Equipment lubrication technology

Thread Content

I. Friction and Lubrication. Tribology is an interdisciplinary field that encompasses various disciplines such as mathematics, mechanics, physics, chemistry, mechanical engineering, as well as materials science and petrochemical engineering. There are three types of friction in objects: sliding friction, rolling friction, and fluid friction. To move an object with the least amount of force, it is necessary to convert sliding friction and rolling friction into flow friction, which causes the least resistance, or to add a lubricant between the two objects in order to reduce friction. The purpose of lubrication is to allow two objects to come into direct contact; therefore, it is desired to form a thicker oil film between the contacting surfaces. Generally, the thickness of the oil film formed on sliding or rolling surfaces depends on the ZN/P value. Here, Z = viscosity (cP), N = revolutions per minute (rpm), and P = load (Kg/cm2). According to this principle: – The higher the viscosity, the thinner the oil film. – The higher the rotation speed, the thicker the oil film. – The lower the load, the thicker the oil film. – At a constant load, the larger the bearing contact area, the less load is exerted per unit area, thus the oil film becomes thicker. The fluid lubrication (friction) zone (ZN/P > A) represents ideal conditions, with a thick lubricant film that completely separates the contact surfaces. Mixed and boundary lubrication (friction) zones (ZN/P＜A): In these zones, although adhesion has not yet fully developed on the friction surfaces, the lubrication film has lost its fluid properties, resulting in higher friction compared to fluid friction zones. There is a high risk of burnout, and this occurs at the moment the machine starts up or shuts down. As the load continues to increase beyond the lubrication limit, the oil film loses its ability to support the load, and the surfaces in contact with each other experience adhesion and wear. This condition is called dry friction. In this case, a chemical reaction occurs between the metal surface in contact and the extreme pressure additive in the lubricating oil. Thus, a thin film of metal compound that acts as a lubricant and allows for easy sliding is formed; this condition is known as extreme pressure lubrication. Friction between two objects causes wear on those objects; friction is the phenomenon, while wear is the result. Lubrication is a method to reduce wear. There are several types of wear on objects; five common types of wear are as follows: Characteristics and examples of each type – Adhesive wear occurs when, due to solid-state bonding that results from relative motion between the frictioning surfaces, the material on the surface of the contact points moves from one surface to another. Adhesive shear failure at contact points: Frictional scarring of the aluminum piston walls in internal combustion engines against the cylinder block; abrasive wear occurs during friction as the protruding particles scrape the friction surface, causing material to detach. Abrasives act on the surface of materials, causing damage to the linings of ball mills as well as to steel balls. In agricultural and mining machinery, wear occurs due to fatigue wear – a type of wear that arises when two contacting surfaces are in a state of rolling or rolling-sliding motion; periodic loads lead to deformation and stress on these surfaces, resulting in cracks in the material and the separation of tiny fragments or particles. Rolling bearings and gear pairs suffer from fatigue failure due to repeated exposure to contact stresses on their surfaces; corrosion and wear occur as a result of chemical or electrochemical reactions between the metal and the surrounding medium during friction, leading to material loss. In cases of chemical or electrochemical reactions, corrosion can damage the crankshaft journals, leading to oxidative wear. In chemical processing equipment, micro-wear occurs on the surfaces of components as a result of low-amplitude oscillations between the contacting surfaces, resulting in material loss through composite wear. This phenomenon also applies to the mating surfaces of the inner and outer friction plates in disc-type friction clutches. 1. Ways to reduce wear: (1) Selection of appropriate materials; (2) Lubrication; (3) Surface strengthening or wear-resistant treatment; (4) Structural design; (5) Proper use and maintenance of equipment. 2. Functions of lubrication: (1) Lubricating effect – reducing frictional resistance to save energy and minimize wear, thereby extending the lifespan of machinery; (2) Cooling effect – dissipating the heat generated by friction; (3) Sealing effect – preventing leaks, dust ingress, and gas leakage; rust prevention – protecting the surfaces of equipment or components from corrosion; (4) Cleaning effect – removing carbon particles or wear debris from moving parts; (5) Shock absorption – distributing stress, buffering forces, and reducing impacts; (6) Transfer of kinetic energy. Overall failure of modern devices such as hydraulic systems, remote-controlled motors, and friction-based variable-speed systems is rare; most failures occur in specific key components, with those caused by friction, wear, and lubrication issues being the most common. Once the friction pairs in modern equipment fail, it not only leads to a series of malfunctions but also results in economic losses. The way to address these failures is not to improve the quality of mechanical components, but to apply tribological principles to deal with them. 3. Wear pattern of parts: (1) Running-in stage, (2) Stable wear stage, (3) Rapid wear stage. According to tribological principles, the shorter the running-in stage, the better ； The longer the stable phase, the better; this helps to avoid a phase of rapid wear. While ensuring the quality of part design and manufacturing, lubricants should be managed scientifically, that is, by selecting them appropriately and by monitoring their use, controlling contamination, and carrying out cleaning procedures. The principles of tribology play a crucial role throughout the life cycle of modern equipment. The level of expertise in tribological techniques possessed by those responsible for equipment management, particularly in terms of equipment lubrication, greatly determines the reliability of the equipment’s operation. 4. Physical forms of lubricants (1) Gas lubrication involves using certain inert gases such as air, steam, or helium as lubricants; this keeps the friction surfaces separated by high-pressure gas. Such as inertial gyroscopes for navigation ； Thrust bearings of vertical turbines in heavy machinery ； Rotating support for large astronomical telescopes ； The bearings and other components of high-speed grinders can be lubricated with gas. The greatest advantage of gas lubrication is its extremely low friction coefficient, which is almost zero. The viscosity of gases is not affected by temperature; therefore, bearings lubricated with gases exhibit low friction and high precision. (2) For reducers, gears, bearings, etc., of liquid-lubricated general machinery and equipment, liquid lubricating oils with different viscosities and properties are used for lubrication. Liquid lubricants include mineral lubricating oils, synthetic lubricating oils, and emulsified oils. Water can also be used as a lubricant and coolant in some situations. (3) Semi-solid lubricating grease is a semi-solid substance in a plastic or paste-like state, lying between a fluid and a solid. It includes various mineral greases, synthetic greases, as well as animal and plant fats. It is widely used in various types of rolling bearings and vertically mounted linear guides. (4) Solid lubrication makes use of solid lubricants with special lubricating properties, such as graphite, molybdenum disulfide, tungsten disulfide, etc., to replace lubricating oils and greases and isolate the frictional contact surfaces, thereby forming a good solid lubrication film that enables effective friction reduction and minimizes wear. II. Composition and physical-chemical properties of lubricating oils
1. Composition of lubricating oils
Lubricating oils generally consist of two components: base oil and additives. Base oil is the main component of lubricants and determines their basic properties, while additives can compensate for and improve the shortcomings of the base oil’s performance, endowing it with certain new properties; they are an important part of lubricants. (1) Lubricant base oils Lubricant base oils are mainly divided into two categories: mineral base oils and synthetic base oils. Mineral base oils are widely used and account for a large proportion (over 95%), but in some applications products formulated with synthetic base oils are necessary, which has led to the rapid development of synthetic base oils. Mineral base oil is derived from crude oil. The main production processes for lubricating oil base stocks include: atmospheric and vacuum distillation, solvent deasphalting, solvent refining, solvent dewaxing, and clay or hydrofinishing. In 1995, China’s current standards for lubricant base oils were revised, primarily by changing the classification method, and standards for two specialized types of base oils—those with low freezing points and those that have undergone advanced refining—were added. In the production of mineral-based lubricants, the most important thing is to select the best crude oil. The chemical composition of mineral base oils includes high-boiling-point, high-molecular-weight hydrocarbons and non-hydrocarbon mixtures. Its composition generally includes alkanes (linear, branched, highly branched), cycloalkanes (monocyclic, bicyclic, polycyclic), aromatics (monocyclic aromatics, polycyclic aromatics), cycloalkyl aromatics, as well as oxygen-containing, nitrogen-containing, and sulfur-containing organic compounds, along with non-hydrocarbon compounds such as resins and asphaltenes. (2) Lubricant additives are the essence of modern high-grade lubricants. By selecting and adding them appropriately, their physicochemical properties can be improved, new special properties can be imparted to the lubricant, or its existing properties can be enhanced to meet higher requirements. Carefully selecting, carefully balancing, and properly formulating additives based on the required quality and performance of lubricants is key to ensuring their quality. Main types of additives and their functions ； 1) Viscosity index improvers: Additives that, when incorporated into oils, can improve visco-temperature properties and raise the viscosity index. 2) Pour point depressants: Additives that can lower the pour point or freezing point of oils. 3) Cleaning additives: Surface-active additives that help suspend solid pollutant particles in oil. 4) Dispersing additive: An additive that can disperse low-temperature sludge in oil. 5) Metal passivators: Additives that can inhibit metals and their compounds from acting as catalysts in the oxidation of petroleum products. 6) Extreme pressure and anti-wear additives: Additives that can react with the metal surfaces in contact to form a high-melting-point inorganic film, thereby preventing welding, seizure, scratches, or gouges under high loads. 7) Oil-based additives: Additives that can increase the strength of the oil film, reduce the friction coefficient, and enhance wear resistance. 8) Antioxidant additives: Additives that are incorporated into oil products to inhibit their oxidation. 9) Antifoam additives: Additives added to oils to prevent or reduce foaming in those oils. 10) Emulsifier: A surfactant that enables oils to be emulsified and maintained in a stable state. 11) Anti-corrosion additives: Additives added to prevent or delay the corrosion of metals. 2. General physical and chemical properties: Each type of lubricant possesses common physical and chemical properties that indicate its inherent quality. For lubricating oils, these general physical and chemical properties are as follows: (1) Appearance (color) – The color of an oil often reflects its degree of refinement and stability. For base oils, generally the higher the degree of refinement, the more thoroughly the hydrocarbon oxides and sulfides are removed, resulting in a lighter color. However, even under the same refining conditions, the base oils produced from crude oils of different sources and base groups may vary in color and transparency. For new finished lubricants, due to the use of additives, color has lost its original significance as an indicator of the degree of refinement of the base oil. (2) Density Density is the simplest and most commonly used physical property indicator for lubricants. The density of lubricating oil increases as the amount of carbon, oxygen, and sulfur in its composition rises; therefore, at the same viscosity or the same relative molecular mass, lubricating oils with a high content of aromatics, as well as those with high levels of gums and asphalts, have the highest density, those with a high content of naphthenes have a medium density, and those with a high content of alkanes have the lowest density. (3) Viscosity: Viscosity reflects the internal friction of an oil and is an indicator of its lubricity and fluidity. Without the addition of any functional additives, the higher the viscosity, the greater the strength of the oil film and the poorer its fluidity. (4) Viscosity index: The viscosity index indicates the degree to which the viscosity of a lubricant changes with temperature. The higher the viscosity index, the less the viscosity of the oil is affected by temperature, indicating better viscosity-temperature properties; conversely, the lower the viscosity index, the worse these properties are. (5) Flash point: The flash point is an indicator of the volatility of oils. The lighter the fraction of the oil, the greater its volatility, and the lower its flash point as well. Conversely, the heavier the distillate of an oil product, the lower its volatility, and the higher its flash point. At the same time, the flash point is an indicator of the fire hazard of petroleum products. The hazard level of oils is determined based on their flash point: oils with a flash point below 45°C are considered flammable, while those with a flash point above 45°C are considered combustible. It is strictly prohibited to heat oils to their flash point temperature during storage and transportation. Given the same viscosity, the higher the flash point, the better. Therefore, when selecting lubricating oil, users should choose based on the operating temperature and the working conditions of the lubricant. Generally, it is believed that a flash point 20–30°C higher than the operating temperature ensures safe use. (6) Freezing point and pour point: The freezing point refers to the highest temperature at which the oil stops flowing under specified cooling conditions. The solidification of oils differs greatly from that of pure compounds. Oil does not have a definite freezing temperature; the so-called “freezing” simply means that it loses its fluidity as a whole, and not all of its components turn into solids. The freezing point of lubricating oil is an important quality indicator that reflects its flowability at low temperatures. It is of great significance for production, transportation, and use. Lubricants with a high freezing point cannot be used at low temperatures. On the contrary, in areas with higher temperatures, there is no need to use lubricants with a low freezing point. Because the lower the freezing point of the lubricating oil, the higher its production cost, resulting in unnecessary waste. Generally speaking, the pour point of lubricating oil should be 5–7°C lower than the lowest temperature in the operating environment. It is particularly important to note that when selecting a lubricant for low temperatures, comprehensive consideration should be given to the oil’s freezing point, viscosity at low temperatures, and viscosity-temperature characteristics. Because oils with low freezing points may also have low-temperature viscosity and viscosity-temperature properties that do not meet the requirements. Both the freezing point and the pour point are indicators of the low-temperature flowability of oils; there is no fundamental difference between them, only slight variations in the methods of measurement. The freezing point and pour point of the same oil product are not exactly equal; generally, the pour point is 2–3°C higher than the freezing point, though there are exceptions. (7) Acid value, alkali value, and neutralization value. The acid value is an indicator of the acidic substances contained in lubricating oil, with the unit being mgKOH/g. The acid value is divided into strong acid value and weak acid value; the sum of the two gives the total acid value (abbreviated as TAN). What we usually refer to as “acid value” actually means “Total Acid Number (TAN)”. The alkalinity value is an indicator of the content of basic substances in lubricating oil, with the unit being mgKOH/g. Alkalinity is also divided into strong alkalinity and weak alkalinity; the sum of the two constitutes the total alkalinity (abbreviated as TBN). What we usually refer to as “alkalinity” actually means “total basic number (TBN)”. The neutralization value actually includes the total acid value and the total base value. However, unless otherwise specified, the so-called “neutralization value” generally refers only to the “total acid value,” which is also expressed in mgKOH/g. (8) Moisture: Moisture refers to the percentage of water contained in the lubricant, usually expressed as a weight percentage. The presence of water in lubricating oil can destroy the oil film formed by the lubricant, reducing its lubricating effect, accelerating the corrosion of metals by organic acids, causing equipment to rust, and leading to the formation of sediment in the oil. In short, the less moisture in the lubricant, the better. (9) Mechanical impurities: Mechanical impurities refer to precipitates or colloidal suspensions present in lubricating oil that are insoluble in solvents such as gasoline, ethanol, and benzene. Most of these impurities are sand, gravel, iron filings, and various organometallic salts that are insoluble in solvents and come from additives. Generally, the mechanical impurities in lubricant base oils are kept below 0.005% (levels below 0.005% are considered to be absent). (10) Ash and sulfuric ash: Ash refers to the non-combustible substances that remain after burning under specified conditions. The composition of ash is generally considered to be various metal elements and their salts. Ash content has different meanings for various types of oils; for base oils or oils without additives, ash content can be used to determine the degree of refinement of the oil. For oils (new oil) to which metal salt additives have been added, ash content becomes a means for quantitatively controlling the amount of additives added. Abroad, sulfuric acid ash is used in place of ash. The method is: after burning the oil sample but before incinerating it to ash, add a small amount of concentrated sulfuric acid to convert the metal elements of the additives into sulfates. (12) Residue: The charblack residue formed after the heating, evaporation, and combustion of oil under specified experimental conditions is called residue. Residue is an important quality indicator for lubricant base oils; it is a parameter specified to determine the properties of the lubricant and the degree of its refinement. In lubricant base oils, the amount of residue is determined not only by its chemical composition but also by the degree of refining of the oil. The main substances that cause residue formation in lubricants are gums, asphaltenes, and polycyclic aromatic hydrocarbons present in the oil. Under conditions of insufficient air, these substances decompose and condense under high heat to form residue carbon. The deeper the refining of the oil, the lower its residue value. Generally speaking, the lower the carbon residue value of the base oil, the better. Today, many oils contain additives made of metals, sulfur, phosphorus, and nitrogen; these additives result in high carbon residue values. As a result, the carbon residue measurement for oils containing such additives has lost its original meaning. Mechanical impurities, moisture, ash, and residue are all quality indicators that reflect the purity of oils, and they indicate the degree of refinement of the lubricating base oil. 3. Special physicochemical properties of lubricants: In addition to the general physicochemical properties mentioned above, each type of lubricant should also possess special physicochemical properties that characterize its usage characteristics. The higher the quality requirements, or the greater the specificity of the oil, the more prominent its special physical and chemical properties become. The test methods reflecting these special physical and chemical properties are briefly introduced as follows: (1) Oxidation stability. Oxidation stability indicates the anti-aging properties of lubricating oils. Many industrial lubricating oils with a long service life must meet this requirement; therefore, it is regarded as a special property required for such types of oils. There are many methods for determining the oxidative stability of oils. Essentially, a certain amount of oil is oxidized at a specific temperature for a certain period of time in the presence of air (or oxygen) and a metal catalyst; thereafter, the acid value, viscosity changes, and the formation of deposits in the oil are measured. All lubricants have different tendencies toward autoxidation, depending on their chemical composition and the external conditions in which they find themselves. Oxidation occurs over time as it is used, gradually resulting in the formation of aldehydes, ketones, acids, as well as substances such as gums and asphalts. Oxidation stability is the property that prevents the formation of these substances that are detrimental to the use of oil products. (2) Thermal stability: Thermal stability refers to a lubricant’s ability to withstand high temperatures, that is, its resistance to thermal decomposition, which is expressed by the thermal decomposition temperature. Some high-quality anti-wear hydraulic oils, compressor oils, etc., have requirements regarding thermal stability. The thermal stability of oils depends primarily on the composition of the base oil; many additives with low decomposition temperatures tend to have an adverse effect on the stability of the oils ； Antioxidants also cannot significantly improve the thermal stability of oils. (3) Oiliness and extreme pressure properties: Oiliness enables the polar substances in lubricants to form a strong physicochemical adsorption film on the metal surfaces at the points of friction, thereby providing resistance to high loads and frictional wear. Extreme pressure properties, on the other hand, involve the polar substances in lubricants breaking down due to frictional chemical reactions under high temperatures and heavy loads on the metal surfaces at the points of friction; these substances then undergo frictional chemical reactions with the surface metal to form a soft (or plastic) extreme pressure film with a low melting point, which provides protection against impacts as well as high loads and high temperatures. (4) Corrosion and rust: Due to the oxidation of oils or the effect of additives, corrosion of steel and other non-ferrous metals often occurs. In corrosion testing, a copper strip is usually placed in oil and left at 100°C for 3 hours, after which the changes in the copper are observed ； In the corrosion test, rust forms on the steel surface under the action of water and water vapor. To determine the anti-corrosion properties, 30 ml of distilled water or artificial seawater is added to 300 ml of test oil; then a steel rod is placed in it. The mixture is stirred at 54°C for 24 hours, after which it is examined to see whether any rust has formed on the steel rod. Oils should have resistance to metal corrosion and rust prevention; in industrial lubricant standards, these two properties are typically required to be tested. (5) Antifoaming property: During operation, lubricants often form foam due to the presence of air. This is especially true when the oil contains surfactant additives, as foam is more likely to form and it is also difficult for such foam to disappear. Foam generated during the use of lubricating oil can damage the oil film, leading to scuffing or increased wear on friction surfaces. It also promotes the oxidation and degradation of the lubricating oil. Additionally, it can cause air blockage in the lubrication system, thereby affecting the circulation of the lubricating oil. Therefore, anti-foaming properties are an important quality indicator for lubricating oils, etc. (6) Hydrolytic stability: Hydrolytic stability refers to the stability of oil products under the action of water and metals (mainly copper). When the acid number of an oil product is high, or when it contains additives that readily decompose into acidic substances upon contact with water, this indicator often fails to meet the required standards. Its determination method involves adding the test oil to a certain amount of water, mixing and stirring it with a copper sheet at a specified temperature for a certain period of time, and then measuring the acid number of the water layer and the weight loss of the copper sheet. (7) Emulsion resistance: Industrial lubricants often inevitably become mixed with some cooling water during use. If the lubricant lacks good emulsion resistance, it will form an emulsion with the water that has mixed in, making it difficult to remove the water from the bottom of the circulation tank; this can lead to poor lubrication. Therefore, anti-emulsibility is a very important physicochemical property of industrial lubricants. For ordinary oils, 40 ml of the oil sample is mixed vigorously with 40 ml of distilled water at a certain temperature for a specified period of time, after which the time it takes for the oil layer, water layer, and emulsion layer to separate into 40–37–3 ml is observed ； Industrial gear oil is prepared by mixing the oil with water, stirring at a certain temperature and at 6,000 revolutions per minute for 5 minutes, allowing it to stand for 5 hours, and then measuring the volumes of oil, water, and the emulsion layer. (8) Air release value: This requirement is specified in the hydraulic oil standards, because in hydraulic systems, if the air dissolved in the oil is not released in a timely manner, it will affect the accuracy and sensitivity of hydraulic transmission; in severe cases, it will fail to meet the requirements for using such hydraulic systems. The method for measuring this property is similar to that for antifoaming capacity, except that it determines the time it takes for the air (mist) dissolved within the oil to be released. (9) Rubber sealing performance: In hydraulic systems, rubber is commonly used as a sealing material. In mechanical devices, oils inevitably come into contact with various sealing components. Oils that have poor sealing properties can cause the rubber to swell, shrink, harden, or crack, thereby affecting its sealing ability; therefore, it is necessary for oils to have good compatibility with rubber. Hydraulic oil standards require a rubber sealing index, which is measured by the change that occurs in a rubber ring of a certain size after being immersed in oil for a specified period of time. (10) Shear stability: In oils to which thickeners have been added, mechanical shear during use can break down the high-molecular polymers present in the oil, resulting in a decrease in its viscosity and thereby affecting proper lubrication. Therefore, shear stability is a specific physical and chemical property that must be measured for such oils. There are many methods for measuring shear stability, including the ultrasonic shear method, the nozzle shear method, the Wicks pump shear method, and the FZG gearbox shear method; all of these methods ultimately aim to determine the rate of viscosity decrease in the oil. (11) Solubility Capacity The solubility capacity is usually expressed by the aniline point. The solubility limit aniline point of composite additives varies with different grades of oils; the limit value for oils with low ash content is higher than that for highly alkaline oils, and the limit value for single-grade oils is higher than that for multi-grade oils. (12) Volatility: The volatility of the base oil is related to fuel consumption, viscosity stability, and oxidation stability. These properties are particularly important for multi-grade oils and energy-saving oils. (13) Rust resistance: This refers specifically to the special physical and chemical properties that rust-preventing greases should possess. The testing methods for this include humidity tests, salt spray tests, laminating tests, and water displacement tests; in addition, there are also greenhouse tests and long-term storage tests. (14) Electrical properties: Electrical properties are unique characteristics of insulating oils, including the dielectric loss angle, dielectric constant, breakdown voltage, pulse voltage, etc. The degree of refinement of the base oil, as well as impurities and moisture, all have a significant impact on the electrical properties of the oil. (15) Special physicochemical properties of greases Besides their general physicochemical properties, greases designed for specific applications possess special physicochemical characteristics as well. Greases with good water resistance are required to undergo a water test ； For low-temperature grease, low-temperature torque needs to be measured ； Multi-effect greases need to be tested for extreme pressure and wear resistance as well as rust prevention properties ； Long-life lubricants require bearing life tests and the like. There are also corresponding test methods for measuring these properties. (16) Other special physical and chemical properties: In addition to their general properties, each type of oil should have its own unique special properties. For example, for quenching oil, the cooling rate needs to be measured ； The emulsification stability of the emulsified oil needs to be determined ； The anti-creep coefficient of hydraulic guide rail oil needs to be measured ； The dispersion of oil mist needs to be measured for spray lubricants ； The freezing point and flocculation point of refrigeration oil need to be measured ； Low-temperature gear oil needs to be tested for pitting, etc. All these properties require a special chemical composition of the base oil, or the addition of certain special additives to be ensured. III. Classification of Lubricants and Introduction to Commonly Used Lubricants 1. Classification of Lubricants (1) Naming Method for Lubricants The naming method for lubricants is specified in the standard GB 7631.1-87 \"Classification of Lubricants and Related Products (Class L)\". The name of each lubricant product is a code consisting of a set of uppercase letters; the first letter indicates the category to which the product belongs, while the meaning of any subsequent letters, when considered alone, is specified in the detailed classification criteria for that category. Lubricant product name: L — AN 32(2). Lubricant product classification: The standard GB 7631.1-87 \"Classification of lubricants and related products (Class L)\\" divides lubricant products into 19 groups. Classification of Lubricants and Related Products (Class L) (by Application Area) (GB7631.1-87): Group, Application Area, Classification Criteria for Each Type. A – Fully lost systems; GB/T 7631.13—1995. B – Demolding. C – Gears; GB/T 7631.7—1995. D – Compressors (including refrigerators and vacuum pumps); GB/T 7631.9—1997. E – Internal combustion engines; GB/T 7631.3—1995. F – Spindles, bearings, and clutches; GB/T 7631.4—1989. G – Guides; GB/T 7631.11—1994. H – Hydraulic systems; GB/T 7631.2—1987. M – Metal processing; GB/T 7631.5—1989. N – Electrical insulation; GB/T 7631.15—1998. P – Pneumatic tools; GB/T 7631.16—1999. Q – Heat conduction; GB/T 7631.12—1994. R – Temporary protection and corrosion prevention; GB/T 7631.6—1989. T – Steam turbines; GB/T 7631.10—1992. U – Heat treatment; GB/T 7631.14—1998. X – Applications requiring grease; GB/T 7631.8—1990. Y – Other applications. Z – Steam cylinders. S – Applications for special lubricants. (3) Viscosity grades of lubricants: The standard GB/T 3141-94 “ISO Viscosity Classification for Industrial Liquid Lubricants” establishes the classification system for the viscosity grades of lubricating oils. Viscosity classification of industrial liquid lubricants: GB3141 uses certain viscosity grades, while ISO uses other viscosity grades. Central value of dynamic viscosity in cst (mm2/s) at 40°C; range of dynamic viscosity in cst (mm2/s) at 40°C: 2 – ISO VG22: 2.21–2.98; 3 – ISO VG33: 3.22–3.52; 5 – ISO VG54: 4.64–5.06; 7 – ISO VG76: 6.86–7.48; 10 – ISO VG101: 10.90–11.0; 15 – ISO VG151: 15.13–16.5; 22 – ISO VG222: 21.98–24.2; 32 – ISO VG323: 28.8–35.2; 46 – ISO VG464: 41.4–50.6; 68 – ISO VG686: 61.2–74.8; 100 – ISO VG1001: 100.90–110; 150 – ISO VG1501: 150.135–165; 220 – ISO VG2202: 219.8–242; 320 – ISO VG3203: 288–352; 460 – ISO VG4604: 414–506; 680 – ISO VG6806: 612–748; 1000 – ISO VG10001: 900–1100; 1500 – ISO VG15001: 1350–1650.

2. Introduction to major lubricant products: (1) Lubricants for Group A (total loss systems): Product category L is divided into 19 groups. Lubricants in Group A are used in total loss systems, but they are not the only ones used for such systems. Other types of lubricants including those for reciprocating compressors in Group D, guide rail oils in Group G, lubricants for pneumatic tools in Group P, and lubricants for steam cylinders in Group Z are also used in total loss systems. Our country classifies Category L, Group A products into three subcategories: AB, AN, and AY. L-AB oil is produced from refined mineral oil and contains asphalt or additives to improve its adhesion, extreme pressure properties, and corrosion resistance; it is primarily used for lubricating the surfaces of open gears and ropes. L-AB oil is similar to L-CKJ open gear oil in Group C and can be used interchangeably; therefore, L-AB oil is not produced in China. L-AN oil is produced from refined mineral oil; a small amount of antifreeze agent may also be added to it. It is classified into ten viscosity grades ranging from 5 to 150, based on the median value of its dynamic viscosity at 40°C. It is mainly used in total-loss lubrication systems for light-duty, old-fashioned, and ordinary machinery, or in oil-bath lubrication systems with short oil change intervals. It is not suitable for circulating lubrication systems. L-AY oil is an unrefined mineral oil with a low freezing point; sometimes, extract oil (a by-product of the refining process of lubricants) is added to it to improve adhesion properties. It is suitable for lubricating the sliding bearings of railway freight cars, available in three viscosity grades for winter, summer, and general use, and is intended exclusively for use by railway authorities. (2) Group C (Gear) oils: Group C oils include industrial gear oils and automotive gear oils. Industrial gear oils are further divided into industrial closed-gear oils and industrial open-gear oils. Industrial closed-gear oils are all used for continuous lubrication (through splashing, circulation, or spraying, etc.), while industrial open-gear oils are all used for intermittent or drip-type lubrication. Only industrial gear oil will be covered below. 1) Industrial closed-type gear oils: GB/T 7631.7-95 classifies industrial closed-type gear oils into six types: CKB, CKC, CKD, CKE, CKS, and CKT. Below is a brief introduction to these six varieties. L-CKB oil is an antioxidant and rust-inhibiting lubricant, commonly referred to as an “R&O” type oil, where “R” stands for rust inhibition and “O” stands for antioxidant properties. Originally named Antioxidant and Rust-Preventing Industrial Gear Oil (enterprise standard). It has anti-foaming and anti-emulsifying properties, making it suitable for lubricating lightly loaded industrial closed gears operating at normal temperatures. L-CKC oil is a extreme pressure-type industrial closed gear oil that further enhances the extreme pressure performance of L-CKB oil. This product is suitable for lubricating gear transmission systems in machinery such as those used in mining, chemical processing, metallurgy, and shipbuilding, where operations take place at moderate oil temperatures under heavy loads without impact forces. L-CKD oil is another extreme pressure-type industrial closed gear oil that further improves the extreme pressure performance and thermal/oxidative stability of L-CKC oil. This product is suitable for lubricating the gear transmission systems of heavy-duty and impact-prone machinery in industries such as metallurgical rolling and underground mining, where operations take place at high temperatures. L-CKE oil improves the anti-friction properties of L-CKB oil further, giving it a low coefficient of friction. It can improve the efficiency of worm and worm gear drives and reduce noise; it is a specialized oil for such drives. In our country, L-CKE oil is temporarily divided into two varieties, L-CKE and L-CKE/P (SH0094-91), due to differences in their formulations. For L-CKE and L-CKE/P oils, there are only five viscosity grades available: 220–1000. When it is necessary to use a worm gear oil with a lower viscosity grade, L-CKC industrial closed-type gear oil or L-HM hydraulic oil can be used as substitutes. L-CKS and L-CKT oils are industrial closed-gear oils produced from refined mineral oil, synthetic oil, or semi-synthetic oil. L-CKS is an R&O type oil suitable for lubricating light-load industrial enclosed gears operating under extreme (higher and lower) temperatures. L-CKT is an EP (extreme pressure) type oil, suitable for lubricating heavy-duty industrial closed gears. L-S4405 and L-S4406 belong to the L-CKS and L-CKT categories respectively, with a viscosity index greater than 170 and a pour point below -40°C. 2) Industrial open gear oils: GB/T 7631.7-95 classifies industrial open gear oils into three types: CKH, CKJ, and CKM. Both L-CKH and L-CKJ oils are asphalt-type products. L-CKH oil has rust-resistant properties and is a standard type of open gear oil. L-CKJ oil is an anti-wear type of open gear oil that improves the extreme pressure and anti-wear properties of L-CKH oil. Both are suitable for the lubrication of cylindrical or helical gears operating under moderate ambient temperatures, typically under light loads (and sometimes under heavy loads) but without shock loads. L-CKM oil not only possesses rust prevention, wear resistance, and extreme pressure properties, but also scratch resistance; it is a high-viscosity product containing polymers and is typically suitable for gears operating under heavy loads or with impact loads. This product cannot be used by spraying. Most open gear oils use intermittent or drip lubrication. For ease of use, L-CKH and L-CKJ oils are sometimes sold diluted with a solvent for use. Undiluted oils have high viscosity; it is generally difficult to determine their dynamic viscosity at 40°C. According to the viscosity classification standards specified in GB/T3141-94, the viscosity grades of these high-viscosity lubricants are determined based on their dynamic viscosity at 1000°C, and in such cases the suffix letter “H” should be added after the viscosity grade. (3) Group D (Compressors) oils: Products in this group include air compressor oils, vacuum pump oils, refrigeration machine oils, and oils for gas compressors (referring to gases other than air and refrigerants). The initial letter “D” of each variety always indicates the group to which that product belongs. The second letter is used as “A” for air, “V” for vacuum, “R” for frozen, and “G” for gas. The third letter has no meaning when it stands alone; it only indicates different varieties of Group D products when combined with the first two letters. Our country has established a classification system for oils used in Group D (air compressors and vacuum pumps) (GB/T7631.9-92); in future revisions of this classification, categories for refrigeration machine oils and oils used in gas compressors will also be added. Here, only oils for air compressors are introduced. Air compressor oils are divided into reciprocating air compressor oils and rotary air compressor oils. The former is divided into DAA, DAB, and DAC oils ； The latter is divided into DAG and DA oil. Among them, DAC and DAJ are synthetic oils, while the rest are refined mineral oil-based oils. 1) L-DAA and L-DAB oils are reciprocating air compressor oils. L-DAA oil is produced from refined mineral oil and is suitable for low-load air compressors ； L-DAB oil exhibits good high-temperature oxidation stability and a low tendency to form carbon deposits; some of its variants also possess certain anti-wear properties, making them suitable for air compressors under moderate load conditions. 2) L-DAG and L-DAH oils are used as lubricants for rotary (vane and screw) air compressors. The exhaust temperature of vane air compressors is usually higher than that of screw compressors, and the oil change interval is also shorter (typically <1000 hours). L-DAG is the oil used in low-load rotary screw air compressors ； L-DAH is an oil for medium loads. 3) L-DAC and L-DAJ oils are synthetic air compressor oils. Heavy-duty air compressor oil made by using synthetics such as organic esters (diesters, triesters, polyesters), synthetic hydrocarbons (polyalpha-olefins), polyethylene glycol acetates, silicons, and phosphates as base oils, to which various additives are then added. L-DAC oil is suitable for reciprocating air compressors, while L-DAJ oil is suitable for rotary air compressors. L-S4502 belongs to the L-DAC category. The main advantages of synthetic oils are their low tendency to form carbon deposits, extremely low risk of fire and explosion in the compressor exhaust system, good oxidation stability, and long service life. (4) Group F (spindles, bearings, and related clutches) – The oil used is GB/T7631.4-89. The products in Group F are divided into two types, FC and FD; both are made from highly refined mineral oil. L-FC is an R&O type oil that does not require extreme pressure and anti-wear properties. It is divided into eleven viscosity grades ranging from 2 to 100, based on the median value of its dynamic viscosity at 40°C, and is primarily used for lubricating spindles (in textile machinery), sliding bearings, rolling bearings, and related clutches where high anti-wear requirements do not apply ； L-FD (commonly referred to as spindle oil) is an oil of the R&O, AW (anti-wear), and EP (extreme pressure) types. It is classified into seven viscosity grades ranging from 2 to 22 based on the median value of its dynamic viscosity at 40°C. It is primarily used for lubricating sliding bearings, rolling bearings (such as those in precision machine tools), and spindles under conditions of high speed, light load, and high temperature. However, it is not suitable for use in clutches, as it can cause slippage in these components. It is appropriate for lubrication via pressure, oil bath, or oil mist methods. (5) Group H (hydraulic systems): According to GB/T7631.2-87, products in Group H are divided into two categories: working fluids for hydrostatic systems and those for hydrodynamic systems. The former is used to transmit the pressure energy of liquids, and is often referred to as hydraulic oil ； The latter is used to transmit the kinetic energy of liquids, and is often referred to as hydraulic oil or hydraulic transmission fluid. (6) The oil for Group G (guides) is specified in GB/T7631-93; only one type of oil is allowed for this group, and its designation consists of either a single letter “G” or the full name L-G. Currently, there are four viscosity grades: 32-150, and it is planned to add a 220 viscosity grade in the future. It is suitable for precision guide rail lubrication systems with low horizontal or vertical feed speeds that may cause \"crawling\". Grades, properties, and applications of commonly used lubricants 3. Classification of greases and introduction to commonly used greases (1) Grease codes GB/T 7631.8—1990 assigns a code to each type of grease, which consists of a set of 5 uppercase letters and a set of numbers; each letter and its order within this sequence have specific meanings. The structure of a grease code is as follows: LX (Letter 1), Letter 2, Letter 3, Letter 4, Letter 5, Number. Letter 1: Indicates the group code of the grease. Letter 2: Indicates the minimum operating temperature – ABCDE: 0, -20, -30, -40, below -40. Letter 3: Indicates the maximum operating temperature – ABCDEFG: 60, 90, 120, 140, 160, 180, above 180. Letter 4: Indicates the grease’s resistance to water and its rust-preventing capabilities under conditions of water contamination. Grades: A, B, C, D, E, F, G, H. Environmental conditions: L, LLL, MMM, MMMM, HHH. Rust-preventing performance: LM, LH, LMH, LMHL, LMHLMH, LMHLMHLM. 1) L denotes a dry environment, M denotes a slightly humid environment, and H denotes exposure to washing. 2) L indicates no rust protection, M denotes rust protection in the presence of fresh water, and H denotes rust protection in the presence of saltwater. Letter 5: Indicates the grease’s lubricating performance under high or low load conditions – A: non-extreme pressure, B: extreme pressure. Grease consistency grades (Appendix A of GB7631.1-87): Consistency grade, penetration range after 60 operations, in 1/10 mm units: 00: 04–47; Liquid: 00: 40–43; Nearly liquid: 03: 55–38; Very soft: 13: 10–34; Extremely soft: 22: 65–29; Soft: 32: 20–25; Medium: 42: 175–205; Hard: 52: 130–160; Extremely hard: 62: 85–115. Example: A grease is to be used under the following conditions: Minimum operating temperature: -20°C; Maximum operating temperature: 160°C; Environmental condition: Exposure to washing; Rust protection requirement: No rust protection needed; Load condition: High load; Consistency grade: 00. The code for this grease would be: L—XBEGB 00. (2) Common types of greases: Characteristics, market prices of grease types. Calcium-based greases have good water resistance but poor heat resistance; the maximum operating temperature is 60°C. Low-sodium based greases have very poor water resistance; their heat resistance and rust prevention properties are average. They are generally used at temperatures around 80°C. Aluminum-based greases offer good rust prevention properties, but have poor heat resistance and water resistance; their maximum operating temperature is 50°C. General-purpose lithium-based greases exhibit good heat resistance, water resistance, and rust prevention properties; their maximum operating temperature is 120°C. Extreme pressure lithium-based greases also possess good heat resistance, water resistance, rust prevention properties, and excellent extreme pressure performance; their maximum operating temperature is 120°C, making them suitable for lubricating machinery, bearings, and gears subjected to high loads. Molybdenum disulfide extreme pressure lithium-based greases have good heat resistance, water resistance, rust prevention properties, and extreme pressure performance; their maximum operating temperature is 120°C, making them ideal for components exposed to high loads or impact loads. Bentonite greases offer good heat resistance and relatively decent water resistance; however, their rust prevention properties are poor. Their maximum operating temperature is around 130°C, and they tend to be quite expensive. Composite calcium-based lubricants: They exhibit good heat resistance, water resistance, and rust prevention properties, as well as decent mechanical stability (shear resistance). Their maximum operating temperature is around 130°C. Extreme pressure composite lithium-based lubricants have excellent heat resistance, water resistance, rust prevention properties, mechanical stability, and extreme pressure performance; their maximum operating temperature is around 160°C. Polyurea-based lubricants offer good heat resistance, oxidation resistance, water resistance, and extreme pressure performance, resulting in a longer service life for bearings. They also possess certain radiation resistance, making them a new type of lubricant. Currently, there are no national or industry standards for these products in China. Common lubricant grades, their properties, and applications: IV. Equipment lubrication methods 1. Manual lubrication: In this method, the operator uses an oil pot or oil gun to fill the oil holes, nozzles, and oil cups at the points where lubrication is needed. This approach is mainly used for sliding surfaces that operate at low speeds under light loads, as well as for open gears, chains, and other individual friction pairs. The amount of fuel added is controlled based on the workers’ senses and experience. 2. Drop lubrication relies on the weight of the oil to deliver it for lubrication through a needle valve or oil wick located in an oil cup mounted at the lubrication point. It has a simple structure and is easy to use, but the oil supply amount is difficult to control; vibrations, temperature changes, and the level of the oil all affect the amount of oil supplied. It is not advisable to use oil with high viscosity; otherwise, the needle valve will become clogged. 3. Splashing lubrication: The parts immersed in the oil tank, or the slinger rings attached to the shafts, stir the oil, causing it to splash onto the friction surfaces. This is a widely used lubrication method for rolling bearings, gear drives, worm drives, chain drives, cams, etc., in enclosed housings. There are certain limitations regarding the immersion depth of the parts. The circumferential speed of the components immersed in the oil tank is generally kept below 12 m/s; too high a speed increases the stirring resistance and accelerates the oxidation of the oil, while too low a speed affects the lubrication effect. 4. Oil ring and oil chain lubrication relies on an oil ring or oil chain fitted around the shaft to bring oil from the oil reservoir to the lubricated areas. As shown in the figure, the lower part of the oil ring 2 mounted on shaft 1 is located in the oil sump; when the shaft rotates, friction drives the oil ring to rotate, thereby carrying oil into the bearings for lubrication. 5. Lubrication using oil wicks and oil pads generally involves a felt pad or oil wick in contact with the friction surface, which absorbs oil from the oil source and then applies it to the working surface. Sometimes there is no oil reservoir; the oil is filled up at the beginning, and then a little more oil is added regularly using an oil bottle. It is mainly used in small or lightly loaded sliding bearings. The main advantages of this method are its simplicity and low cost; felt and oil ropes can serve as filters, making it suitable for dusty environments. However, due to the small amount of oil, it is not suitable for large and high-speed bearings, and the oil supply cannot be adjusted. 6. Self-lubrication: Self-lubrication is achieved by mixing solid lubricant powders with lubricating properties with other solid materials and then compressing and sintering them into a material, or by impregnating porous materials with solid lubricants ； Or, a solid lubricant can be directly compressed into a material to serve as the friction surface. In this way, throughout the entire friction process, no lubricant needs to be added, yet good lubrication is still achieved. 7. The oil mist lubrication system consists of an oil mist lubrication device, pipes, and a condensation nozzle. The oil mist lubrication device mainly consists of a water and air separator, a pressure regulating valve, and an oil mist generator. Oil mist lubrication is mainly used for chains and similar components in high-speed rolling bearings under high-temperature operating conditions. This method not only serves the purpose of lubrication but also provides cooling and waste removal functions, with low fuel consumption. Its drawback is that the exhaust gas contains suspended oil mist, causing pollution. This method will be replaced by oil-gas lubrication. 8. Centralized lubrication: Centralized lubrication is mainly used in mechanical equipment with a large number of lubrication points, as well as in lubrication systems in workshops and factories. The use of centralized lubrication can reduce maintenance efforts and improve reliability. The figure shows the XHZ—6.3～125 type light oil station system. In the diagram, 7 is the pressure gauge that displays the pressure in the pipelines, 8 is the differential pressure gauge that shows the pressure difference between the inlet and outlet of the oil filter, 9 is the thermometer used to measure the oil temperature, 10 is the pressure relay, 11 is the safety valve, and 12 is the oil filter used to remove some debris from the return oil. Lipid centralized lubrication systems can be divided into single-line and double-line types based on the layout of the pipes. It can also be divided into manual and electric types. It is a manual dual-tube centralized lubrication system; the operating pressure is typically 7 MPa, there are usually more than 30 lubrication points, and the radius of the lubrication area is 2215 m. The electric centralized grease lubrication system typically operates at a working pressure of 10 MPa. It can serve hundreds of lubrication points, with a lubrication radius ranging from 5 to 120 meters. The figure shows a schematic diagram of a centralized lubrication system for electric dual-line grease lubrication. Item 1 is the grease pump; the grease is discharged from the pump, passes through filter 3, and then travels via the main oil line 4, branch oil lines 6, and lubricators 5 to various lubrication points. If all the grease feeders are filled with grease, the pressure in the main oil pipeline rises to a level sufficient to activate the pressure control valve, thereby causing the solenoid directional valve 2 in the control dry oil station to change direction, and the other main oil pipeline is connected for grease supply. 9. Pressure cycle lubrication: In this lubrication method, the lubricating oil is sent from the tank to various lubrication points by an oil pump, and then returns to the tank; thus the oil can be reused, which allows for the use of large amounts of lubricant with very little loss. Thanks to the adequate supply of oil, which can also carry away heat, it provides excellent cooling effects, and is widely used in various large-scale, heavy-duty, high-speed, precision, and automated mechanical devices. There are two forms of pressure circulation lubrication systems. In one form, a hydraulic pump directly delivers oil from the oil reservoir to the lubricated parts (spraying), and then gravity causes the oil to return to the reservoir. This system is relatively simple, but the oil supply must be stopped immediately if the pump fails. The first method involves using a high-positioned tank to deliver oil to various lubrication points by means of gravity, with the amount of oil supplied being controlled by a regulating valve. Use the oil gauge to observe the oil supply condition. The hydraulic pump sends oil from the oil sump at the bottom of the tank to the high-level oil tank, continuously replenishing the oil supply. With this circulation system, once the hydraulic pump stops operating, the oil stored in the high-level tank ensures that lubrication is not interrupted immediately. For small, simple, low-speed, and lightly loaded machinery, or when only a small amount of oil is required and there is no value in oil recovery, simple lubrication methods such as manual oiling, dripping, or oil pads can be used. For large, complex, or high-speed heavy-duty machinery that requires continuous oil supply, splash lubrication, oil ring lubrication, or circulating lubrication can be employed ； Oil mist lubrication is commonly used for high-speed bearings or gears ； Pressure circulation lubrication is preferably used for critical components that require a large amount of oil. V. Lubrication Management: Lubricants are the “blood” of mechanical equipment, while lubrication methods and devices serve as the “heart” that transports this blood” ； Every aspect of lubrication technology, such as the selection and replacement of lubricants as well as the use of lubrication devices, can lead to equipment failures if not handled properly. This in turn can cause failures throughout the entire production line, resulting in significant economic losses. Does enterprise upgrading give veto power over equipment management? ； Equipment management has been upgraded, with veto power over lubrication management. 1. Improving lubrication management has the following benefits: (1) Extending equipment lifespan; (2) Reducing maintenance costs; (3) Cutting electricity and material costs; (4) Decreasing labor requirements; (5) Improving production efficiency; (6) Reducing safety incidents. 2. Contents of lubrication management work ； (1) Establish a lubrication management system and staffing ； (2) Implement the “five fixed principles” and “three-stage filtration” for equipment lubrication” ； (3) Preparation of equipment cleaning and oil change plans (4) Quota management for lubricating oils used in equipment ； (5) Recovery of lubricating oils and waste oil recycling ； (6) Management of the lubrication system. 3. Staffing: (1) Large and medium-sized enterprises can adopt a hierarchical management approach: the head office shall establish a central lubrication station, staffed with full-time lubrication engineers responsible for managing lubrication techniques across the entire facility. Each branch factory and workshop has dedicated lubrication workers responsible for the specific tasks. (2) Small enterprises are well-suited for centralized management: a lubrication station should be established in the department responsible for equipment, with dedicated lubrication technicians and workers assigned to directly manage the lubrication of all equipment throughout the factory. (3) In their lubrication management, enterprises should assign full-time or part-time laboratory technicians, depending on the number of equipment, to conduct quality inspections at all stages of purchasing, storing, and using the required oils. 4. Lubrication station management system (1) Categorize and label stored oils and greases at the lubrication station ； Designed for use with various appliances, and are cleaned regularly to remain tidy ； (2) Strictly implement the three-stage filtration system for oil intake, delivery to the workshop, and oil filling/replacement. (3) Ensure timely distribution of fuel, keep records, and submit reports regularly. (4) Regularly check the equipment’s lubrication status together with maintenance personnel, and address any issues found promptly. (5) All facilities within the oil depot comply with safety and fire prevention regulations. (6) Oil distribution shall follow the principle of using the oil that was delivered first before the oil that was delivered later. (7) Clear assignment of roles and responsibilities for personnel within the station. 5. Lubricant inventory system: (1) Before lubricants are purchased and stored, they must pass testing by relevant personnel and obtain a certificate of conformity before they can be stored. (2) Oil products must be stored and retrieved in order of category and type; barrels must not be stored outdoors or with open tops. (3) Oil that has been stored for more than two years should be retested before it can be used. Establish and improve the records and forms for the receipt, distribution, and test reports of oil products. (4) Establish a system for cleaning and changing oil in equipment, as well as systems for cleaning and maintaining the lubrication systems and related devices, and a system for recycling used oil; there should also be systems for managing oil and grease storage as well as ensuring safety and fire prevention. Each company can formulate these systems according to its actual circumstances. 6. Responsibilities of lubrication engineers and technicians: (1) Organize the formulation of various lubrication management systems, define job roles and responsibilities, as well as establish inspection and evaluation methods. (2) Guide each workshop in preparing annual and monthly procurement plans for lubrication tools, equipment, and materials, and submit the compiled plans to the supply department. (3) Prepare lubrication procedures and charts (lubrication charts generally indicate the model of the lubrication equipment or tools, the locations and number of holes for oil filling, the oil change interval, the brand of oil to be used, the amount of oil to be added or replaced, as well as information related to some maintenance personnel) for use by lubrication technicians. (4) Responsible for the selection of lubrication tools, as well as the determination and modification of oil types. (5) Analyze and address oil quality issues related to lubrication failures, propose improvement suggestions, and verify the effectiveness of these improvements. (6) Keep track of the lubrication status of the equipment, guide efforts to prevent and fix leaks, and propose corrective measures for inappropriate lubrication methods. (7) Guide the recycling and regeneration of used oil. (8) Guide oil product analysis and testing. (9) Responsible for providing technical training to relevant personnel. (10) Keep abreast of advanced management and lubrication techniques, as well as new equipment and materials ； Continuously improve the quality of lubrication and the level of equipment lubrication. 7. Responsibilities of the lubrication worker: (1) Be familiar with the lubrication points of all equipment within the designated area, as well as the grade, type, quantity of oils used, and the schedule for oil replacement. (2) Implement the \"five fixations\" policy and the three-level filtering system. (3) Conduct inspections during each shift, and promptly top up the fuel tanks and oil sumps. Identify lubrication and management issues, and resolve them promptly. (4) Carry out oil change work in a timely manner as planned. (5) Ensure proper recycling of used oil. (6) Under the guidance of professionals, carry out promotion tests for new devices and new oils. (7) Supervise the lubrication work for operators of small equipment (such as lathes). 8. Selection of lubricating oil: The selection of lubricating oil is the first step in its use, and it is crucial for ensuring proper lubrication of the equipment as well as maximizing the performance of the lubricant. (1) When selecting lubricating oil, the following three factors should be taken into consideration: 1) The operating conditions under which the mechanical equipment is actually used (i.e., the working conditions) ； 2) Designation or recommendation in the manufacturer’s instructions for mechanical equipment ； 3) Regulations or recommendations from lubricant manufacturers. (2) Selection of lubricant performance indicators 1) The viscosity of the lubricant to be used in the equipment is determined by referring to relevant charts based on design or calculation data. 2) Experience has shown that the operating temperature of general lubricants must be 5~10 ℃ higher than their pour point. 3) The principle for specifying the flash point index of lubricating oil is to apply a safety factor of 1/2 in accordance with safety regulations, that is, to set it 1/2 higher than the actual operating temperature. Since the oil temperature in the crankcase of internal combustion engine oils should not exceed 120 ℃, it is specified that the flash point of such oils must be at least 180 ℃. 4) Make a reasonable decision based on the operating conditions of the equipment, manufacturer requirements, and descriptions and introductions of the oil products. To meet the requirements of lubrication technology while remaining cost-effective. 9. Mixing lubricants: Care must be taken when mixing lubricants with unknown properties. To avoid adverse consequences or even equipment lubrication failures. Oils of different grades, from different manufacturers, and new versus used oils should be avoided from being mixed whenever possible. (1) Mixing is prohibited: 1) Military specialty oils and specialized fuels must not be mixed with other types of oils. 2) Oils with anti-emulsification requirements must not be mixed with oils that do not have such requirements. 3) Anti-ammonia turbine oil must not be mixed with other turbine oils. 4) Zn-containing anti-wear hydraulic oil must not be mixed with silver-resistant hydraulic oil. 5) Gear oil must not be mixed with worm gear oil. (2) Can be mixed: 1) Products of the same manufacturer with similar quality and basic equivalence. 2) Products of the same type but different grades from the same manufacturer. 3) For different types of oils, provided it is known that neither component in the mixture contains additives. 4) When different types of oils are mixed together, no abnormal phenomena or significant changes in performance occur. 10. Substitution of lubricating oils (1) Different types of lubricating oils have their own specific characteristics or differences in terms of performance. Therefore, it is necessary to select lubricants correctly and appropriately, avoid using substitutes, and under no circumstances use inappropriate substitutes. (2) Principles for substituting lubricating oils 1) Try to use oils of the same type or those with similar properties as substitutes. 2) The viscosity must be comparable; the viscosity of the substitute oil shall not exceed ±15% of that of the original oil. Oils with slightly higher viscosity should be given priority for substitution. 3) Higher quality is preferred over lower one. 4) When selecting alternative oils, attention should also be paid to the equipment’s operating environment and temperature. 11. Replacement of lubricating oil: After being used for a period of time (months, years, or even decades), lubricating oil deteriorates gradually due to oxidation and the influence of external factors during use, resulting in a decline or change in its properties; therefore, it must be replaced at the appropriate time. (1) Determination of oil change timing 1) Determine the oil change timing based on the results of inspections and evaluations ； However, the current difficulty is the relative lack of reporting standards for various types of oils. 2) Replace it regularly in accordance with the recommendations of lubricant manufacturers and equipment producers, as well as practical usage experience. (2) Precautions for oil changes 1) Avoid making hasty decisions regarding oil changes; strive to extend the service life of the oil. 2) Try to change the oil during the maintenance period. 3) When changing oil, don’t discard it casually. If the oil is still in good condition, it can be slightly treated (such as sedimentation and filtration to remove water and impurities) before reuse or for use in less critical equipment. Used oil should be collected properly to facilitate further processing and prevent environmental pollution. 12. Lubricant contamination control: In addition to improper selection or use of lubricants, lubrication failures are mainly caused by contamination. (1) Substances that contaminate lubricating oil include dust, impurities, and moisture. (2) Control of contamination level is crucial for the anti-wear performance of hydraulic oil, turbine oil, hydrostatic oil film bearing oil, and high-speed bearing oil. (3) Measures to control pollution: 1) The containers used for storing and transporting lubricants must be clean and airtight, and must not come into contact with metals such as copper and tin, which can facilitate the oxidation and deterioration of lubricants. 2) The oil must undergo sedimentation and filtration before being fed into the equipment, to ensure that its clarity reaches level 5 or higher. 3) Fuel containers must not be left exposed to the atmosphere; in particular, containers holding fuel must not be left uncovered. 4) The oil tanks used for storing lubricating oil should be cleaned regularly, and waste oil should be removed promptly. 5) Install air-filtered respirators on oil tanks or containers; use filters with a mesh size of 100 or finer along with dust caps at the filling ports. Ensure proper sealing in all areas, and install filters and drain valves at appropriate locations in the lubrication system. (4) Electrical oils such as transformer oil have high requirements regarding moisture content; oil should be changed whenever the weather is dry. Moreover, the oil should be added to the equipment immediately. 13. Condition monitoring of lubricating oil: It is an inevitable phenomenon that lubricating oil gradually ages and deteriorates over time as it is in use. There are two types of aging and deterioration: one is normal aging and deterioration ； Another type is abnormal deterioration caused by abnormal factors such as water pollution. Monitoring the usage condition of lubricating oil allows for timely awareness of its technical condition, helps prevent lubrication-related equipment failures, and extends the service life of the oil. (1) Methods of monitoring: 1) Randomly inspect whether operators follow the ‘five fixed principles’ for equipment lubrication. 2) Sample and observe the appearance of the oil, checking its color, transparency, odor, etc. 3) Regularly test key physical and chemical parameters that reflect changes in oil quality, such as viscosity, flash point, moisture content, and acid value (or alkalinity value). 4) Those without a laboratory can conduct tests such as the moisture pop test and spot test. 5) Analyze using modern instruments. If an infrared spectrometer is used to determine changes in additives in the oil, then an iron spectrometer or ICP emission spectroscopy is used to detect changes in metal particles or elements in the oil. Instrumental analysis is fast and accurate, and it is of great significance for the lubrication management of large-scale critical equipment such as generator sets. (2) Several simple methods for identifying lubricating oil: 1) Place an appropriate amount of oil in a transparent glass bottle and observe it under sunlight; if there is a blue reflection on the surface of the oil, it indicates that it is fresh oil, while used or deteriorated oil does not show this phenomenon. 2) The new oil should be clear without any precipitates ； Old oil, spoiled oil, or low-quality oil exhibits phenomena such as turbidity, sedimentation, and suspended particles. 3) Old oil, spoiled oil, or low-quality oil often has an acidic and irritating odor. 4) Heat a small amount of oil in a test tube; if a bubbling sound is heard, it indicates the presence of moisture. Filtering through a 100-mesh sieve can help determine whether there are any mechanical impurities present. (3) Centralized identification methods for grease 1) Visual identification: Refer to Article 1 of \"Main quality indicators of grease\". 2) Various fatty acid soap-based greases have an oily smell and fragrance, whereas hydrocarbon-based greases lack this characteristic and usually have a waxy or mineral oil smell. 3) Use a finger to pick up a small amount of the grease, moisten it with water, and apply slight twisting pressure; if emulsification occurs rapidly, it is a sodium-based grease. Barium-based greases have strong water resistance and are difficult to emulsify, while calcium-sodium based greases exhibit mild emulsification. 4) Use a beaker to take a small amount of the grease and heat it to melt it; greases that melt completely at 70°C are hydrocarbon-based greases, while those that melt at 90–100°C are calcium-based greases. 14. Preventing lubricants from harming health: Many petroleum products are harmful to the human body; if they come into contact with the skin and are not cleaned off promptly, they may cause mild conditions such as dermatitis or bumps, or more severe issues like rashes or skin tumors. If it enters the mouth or is inhaled, it can cause gastrointestinal problems or pneumonia in mild cases; in severe cases, it may lead to cancer. Therefore, it is essential to be careful not to let oil get on food, not to allow it to enter the respiratory tract, and to avoid having oil all over one’s body or on the floor. This not only results in waste but also undermines personal hygiene. Animal tests have shown that refined mineral oil lubricants have low toxicity, but the hazard of lubricants with additives increases, so caution is necessary. Even if new oil is non-toxic, it can become harmful due to deterioration and contamination during use; therefore, care must be taken to avoid contact with the skin, and it must especially not be inhaled or ingested. If it comes into contact with the skin accidentally, rinse it thoroughly with clean water immediately. The lubricating oil obtained from the treatment of used oil has deteriorated and can only be treated as waste oil. This waste oil must be disposed of properly to prevent environmental pollution. (1) These waste oils should be collected and disposed of uniformly. Barrels or bottles containing lubricating oil should not be discarded carelessly; instead, they must also be properly disposed of to prevent any adverse effects on the environment. (2) Used lubricating oil, especially those containing a high amount of additives, is difficult to recycle. But generally, it can be burned as fuel oil.