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Equipment lubrication is an important part of equipment maintenance work, and its role is increasingly prominent. Equipment lubrication includes lubrication management and lubrication technology. In recent years, lubrication technology has developed rapidly, and its status in the field of equipment engineering has been significantly improved, becoming one of the four major engineering technologies.

I. Introduction

All kinds of mechanical equipment rely on the operation of its mechanism to achieve its intended function. The machine parts in contact with each other inevitably produce friction during movement, and lead to wear of the parts. Friction can be divided into dry friction, boundary friction and liquid friction according to different lubrication states. In order to reduce friction, reduce wear, reduce energy consumption, and improve equipment operation efficiency, the common measure is to lubricate the parts of the equipment relative to the movement. As far as the boundary friction is concerned, the lubrication principle is: the molecules of the lubricant combine with the friction surface of the part to form a boundary film, thereby reducing the coefficient of friction to varying degrees and reducing or preventing the wear of the part.

There are more than 600 kinds of lubricants used for equipment lubrication. Lubricants can be divided into two categories: lubricating matrix and lubricating additives. The lubricating matrix is divided into natural lubricants and synthetic lubricants.

Second, the development and application of lubrication technology

At present, there are four aspects worthy of attention in the development of equipment lubrication technology, which are described as follows.

1. Development and application of synthetic oil products

Mineral oil is the most widely used in natural oil products. Whether mineral lubricating oil or grease, there are obvious lubrication effects and deficiencies. The outstanding disadvantages of natural lubricating oil are: (1) the viscosity of the oil changes with the change of the working environment temperature, which affects the lubrication effect of the machine; (2) It is easy to oxidize and deteriorate in the air, especially at high temperatures, and its stability is poor; (3) The friction coefficient is too large, and the motion power consumption is too large; (4) The oil is not easy to degrade and pollute the environment.

In order to overcome the many problems existing in natural lubricants, since the 1930s, lubrication scientists began to develop synthetic lubricants. The United States and Germany have successively produced various specifications of synthetic lubricants and gradually promoted their application.

The advantages of synthetic lubricating oil are: (1) good viscosity and temperature performance; (2) High temperature antioxidant stability, long service life, about six times that of mineral oil. Therefore, the number of oil changes can be reduced and materials can be saved. (3) Low volatility; (4) Reduce the friction coefficient by 20%-35%, reduce the power consumption by 4.4%-13.5%, and the individual reaches more than 30%; (5) Some brands are biodegradable and conducive to environmental protection.

Although the price of synthetic lubricating oil is more expensive, it is generally 4-5 times that of mineral oil, but if it is selected appropriately, its total cost can still be reduced, and some can be reduced by 1/2.

At present, the world's industrial developed countries generally attach importance to the use of synthetic lubricants, especially in automobiles. For example, in the United States, more than 90% of gasoline engines and more than 60% of diesel engines use multilevel synthetic oil; In Japan, 100% of gasoline engines and 52% of diesel engines use multigrade synthetic oils. In our country, only 13% of gasoline engines and 16% of diesel engines use multilevel synthetic oil.

2. Development and application of precision filtration technology

In order to maintain the cleanliness of the machine lubricating oil, it is stipulated in the equipment maintenance procedures that the oil should be filtered at any time or regularly to remove impurities. However, with the in-depth analysis of the failure of machine parts, there are new gains in the application of precision filtration technology. The failure of machine parts in operation is mainly manifested in four forms. For the prevention of fracture, deformation and corrosion, especially the first two failures, there are relatively reliable solutions. If measures are taken from the design (including the selection of materials, manufacturing and monitoring), wear is difficult to prevent.

In recent years, the equipment engineers at home and abroad through the experimental research that the wear of the mechanical parts is manifested in three forms: friction wear, adhesive wear and abrasive wear. The first two kinds of wear can be prevented with good lubrication. The understanding of abrasive wear is not sufficient. A large number of experiments have proved that the particle impurities falling off metal parts in oil are the main cause of parts wear. Therefore, the number and shape of abrasive particles in the oil should be regularly detected to achieve timely removal. The commonly used method is to precisely filter the oil and filter out the impurities of 5μm, and the effect is remarkable. Swedish SKF bearing company's tests show that after removing 2 ~ 5μm of solid particles in the oil, the life of the bearing can be extended by 10-50 times; Japan BHP Steel company NSC rolling mill for a long time to implement "wet

"Slip pollution prevention and control" has achieved remarkable results, with equipment failures reduced from more than 300 per year to 85, and the hydraulic pump update rate reduced by 80%.

For precision filtration technology, some engineers call it "active maintenance", and defined as "monitoring and control of the root causes of damage (failure) of equipment parts, preventing parts failure, reducing equipment failure, and reducing maintenance of an active measure." Some academic papers refer to such measures as "true preventive maintenance". According to the report analysis of relevant units in the United States, the cost of "active maintenance" to ensure the normal operation of the hydraulic system of the equipment at a low cost is 1/180 of the cost of fault (after the event) maintenance, 1/130 of the regular (preventive) maintenance, and 1/80 of the state (predictive) maintenance. So, it calls this approach fourth generation maintenance.

3. Development and application of lubricating additives

With the progress of industrial technology and the improvement of equipment performance, ordinary mineral lubrication grease has been difficult to meet the needs of equipment operation. To this end, scientific and technological workers began to study the addition of a small amount (3%-5%) of special substances in the lubricant to improve its lubrication performance, this special substance is called lubrication additives. Lubricating additives generally do not change the viscosity and other properties of the lubricating matrix, nor do they react chemically with the lubricant. In summary, lubricating additives have the following effects: (1) improve the performance of the lubricant. Such as increasing the strength of the oil film; (2) Improve the working adaptability of the lubricant. Such as improving viscosity and temperature characteristics, reducing oil condensation point, eliminating foam in oil, etc.; (3) Increase the stability of the lubricant. Such as improving oxidation resistance and corrosion resistance; (4) Improve the surface of the parts

Performance and working condition. Such as improving the wear resistance of parts, repairing the wear of parts, and realizing the adaptive function.

At present, the lubrication additives developed by countries in the world have 11 categories and thousands of varieties, of which the best is nano additives. This technology greatly improves the application effect of equipment lubrication.

(1) Mechanism of nano additives

When the particle size of the substance is small to the nanometer level, usually in the range of 1-100nrn, many of the inherent properties of the substance itself are soil changes. This phenomenon is called the nano effect. Surface and interface effects, one of the nano effects, will make a leap in the family of lubricating additives.

When particles of matter are refined, their surface area increases significantly, as does the number of atoms and molecules at the surface position. In general, the number of atoms and molecules on the surface of particles with a particle size of 100nrn only accounts for 2% of the total number of atoms and molecules. For the particle size of 10nrn, the number of atoms and molecules on the surface is 20%. The number of atoms and molecules on the surface of particles with a particle size of 1nm accounts for more than 90%.

The crystal field environment and binding energy of the atoms and molecules on the surface of the particle are different from the atoms and molecules inside the particle. The surface atoms lack electrons around them, have many empty bonds, behave in an unsaturated state, and have extremely high chemical activity. Using this effect can greatly improve the effectiveness of lubricants.

(2) Performance analysis of nano-additives

At present, nano-additives mainly include nano-inorganic substances, nano-inorganic salts, nano-organic compounds, nano-organic polymer materials and nano-metal five categories. They have their own excellent performance, the most prominent are the following three aspects.

① Improve the oil film strength. Due to the surface interface effect of nanoparticles, when the lubricating oil containing additives is in contact with the friction surface of the part, the nano adsorption film can be formed, and the nano reaction film can be formed during operation. Its strength is much stronger than the physical adsorption film, chemical adsorption film and chemical reaction film produced by traditional additives. And because its particle size is very small, it can drill ultra-fine gaps that micron grade additives cannot enter, making the lubrication effect better.

② Improve the suspension density and uniformity of additives. Because of the small size and light weight of the nanoparticle, it is easy to suspend stably in the lubricating oil for a long time. For example, a 1μm3 additive particle, when it is refined into 10nrn particle size, the number of particles can be increased to 106. This is called the volume effect and the quantity effect of nanoparticles. The above properties are not available in ordinary additives.

③ Realize the repair function of the parts. The repair function of nano-additives is reflected in two aspects. On the one hand, the nano-metal particles in the additive combine with the surface layer of the metal parts under the action of the catalyst to form a new lattice structure and fill up the wear marks. At the same time, the effect of optimizing the clearance of friction pair is achieved. On the other hand, when extreme pressure friction occurs in moving parts, nano-additives can form a metal ceramic magnetic protective layer on the surface of the parts, so that its hardness is greatly improved, so as to prevent new wear of the parts.

4. Oil-gas lubrication technology

Equipment lubrication because of the structure of the equipment and the use of lubrication materials have a variety of lubrication methods. More advanced is the automatic timing oil feeding device, in which the application of oil mist lubrication is more common.

At present, lubrication engineers are studying a new type of lubrication, that is, oil and gas lubrication technology. Compared with oil mist lubrication, it has obvious improvement in lubrication effect and oil consumption.

The traditional oil mist lubrication is to atomize the oil into 0.5-2μm fog particles, which advance to the machine with the compressed air at the same speed. Oil and gas lubrication is to use a stepping oil feeder with 0.3-0.4MPa compressed air, at a flow rate of 30-80m/s, regularly and quantitatively spray oil droplets to the lubrication part at a speed of 0.02-0.05m/s.

The main advantages of oil and gas lubrication are: (1) the oil consumption is 1/10-1/30 of the oil mist lubrication; (2) Less oil spill, which is conducive to improving the working environment; (3) Suitable for lubrication of parts working at high speed, heavy load and high temperature.

Iii. Conclusion

The above several new lubrication technologies do have their outstanding advantages, but any advanced technology has its scope of application, and the above lubrication technology has some foreign experience. Lubrication engineers in the use of new lubrication technology and lubrication materials, should be based on the structure and operating conditions of their own equipment reasonable selection to achieve the best results.