Intelligent Industry

Intelligent industry is the continuous integration of various terminals with environmental awareness, ubiquitous technology based computing modes, mobile communication, etc. into various aspects of industrial production, greatly improving manufacturing efficiency, improving product quality, reducing product costs and resource consumption, and elevating traditional industry to a new stage of intelligence.

How to Choose Lubricating Greases in the Intelligent Industrial Industry

When selecting lubricating grease, the first step is to clarify the purpose of using the grease. According to the main functions of lubricating grease, it can be roughly divided into three categories: friction reduction, protection, and sealing. It depends on the parts that need to be coated with lubricating grease, which one should play the main role, and choose the lubricating grease that meets the requirements.       

As a lubricating grease for reducing friction, the main considerations should be the range of high and low temperature resistance, the limit of speed resistance, and the size of load.       

As a protective lubricating grease, it should focus on the metal in contact, whether the medium in contact is water vapor or chemical gas. In terms of the performance of the lubricating grease, it should focus on the indicators of metal protection, oxidation resistance, water resistance, and other aspects of performance.      

As a sealing grease, the first consideration should be whether the sealing material in contact is rubber, plastic, or metal. Especially when using rubber and plastic as sealing components, it is important to understand the grade of the rubber and choose a suitable lubricating grease based on the compatibility between the lubricating grease and the rubber. Secondly, the medium in contact, such as water, alcohol, and oil, should be considered whether it is a static seal or a dynamic seal. If it is a static seal, a thicker sealing grease should be selected. If it is a dynamic seal, a lubricating grease with a base oil viscosity that cannot be too high should be selected. If the medium is water or alcohol, a high viscosity paraffin based base oil amide grease or urea based lubricating grease should be selected. If the medium is oil, the 7903 oil resistant sealing grease produced by Yiping High Grade Lubricant Company should be selected.  

（1） Consider the working temperature of the lubrication area 

The working temperature of the lubricating part is an important basis for selecting lubricating grease. The typical component using lubricating grease is rolling bearings. From the relationship between bearing temperature and the lifespan of lubricating grease, for every 10-15 ℃ increase in bearing temperature, the lifespan of lubricating grease decreases by about half. Generally speaking, the temperature of the outer ring of a bearing is about 15 ℃ lower than that of the inner ring. The bearing temperature operating at medium to low speeds (3000-5000r/min) is similar to the temperature of the internal medium. 

For machine bearings used indoors, such as machine tools, intermittent starting motors, manual tools, instruments, and precision machinery, the general operating temperature range is 10-50 ℃. For mechanical bearings used for outdoor work such as transportation machinery, construction machinery, and agricultural machinery, the working temperature generally varies with atmospheric temperature. The atmospheric temperature in most regions of China varies from -40 to 40 ℃. Factors such as increasing load, increasing speed, increasing ambient temperature, overfilling of lubricating grease, and long-term continuous operation all cause the temperature of rolling bearings to rise. For example, the 204 bearing operating under radial load of 1470N and rotational speed of 8000r/min can reach a temperature of 40-70 ℃. For the hub bearings of trucks driving along the main road, the temperature can reach 40-80 ℃. Large generator bearings can reach temperatures up to 80-90 ℃, and rolling bearings for aircraft landing gears, high-temperature motors, etc. can reach temperatures of 150-200 ℃ or higher.     

When considering the temperature resistance of lubricating grease, not only the drop point of the grease, but also the type of base oil, antioxidant performance, evaporation performance, etc. should be considered. The following table lists the approximate types of lubricants selected based on the highest usage temperature. When selecting lubricating grease, the first step is to clarify the purpose of using the grease. According to the main functions of lubricating grease, it can be roughly divided into three categories: friction reduction, protection, and sealing. It depends on the parts that need to be coated with lubricating grease, which one should play the main role, and choose the lubricating grease that meets the requirements.

Select the type of lubricating grease according to the highest temperature. The highest temperature thickener type is the base oil type, which is 40-50 ℃ calcium soap, lithium soap mineral oil, 100-120 ℃ lithium soap, composite soap mineral oil, 150 ℃ composite lithium, composite aluminum, composite barium mineral oil, and polymer α- olefin

180-200 ℃ composite lithium, polyurea, bentonite, amide ester oil, polyurea α- Olefins, alkyl silicone oil 250 ℃ urea organic compounds, fluorinated compounds phenyl silicone oil, perfluoropolyether 300 ℃ boron nitride, silica gel and other high phenyl silicone oils (Table 1)

The above refers to high temperature situations. In some cases, the working temperature of the lubrication area is at a lower temperature. Generally speaking, if the temperature is below -30 ℃, synthetic oil lubricating grease must be used, especially for some instrument micro bearings, which have too little starting power. Therefore, special attention should be paid when selecting lubricating grease. The minimum limit temperature for synthetic oil lubricating grease is -80 ℃.   

（2） Consider the load on the lubricated area with lubricating grease

The shafts of machinery such as ore crushers and ball mills bear significant impact loads; The stator weight of a large motor is over tons, so the bearing load is relatively large; The lubrication conditions of gears are quite harsh, with rolling friction and sliding friction. Generally, the forces transmitted by gears are relatively large; Worm gears and worms also bear large loads. The selection of lubricating grease in these areas must consider wear resistance and extreme pressure resistance. Nowadays, many equipment management personnel believe that MoS2 grease or graphite grease should be used for areas with high loads. In fact, adding anti wear and extreme pressure additives to the grease should be considered.   

（3） Consider the speed of the grease lubricated area       

As mentioned earlier, speed has a significant impact on the bearing life of lubricating grease. Therefore, when selecting lubricating grease, it is important to consider the speed of the lubrication area.       

For rolling cylindrical roller bearings, generally speaking, for those with an inner diameter below 50mm, lubricating grease is used when the DN value is less than 300000; When the DN value is greater than 300000, lubricating oil is used.       

If the inner diameter is above 50mm, lubricating grease should be used when the DN value is less than; DN value>using lubricating oil.       

For tapered and roller bearings, generally speaking, if the inner diameter is above 50mm, lubricating grease should be used when the DN value is less than; DN value>using lubricating oil.       

At present, many large motors in China often experience so-called "shaft holding" accidents, which are caused by the lubricating grease not meeting the speed requirements, resulting in poor lubrication during a short period of operation and sudden burning of bearings. Nowadays, motor manufacturers often choose No. 2 or No. 3 universal lithium based grease. If a 400KW three-phase asynchronous motor has a bearing model of 6222, the inner diameter of the bearing is 110mm, and the motor speed is 2975r/min, the DN value is 327000. Obviously, choosing No. 2 or No. 3 lithium based grease cannot meet the requirements. All refineries and chemical plants affiliated with Sinopec Group have used 7019-1 extreme pressure composite lithium based grease developed and produced by Yiping Advanced Lubricant Company, which meets the requirements. Adding the grease once can use it for more than one year, eliminating the "axle holding" accident.

（4） Consider the environment of the lubrication area and the medium in contact     

The environment in which the lubricating part is located and the medium in contact with it have a significant impact on the performance of the lubricating grease. Therefore, when selecting lubricating grease, careful consideration should be given.       

Sodium based grease is not suitable for damp or easily water contact areas, and lithium based grease can even be omitted. Because sodium based lubricants have poor water resistance, they are prone to thinning, loss, and emulsification when exposed to water. Some parts cannot meet the requirements even with lithium based grease, such as the bearings of vertical water pumps that are often immersed in water. Lithium based grease also emulsifies, resulting in a short lifespan and easy damage to the bearings. Composite aluminum based grease or urea based grease with good water resistance should be used in such areas. Automobile, tractor, and tank chassis often work in humid and easily water contact environments. Currently, calcium based or lithium based greases are commonly used in China, while lithium calcium based or urea based greases with better water resistance are commonly used in foreign countries.  

Lithium based grease or composite calcium, composite aluminum, or bentonite lubricating grease should not be used for areas in contact with acid or acidic gases. These lubricating greases come into contact with acids (weak acids) or acidic gases, such as trace amounts of HCI in the air, causing the grease to become thinner and lose, resulting in poor bearing protection, easy corrosion, and more importantly, poor lubrication. Some printing and dyeing factories also use reactive dyes to emit HCI gas, which not only causes corrosion to the equipment, but also makes the lubricating grease inside the bearings easily deteriorate. In these areas, Beijing Opera chooses composite barium based grease or urea based grease with good acid resistance. If it comes into contact with strong acid or oxidizing media, perfluorinated grease should be used.          

Composite aluminum based grease should be used for areas in contact with seawater or salt water; For parts that come into contact with natural rubber or paint, it is advisable to avoid using ester oils, especially diester type oils, as the base oil for lubricating grease; Special oil resistant sealing grease such as 7903 should be used for parts that come into contact with fuel oil or petroleum based lubricating oil media; Special NC-071 grease from Yiping Advanced Lubricant Company or methanol resistant grease produced by Shanghai Gaoqiao Petrochemical Company's refinery should also be used for those in contact with methanol.

（5） Consider the method of adding lubricating grease, etc     

The filling methods for lubricating grease include manual filling and centralized pump filling. Application or filling, grease gun filling, grease cup filling, etc. are all manually filled. When lubricating grease is used on cars, manual filling is adopted, such as manual filling method for hub wheel bearing, manual coating method for leaf spring, grease gun filling method for leaf spring pin, etc. (equipped with grease nozzle), and grease cup filling method for distributor transmission shaft. For parts that are manually filled, the main consideration in selecting lubricating grease is its consistency. Generally, lubricating grease with a consistency of 1-3 should be used, and it is best to choose grease with a consistency of 2. It is easier to fill and has a longer lifespan.      

Some lubrication equipment adopts the centralized filling method. These parts of the submarine's head and tail elevator movable joints are outside the cabin. When the submarine is working underwater, it is impossible to fill these parts with grease, so it is necessary to regularly and quantitatively press grease to these parts through pipes in the cabin for lubrication. In industry, centralized lubrication is more widely used, such as for conveyor roller bearings in steel mills. Due to the long distance and large number of rollers arranged, it is more convenient to use centralized lubrication. Centralized lubrication needs to be done through a long pipeline. In order to facilitate lubrication and avoid excessive pump pressure, the viscosity of the lubricating grease used is generally 1 to 0, and it is best to use grease with a viscosity of 0.       

From the perspective of lubricating grease consistency, general sealing grease, such as the sealing grease for valve stems, adopts consistency 4-5; For areas with high or ultra-high rotational speeds, consistency should be used from No. 3 to No. 2; Generally, the consistency between No. 2 and No. 1 is commonly used; Concentrated lubrication grease with a consistency of 1 to 0; The grease used for the gearbox gear adopts a consistency of 00-000.   

（6） From an economic perspective    

Choosing the appropriate lubricating grease from an economic perspective is a matter of great concern for every grease user. The selection of lubricating grease should not only be based on which one is cheap, but more importantly, on the performance of this type of grease. It is necessary to comprehensively examine whether a lubricating grease has extended the lubrication cycle, reduced filling times, consumption of lubricating grease, as well as the consumption of bearings, maintenance costs, and production losses caused by downtime. For example, the stacking machine in the hot rolling workshop of a certain steel plant traditionally uses calcium based lubricating grease (priced around 4000 yuan/t). Although it is relatively cheap, its performance cannot meet the requirements. The rolling mill is frequently repaired once a month, and each maintenance takes about 16 hours. Later, No. 2 composite lithium grease (priced at about 12000 yuan/t) was chosen. On the surface, the price was three times that of calcium grease, but the performance was excellent. The maintenance was extended every four months, and each maintenance only took 12 hours (shortened by 4 hours). Moreover, unlike when using calcium grease, every maintenance was not completely replaced, but only slightly added.