Specifications of lubricating oil

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1. What are the requirements for lubricating oil in pump lubrication? Answer: The requirements for lubricating oil in mechanical pumps are as follows: ① It must have good fluidity, which refers to the ability of the lubricating oil to spread and adhere firmly to the metal surface, thereby forming a thin oil film. ②It should have an appropriate viscosity. It is required that there be a certain resistance between the molecules of the lubricating oil as it flows, so that a flowing oil film can be formed under certain conditions. ③A certain level of stability. It refers to the requirement that, under the operating conditions and requirements of the lubricant, its quality remains within specified limits throughout its useful life. Due to the different operating conditions and usage periods of lubricants, varying requirements are placed on their stability. ④Required purity. It means that the impurity content in the oil does not affect the proper use of the lubricant. ⑤Reliable adaptability. In other words, the lubricant to be used must be able to reliably cope with the special working conditions of the lubricated area. 2. What are the functions of lubricating oils (greases)? Answer: Generally speaking, lubricants (greases) have seven functions: ① Lubrication: Lubricants (greases) form an oil film between the friction surfaces, eliminating or reducing dry friction and improving the friction conditions; this is what is known as the lubrication function. ②Cooling effect: When the pump is in operation, the energy consumed due to friction is converted into heat. When lubricated with oil, most of the heat generated by friction is carried away by the oil, while a small amount of heat is dissipated directly into the surrounding environment through conduction and radiation. ③Flushing effect: It carries away the metal debris that is worn off during operation; this is known as the flushing effect of lubricating oil. The effectiveness of the flushing action has a significant impact on wear. The thickness of the oil film formed between the friction surfaces is generally very thin; metal debris remaining on the friction surfaces can destroy this oil film, leading to dry friction and thus abrasive wear. Especially for equipment that has undergone major repairs with replacement of friction components, the flushing effect of the lubricating oil is even more important during the initial running-in phase. ④Sealing effect: In steam reciprocating pumps, the sealing performance is improved by using lubricating oil to fill the gaps between the cylinder, the piston rings, and the piston grooves. ⑤Vibration damping: Lubricating oil or grease forms an oil film on the friction surfaces; the moving parts move on this oil film as if they were floating on an \"oil cushion,\" which provides a certain degree of cushioning against the vibrations of the equipment. ⑥Protective function: Prevents rust and dust to protect the equipment. ⑦Unloading effect: Due to the presence of an oil film between the friction surfaces, the load acting on them is distributed evenly across those surfaces through the oil film. This effect of the oil film is called unloading. Furthermore, when the oil film on the friction surface is locally damaged and dry friction occurs, the oil film still bears part or most of the load. This prevents the load acting on the local dry friction point from being concentrated as it is in the case of dry friction. 3. What is the oiliness of lubricating oil? What is its relationship with the “boundary oil film”? Answer: The property of lubricating oil that enables it to spread and adhere firmly to the metal surface to form a thin film is known as the \"lubricity\" of the lubricating oil. Oiliness is also known as “lubricity” or adhesiveness. Apply lubricant to the metal surface and then wipe it off until, even though no oil can be felt by hand anymore, a thin layer of shiny oil film remains on the metal surface – this is the boundary oil film. It is formed due to the oiliness of the lubricating oil (grease), and it can withstand very high pressures without being damaged. The oiliness of lubricating oil generally refers to the thickness of the boundary oil film formed by the lubricant, its viscosity, and its ability to recover quickly after the boundary oil film is broken. (The strength of the boundary oil film includes the strength of the oil film itself and the bonding strength between the oil film and the metal surface.) ) 4. What is the viscosity of lubricating oil? Answer: Viscosity is one of the most important quality indicators of lubricating oil. When molecules in liquids move relative to each other under the action of an external force, a type of resistance arises between these molecules, hindering their relative motion. This property of liquids is called the liquid’s “viscosity”. The parameter used to indicate the degree of viscosity of a liquid is called “viscosity”. The magnitude of viscosity is determined by the internal frictional resistance between liquid molecules. The higher the viscosity of a liquid, the greater the internal frictional resistance generated when its molecules move relative to each other, and thus the poorer the fluidity of the liquid. Conversely, the lower the internal friction force of a liquid, the lower its viscosity and the better its fluidity. 5. What do the freezing point and flash point of lubricating oil respectively mean? Answer: The freezing point indicates the low-temperature fluidity of lubricating oil. Because lubricating oil is different from water. Water can change from a liquid to a solid at 0°C. When the temperature of lubricating oil drops, it gradually loses its fluidity, rather than changing from a liquid to a solid at a certain temperature. Therefore, the temperature at which the lubricant solidifies merely serves as a general indication of the lubricant’s “low-temperature fluidity”. Flash point is a safety parameter for lubricants. The temperature at which, under standard conditions, when lubricating oil is heated and a mixture of its vapor and air comes into contact with an ignition source, it begins to flash and then extinguishes immediately, is known as the flash point. The flash point can also indicate the evaporation properties of lubricating oil. The higher the flash point, the lower the evaporation rate of the lubricant. 6. What are mechanical impurities in lubricating oil? Answer: All substances that exist in lubricating oil in a precipitated or suspended state, are insoluble in gasoline (or benzene), and can be filtered out, are collectively referred to as “mechanical impurities”. Mechanical impurities are mainly things such as sediment and metal powder; they not only significantly increase wear on the friction surfaces and clog the oil delivery pipelines, but also reduce the antioxidant stability of the lubricating oil. 7. What are the harms of water in lubricating oil to the lubricant? Answer: The harms of moisture to lubricating oil are as follows: ① Moisture can reduce the viscosity of lubricating oil, weaken the strength of the oil film, and thus diminish the lubrication effect. ②Water freezes below 0°C, severely affecting the low-temperature fluidity of lubricating oils. ③Moisture can accelerate the oxidation of lubricating oil and promote the corrosion of metals by low-molecular-weight organic acids. ④Moisture increases the foaming tendency of lubricating oil, making it prone to forming foam. ⑤Moisture can cause metal parts to rust. 8. What is the antioxidant stability of lubricating oil? Answer: The ability of lubricating oil to resist oxidation when heated and in the presence of metal catalysts is known as antioxidant stability. The better the antioxidant stability of the lubricating oil, the longer its service life. Lubricants with poor antioxidant stability tend to oxidize during use, producing organic acids, gums, and asphalts, which cause the lubricant’s color to darken, its viscosity to increase, its acid value to rise, and precipitation to occur. 9. What is the anti-emulsification capacity of lubricating oil? Answer: Under specified conditions, the time (in minutes) required for lubricating oil and water to mix together to form an emulsion, and then to remain at a certain temperature until the lubricating oil and water are completely separated, is known as the “anti-emulsification capacity,” or also referred to as the “anti-emulsification time.” The shorter the anti-emulsification time, the better the anti-emulsification performance of the lubricant. Lubricants with good anti-emulsification properties mean that oil and water cannot form a stable emulsion; after being mixed, they can separate quickly.