to apply grease parts, the role of grease to play which one to choose to meet the requirements of the grease.

As anti-friction grease, the main consideration should be high and low temperature range, speed limit, the size of the load.

As a protective grease, it should focus on contact with the metal, the contact medium is water vapor, or chemical gases, grease performance, should focus on metal protective indicators, oxidation resistance, water resistance and other aspects of performance.

As seal grease, consider first the material of the contact seal, whether rubber or plastic, or metal. Especially with rubber and plastic seal components, we must make clear the rubber grade, according to the compatibility of the grease with rubber to choose the appropriate grease. Followed by contact with the media should be considered, such as water, alcohols, oil, is static or dynamic seal. If the static seal should choose a thicker sealing grease, if the dynamic seal, should choose the base oil viscosity can not be too large grease, the medium is water or alcohol should be selected large viscosity paraffinic base oil amide, urea Grease, the medium is the oil should be used in a high-level oil company Ping No. 7903 oil seal grease.

(A) consider the working temperature of the lubrication site

Lubrication parts of the operating temperature is an important basis for the selection of grease. A typical part of the grease used is a rolling bearing. Regarding the relationship between the bearing temperature and the life of the grease, when the bearing temperature is increased by 10 to 15 ° C, the life of the grease is reduced by about 1/2. In general, the bearing outer ring temperature lower than the inner temperature of about 15 ℃. Bearing temperature in the medium and low speed (3000 ~ 5000r / min) work and the temperature of the internal medium is similar.

For indoor use of machine bearings, such as machine tools, intermittent starting motor, hand tools, instruments and precision machinery, the general operating temperature range of 10 ~ 50 ℃. For transport machinery, construction machinery, agricultural machinery and other outdoor work of mechanical bearings, the general operating temperature changes with the atmospheric temperature. In most parts of China, the temperature changes from -40 ℃ to 40 ℃. Increasing the load, increasing speed, ambient temperature, grease too full and long-term continuous operation of rolling bearings and other factors make the temperature increase. For example, in the radial load of 1470N, speed of 8,000 r / min 204 bearings work under the conditions of temperature up to 40 ~ 70 ℃. Wheel hub bearings along the road driving truck, the temperature up to 40 ~ 80 ℃. Large generator bearings, temperature up to 80 ~ 90 ℃, aircraft landing gear, high temperature motors and other rolling bearings temperature up to 150 ~ 200 ℃ or higher.

Considering the temperature resistance of grease, not only to see the level of grease dropping point, but also should consider the type of base oil, oxidation resistance, evaporation performance. The following table lists the types of greases selected for maximum service temperature. The choice of grease, the first should be clear the purpose of the use of grease. According to the main role played by grease, grease can be roughly divided into anti-friction, protection, sealing three categories. Look at the need to apply grease parts, the role of grease to play which one to choose to meet the requirements of the grease.

According to the highest temperature, choose the type of grease Maximum temperature Thickener type Base oil type 40 ~ 50 ℃ Calcium soap, lithium soap Mineral oil 100 ~ 120 ℃ Lithium soap, complex soap Mineral oil ~ 150 ℃ Lithium complex, aluminum complex, Mineral oil, polyalphaolefin

180 ~ 200 ℃ Lithium Complex, Polyurea, Bentonite, Amide Salt Ester Oil, Polyalphaolefin, Alkyl Silicone Oil 250 ℃ Urea Organics, Fluorine Compound Phenyl Silicone Oil, Perfluoropolyether 300 ℃ Boron Nitride, Silica Gel Contour phenyl silicone oil (Table 1)

The above is the case of high temperature, lubricating part of the working temperature in some cases at a lower temperature, in general, the temperature is below -30 ℃, you must use synthetic grease, especially some instrument miniature bearings, starting power is too small , Pay special attention when using grease. The lowest limit temperature for synthetic greases is -80 ° C.

(B) consider the grease lubrication site load

The bearings of the mill such as the ore mill and the ball mill are subjected to a large impact load; the stator weight of the large motor is over a ton, so the bearing load is relatively large; the lubrication condition of the gear is quite harsh, there are rolling friction and sliding friction, The force transmitted by the general gear is relatively large; there are worm gears are to bear a greater load. Grease selection in these areas must consider the anti-wear and extreme pressure. Now many equipment managers, as long as the site is heavily loaded with MoS2 grease or graphite grease, in fact, should be considered anti-wear grease plus extreme pressure additives.

(C) consider the speed of grease lubrication parts

As already mentioned, the speed of grease bearing life greatly affected. Therefore, the choice of grease, we must consider the speed of lubricating parts.

For rolling cylindrical roller bearings, in general, the following diameter 50mm, when the DN value <300000 with grease; DN value> 300000, the use of lubricating oil.

The inner diameter of 50mm or more, when the DN value <using grease; DN value> using lubricants.

For tapered and roller bearings, in general, the inner diameter of 50mm or more, when the DN value <using grease; DN value> using lubricating oil.

At present, many large motors in China often happen so-called "axle-holding" accident, because the grease can not meet the speed requirements, poor lubrication occurs in a short run, causing the bearing to suddenly burn out. Motor manufacturers are now usually used 2 or 3 Universal Lithium Grease. Such as 400KW three-phase asynchronous motor, bearing type: 6222, the bearing diameter of 110mm, the motor speed is 2975r / min, the DN value of 327,000. Obviously the choice of No. 2 or No. 3 lithium grease is unable to meet the requirements. China Petrochemical Corporation owned refinery and chemical plant are using a high-level oil company developed and produced 7019-1 extreme pressure lithium complex grease, to meet the requirements, plus a grease can be used for more than a year, eliminating "Axle" accident.

(D) consider the lubricating parts of the environment and the media in contact

Lubricating parts of the environment and the media in contact with the performance of grease have a tremendous impact, so the choice of grease, should be carefully considered.

Wet or easy to contact with water sites, should not choose sodium-based grease, lithium-based grease can not even choose. Because sodium-based grease poor water resistance, easy to thin water loss and emulsification. Some parts of lithium grease can not meet the requirements, such as vertical water pump bearings can be said to be often soaked in water, lithium grease also occurs emulsification, life is very short, the bearing is easily damaged. In such parts should be good water resistance composite aluminum grease or urea-based grease. Cars, tractors and tank chassis, often wet and easy to work in contact with water environment, our current use of calcium-based grease or lithium-based grease, more foreign use of water resistance better lithium-calcium-based grease or urea-based grease.

Acid or acid gas contact with the site, should not use lithium grease or calcium complex, aluminum composite, bentonite grease. These greases meet with acid (weak acid) or acid gas, such as trace HCI in the air, the grease thinning loss, resulting in poor bearing protection, easy to corrode, more serious is poor lubrication. There are also some printing and dyeing plants use reactive dyes to emit HCI gas, not only cause corrosion of equipment, but also to grease the bearings are easily deteriorated, these parts of the Beijing Opera selected anti-acid performance of complex barium-based grease or urea-based grease, In case of contact with strong acids or strong oxidizing media, use perfluorinated greases.

In contact with seawater or salt water should be selected composite aluminum grease; contact with natural rubber or paint should avoid the use of ester oils, especially diester type oil as base oil grease; contact with fuel oil or oil Quality lubricating oil medium parts should be used special, such as oil seal grease No. 7903; contact with methanol should also use a special, such as a high-level oil company NC-071 grease, or Shanghai Gaoqiao Petrochemical Company refinery production Such as methanol-resistant grease.

(E) consider the method of filling grease

Grease filling methods, there are artificial filling and pump focus on filling. Apply or fill, grease gun, fat cup, etc. are raised manually. When using grease on automobiles, manual filling is adopted. For example, artificial wheel filling method for wheel hub bearings, artificial smearing method for leaf spring, leaf spring pin, etc. (with grease nipples), grease gun filling method, Use fat cup filling method. The use of artificial filling site, mainly in the choice of grease should consider its consistency, generally 1-3 consistency of grease, the best choice of consistency of fat No. 2, filling easier and longer life expectancy.

Some lubrication equipment using central filling method, the first and last submarine elevator joints, these parts are in the warehouse, when the submarine to work underwater, these parts can not be filled with grease, so the warehouse through the pipeline to these parts Regular quantitative delivery of grease lubrication. Industry, focus on filling grease more widely, such as the steel conveyor roller bearings, roller arrangement for a long distance, the number of more concentrated lubrication using more convenient. Concentrated filling lubrication to go through a long pipeline, in order to facilitate the filling, will not cause the pump pressure is too large, the consistency of the grease is generally No. 1-0, the best choice for the consistency of fat 0.

Considered from the grease consistency, the general seal grease, such as valve stem seal grease, the consistency of No. 4 -5; parts of high speed or ultra-high speed, the consistency of No. 3 -2 should be used; No. 1 No. 1 Consistency; Concentrated filling grease No. 1 -0 Consistency; Gear reducer Gear Consistency 00 -000 Consistency.

(F) from the economic aspects

From the economic considerations to choose the right grease, grease every user is very concerned about things. The choice of grease can not only see which one grease cheap, more important is to see how the performance of this grease should be comprehensive examination of whether a grease extended lubrication cycle, reduce the number of filling and grease consumption And bearing the number of consumption, overhaul costs, lost production caused by suspension and so on. Such as a hot-rolled steel mill workshop lamination machine, traditionally use calcium-based grease (the price of about 4,000 yuan / t or so), although the price is cheaper, but the performance can not meet the requirements of frequent maintenance mill overhaul once a month, Each maintenance takes about 16h. Later, the choice of No. 2 lithium complex grease (the price is about 12,000 yuan / t), on the surface, the price is three times the calcium-based fat, but the performance is excellent, maintenance extended four months a repair, each maintenance only 12h (Shortened 4h), and each maintenance is not as full replacement with calcium-based fat, just a little more to add some on the line. Even more impressive is that the original use of calcium-based grease each time the screw and worm gear replacement once, and now the No. 2 lithium complex grease,