General Guidelines for Lubricant Training and the Use of Synthetic Lubricants in Processing and Compounding Gas Compressors

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The use of synthetic lubricants in processing and hydrocarbon compressors. CPI Engineering Services Inc., USA (Sales representative in China: Mr. Wang, 13926549484; website: http://cpicpi.b2b.youboy.com), Michigan, USA. The use of synthetic lubricants in positive-displacement devices, as well as in lubricant processing and hydrocarbon compressors, is a matter of debate. Many of these applications require synthetic products to limit toxic catalysts, reduce gas solubility and thereby lead to a loss of viscosity, as well as to restrict reactions with gases. The lubrication requirements for rotary screws, reciprocating engines, and rotary vane compressors in the processing of hydrocarbons and gases are reviewed. The physical and chemical properties of synthetic lubricants have a crucial impact on compressor lubrication. The effect of gas in the synthetic lubricant under compressor operating conditions is also important. In many applications, synthetic lubricants can extend the oil change interval, reduce fuel consumption, improve efficiency, and prolong the lifespan of compressors. 1. Lubricants for hydrocarbon and process gas compressors: Historically, compressors used for hydrocarbons, chemical processing, and inert industrial gases have utilized traditional mineral oil-based lubricants. However, mineral oil cannot meet the requirements of many modern rotary compressor designs and other complex applications. Typical gas processing applications involve outlet temperatures ranging from 80 to 1100°C and pressures of 7 to 70 barg. Under these conditions, mineral oil may undergo thermal degradation. Their instability causes the vapor phase of the lubricating oil in the compressor to remain and flow downward. In many applications, chemically reactive gases are present, which can cause chemical degradation of mineral oils. In some applications, mineral oil may be severely diluted by compressed gas. This dilution will reduce the viscosity of the lubricating oil, often resulting in insufficient lubrication in certain areas. Corrosion protection of the system is another area where mineral oils often perform poorly. Synthetic and semi-synthetic lubricants meet the demands of these complex applications. They offer many advantages over traditional mineral oils. Some of these include excellent chemical inertness, a high viscosity index, a low pour point, good hydrolytic stability, and complete demulsification. These products also offer excellent natural lubricity, outstanding thermal stability, resistance to dilution by hydrocarbons, low volatility, and compatibility with elastic materials and metals. Since not every type of fluid possesses all the advantages, it is very important to understand the physical and chemical properties of each synthetic and semi-synthetic base fluid. It is also important to understand the requirements of compressors and their applications in order to select the most suitable fluid with the best performance. The semi-synthetic lubricants discussed in this article are high viscosity index oils that have undergone rigorous hydrogenation treatment. A two-stage hydrogenation process produces a high-quality base oil. The raw material is hydrogenated under high pressure and high temperature, followed by distillation, dewaxing, and a second stage of hydrogenation. It eventually becomes a high-molecular-weight isotonic oil. The viscosity index is in the range of 105–120. 2. Compressor lubricant 2.1 Rotary vane compressors: Each model of compressor has different requirements regarding the lubricant to be used. The function of the lubricating oil in a rotary vane compressor is to lubricate the vanes that slide in and out during the compression process. Lubricating oil is also used as a seal between the blades and the frame, enabling gas compression. Typically, ISO68-150 products meet the viscosity requirements for rotary vane compressors. 2.2 Reciprocating compressors Reciprocating compressors offer a very wide range of discharge pressure capabilities, from 1 bar g to 1000 bar g (4). The oil-lubricated cylinders, crankcase components, coils, pistons, valves, and filling rods of reciprocating compressors. Crankcase components include crosshead bearings, crossheads, crosshead guides, and crank pins. Recent refrigeration applications have shown that ISO 15 lubricants with an operating viscosity of less than 10 cSt can provide adequate lubrication. However, the classic application of reciprocating compressors for processing and hydrocarbon gases, operating on the basis of gas molecular weight and flow pressure, is ISO68-680 products. In most reciprocating compressors, a fluid is used as a lubricant for all components. Smaller reciprocating compressors use splash lubrication. Larger units typically use an oil pump system to lubricate the components in the crankcase above. Some large equipment uses two different lubricants, one for the cylinders and another for other components that require lubrication. Since the cylinder lubricant must coexist with the gas, it must be compatible with the downward fluid flow process. Cylinder lubricant can be designed to provide lubrication under specific gases or operating conditions. (2) 2.3 Screw compressors: Screw compressors are typically filled with compressed hydrocarbons and process gases, with a pressure range of 1–25 bar g (5). They have many advantages, including improved compression efficiency, low outlet temperature, high reliability, and less maintenance due to their simple mechanical design. Spiral gas compressors must possess several functions. They lubricate the bearings, provide adequate sealing between the screw and the frame, remove heat generated during compression, flush out any particles in the compressor, and protect the system from corrosion. The lower viscosity limit is 10–20 cSt at the oil supply temperature to the bearings, and 5 cSt under outflow conditions to ensure proper sealing. The viscosity of the lubricating oil at the upper part depends on the ability to provide sufficient lubricating oil to the bearings. The typical upper viscosity limit is 30-100 cSt. Typically, ISO68-220 lubricants meet the viscosity requirements for screw compressors. The exact viscosity grade depends on the operating conditions and gas flow composition. Due to the closed-loop design of the system, the synthesized product is particularly suitable for screw compressors (Figure 1). Lubricating oil and compressed gas enter the separator. The separated oil passes through an oil cooler before returning to the compressor. During this process, the degradation of lubricating oil can lead to compressor problems such as bearing failures, inadequate sealing, or corrosion. In many applications, the use of synthetic compressor lubricants enables efficient hydrocarbon compression and gas production (7). Applications of synthetic lubricants in processing and hydrocarbon compressors 3. Selection of lubricants Choosing the appropriate viscosity for hydrocarbon and process gas compressors is crucial. The dilution of lubricating oil by gas is the main problem. Viscosity-temperature curve for dilution (Figure 2): Dilution causes a direct decrease in viscosity. The lubricating oil, which at undiluted conditions is above the viscosity limit of the compressor, can be reduced below this limit by dilution. This condition often leads to increased wear and/or failure of the compressor. It can also be a side effect of compressor performance. The information required to predict the dilution degree of lubricating oil includes the compressor model, operating conditions, and the complete gas composition, that is, the amount of each gas component present. The equilibrium calculation is based on the vapor pressure of the gas components and the potential dilution of the lubricating oil provided by Raoult’s law. The effect of dilution on the viscosity of lubricating oil can be determined by mixing the lubricating oil with a known amount of hydrocarbons. The relationship between viscosity and temperature can also be determined using these diluted mixtures. The dilution level, operating temperature, and dilution effect all affect the actual operating viscosity of the lubricating oil. If necessary, increasing the operating temperature can help minimize the dilution of the compressed gas. The equipment model is also a factor in choosing lubricant. In some applications, the gas stream contains a large amount of contaminants, including water, hydrogen sulfide (an acidic gas), asphaltenes, or other trace pollutants. Other applications are particularly sensitive to the operation of the oil and the chemistry of the lubricants/additives. These factors and viscosity dilution can be used to determine the optimal lubricant. 4. Applications of hydrocarbon gases The applications of hydrocarbon gases include natural gas, refinery gas, biogas, gas turbochargers, refrigeration units, steam recovery boilers, as well as the use in refinery exhaust gases and process gases. The differences in gas composition mainly depend on the model of the equipment being used. Furthermore, the application site can affect the gas composition of many applications (Table 1). It is very important that the lubricating oil meets the viscosity requirements specified by compressor manufacturers for all hydrocarbon applications under diluted conditions. There are also many other factors that can influence the selection and performance of lubricants. Gas containing moisture can cause corrosion in the system. Operating the compressor at a temperature higher than the dew point of the gas flow can minimize it. Rust inhibitors included in the lubricant formula help protect metal components that come into contact with water. Due to the presence of hydrogen sulfide, the use of acidic gases requires lubricants to contain specialized anti-corrosion additives in order to protect the system from corrosion. Volatile additives can accomplish this task through vaporization under operating conditions. They enclose the metal components of the system, preventing them from coming into direct contact with the lubricating oil. Material selection for acid gas systems is important, as some yellow metals corrode significantly when exposed to gases containing hydrogen sulfide. 4.1 Light natural gas, refinery gas – Appropriately formulated semi-synthetic lubricants are suitable for use with natural gas and acidic gases when the degree of dilution is not severe. Distillation gas, which is primarily composed of methane and carbon dioxide with trace amounts of hydrogen sulfide, can also use semi-synthetic lubricants. Semi-synthetic lubricants have a higher viscosity index than mineral oils, thus meeting the viscosity requirements of compressors over a wide temperature range. The low volatility of these materials minimizes residue. Natural gas containing asphaltenes must use a PAO or semi-synthetic oil in its applications. These lubricants dissolve asphaltenes and keep them in a dissolved state. Poly(alkylene) glycols (PAGs) cannot dissolve asphaltenes, and their use may lead to clogging of filters and oil pipes. 4.2 Heavy natural gas, refinery off-gases, and steam recovery boiler gases: Some natural gases, refinery off-gases, and steam recovery boiler gases produce hydrocarbon gases with higher molecular weights. This can lead to an increase in the dilution level of the lubricating oil. These applications require appropriately formulated poly(alkylene) glycols (PAGs). There are several different types of PAGs, which are classified by the monomers used to produce them (Figure 3) (9). Polyethylene and polypropylene glycol copolymers limit the dilution of hydrocarbons. By controlling the proportion of ethylene oxide in its polymerization with propylene oxide, lubricants with a dilution limit of 10–20% can be produced. Above this level, the lubricating oil becomes saturated. Some polyethylene and polypropylene glycol copolymers possess unique blendability. They are less soluble in water at high temperatures than at low temperatures (Figure 4). This reversed miscibility may offer advantages in corrosion prevention in compressor applications where moisture is present. Polyethylene and polypropylene glycol copolymers are soluble in condensed water at room temperature. This prevents the formation of a corrosive environment in the system due to the accumulation of free water during shutdown periods. Once the compressor restarts and reaches normal operating temperature, the lubricating oil becomes less soluble in water. Then this water vaporizes and coexists with the exhaust gas in the compressor. Some hydrocarbon compressors use lubricants that are completely soluble in hydrocarbons, which causes severe dilution; polyethylene glycol can be used instead. Polyethylene glycol is completely insoluble in hydrocarbons. Experiments show that the viscosity of the lubricant remains unchanged when it comes into contact with hydrocarbon gases at 13,790 kPa. There is a lack of attraction between the hydrocarbon gas and this lubricant, which allows the gas in the oil separator to be separated from the lubricant more effectively compared to other types of lubricants. One method to improve the design of compressor systems used with ethylene oxide containing PAGs is to remove all excess concentrated hydrocarbons from the oil tank. The concentration of hydrocarbons has become a focus in applications involving gases with butane or higher molecular weights. Concentration can also occur under conditions of rising pressure or falling temperature. A drain valve inserted into the fuel tank, slightly above the fuel filling tube, can remove any accumulated hydrocarbons. A steam recovery boiler unit collects liquid (n)-hexane for production, providing a six-month recovery period for a complete compressor system (3). 4.3 Biogas – Compressing biogas and burning it for energy is another application of hydrocarbon gases. The most important consideration for biogas compressors is protecting the compressor system from corrosive trace pollutants (7). Regarding these pollutants, PAO is characterized by its excellent chemical inertness. PAO also offers advantages such as a high viscosity index and low vapor pressure. Low vapor pressure not only minimizes the amount of combined oil but also reduces airflow residue to a minimum. Minimizing residual gases in gas compression applications for supplying hydrocarbon gas turbines is a key requirement. A typical requirement for gas turbines is a gas injection pressure of 1500–4500 kPa. Gas compressors increase the pressure of gas from atmospheric pressure to the injection pressure. The residue of lubricating oil can lead to the formation of carbon deposits, which in turn can clog devices downstream, or create hot spots in the combustion chamber that cause damage. Due to its minimization of residual characteristics, PAO is often chosen as a lubricant. The compressed hydrocarbon gas in these devices generally does not cause significant dilution. 4.4 Production gases: The purity of gases, as well as the toxic catalysts derived from metals and other inorganic compounds that remain or are found in lubricant additives, are important considerations in certain applications involving hydrocarbon production gases. The gas must be separated from the impurities in the lubricating oil in order to function properly during the production process. The residue of lubricating oil must be minimized to reduce lubricant-related problems in downstream production units. Any small amount of residues that reach the downstream area must contain no catalysts with side effects. Many catalysts have high replacement costs, so it is economical to replace them during shutdowns. The basic raw materials or additives used in the lubricants for gas production devices must be free of any metals or other impurities, and no toxic catalysts are used in the production process. 4.5 Refrigeration Equipment: The low-temperature physical properties and miscibility of lubricating oils with hydrocarbon gas refrigerants are important factors to consider when selecting appropriate lubricating oils for refrigeration systems. An appropriate separation device will minimize the amount of oil that reaches the downstream section. Any lubricating oil that reaches the frozen surface of the system must not freeze within the evaporator’s piping system, otherwise it will lead to a loss of the system’s thermal efficiency. The lubricating oil that reaches the downstream section must have a pour point lower than the temperature of the evaporator, or it must be able to mix with the refrigerant at the evaporator temperature. If it is miscible, the lubricant/refrigerant mixture can return to the compressor in a single phase. Refrigeration equipment typically uses gases free of impurities, so the amount of additives required in the lubricating oil should be minimized. Polypropylene glycol has a lower solubility in hydrocarbon gases compared to other types of lubricants. At low concentrations, polypropylene glycol can mix with hydrocarbons at low temperatures (Figure 5). Their dilution is less than that of hydrocarbon-based lubricants such as mineral oil and PAO. This dilution limitation in the compressor environment enables the lubricating oil to provide better sealing, thereby increasing the volumetric efficiency of the compressor. For this reason, they are often used in hydrocarbon gas refrigeration systems to improve performance. Hydrocarbon refrigeration systems designed to minimize residues use polyethylene glycol lubricants. They are completely insoluble in hydrocarbons. Since there is no attraction between the lubricant and the gas, the lubricant/gas can be separated more effectively compared to other lubricants. Polyethylene glycol does not mix with the liquid refrigerant in the evaporator. If the evaporator temperature is below the pour point of the lubricant, the lubricant will solidify. For this reason, typical low-temperature applications do not use polyethylene glycol. Hydrocarbon gas refrigeration systems with low dilution levels can use a PAO-based lubricant. PAO is completely miscible with hydrocarbon gases. Both PAG and PAO have extremely low volatility, thus minimizing the gaseous residue of lubricants. 5 Gas Production Compressors 5.1 Inert Gases Gas production compressors can handle inert or reactive gases. Typical inert gases include hydrogen, helium, carbon dioxide, and nitrogen. Apart from carbon dioxide, most inert gases do not cause a loss of viscosity when used with most lubricants. Just like gas compressors used in hydrocarbon production, the two key considerations in inert production gas compressors are gas purity and catalyst toxicity. Most inert gas equipment uses lubricants based on PAO or PAG. The low volatility of these materials minimizes impurities in the gases and lubricant vapor. Furthermore, the low vapor pressure of these lubricants helps to minimize residues. When selecting the right lubricant, the type of catalyst is a factor. The base fluid and additives of the lubricant must not affect the catalyst’s lifespan or the reaction rate in production. 5.2 Active Gases The lubricating oil for active gas compressors must meet the same criteria as that for inert gas compressors, in addition to which there are additional requirements. The basic raw materials and additives of lubricating oil must not react with the production gas. Some so-called reactive gases are chloromethane, dichloromethane, chlorine, hydrogen chloride, sulfur dioxide, and oxygen. Pure oxygen is a very strong oxidizing agent. It requires the use of fully fluorinated or chlorinated lubricants. Most other production gas compressors use PAO types because they have the ability to resist chemical reactions. The formulation of this lubricant generally includes only additives that do not react with gases. These additives help protect the system from corrosion and extend the lifespan of the lubricant to the greatest extent possible. Analysis of 6 oils: Lubricating oils used in production and hydrocarbon gas plants require routine sampling. Proper sampling and analysis ensure that lubricant maintains its original properties. This is also the best way to determine the oil change interval. A typical sampling interval is 3 to 6 months. The experiments include corrosion analysis of the product, moisture, impurities, particle count, particle size, and worn metal. The viscosity of the lubricating oil used, the level of additives, and changes in the total acid value are the key parameters that determine when to change the oil. 7 Cost Savings 7.1 Reducing Lubricant Costs Synthetic and semi-synthetic lubricants can result in significant cost savings in terms of production as well as in hydrocarbon gas compressors. Their chemical inertness and thermal stability extend the oil change interval. This reduces the cost of new oil each year, as well as the costs associated with oil treatment and maintenance time. The low volatility of the synthetic product minimizes the gaseous residue in the lubricant. This reduces the requirements for the oil mixture. 7.2 Improving equipment efficiency: These products have a high viscosity index, which makes them better sealing fluids in rotary compressors and high-temperature environments. PAG-based products can resist dilution by hydrocarbons, allowing them to maintain their viscosity at the outlet temperature and further improving sealing performance. These features help increase the volumetric efficiency of the compressor by 18% (11). In gas production units, low volatility also helps to minimize the amount of lubricant that contaminates downstream processes. This improves the efficiency and cost-effectiveness of downstream devices. 7.3 Extending the service life of the device: When the device is started in cold environments, a high viscosity index enables synthetic and semi-synthetic products to provide a lower viscosity. This helps increase oil flow and reduce wear during startup. The ability to maintain sufficient viscosity at high temperatures provides additional protection against wear at such temperatures. Finally, during use, the moisture content of PAO and semi-synthetic products is minimized. This can significantly extend the lifespan of the bearings. 8 Conclusion Synthetic lubricants possess many unique physical properties that enable them to be ideally used in hydrocarbon and process gas equipment. Dilution of viscosity ； Compatibility with gases ； Selection of equipment ； Design of the production process ； Corrosion resistance, along with other factors, must all be taken into consideration when selecting the appropriate lubricant. Synthetic lubricants include PAO, PAG, and hydrogenated oils, which meet the requirements of these systems. The suitability for application in compressors is key to selecting the optimal lubricant. General Outline for Lubricant Training I. What is lubrication? What is the function of lubricant? http://cpicpi.b2b.youboy.com Lubrication involves adding a lubricant between two contacting surfaces that are in relative motion, thereby creating a lubricating film between these surfaces. This film separates the directly touching surfaces, turning direct friction into internal friction between the molecules of the lubricant. The goal is to reduce friction, minimize wear, and extend the service life of mechanical equipment – and this is what is meant by lubrication. The function of lubricant is as follows: 1. Reducing friction: By adding a lubricant to the friction surfaces, the coefficient of friction is reduced, which in turn lowers frictional resistance and saves energy consumption. 2. Reducing wear: Lubricants can reduce wear caused by abrasive wear, surface fatigue, adhesive wear, and other forms of wear that occur between friction surfaces. 3. Cooling effect: Lubricants can absorb heat, transfer heat, and dissipate heat, thereby reducing the temperature rise caused by frictional heat. 4. Rust prevention: The presence of a lubricant on the friction surface prevents rusting caused by air, water droplets, water vapor, corrosive gases and liquids, dust, and oxides. 5. Power transmission: In many cases, lubricants have the function of transmitting power, such as in hydraulic systems. 6. Sealing function: Lubricants create a seal around certain exposed components, preventing moisture and impurities from entering. 7. Shock absorption: It can absorb shock energy when subjected to impact loads, such as in car shock absorbers. 8. Purification function: The circulation of lubricating oil helps to carry away impurities, which are then removed by the filter. II. What are the categories of lubricants in our country? Lubricants are a very important category among petroleum products. Although they account for only 2%-3% of total petroleum fuel consumption, their wide range of applications results in them being the largest category in terms of the number of different types and grades available. Lubricants are classified according to the applications for which they are used. ISO classifies lubricants, industrial lubricants, and related products into 18 categories. China has adopted the ISO 6743/0-1981 standard on an equivalent basis and formulated **Standard GB7631.1-87**, which divides lubricants and related products into 19 groups, as shown in the table below. III. What are the main components of lubricating oil? Currently, all finished lubricants are composed of base oil and additives, with the base oil accounting for over 70 percent to nearly 100 percent. Additives account for a few parts per million to thirty or forty percent. Base oils are divided into two main categories: mineral oil type and synthetic type, with the vast majority being of the mineral oil type. According to the latest standards, mineral-based base oils in our country are classified into eight categories: very high viscosity index base oils (VHVI, 120≤VI＜140), high viscosity index base oils (HVI, 90≤VI＜120), medium viscosity index base oils (MVI, 40≤VI＜120) and low viscosity index base oils (LVI, VI＜40), high viscosity index low-wax base oils (HVIW), medium viscosity index low-wax base oils (MVIW), high viscosity index highly refined base oils (HVIS), and medium viscosity index refined base oils (MVIS). They are divided into several grades according to viscosity, totaling 63 types. There are many types of additives, with the main categories including detergents and dispersants, antioxidants and anti-corrosion agents, anti-wear agents, oiliness agents, antioxidants, viscosity index improvers, rust inhibitors, antifreeze agents, and antifoam agents. IV. How is mineral-based base oil produced? Natural petroleum is a highly complex mixture of hydrocarbons. In addition to containing a large amount of light components and solid hydrocarbons, it also contains compounds such as resins, asphaltenes, sulfur, nitrogen, and oxygen compounds. The presence of these substances is harmful to the color, thermal stability, oxidation stability, and corrosion resistance of lubricants; therefore, purification is necessary to remove these harmful components. Its production process is roughly as follows: (I) Distillation 1. Distillation: First, the crude oil is subjected to atmospheric distillation, which separates gaseous fuels, gasoline, kerosene, and diesel from the petroleum. The remaining residue oil can be used as a raw material for producing lubricants, or it can be cracked to produce light petroleum products. 2. Vacuum distillation: The residue oil (heavy oil) obtained through atmospheric distillation is further processed using vacuum distillation. A first-stage vacuum distillation is carried out, and the distillate coming from the highest side stream of the vacuum distillation tower is referred to as the first-stage distillate; this can be used as raw material for transformer oil ； The distillate obtained from the second highest side line is called the reduced second line ； Successively, it is the minus-three line ； Subtract four lines ； The residue oil at the bottom of the tower can be used as boiler fuel oil. (II) Refining: The lubricating oil distillates obtained through vacuum distillation are merely semi-finished products, and further processing is required to obtain the desired lubricating oil. These lubricants made from vacuum distillates are commonly referred to as fractionated lubricant base stocks. Lubricating oils obtained from residue oil are commonly referred to as residue lubricant materials. Whether it is fractional lubricating oil or residue lubricating oil, both contain many harmful substances that must be removed, so further refining is required. Currently, as refining methods for base oils, they can be divided into two main categories based on the characteristics of the production processes: one is the traditional three-step method, which consists of solvent refining, solvent dewaxing, and clay treatment for further refinement ； Another category is the newly developed hydrogenation processes. 1. Solvent refining: This involves using a solvent to dissolve and separate the undesirable components such as oxygen, nitrogen, and sulfides present in the lubricant material, thereby retaining the desired components. 2. Solvent deasphalting: Vacuum residue is used to produce residual lubricant base stocks; since these base stocks contain large amounts of asphaltenes, it is necessary to remove them prior to dewaxing and refining. Oil from which asphaltenes have been removed is called deasphalted oil. 3. Wax removal: To ensure that lubricants maintain good fluidity at low temperatures, it is necessary to remove the waxes that tend to solidify within them; this process is known as wax removal. 4. Refining of white clay: After undergoing processes such as solvent refining and dewaxing, the raw materials for lubricants achieve a quality that meets the requirements to a large extent. However, the resulting oil still contains small amounts of solvents that have not been removed, as well as condensates and gums formed due to the heating used in solvent recovery. To remove impurities, further improve the color of the lubricant, enhance stability, and reduce residue carbon, clay supplementation for refining is required. 5. Lubricant hydrogenation: The lubricant raw materials react with hydrogen to remove harmful elements such as sulfur, oxygen, and nitrogen, retain the ideal components of the lubricant, or convert non-ideal components into ideal ones, thereby improving the quality of the lubricant. The hydrogenation processes currently used in lubricant production are divided into hydrogenation supplementary refining, hydrogenation treatment (also known as hydrocracking), and hydrogenation pour point reduction. In our country, hydrogenation is mostly used as a supplementary refining method; that is, on the basis of solvent deasphalting, solvent refining, and solvent dewaxing, hydrogenation refining is employed in place of clay-based supplementary refining. 5. Why are additives added to lubricants? Lubricant base oils possess the basic characteristics of lubricants as well as certain performance traits, but merely improving the processing techniques for lubricants is not sufficient to produce lubricants whose properties meet all the requirements for use. To compensate for certain deficiencies in the properties of lubricants and to endow them with new, improved properties, various additives with different functions are added to the lubricants. Its addition level ranges from a few parts per million to several tens of percent. The functions of additives are mainly twofold: one is to alter the physical properties of lubricating oil, such as viscosity and freezing point ； Second, it increases or enhances the chemical properties of the lubricating oil, such as antioxidant and anti-corrosion properties. The use of lubricant additives not only meets the requirements of various new types of machinery and engines, but also extends the service life of lubricants, thereby reducing their proportion in petroleum products. VI. What is synthetic lubricant? What is the difference from mineral-based lubricants? Synthetic lubricants are lubricants that are created by chemical synthesis to produce high-molecular-weight compounds, which are then formulated or further processed. Syntheses are divided into 6 categories: organic esters, synthetic hydrocarbons, polyethers, polysiloxanes (silicone oils), fluorinated oils, and phosphates. Compared to mineral-based lubricants, it has the following properties: 1. It exhibits good high-temperature performance ； Synthetic lubricants have better thermal stability than mineral oils; they possess higher temperatures of thermal decomposition, flash points, and auto-ignition points, as well as better thermal oxidation stability, allowing them to be used at higher temperatures. 2. It possesses excellent viscosity-temperature properties and low-temperature performance. 3. Most synthetic lubricants have a higher viscosity index than mineral oils, with less variation in viscosity as temperature changes. At the same high-temperature viscosity, most synthetic oils have a lower pour point (or freezing point) than mineral oils, and lower viscosity at low temperatures. 4. It has low volatility. Synthetic oils are generally pure compounds with a narrow boiling range and low volatility, thereby extending the service life of the oil. 5. Excellent chemical stability. It has significant practical value in the defense and chemical industries. 6. It has flame resistance. 7. It has good radiation resistance. Certain synthetic oils possess good radiation resistance. 8. Compatibility with rubber seals. VII. What are the main types of industrial lubricants? 1. Hydraulic oil – hydraulic transmission systems (such as injection molding machines, excavators). 2. Engine oil – engines (such as internal combustion engines, power machinery). 3. Gear oil – gear transmission mechanisms (different oils are used for open and closed gears). 4. Circulating oil – circulation systems (such as those in papermaking machines). 5. Compressor oil – air compressors (including reciprocating, screw, and vane types). 6. Refrigerant oil – refrigeration compressors (used in cooling equipment). 7. Guide rail oil – machine tool guide rails and slides (requiring a strong oil film). 8. Spark plug oil – used in electrical cutting processes (such as CNC cutting machines). 9. Rust preventive oil – used to prevent rusting of mechanical parts (such as steel plates, steel cables, chains). 10. Oil film bearing oil – used in oil film bearings (such as in textile machinery). 11. Cutting oil – used in metal processing (available in oil-based and water-soluble forms). 12. Rolling mill oil – used in steel and aluminum rolling processes (for cold and hot rolling). 13. Insulating oil – used for circuit insulation (such as in transformers, insulating switches). 14. Grease – used in various bearings and rollers (available in lithium-based, calcium-based, aluminum-based, etc.). VIII. What are the methods and aspects used to evaluate the quality and performance of lubricants? The tests and evaluations used to assess the quality and performance of lubricants can be broadly classified into three categories: physical and chemical property tests, simulation tests, and bench tests. Physical and chemical property tests include: density (or specific gravity), color, viscosity, viscosity index, pour point, flash point, acid value, water-soluble acids and bases, total basic number, mechanical impurities, moisture, ash, and sulfate ash, as well as residue. The simulation test items include: low-temperature properties (viscosity at low temperatures, pumping performance at low temperatures, flow start temperature, etc.), corrosion resistance, rust resistance, antifoaming property, gas release property, anti-emulsification property, oxidation stability, thermal stability, shear stability, hydrolysis stability, rubber sealing property, detergency and dispersion property, and extreme pressure resistance (four-ball test, Timken test, vane pump test), etc. Bench tests include: gasoline engine bench tests, diesel engine bench tests, gear oil rear axle bench tests, etc. IX. What is chroma? What is the meaning of measuring chromaticity? 　　China’s method for determining the color of petroleum products classifies their color into 16 color codes. It gradually increases to 1.0, 1.5, 2.0…… with the darkest color being 8.0. The color of lubricating oil ranges from light yellow to dark brown, with the intensity of the color depending on the amount of gums present in the oil; the more gums that are removed, the lighter the color becomes. Therefore, color can be used as a parameter to determine the degree of refinement of the base oil. However, in finished lubricants, various additives are added, and many of these additives have color; therefore, using colorimetry to determine the quality of lubricants is no longer appropriate. X. What is viscosity? Are there several ways to express it? How are viscosity grades classified? 　　Viscosity is a measure of the frictional resistance that arises between molecules of a liquid as it moves under the action of an external force. The greater the frictional resistance, the greater the viscosity ； The lower the frictional resistance, the lower the viscosity. Viscosity is generally expressed in five ways: dynamic viscosity, kinematic viscosity, Engler viscosity, Leidenfrost viscosity, and Sayus viscosity. Currently, kinematic viscosity is the internationally standard. Kinematic viscosity is a measure of the internal frictional resistance experienced by a liquid as it flows under the effect of gravity; its value is expressed in meters squared per second (m2/S), though millimeters squared per second (mm2/S) is also commonly used. 11. What property of oil does the viscosity index (VI) indicate? 　　The viscosity index is the relative value of the degree to which the viscosity of a oil changes with temperature, as compared to the degree to which the viscosity of a reference oil changes with temperature. The higher the viscosity index, the less the oil is affected by temperature, indicating better viscosity-temperature performance. The viscosity index can generally be determined by using the kinematic viscosities of the oil at 40°C and 100°C, in accordance with the GB/T1995 or GB/T 2541 methods. It should be noted that the viscosity index can only indicate the flatness of the viscosity-temperature curve of lubricating oil between room temperature and 100°C; it does not necessarily reflect the viscosity characteristics of the oil at lower temperatures. XII. What are the pour point and freezing point? What property of the oil does it indicate? The pour point refers to the lowest temperature at which a cooled sample of an oil can flow under specified test conditions. The freezing point refers to the highest temperature at which, under specified test conditions, the surface of the cooled oil sample stops moving, and it is expressed in oC. It is a standard indicator used to measure the low-temperature flowability of lubricants. For the same type of oil, its pour point is a few degrees higher than its freezing point; in the past the freezing point was commonly used, but nowadays the pour point is the internationally accepted standard. 　　A high pour point or freezing point means that the oil has poor flowability at low temperatures. Based on the pour point of oils, people can determine the measures that should be taken during transportation, storage, and receipt in low-temperature conditions, and it can also be used to evaluate the low-temperature performance of certain oils. However, when evaluating the low-temperature performance of multi-grade diesel engine oils and vehicle gear oils, low-temperature dynamic viscosity, boundary pumping temperature, and pour point should be used as the main parameters. 13. What is the flash point? What is the significance for production and application? 　　The value obtained using a specified open-cup flash point tester is called the open-cup flash point, and it is commonly used to determine lubricants. The value obtained using a specified closed-cup flash point tester is called the closed-cup flash point, and it is commonly used to determine the flash points of kerosene, diesel fuel, transformer oil, etc. The flash point is a parameter that indicates the evaporation tendency and safety properties of petroleum products. The hazard level of oils is determined based on their flash point; those with a flash point below 45°C are classified as flammable substances ； Substances with a temperature above 45°C are flammable. During storage and use, it is prohibited to heat the oil to its flash point; the maximum heating temperature should generally be 20–30°C below the flash point. During the use of oils, flash point also holds significant importance. For example, if the flash point of the engine oil in use drops significantly, it indicates that the oil has been diluted by fuel; in such a case, the engine should be inspected and the oil replaced. 14. What is the acid value, and what significance does it have for production? 　　The number of milligrams of potassium hydroxide required to neutralize the acidic substances in 1 gram of test oil is called the acid value. Modern finished lubricants often contain additives, some of which are acidic while others are alkaline; therefore, the acid value of the oil should be determined before the addition of these additives. Measuring the acid value of the oil before adding additives allows one to understand the basic degree of refining ； Measuring the acid value of oil in use allows one to understand changes in the oil’s quality, serving as a parameter for replacing it with fresh oil. A high acid value indicates severe oxidation and deterioration of the oil, and oil change should be considered. 15. What are the neutralization value and total alkalinity? 　　The neutralization value is a *common term for the acid number or alkali number of oils. It is a measure of the acidity or alkalinity of an oil, expressed as the equivalent amount of base or acid required to neutralize that oil. The total alkalinity refers to the amount of acid required to neutralize all the alkaline components in 1 gram of sample under specified conditions, expressed in milligrams of equivalent potassium hydroxide. 　Changes in the acid value of oils can indicate the consumption of basic additives (such as detergents) in the oil and the decline in its performance, but they cannot be used to accurately predict the operational performance of the oil. 16. What are mechanical impurities? What impact does this have on applications? 　　Mechanical impurities refer to substances that contaminate oil from external sources; they mainly include sludge, sediment, dust, rust, metal shavings, fibers, etc., and most of them get mixed in during storage, transportation, handling, and use. These impurities, when mixed into the oil, can easily clog filters and pipes; in large quantities, they can cause abnormal oil supply ； Entering the equipment causes mechanical wear. Therefore, special attention must be paid to cleanliness during storage, transportation, and use; it is best to filter it first before use. Generally, the mechanical impurities in lubricant base oils should be kept below 0.005% (levels below 0.005% are considered to be none). However, for some oils containing a large amount of additives, the level of mechanical impurities is slightly higher. The reason is that after adding various additives, there may be some solvent-insoluble substances; these gel-like metal organic compounds do not affect its performance. Therefore, it is not possible to simply judge the quality of oil based on the size of mechanical impurities; rather, the nature and type of these impurities need to be analyzed. 17. What is the impact of moisture in lubricating oil on its quality? Moisture refers to the amount of water contained in the oil, expressed as a percentage. In oils, most types allow only trace amounts of water (with a water content of less than 0.3%), while some oils do not permit any water at all. Because water can emulsify lubricating oils, degrade additives, accelerate the oxidation of oils, and enhance the corrosion of machinery by low-molecular-weight organic acids, thereby affecting the low-temperature fluidity of oils. The sources of moisture in oil products are mainly surface water that enters due to inadequate container sealing, or condensate that enters as a result of the container’s breathing effect; it can also be caused by dirt on the transfer equipment and storage containers. 18. What are ash and sulfate ash? What is their significance for production and application? Ash refers to the non-combustible residues left after combustion under test conditions, namely the inorganic substances resulting from combustion, expressed as a weight percentage. This indicator is primarily used to check whether base oils or petroleum products free of ash-containing additives contain naphthenates. Lubricants contain naphthenates and similar substances, which can easily form hard carbon deposits on machine parts. Therefore, this parameter is also a quality control indicator in the oil refining process, and it is used only for testing in refined oils before additives are added. Sulfate ash refers to the burned residue resulting from the treatment of the residues left after the oil has been carbonized under specified conditions with sulfuric acid, expressed as a weight percentage. Internal combustion engine oils all contain detergents and dispersants, and some of these detergents and dispersants have ash content, some have low ash content, while others have no ash at all; therefore, the standard does not specify a criterion for sulfate ash content. However, the actual measurement data should be recorded on the product quality report, and together with other indicators such as metal element content, this information can be used to roughly determine the type and quality of the additives, thereby facilitating their proper use. 19. What is oxidation stability? What is the significance for production and application? The ability of petroleum products to resist the effects of the atmosphere (or oxygen) and maintain their properties without permanent changes is called oxidative stability. During storage and use, it is inevitable for oils to oxidize when in contact with air. The longer the contact time and the higher the temperature, the greater the degree of oxidation, which causes irreversible changes in certain properties of the oil, such as an increase in acid value, increased viscosity, more sedimentation, and a darker color. These changes **reduce the service life of the oil. The oxidative stability of oils is closely related to the properties of the base oil used, the degree of refining, the characteristics and quality of additives, compatibility, and the blending process. 20. What is an antioxidant corrosion inhibitor? What is the significance for production and application? When lubricants are in use, they are often exposed to air; therefore, oxidation of the lubricants is inevitable. The oxidation of lubricating oil is one of the main reasons for its deterioration and increased consumption. Oxidation increases viscosity, generates acidic components, paint film, and carbon deposits, and increases wear, thereby reducing the lubricating, protective, and heat-conducting properties of the lubricant. Although the antioxidant properties of lubricating oil are related to the composition of the base oil, as well as the refining methods and degree of refinement, even the best-refined lubricating oils will inevitably oxidize under operating conditions. To inhibit or reduce the oxidation of lubricating oil and prevent or mitigate the corrosion of metals by oxidation products, antioxidant and anti-corrosion additives must be added to the lubricating oil. Antioxidant and antirust agents also have anti-wear properties, making them multi-functional lubricant additives. 21. What is an anti-wear agent? What is the significance for production and application? 　　Anti-wear agents are additives that, under conditions of boundary lubrication at high temperatures and pressures (*this most severe form of boundary lubrication is commonly referred to as extreme pressure lubrication*), are capable of forming a chemical reaction film on metal surfaces to prevent localized sintering of the friction surfaces; *they are also commonly known as extreme pressure additives*. The function of an anti-wear agent is to decompose at high friction temperatures and react with the metal, forming compounds that have lower shear stress and melting points than the metal itself, thereby preventing galling and welding at the contact surfaces. Mr. Wang from CPI Lubricants in Shenzhen, China: 13926549484 QQ: 819596775 www.cpihualai.com Storage of lubricants: Barrel-packed and can-packed lubricants should be stored in a warehouse whenever possible to protect them from weather conditions; packaged lubricants that have already been opened must also be stored in a warehouse. Oil drums should be placed in a horizontal position, with both ends secured using wedges to prevent them from rolling. When placing the barrel upright, it is advisable to tilt it slightly to prevent rainwater from accumulating on its surface and covering the copper plugs. Water has a negative effect on any lubricant. In addition, the oil tank should be regularly checked for leaks, and it is necessary to verify that the markings on the tank surface are clear. To extract the oil, the oil barrel should be placed horizontally on a wooden frame at an appropriate height; a faucet should be installed on the lid of the barrel for draining the oil, with a container placed under the faucet to catch any drips. Alternatively, the barrel can be placed upright, and a hand pump can be used with an oil tube inserted through the lid of the barrel to draw out the oil. In bulk oil storage tanks, condensate water and pollutants inevitably seep in, accumulating at the bottom of the tank to form a sludge-like substance. As a result, the lubricating oil becomes contaminated; therefore, it is advisable to design the bottom of the tank in a troughed or inclined shape. It must also be equipped with a discharge plug to allow the slag to be removed on schedule. To the extent possible, the interior of the oil tank should be cleaned regularly. Temperature has a greater impact on grease than on lubricating oil; prolonged exposure to high temperatures can cause the oils contained in the grease to separate. Therefore, grease containers should be stored in a warehouse, with the opening facing upward. The opening of the bucket used to hold grease is large, allowing dirt and water to penetrate more easily; the lid should be tightened after use. Temperatures that are too low or too high have an adverse effect on lubricants; therefore, it is not advisable to store lubricants for long periods in places that are either too hot or too cold. Treatment of lubricating oil: In addition to paying attention to the various storage requirements for lubricating oil, careful handling of it should also not be overlooked. From the storage compartment to disposal, containers used to store small amounts of lubricant and for refilling must have lids and be kept clean; they should be cleaned regularly, dried with a cloth, and then used. Funnels and other containers used for lubricants must be treated in the same way; it is better to wipe them with rags, and old cotton yarns or blankets from which fibers can easily fall off should not be used, as their fibers can transfer from the containers into the machine and into the lubrication system, blocking the flow of lubricant. Each type of lubricant should have its own dedicated container, and the name of the lubricant contained within it must be indicated on the container to prevent mixing. Used oil or waste should be contained in designated containers until it is disposed of. Be sure to be careful and keep used oil separate from new oil to prevent the new oil from getting contaminated. Generally speaking, the inclusion of harmful impurities in lubricating oil is more serious than their inclusion in other types of oils, as the impurities in oil can settle at the bottom of the oil tank or container, reducing the likelihood that they will end up in mechanical lubrication systems. But when impurities mix into the grease, since they do not settle, they will eventually end up inside the machinery and lubricators. Mechanical lubrication should be carried out by specialized personnel and become part of routine procedures. The storage room keeps records of the quantity of all lubricants distributed, and each piece of machinery should also have a record sheet to enable verification of whether the consumption of all lubricants is normal. If any significant changes are detected, an investigation and analysis should be conducted promptly to decide whether the machinery should be scrapped or downgraded. Fire and explosion prevention for oils (I) Controlling combustibles (1) Preventing oil leakage from storage containers. Any leaks, spills, or oil runoff that occur during oil loading and unloading operations must be removed and dealt with promptly. (2) It is strictly prohibited to discharge oil stains, sludge, used oil, etc. into the sewer system; they must be collected at designated locations and disposed of properly. (3) Near buildings such as oil tanks, warehouses, pump rooms, fuel dispensing areas, and oil blending workshops, all flammable materials such as leaves, straw, and miscellaneous debris must be removed. (4) Used oil-soaked cotton yarn, rags, gloves, oil-paper, and similar items should be placed in covered iron barrels outside the workshop and removed promptly. (II) Eliminate sources of fire: (1) It is prohibited to bring matches, lighters, or other ignition sources into oil depots, oil storage areas, and areas where oil is received or dispatched. Strictly control the movement of fire sources and open-flame operations. (2) Open flames are strictly prohibited in the oil depot. When open flames are necessary for repair work, an application must be submitted to the relevant authorities for approval, and safety precautions must be taken before work can proceed. (3) Before cars and tractors are brought into the warehouse, a fire shield must be installed at the exhaust pipe outlet; the engine must be turned off immediately after the vehicle is parked. It is strictly prohibited to perform maintenance on vehicles within the warehouse area, nor is it allowed to start the engine during operations. (4) When railway locomotives enter the depot, isolation cars must be attached, the ash box baffles must be closed, and it is prohibited to clean the furnaces inside the depot area or to stay in areas not designated for operations. (5) Open flames are strictly prohibited when oil tankers are berthed at the dock. The carrying of open flames on board is prohibited. (III) Preventing combustion and explosions caused by electric sparks (1) All electrical equipment used in oil depots and all work areas must be explosion-proof, installed in accordance with safety requirements, and the wires must not be damaged, exposed, or cause short circuits. (2) High-voltage power lines are strictly prohibited from crossing above the oil depot. The distance between the oil storage area and the barrels of light oil, as well as the warehouses, and the electrical wires must be more than 1.5 times the length of the utility poles. (3) For the rails leading into the oil depot, insulating partitions must be installed before the entrance to prevent external power sources from reaching the rails inside the depot and causing electrical sparks. (IV) Prevent combustion and explosion caused by sparks generated by metal friction (1) Strictly enforce the relevant regulations regarding entry, exit, and the work area. It is prohibited to enter oil depots wearing shoes with nails or metal soles; climbing onto oil tanks, oil tankers, tank trucks, and oil drums is also forbidden. Mules, horses, or wheeled vehicles are not allowed to enter the depot area. (2) It is prohibited to use iron tools to strike the lid of the oil storage container; when opening the lids of large tanks and tank trucks, copper wrenches or alloy wrenches that do not generate sparks upon impact should be used. (3) Inside the warehouse, collisions between metal containers should be avoided. It is even more forbidden to roll mailboxes without washers on concrete floors. (4) During oil transfer operations, care should be taken to prevent the transfer hose from colliding when it is inserted into or withdrawn from the tank truck’s hatch or the oil tanker’s hold. Wherever there is oil or gas, iron metal must not be touched. (5) Preventing the accumulation of oil vapors that could lead to fires and explosions (1) It is strictly prohibited to perform repairs or welding on uncleaned oil drums, tanks, containers, and other storage vessels. After cleaning, the various containers should have their lids removed for ventilation before welding; if necessary, a test explosion should be conducted first. (2) The barrel-packed light oils stored in the warehouse should be inspected regularly, and any leaks should be addressed by replacing the containers promptly. Air circulation should be maintained in the warehouses, sheds, and receiving/distributing areas for barrels of light oil. (3) In underground and cave-type oil tank areas, strict measures must be taken to prevent oil leaks; ventilation equipment should be installed to ensure good air circulation and avoid the accumulation of oil vapor. Antistatic measures for oils (I) Generation of static electricity: During the receiving, transferring, and filling of oils, friction between oil molecules as well as between the oil and other substances can generate static electricity. The voltage increases as the friction intensifies; if this electricity is not discharged in time, once the voltage reaches a certain level, a spark will be generated between the two charged objects (i.e., static discharge), which can lead to the explosion or ignition of the oil. The higher the static voltage, the easier it is for discharge to occur. The level of voltage or the amount of static charge is mainly related to the following factors: (1) The faster the oil filling speed. The greater the friction, the higher the static voltage generated. (2) The drier the air, the less likely static electricity is to dissipate from it, and the easier it is for the voltage to rise. (3) The greater the distance between the oil pipe outlet and the oil surface, the more intense the friction between the oil and air, and the more severe the disturbance and impact of the oil flow on the oil surface; as a result, the voltage becomes higher. (4) The rougher the inner wall of the pipe, and the more elbows and valves it has, the higher the static voltage generated. When oil contains moisture during transfer, the voltage generated is several times to dozens of times higher than that produced when there is no moisture present. (5) Non-metallic pipes, such as those made of canvas, rubber, asbestos, cement, plastic, etc., generate static electricity more easily than metal pipes. (6) The denser the mesh of the oil filter installed on the pipeline, the higher the static voltage generated. The silk felt filter mesh generates a higher static voltage. (7) Static electricity is highly likely to occur when the atmospheric temperature is high (22–40°C) and the relative humidity of the air is between 13% and 24%. (8) Under the same conditions, light fuel oil generates static electricity more easily than lubricating oil. (II) Methods to prevent static electricity discharge: (1) All oil tanks, pipelines, and loading/unloading equipment used for storing and transporting oil must be equipped with proper grounding systems to conduct static electricity into the ground promptly. It is also necessary to regularly check the technical condition of these grounding systems and measure the grounding resistance. The grounding resistance of oil tanks in the oil depot should not exceed 10Ω, while the grounding resistance of other equipment should not exceed 100Ω (including static and safety grounding). For vertical oil tanks, the grounding electrodes are arranged along the circumference of the tank, with one set every 18 meters; horizontal oil tanks must have no fewer than two sets of grounding electrodes. (2) When filling oil tanks, tank trucks, and railway tank cars, the oil transfer pipe must be inserted below the oil level or near the bottom of the tank in order to reduce the impact of the oil and friction with air. (3) During seasons when the air is particularly dry and the temperature is high, special attention should be paid to checking the grounding equipment; the speed of oil filling should be reduced as appropriate, and water can be poured around the work area and the static electricity grounding electrodes if necessary. (4) Static discharge accidents are likely to occur at the start of oil transfer and filling, as well as from when three-quarters of the container is filled until filling is complete; in such cases, the flow rate should be kept below 1 m/s. (5) When loading oil into the ship, it is necessary to maintain metal contact between the oil outlet of the fueling pipeline and the oil inlet of the tanker. (6) It is strictly prohibited to pour light fuel oil into plastic barrels inside the oil depot, and it is forbidden to use plastic containers to transfer light fuel oil in areas that could affect the safety of the oil depot. (7) All personnel who board the oil tank and are involved in fuel oil filling operations must not wear synthetic fiber clothing (except for certified anti-static work clothes). Before climbing into the tank, the personnel entering it should hold onto the paint-free ladder of the oil tank for a moment to discharge static electricity from their bodies. (III) Installation of grounding devices (1) Grounding wires: Grounding wires must have good electrical conductivity, an appropriate cross-sectional area, and sufficient strength. For the grounding wires of oil tanks, pipelines, and loading/unloading equipment, flat steel with a thickness of not less than 4 mm and a cross-sectional area of not less than 48 mm2 is commonly used ； Tank trucks and oil tankers can use copper or aluminum wires with a diameter of not less than 6 mm ； Rubber hoses generally use multi-strand copper wires with a diameter of 3–4 mm. (2) Ground electrode: The ground electrode should be made of a steel pipe with a diameter of 50 mm, a length of 2.5 m, and a wall thickness of not less than 3 mm. Remove any rust or dirt from the surface of the pipe (no anti-corrosion treatment is required). Dig a pit about 0.5 m deep, and insert the ground electrode vertically into the soil at the bottom of the pit. The grounding electrode should be buried as deep as possible in areas with high humidity and high groundwater levels. All connections between the grounding electrode and the grounding wire shall be bolted or clamped to ensure good contact. Poison prevention for oils: Oils possess certain toxicity, which varies depending on their chemical structure, evaporation rate, as well as the properties and amounts of additives contained in them. It is generally believed that aromatic hydrocarbons and naphthenic hydrocarbons in base oils are highly toxic, and various additives added to oils, such as anti-knock agents (tetraethyl lead), rust inhibitors, and anticorrosive agents, also possess high toxicity. These toxic substances enter the body mainly through the respiratory tract, digestive tract, and skin, causing poisoning. Therefore, it is necessary to strictly follow the operating procedures to prevent poisoning incidents. Practice has shown that as long as we understand the properties of various oils and take necessary preventive measures, poisoning accidents can be completely avoided. (1) Minimize the inhalation of oil vapors. (1) Oil storage areas must maintain good ventilation. Before entering the light oil storage area to carry out work, the windows and doors should be opened first to allow the oil vapors to dissipate as much as possible before entering the area to work. (2) Oil tanks, fuel containers, pipelines, oil pumps, and refueling equipment must be kept airtight to prevent leaks. If any leakage is detected, it should be repaired promptly, and the spilled oil must be completely collected and removed to avoid the formation of vapors that could increase air pollution in the work area. (3) When entering light oil tanks or ship fuel holds for work, it is necessary to open the manholes for ventilation in advance, wear gas-proof equipment equipped with a ventilation system, as well as safety belts and signal ropes. During operation, a dedicated person must be on duty outside the tank to maintain constant contact with the personnel inside and to ensure shift rotation. (4) When cleaning residual oil from steam and kerosene tanks, vehicles, and other small containers, it is strictly prohibited for workers to enter the tanks to carry out the work. When it is necessary to enter the tanks to clean up other residual oils, effective safety measures must be taken. (5) When performing operations with light oil, the operator must stand in the upwind direction to minimize inhalation of oil vapors. (6) In areas where oil quality is adjusted, ventilation systems should be installed to prevent the generation of large amounts of oil vapor during heating and mixing, which could harm the health of the operators. (II) Avoid contact of the mouth and skin with oils. (1) It is strictly prohibited to suck leaded gasoline or other oils through the mouth; if it is necessary to draw gasoline out of the tank using a hose, a rubber bulb or a suction device can be used. (2) After completing the task, wash your hands with alkaline water or soap; do not smoke, drink water, or eat until you have washed your hands, face, and mouth. (3) It is strictly prohibited to use leaded gasoline to wash hands, clean clothes or machinery, fill lighters, or as fuel for blowtorches. (4) Do not bring work clothes, gloves, shoes, and socks contaminated with oil or grease into the cafeteria and dormitories; they should be placed in designated changing rooms and cleaned regularly. Corrosion prevention of oil products: During storage and transportation, petroleum products can cause damage to containers, pipelines, and equipment due to metal corrosion, which may even lead to oil leaks. The oxidation products resulting from metal corrosion increase the level of mechanical impurities in the oil and accelerate its oxidation, thereby affecting the quality of the oil. Therefore, attention must be paid to the anti-corrosion of metal equipment in oil depots. (1) Causes of corrosion: During storage, the main reasons for corrosion of metal containers and pipelines caused by oil products are as follows: 1. Chemical corrosion: Inorganic salts present around metal containers and equipment, such as calcium chloride, sodium chloride, calcium sulfate, etc., undergo chemical reactions with the metal surface, leading to corrosion of the metal. This type of corrosion mainly occurs in oil storage tanks and pipelines that are in contact with seawater or buried underground. 2. Atmospheric corrosion: Chemical corrosion is a type of electrochemical corrosion. The surfaces of metal devices exposed to the atmosphere have a layer of condensed water on them due to the evaporation of environmental moisture. As this thin layer of condensed water forms, certain gases dissolve into it, creating a conductive solution (an electrolyte solution). Oxidation-reduction reactions occur between the metal and the medium, resulting in damage to the metal. (II) Coating for corrosion protection: (1) Regularly spray a corrosion-resistant coating on the inner walls of metal oil storage tanks. Such as epoxy resin layers or raw lacquer layers. (2) Regularly spray anti-rust paint on oil pipelines and equipment such as oil pumps that are exposed to the atmosphere. (3) For oil pipelines installed at the surface, water accumulation should be removed to prevent soaking, which could otherwise cause the coating to peel off. (4) Moving metal parts in oil depot equipment, such as valves in oil pipelines, should be coated with rust preventive grease or lubricating grease to prevent moisture from seeping into the valve screws and causing corrosion. Protective covers should be installed on the leak-proof valves to prevent rainwater from washing away the anti-rust coating. (5) On the oil transfer pipelines and equipment located at the dock, which are often exposed to splashing water, in addition to applying an anti-corrosion and rust-proof coating on their surfaces, rust preventive grease or a protective lubricant with good adhesion should also be applied. (6) Oil pipelines and storage containers buried underground, as they are in direct contact with moisture, salts, alkalis, acids, and other substances in the soil, should have an anti-rust paint applied to their outer surfaces, followed by a layer of asphalt for protection. (III) Corrosion protection (1) Shield corrosion protection: The principle of shield corrosion protection is to allow the metal of the anode to corrode, thereby protecting the cathodic metal from corrosion. (2) Cathodic protection by impressed current: In this method of cathodic protection, the metal pipelines and oil storage tanks to be protected are connected to the negative pole of a direct current power supply; under the influence of this external direct current, the pipelines and tanks become cathodes, thereby achieving protection against corrosion ； The scrap metal connected to the positive terminal of the power supply is corroded. I. Is it normal for the lubricant to turn black during use? Answer: There are three reasons for the blackening of the lubricant: (1) deterioration of the lubricant, (2) wear of the parts, and (3) entry of impurities into the tank. If no impurities enter the tank during use, then it can be assumed that there is a problem with the quality of the lubricant itself, and it should be replaced with another brand. It is normal for the color of the lubricant to darken slightly after being used for some time, but it should not turn very black (this does not apply to engine oil). 　　 II. Can older equipment use lower-quality oil? Answer: Under normal circumstances, the worn parts of equipment are surface-treated, which gives them a higher surface hardness and makes them less prone to wear; however, the interior of these parts is softer. In older equipment, some parts already have worn surfaces, so using lower-quality lubricant will accelerate the wear of those parts. We recommend not using lower-grade or inferior lubricants. 　 III. Why can’t other oils replace gear oil? Answer: We have observed cases where some users have used anti-wear hydraulic oil, guide rail oil, turbine oil, or ordinary machine oil as substitutes for gear oil. All of this is incorrect, as the power of the entire machine is transmitted through gear mechanisms. The contact lines on the gear teeth are subjected to enormous loads, which requires lubricants to have extreme pressure properties; other types of oils lack such additives and therefore cannot protect the gear teeth, leading to phenomena such as pitting and cracking of those teeth. 　　 IV. Can different types of gear oil be used interchangeably as long as their viscosity is the same? Answer: No! There are also different grades for gear oils; heavy-duty gear oils can be used as a substitute for light-duty gear oils, but the reverse is not true. At present, most domestic ordinary gear oils are of medium-duty or lower grade, and they are not suitable for use in high-speed, high-load equipment. 　　 V. What causes oil to turn white? Answer: Under normal circumstances, oil turning white is caused by water entering the oil tank, which results in emulsification. It is necessary to prevent water from entering the lubricant tank or to stop rainwater from getting into already opened oil containers. In practice, the equipment should be checked to ensure that the oil seals are not damaged; when changing the oil, it is necessary to check whether there is water inside the tank, and the oil drums should be stored in a place protected from rain. 　　 VI. Is it not important to use lubricant? As long as the equipment has oil, that’s enough; any lubricant available on the market can be used? Answer: It is absolutely essential to pay attention to the use of lubricant. Lubricant is like blood in the human body; poor-quality lubricants can damage your expensive equipment. Different lubricants contain various additives to meet the needs of different parts of the equipment. For example, antioxidants prevent the oil from oxidizing, rust inhibitors prevent the equipment from rusting, and anti-wear agents prevent wear and tear on the equipment. 　　 VII. Can the lubricating oil that has been replaced after its useful life still be used? Answer: Some users reuse the replaced oil after settling it, but this is not appropriate. The various properties of the oil deteriorate over time as it is used, and using such replaced oil is equivalent to using substandard product. 　　 VIII. When it’s time to change the oil, is it possible to drain some of the lubricant and then add some new lubricant? Answer: The oil should be drained as much as possible; mixing used lubricant with new lubricant reduces the quality of the lubricant, which in turn shortens its useful life. 　　 IX. How to judge the quality of lubricant by its appearance? Answer: Qualified lubricants are generally light yellow, uniform, and transparent liquids; those with higher viscosity have a slightly darker color. (This phenomenon generally occurs only when the viscosity is above 460#.) If the oil turns black, contains impurities, or has water in it, it can be considered low-quality lubricant. For high-end equipment, it is essential to use lubricants produced by reputable brands from established lubricant manufacturers. Products without a brand name hardly offer any quality assurance, and there are many fake lubricants on the market, so this issue must be taken seriously. 　　 X. How to select alternative oils for imported equipment? Answer: Imported equipment usually comes with recommended products; for convenience or cost reasons, it is possible to find alternative products domestically, but care must be taken to choose the right model. Some oils have specific requirements, so it is advisable to consult specialized lubricant companies. We welcome manufacturers to contact us by phone or mail; we will provide free consultation services. 　　11. As long as the oil is changed frequently, can lower-quality lubricant be used? Answer: No. Lower-quality lubricants will damage the friction surfaces of the frictioning parts; once the hard layer on these parts is damaged, wear increases, and this damage cannot be repaired. The damaged surfaces become rougher, which further leads to wear, creating a vicious cycle. 　 12. What does lubricant viscosity mean? Answer: Simply put, lubricant viscosity refers to the flow rate of the lubricant under certain conditions; it changes with temperature. Currently, the viscosity at 40°C or 100°C is used as a standard internationally. 13. Does a high viscosity of lubricating oil indicate good quality? Answer: No! Under normal circumstances, when the operating speed of a component is high, the load on its surface is relatively low, so the viscosity of the lubricant suitable for use is lower (e.g., spindle oil); conversely, when the operating speed is low, the load on the surface is higher, and thus the viscosity of the appropriate lubricant is greater (e.g., gear oil). Of course, in the end it is necessary to follow the equipment supplier’s specifications regarding the choice of lubricant. The quality of a lubricant depends on many factors beyond just its viscosity; therefore, viscosity alone cannot be used to assess the quality of a lubricant. 　　 14. What causes foaming of lubricating oil during equipment operation? Answer: It is generally due to a quality issue with the lubricating oil; qualified lubricating oil should not produce excessive foam during use, and users should avoid using lubricating oils that cause foaming. Another possible reason is that mixing oils can cause foaming; therefore, care should be taken to avoid mixing lubricants with different properties. 15. How is lubricant produced? Answer: Lubricant is produced by refining base oil derived from petroleum and then adding various additives to it. Therefore, high-quality base oils and additives are the guarantee for producing high-quality lubricants. 　　 16. What does the grade of lubricating oil mean? Answer: According to ISO standards, industrial lubricating oils are classified into various viscosity grades based on their viscosity at 40°C. The higher the value, the greater the viscosity; therefore, the grade of a lubricating oil refers to its viscosity grade. 　　 17. Why do lubricants with the same grade number have different viscosities? Answer: Each viscosity grade of lubricant has a specific range for its viscosity (equivalent to a tolerance band in machining), usually ranging from ±10%. For example, the viscosity range for 100# gear oil is 90–110, while that for 150# gear oil is 135–165; any value within these ranges is considered acceptable. 　　 18. What does the viscosity index mean? Answer: The viscosity of any lubricant changes with temperature. The viscosity index is a value that indicates the rate at which the viscosity of an oil changes with temperature; the higher the viscosity index, the smaller the change in viscosity due to temperature changes. The viscosity index of industrial lubricants is generally above 90. 　　 19. After the running-in period of new equipment, is it necessary to change the lubricant? Answer: It is necessary to change the lubricant! This is because new equipment generates a large number of metal particles in the lubricating oil during its initial operation, and these metal particles in turn accelerate the wear of the components. 　　 20. Why do new machines have a running-in period, and can poor-quality oil be used during this period? Answer: Under normal circumstances, in the initial stage of use, new machines suffer from uneven stress distribution as a result of the fact that the precision of component manufacturing cannot be 100% accurate; this leads to wear on the surfaces of these components, which is what is known as running-in wear. Based on experience, most equipment suppliers specify a running-in period of one month. After going through the running-in period, the machine operates with more harmonious coordination between its components, resulting in smoother operation. However, since there are certain amounts of wear particles in the lubricating oil, it is necessary to replace the lubricating oil; otherwise, these wear particles will cause further wear of the machine parts, thereby shortening the service life of the equipment. 　　 Although lubricant is used only for one month during the break-in period, some users mistakenly think that since it’s only used for a month, any type of oil will do. Here, we would like to especially remind users: never use poor-quality engine oil during the running-in period. 　 The reasons are as follows: 1. Different parts of the machine have varying requirements for lubricant; during the running-in period, the requirements for the properties of the lubricant do not decrease – on the contrary, they become even higher. During the machine running-in phase, due to the machining errors of the components, greater impact forces act on their surfaces; therefore, high-quality lubricants are needed to protect these working surfaces from damage. 　　 II. During the running-in period, only those areas where there is poor coordination in the operation of the machine parts wear out. If the use of low-quality lubricant leads to significant wear on the surface of the parts, it will shorten the equipment’s lifespan. 1. Generally, parts undergo surface heat treatment, resulting in higher hardness on their surfaces and lower hardness inside. If the quality of the lubricant used is poor and it damages the hard layer on the surface of the parts, this will cause rapid wear of those parts. 　　 2. Wear and damage are irreversible; once wear occurs and cannot be repaired, the parts must be replaced. 　　 In summary, use the right oil during the break-in period, and change the oil promptly after it is over! 　　21. Is part wear mainly caused by issues with part manufacturing or material, with lubricant playing a secondary role? Answer: No! Part wear is related to the material of the parts, manufacturing precision, and heat treatment, but proper use of lubricant is equally important! With the same equipment, some users have a long usage period while others have a short one; some users experience a high rate of part replacements while others have a low rate. This is directly related to the quality of the lubricant used. In our work, we’ve encountered a client who didn’t replace any parts over three years, whereas another company replaced the same parts several times – which illustrates the importance of lubricants. 　 22. Is the lifespan of an oil seal related to the use of lubricating oil? Answer: The lifespan of an oil seal is directly related to the use of lubricating oil! Some users have found that the oil seals on their equipment fail within just half a year of operation. The use of low-quality lubricants is one of the main causes of seal damage; such lubricants have poor anti-wear properties, which leads to wear between the shafts, bearing shells, and holes. This results in an increase in the gaps between the components, causing lateral vibration of the shaft. Under such unstable operating conditions, the oil seals are quickly damaged, and this damage is irreversible. Using new oil seals on worn components will also lead to rapid damage, so it is essential to use high-quality lubricants. 23. How to identify the quality of lubricant? Answer: Lubricant is like the blood of machinery and equipment; high-quality lubricants enable machines to operate properly, whereas the use of inferior lubricants is akin to a blood cancer in the machine, leading to irreversible wear of its components and a shortened lifespan. Therefore, it is very important to use high-quality lubricant. There is a wide variety of lubricants available on the market, and a certain proportion of fake and inferior lubricants are present there. Purchasing low-quality lubricants can cause significant losses to users. Generally, there are three main approaches to selecting lubricants: 1. Purchase lubricants from brands recommended by the equipment supplier. 　　 2. Make purchases based on recommendations from users of similar equipment (peers in the same field). 　　 3. Purchase lubricant based on the user’s own experience. 　　 How can one tell the quality of the lubricant purchased? Here are some tips that may be useful as a reference: 1) Pay attention to whether the product has a brand name and whether it comes from a legitimate source. Be sure not to buy products without a brand name. 　　 2) Insert a slender tube (e.g., stainless steel tube) into the bottom of the tank to draw a sample of oil, and examine the appearance of the sample for any impurities, moisture, or turbidity; the presence of such conditions indicates that the lubricant product is unsuitable. 　　 3) Judge based on experience whether the lubricant viscosity is accurate. 　　 The following are some experiences gained by users in observing and assessing the condition of lubricating oil during use: ▲ Abnormally high temperature of the lubricating oil: This may be due to poor anti-wear properties of the lubricating oil, or the presence of external heat sources. 　　 ▲ The lubricating oil turning white is usually caused by water entering the oil tank. 　　 ▲ Blackening of lubricating oil: 1. External impurities enter the oil tank. 　　　　　　　　　 2. Oil degradation. 　　　　　　　　　 3. The oil change interval has been exceeded. 　　　　　　　　　 4. Wear of machine parts. 　　 Part wear may be caused by poor quality of lubricant, or it could be due to issues with equipment maintenance. Please check the worn parts. If a large number of parts are worn, it is generally indicative of a quality issue with the lubricant. If only some of the similar parts are worn while most remain intact, then it is necessary to determine whether the lubricant flow is unobstructed and whether the lubricant reaches all the friction areas. If some friction components lack lubricant, those areas will wear out, and the lubricant will also turn black. 　　 Quality lubricant should ensure that the equipment suffers minimal wear during the oil change interval; inferior lubricants cause extensive damage to machinery, so be sure to choose high-quality lubricant! Mr. Wang from CPI Lubricants in Shenzhen, China: 13926549484; QQ: 932929010, 819596775; Website: www.cpihualai.178b2b.com