Sharing of knowledge related to lubricants

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Slide 1: Lecture Notes on Lubricant Knowledge. Slide 2: I. Basic Knowledge of Lubricants. Lubricants are oily lubricating agents. Based on their origin, they are divided into three categories: animal and vegetable oils, petroleum lubricants, and synthetic lubricants. Petroleum-based lubricants account for over 97% of the total usage, so lubricants often refer to petroleum-based lubricants. . Primarily using lubricating oil fractions and residue fractions from crude oil distillation units as raw materials, processes such as solvent deasphalting, solvent dewaxing, solvent refining, hydrorefining or acid-base refining, and clay refining are employed to remove or reduce components that cause the formation of free carbon, substances with low viscosity indices, materials with poor oxidation stability, paraffins, and chemical substances that affect the color of the finished oil. This yields qualified lubricating oil base oils, which, after blending and the addition of additives, become lubricant products. Slide 3 1. Functions of lubricating oil: (1) Reducing friction and wear, thereby lowering frictional resistance to save energy; reducing wear to extend the lifespan of machinery and improve economic efficiency ； (2) Cooling: It is necessary to remove the friction heat from the machine at all times ； (3) Sealing: leakage prevention, dust protection, and air leakage prevention are required ； (4) Corrosion and rust resistance; it is necessary to protect the friction surfaces from oil degradation or external corrosion ； (5) Clean rinsing: it is necessary to remove the dirt accumulated on the friction surface ； (6) Stress dispersion buffering, load distribution, and impact mitigation as well as shock absorption ； (7) Kinetic energy transmission, hydraulic systems, remote-controlled motors, and frictionless variable speed transmissions, etc. Slide 4: 2. Basic properties of lubricating oils (in red are the parameters we have analyzed). General physical and chemical properties: (1) Appearance (colority); (2) Density; (3) Viscosity (dynamic viscosity); (4) Viscosity-temperature index; (5) Flash point; (6) Pour point; (7) Acid value, alkali value, and neutralization value; (8) Water content; (9) Mechanical impurities; (10) Residue. Slide 5: Special physical and chemical properties: (1) Oxidation stability; (2) Thermal stability; (3) Antifoaming property; (4) Anti-emulsification property. Slide 6: Viscosity (dynamic viscosity): Viscosity is an indicator of the fluidity and flow characteristics of an oil. In applications with low speeds and high loads, oils with higher viscosity are typically used to ensure an adequate oil film thickness and proper lubrication ； In applications involving high speed and low load, oils with lower viscosity should be used to ensure proper startup of mechanical equipment as well as sufficient operating torque, while minimizing temperature rise during operation. The viscosity of a fluid is significantly affected by the ambient temperature (pressure also has some influence, but it is generally negligible). This effect is also mediated through intermolecular interactions: the general principle is that as temperature rises, the volume of the fluid expands, the distance between molecules increases, the interactions weaken, and thus the viscosity decreases ； As the temperature decreases, the volume of the fluid shrinks, the distance between molecules decreases, the interactions between them increase, and the viscosity rises. Since viscosity is closely related to temperature, any viscosity data must specify the temperature at which it was measured. Furthermore, in accordance with the regulations set out in GB3141, hydraulic oils generally follow the viscosity classification system of ISO, with grade classifications determined by the central value of their dynamic viscosity at 40°C. We mainly measure the percentage change in dynamic viscosity; specifically, we determine the time in seconds it takes for a certain amount of sample to flow through the capillary of the dynamic viscometer at a specified temperature (40°C), and then multiply this value by the calibration constant of the viscometer to obtain a comparison between the viscosity of the sample and the central value indicated by its grade. Slide 7 Flash point: The flash point is an indicator of the volatility of oils. The lighter the fraction of the oil, the greater its volatility, and the lower its flash point as well. Conversely, the heavier the distillate of the oil, the lower its volatility, and the higher its flash point. At the same time, the flash point is an indicator of the fire hazard of petroleum products. The hazard level of oils is determined based on their flash point: oils with a flash point below 45°C are considered flammable, while those with a flash point above 45°C are considered combustible. It is strictly prohibited to heat oils to their flash point temperature during storage and transportation. At the same viscosity, the higher the flash point, the better. Therefore, when selecting lubricants, users should make their choice based on the operating temperature and working conditions of the lubricant. It is generally believed that a flash point 20–30°C higher than the operating temperature allows for safe use. Slide 8: Cloud point: The cloud point is the highest temperature at which the oil stops flowing under specified cooling conditions. The solidification of oils differs significantly from that of pure compounds. Oil does not have a definite freezing temperature; the so-called “freezing” simply means that it loses its fluidity as a whole, and not all of its components turn into solids. 　　The pour point of lubricating oil is an important quality indicator reflecting its low-temperature fluidity. It is of great significance for production, transportation, and usage. Lubricants with a high freezing point cannot be used at low temperatures. Conversely, in regions with higher temperatures, there is no need to use lubricants with a low freezing point. Because the lower the freezing point of the lubricating oil, the higher its production cost, resulting in unnecessary waste. Generally, the freezing point of lubricating oil should be 5~7°C lower than the lowest temperature of the operating environment. It is particularly important to note that when selecting lubricants for low temperatures, a comprehensive consideration of the oil’s freezing point, viscosity at low temperatures, and viscosity-temperature characteristics is necessary. Because oils with low freezing points may also have low-temperature viscosity and viscosity-temperature properties that do not meet the requirements. Slide 9: Acid number, alkali number, and neutralization value: The acid number is an indicator of the amount of acidic substances present in lubricating oil, expressed in mgKOH/g. The acid value is divided into strong acid value and weak acid value; the sum of the two constitutes the total acid value (abbreviated as TAN). What we usually refer to as the “acid value” actually denotes the total acid number (TAN). The alkalinity value is an indicator of the content of basic substances in lubricating oil, with the unit being mgKOH/g. Alkali value is also divided into strong alkali value and weak alkali value; the sum of the two constitutes the total alkali value (abbreviated as TBN). What we usually refer to as “alkalinity” actually means “Total Base Number (TBN)”. The neutralization value actually includes the total acid value and the total base value. However, unless otherwise specified, the so-called “neutralization value” generally refers only to the “total acid value,” which is also expressed in mgKOH/g. It specifically refers to the number of milligrams of potassium hydroxide required to neutralize the free acid present in one gram of the substance being tested. Slide 10: Moisture: Moisture refers to the percentage of water contained in lubricating oil, usually expressed as a weight percentage. The presence of water in lubricating oil promotes its oxidation and deterioration, destroys the oil film formed by the lubricant, reduces its effectiveness, accelerates the corrosion of metals by organic acids, causes equipment to rust, leads to the formation of sediment in the oil, and also causes additives (especially metal salts) to undergo hydrolysis and become ineffective, resulting in precipitates that block the oil passages and hinder the circulation and supply of lubricating oil. Not only that, but the moisture in lubricating oil reduces its fluidity and deteriorates its viscosity-temperature properties at low operating temperatures, as it approaches the freezing point ； At high operating temperatures, water vaporizes, which not only destroys the oil film but also creates air resistance, affecting the circulation of the lubricating oil. In short, the less water in the lubricant, the better. Slide 11: Mechanical impurities: Mechanical impurities refer to precipitates or gelatinous suspensions present in lubricating oils that are insoluble in solvents such as gasoline, ethanol, and benzene. Most of these impurities are sand, gravel, iron shavings, and other such substances, as well as some organometallic salts that are insoluble in solvents and result from additives. The determination of mechanical impurities is carried out in accordance with GB/T 511-88, Method for Determining Mechanical Impurities in Petroleum Products and Additives (Gravimetric Method). The process is as follows: Weigh 100 g of the oil sample and heat it to 70–80°C. Add 2–4 times as much solvent, filter it through paper in a pre-weighed empty bottle, wash the filter paper and the bottle with hot solvent, and then weigh them again. The difference in weight before and after filtering represents the weight of the mechanical impurities; from this, the mass fraction of mechanical impurities can be determined. Slide 12: Residue: The dark brown residue formed when oil is heated, evaporated, and burned under specified experimental conditions is called residue. Residue is an important quality indicator for lubricant base oils; it is a parameter specified to determine the properties of the lubricant and the degree of its refinement. In lubricant base oils, the amount of carbon residue is determined not only by its chemical composition but also by the degree of refining of the oil. The main substances that cause carbon residue to form in lubricants are gums, asphaltenes, and polycyclic aromatic hydrocarbons present in the oil. Under conditions of insufficient air, these substances undergo decomposition and condensation under high heat to form residue carbon. The greater the degree of refining of the oil, the lower its residue value. Generally speaking, the lower the carbon residue value of the base oil, the better. 　　Today, many oils contain additives made of metals, sulfur, phosphorus, and nitrogen; these additives result in high carbon residue values. As a result, the carbon residue measurement for oils containing such additives has lost its original meaning. Slide 13: Special physical and chemical properties: Oxidation stability. Oxidation stability indicates the anti-aging properties of lubricating oils. Many industrial lubricating oils with a long service life must meet this requirement; therefore, it is considered a special property required for such types of oils. There are many methods for determining the oxidation stability of oils. Basically, a certain amount of oil is oxidized at a specific temperature for a set period of time in the presence of air (or oxygen) and metal catalysts, after which the acid value, changes in viscosity, and the formation of precipitates in the oil are measured. All lubricants have different tendencies toward autoxidation, depending on their chemical composition and the external conditions in which they find themselves. Oxidation occurs over time as it is used, gradually producing substances such as aldehydes, ketones, acids, as well as gums and asphaltenes. Oxidation stability is the property that prevents the formation of these substances that are detrimental to the use of oil products. Slide 14: Anti-emulsification property: Industrial lubricants often inevitably get mixed with some cooling water during use. If the lubricant does not have good anti-emulsification properties, it will form an emulsion with the water that has mixed in, making it difficult to remove the water from the bottom of the circulation tank – which can lead to poor lubrication. Therefore, anti-emulsibility is a very important physicochemical property of industrial lubricants. Oils with generally low viscosity are tested using the GB/T 7305-86 method: 40 ml of the oil sample is mixed with 40 ml of distilled water at a certain temperature (54°C or 82°C), and the mixture is stirred at 1500 r/min for 5 minutes; thereafter, the time it takes for the oil layer, water layer, and emulsion layer to separate into volumes of 40–37–3 ml is observed. Slide 15 II: Indicators for Lubricant Sample Analysis 1. TSA46 (1) Equipment used: C1001 bearings and control systems, centrifugal pump bearings, bearings of fans F1001-F1003, lubricant systems for Unit 2, lubricant systems for Unit 3, and lubricant system for the air pressure unit. (2) Analysis of project indicators
Project: Oil change indicators
Test methods:
Viscosity grade (according to GB3141): 46
Change rate of kinematic viscosity at 40°C, %: More than ±10
Acid value, mgKOH/g: Increase greater than 0.1
GB/T264: Oxidation stability, minutes: Less than 60
SH/T0193: Moisture content: Greater than 0.1
GB/T264: Flash point (open cup), °C: Less than 185
GB/T3536: Demulsification value, (40–37–3), minutes: Greater than 60
GB/T7305: Mechanical impurities: Greater than 0.01
GB/T11143: Slide 16
2. DAB150
(1) Equipment used: C1002A/B, C3002A/B crankcase oil fillers. (2) Analysis of project indicators
Project: Oil change indicators
Test methods:
Viscosity grade (according to GB3141): 150
Change rate of kinematic viscosity at 40°C, %: More than ±15
Acid value, mgKOH/g: Increase of more than 0.01
Oxidation stability (according to GB/T264): Less than 60
Water content (according to SH/T0193): More than 0.1
Flash point (open cup), °C: Less than 215
Demulsification value (40–37–3), min: More than 30
Mechanical impurities (according to GB/T7305): More than 0.01
(Slide 17)
3. Overall factors affecting the analysis of project indicators
(1) Equipment and instruments used for analyzing oil samples
(2) Quality of the oil itself
(3) Location from which the oil sample is taken
(4) Procedures for taking oil samples
(5) Operating condition of the machine (condition of bearings, sealing surfaces) and the oil circuit system
(6) Procedures for refueling
(Slide 18)
4. Analysis and handling of cases where project indicators exceed limits
Reasons for exceeding limits and corresponding actions:
For high viscosity: Change the oil after prolonged use.
For low flash point: Change the oil after prolonged use.
For high neutralization value or contamination by other substances: Change the oil.
For mechanical impurities: Switch to a backup unit and change the oil; if it’s due to problems with the oil station filter, switch to a backup filter and change the oil.
If the three-stage filtration process is not properly followed during refueling, change the oil and ensure that the three-stage filtration process is followed.
If the sampling location is incorrect or if the sample has not been properly replaced, take a new sample.
If water from the oil station’s cooling system gets into the system, repair the cooler and change the oil.
If the oil is prone to oxidation or if water from the cooling system gets in, repair the cooler and change the oil.
Note: It is assumed that the quality of the original oil is satisfactory and that the equipment and instruments used for analyzing oil samples are functioning properly. Slide 19 III. Analysis Data Table for Lubricating Oil Samples Used in Hydrocracking Units Name, Sampling Location, Sampling Time, Kinematic Viscosity (40°C), Flash Point (°C), Neutralization Value (mgKOH/g), Mechanical Impurities (%), Moisture (%), Emulsification Resistance: TSA46 – Oil storage tank in the warehouse, 07.9.20, 44.96, 246, 0.08, 0.0018, trace amounts; 40-37-3 (15 min). C1001 – Fuel tank, 07.10.05, 44.98, 237, 0.09, 0.0093, trace amounts; 40-37-3 (15 min). C1001 – Fuel tank, 07.10.23, 44.58, 226, 0.08, 0.0042, trace amounts; 40-37-3 (15 min). P1001 – Fuel tank, 07.10.05, 44.78, 226, 0.10, 0.0026, trace amounts; 40-37-3 (15 min). P1001 – Fuel tank, 07.10.23, 44.62, 226, 0.11, 0.0044, trace amounts; 40-37-3 (15 min). DAB150 – Oil storage tank in the warehouse, 07.9.20, 113.32, 440, 0.16, 0.0029, trace amounts; 35-38-7 (30 min). C1002 – Fuel tank C1002A, 07.10.23, 139.82, 450, 0.16, 0.0188, trace amounts; 40-37-3 (10 min). C1002B – Fuel tank, 07.10.23, 143.82, 460, 0.16, 0.019, trace amounts; 40-37-3 (10 min). C3002 – Fuel tank C3002A, 07.10.23, 142.42, 450, 0.16, 0.009, trace amounts; 40-37-3 (5 min). C3002B – Fuel tank, 07.10.23, 144.22, 430, 0.16, 0.0064, trace amounts; 40-37-3 (5 min). L-CKD150 – Oil storage tank in the warehouse, 07.9.20, 153.22, 222, 0.57, 0.0034, trace amounts; 10-5-65 (30 min). HS-32 – Oil storage tank in the warehouse, 07.9.20, 31.12, 184, 0.63, 0.0115, trace amounts; 40-37-3 (15 min). HSC634 – Oil storage tank in the warehouse, 07.9.20, 456.82, 252, 0.55, 0.0032, trace amounts; 40-37-3 (15 min). DTE24 – Oil storage tank in the warehouse, 07.9.25, 20.14, 222, 1.35, 0.0023, trace amounts; 40-37-3 (20 min). Slide 20 IV. Recommendations 1. Conduct regular inspections to closely monitor the condition of the lubrication areas of large equipment such as C1001, C1002, and P1001 (including aspects like noise, vibration, temperature, etc.). 2 Regularly replace the oil station filter. 3 Regularly take samples at the cooling water outlet of the cooler to analyze the lubricant content. 4 Take oil samples for analysis regularly. 5 Standardize the sampling location and sampling procedures. Slide 21 Thank you, everyone!