The basic performance of lubricating oil
Lubricating oil is a technologically advanced product, which is a complex mixture of hydrocarbons, and its true performance is the comprehensive effect of complex physical or chemical changes.
The basic performance of lubricating oil includes general physical and chemical properties, special physical and chemical properties, and bench test simulations.
General Physical and Chemical Properties
Each type of lubricating grease has common general physical and chemical properties, which indicate the inherent quality of the product.
The general physical and chemical properties of lubricating oil are as follows:
Appearance (color)
The color of the oil can often reflect its degree of refinement and stability.
For base oils, the higher the degree of refining, the cleaner the removal of hydrocarbon oxides and sulfides and the lighter the color.
However, even under the same refining conditions, the color and transparency of base oils produced from different petroleum sources and crude base oils may be different.
For new finished lubricating oil, the color has lost its original meaning as an indicator of the refining degree of the base oil due to the use of additives.
Density
Density is the simplest and most commonly used physical property index of lubricating oil. The density of lubricating oil increases with the increase in the amount of carbon, oxygen and sulfur in its composition.
Therefore, under the same viscosity or same relative molecular weight, lubricating oils with more aromatic hydrocarbons and more asphaltene and resin have the highest density, those with more cycloalkanes are in the middle, and those with more alkanes have the lowest density.
Viscosity
Viscosity reflects the internal friction of the oil and is an index that indicates the oiliness and fluidity of the oil.
Under the premise of not adding any functional additives, the higher the viscosity, the stronger the oil film resistance and the worse the fluidity.
Viscosity Index
The viscosity index represents the degree of change in the viscosity of the oil with temperature.
The higher the viscosity index, the less the oil's viscosity is affected by temperature and the better its viscosity-temperature performance.
On the other hand, the lower the viscosity index, the worse the performance.
Flash point
The flash point is an index that indicates the volatility of oil. The lighter the oil fraction, the greater its volatility and the lower its flash point.
On the other hand, the heavier the oil fraction, the lower its volatility and the higher its flash point.
In addition, the flash point is also an indicator of the fire risk of petroleum products. The oil's danger level is divided based on its flash point, with flash points below 45°C considered flammable and those above 45°C considered combustible. It is strictly prohibited to heat the oil to the flash point temperature during storage and transportation.
In the case of the same viscosity, a higher flash point is better. Therefore, users should choose lubricating oil according to the use temperature and working conditions. Generally, a flash point 20-30°C higher than the use temperature is considered safe for use.
Pour point and tipping point
The pour point is the highest temperature at which oil stops flowing under specified cooling conditions. The solidification of oil is different from the solidification of pure compounds.
Oil does not have a specific solidification temperature, and the so-called “solidification” just means that it has lost its fluidity as a whole and not all components have turned into solids.
The pour point of lubricating oil is an important quality indicator that represents its fluidity at low temperature and is significant for production, transportation and use. Lubricating oil with a high pour point cannot be used at low temperatures.
On the other hand, it is not necessary to use lubricating oil with a low pour point in areas with higher temperatures, as the lower the pour point of the oil, the higher the production cost, generating unnecessary waste.
Generally, the pour point of lubricating oil should be 5-7℃ lower than the lowest temperature of the use environment.
However, it is important to consider the pour point, low-temperature viscosity and viscosity-temperature characteristics of the oil comprehensively when choosing a low-temperature lubricating oil.
This is because low pour point oils may not meet the requirements for low-temperature viscosity and viscosity-temperature characteristics.
Pour point and tipping point are both indicators of low-temperature oil fluidity, and there is no fundamental difference between them except for slightly different measurement methods. The pour point and pour point of the same oil are not completely the same, and in general the pour point is 2-3°C higher than the pour point, but there are exceptions.
Acid value, alkaline value and neutralization value
The acid number is an indicator of the presence of acidic substances in the lubricating oil, with a unit of mgKOH/g.
The acid number is divided into the strong acid number and the weak acid number, and the two combined constitute the total acid number (TAN). Typically, what we call “acidity value” actually refers to “total acidity value (TAN)”.
The alkaline value is an indicator of the amount of alkaline substances in the lubricating oil, with a unit of mgKOH/g.
Alkaline value is also divided into strong alkaline value and weak alkaline value, and the two combined constitute total alkaline value (TBN). Typically, what we call “alkaline value” actually refers to “total alkaline value (TBN)”.
The neutralization value actually includes both the total acid value and the total alkaline value. However, unless otherwise noted, what we generally call the “neutralization value” actually just refers to the “total acidity value,” with a unit of mgKOH/g.
water content
Water content refers to the percentage of water in the lubricating oil, usually expressed as a percentage by weight.
The presence of water in lubricating oil can damage the oil film formed by the oil, resulting in reduced lubrication effectiveness, accelerate the corrosion of metals by organic acids, cause rust on equipment and make the oil prone to producing sediment.
In general, the less water there is in the lubricating oil, the better.
Mechanical Impurities
Mechanical impurities refer to precipitates or gelatinous suspensions in lubricating oil that are insoluble in solvents such as gasoline, ethanol and benzene.
Most of these impurities are sand, stone, iron filings and some organic metal salts that are difficult to dissolve in solvents brought by additives.
Typically, mechanical impurities in lubricating oil base oil are controlled below 0.005% (mechanical impurities below 0.005% are considered non-existent).
Ash Content and Sulfated Ash Content
Ash content refers to the non-combustible substance that remains after burning under specific conditions.
The composition of ash is generally considered to be some metallic elements and their salts.
Ash content has different concepts for different types of oil. For base oil or oil without additives, the ash content can be used to determine the degree of refinement of the oil.
For oil with added metal salt additives (new oil), ash content becomes a means of quantitatively controlling the amount of additives added. Sulphated ash content is used in place of ash content in foreign countries.
The method consists of adding a small amount of concentrated sulfuric acid to the oil sample before combustion and calcination to convert the metallic elements in the additives into sulfate.
Residue
Residue refers to the black residue left after heating and combustion of oil under specified experimental conditions.
It is an important quality indicator of lubricating oil base oil and is used to determine the nature and refining depth of lubricating oil.
The amount of residue in the lubricating oil base oil is related not only to its chemical composition, but also to the oil's degree of refinement.
The main substances that form residues in lubricating oil are colloids, asphaltenes and polycyclic aromatic hydrocarbons. These substances decompose and condense under conditions of inadequate air supply to form residues.
The deeper the lubricating oil is refined, the lower the value of the residue. Generally speaking, the lower the residual value of the base oil blank, the better.
Nowadays, many oils contain additives such as metals, sulfur, phosphorus and nitrogen, which have high residue values.
Therefore, the residual value of oils containing additives has lost its original meaning. Mechanical impurities, water content, ash content and residues are quality indicators that reflect the purity of the oil and the degree of refinement of the lubricating base oil.
Special Physical and Chemical Properties
In addition to the above general physical and chemical properties, each type of lubricating oil must also have special physical and chemical properties that characterize its usage characteristics.
The higher the quality requirements or the stronger the specialization of the oil, the more prominent its special physical and chemical properties will be. Test methods that reflect these special physical and chemical properties are briefly described below:
Oxidation stability
Oxidation stability indicates the anti-aging properties of the lubricating oil. Some long-life industrial lubricants require this indicator, making it a special performance requirement for these types of oils.
There are many methods for measuring the oxidation stability of oil.
Basically, a certain amount of oil is oxidized with air (or oxygen) and a metal catalyst at a certain temperature for a certain period of time.
The oil's acid number, viscosity changes and precipitate formation are then measured. All lubricating oils have different automatic oxidation tendencies depending on their chemical composition and external conditions.
As oxidation occurs during use, aldehydes, ketones, acids, colloids, asphaltenes and other substances are gradually formed.
Oxidation stability is the ability to suppress the formation of substances harmful to the use of oil.
Thermal stability
Thermal stability refers to the ability of petroleum products to withstand high temperatures, that is, the resistance of lubricating oil to thermal decomposition, which is indicated by the thermal decomposition temperature.
Some high-quality anti-wear hydraulic oils, compressor oils and other lubricants require high thermal stability.
The thermal stability of petroleum products mainly depends on the composition of the base oil, and many additives with low decomposition temperatures often have an adverse effect on the stability of petroleum products. Antioxidants cannot significantly improve the thermal stability of petroleum products.
Oily and Extreme Pressure (EP) Properties
Oiliness refers to the formation of a strong physical and chemical adsorption film of polar substances in the lubricating oil on the metal surface in the friction zone, which plays a role in high load resistance and anti-friction wear.
EP properties refer to the polar substances in the lubricating oil in the friction zone, subjected to chemical reactions of friction and decomposition under high temperature and high load, reacting with the surface metal to form a soft (or plastic) EP film of low melting point, thus providing lubrication resistance to impact, high load and high temperature.
Protection against corrosion and rust
Due to the oxidation of petroleum derivatives or the action of additives, corrosion of steel and other non-ferrous metals often occurs.
Corrosion testing generally involves placing a strip of purple copper in oil and observing the changes in the copper after it is placed at 100°C for 3 hours. The rust protection test is carried out under the action of water and water vapor, and the steel surface will produce rust.
Rust resistance is measured by adding 30ml of distilled water or artificial seawater to 300ml of test oil, placing a steel bar in it, stirring at 54°C for 24 hours, and observing whether there is rust on the steel bar.
Petroleum products must have metallic anti-corrosive and rust-protective properties. In industrial lubricating oil standards, these two items are generally mandatory test items.
Foam resistance
Foam resistance refers to the ability of lubricating oil to resist foaming under mechanical agitation or aeration.
Foam can cause problems in lubrication systems, such as reducing lubrication efficiency and causing cavitation erosion. The foam resistance of lubricating oil is generally measured by a standardized test method, and the test results are used to classify the foam resistance level of lubricating oil.
Hydrolytic Stability
Hydrolytic stability refers to the stability of petroleum derivatives under the action of water and metals (mainly copper).
When the acid number of the petroleum product is high or when it contains additives that easily decompose into acidic substances in contact with water, this indicator may not meet the requirements.
The measurement method involves adding a certain amount of water to the test oil, mixing and shaking it with a copper foil at a certain temperature, and then measuring the acidity of the water layer and the weight loss of the copper foil.
Emulsion Resistance
In industrial lubricating oil, it is often unavoidable to mix some cooling water during use.
If the emulsion resistance of the lubricating oil is low, it will form an emulsion with the mixed water, making it difficult to discharge water from the bottom of the circulating oil tank, which may cause poor lubrication.
Therefore, emulsion resistance is an important physical and chemical property of industrial lubricating oil.
Generally, the oily product is vigorously stirred with 40ml of test oil and 40ml of distilled water at a certain temperature for a certain time, and then the time for the separation of the oil layer-water layer-emulsion layer into 40-37-3ml is observed.
For industrial gear oil, the test oil is mixed with water, stirred at a certain temperature and 6000 rpm for 5 minutes, left for 5 hours, and then the volume of oil, water and emulsion layer is measured.
Air release value
This is a requirement in hydraulic oil standards because in hydraulic systems, if the air dissolved in the oil cannot be released in time, it will affect the accuracy and sensitivity of the hydraulic transmission.
In severe cases, it may not meet the requirements of the hydraulic system. The method of measuring this property is similar to that of foam resistance, but measures the time for the release of air (mist) dissolved in the oil.
Rubber seal
Rubber seals are commonly used in hydraulic systems, and petroleum products in machines inevitably come into contact with some seals.
Petroleum products with poor rubber sealing can cause rubber swelling, shrinkage, hardening and cracking, affecting its sealing performance.
Therefore, petroleum products must have good adaptability to rubber. Hydraulic oil standards require a rubber seal index, which is measured by changing a certain size rubber ring after being immersed in oil for a certain period of time.
Shear stability
Petroleum products with the addition of viscosity improvers, during use, due to mechanical shear, the high molecular weight polymers in the oil are sheared, resulting in a decrease in the viscosity of the oil, affecting normal lubrication.
Therefore, shear stability is a special physical and chemical property that must be measured for such petroleum products.
There are many methods for measuring shear stability, including ultrasonic shear method, nozzle shear method, Weksler pump shear method and FZG gear machine shear method. Ultimately, these methods measure the rate of decrease in viscosity in the oil.
Solubility
Solubility is generally represented by the aniline point. The solubility limits of compound additives in oils of different grades are different, and the limit value of low-ash oil is greater than that of excessively alkaline oil, and the limit value of single-grade oil is greater than that of of multigrade oil.
Volatility
The volatility of base oil is related to oil consumption, viscosity stability and oxidation stability. These properties are particularly important for multigrade oils and energy-saving oils.
Rust-proof performance
Refers to the specific physicochemical properties that the anti-rust grease must have. Testing methods include wet test, salt spray test, stacked plate test, water displacement test, as well as slide box test and long-term storage test.
Electrical Performance
Electrical performance is a unique property of insulating oil, mainly including dielectric loss angle, dielectric constant, breakdown voltage and pulse voltage.
The degree of refining, impurities and water content of the base oil have a significant impact on the electrical performance of the oil.
Special physicochemical properties of lubricating grease
In addition to general physicochemical properties, special purpose grease has its own unique physicochemical properties.
For example, a lubricating grease with good water resistance requires a water resistance test; low temperature grease requires a low temperature torque test; multipurpose grease requires wear resistance under extreme pressure and rust prevention testing; long-life grease requires bearing life testing and so on.
There are corresponding test methods for determining these properties.
Other special physicochemical properties
In addition to general properties, each type of oil must have unique special properties.
For example, quenching oil requires determining the cooling rate; emulsified oil requires determination of emulsification stability; hydraulic guide rail oil requires determination of the anti-skid coefficient; spray lubricating oil requires determination of oil mist diffusivity; refrigeration oil requires pour point determination; low temperature gear oil requires cold start simulator test, etc.
These properties require a special chemical composition of the base oil or the addition of certain special additives to ensure them.
Notes on using lubricating oil:
Oil Storage:
Do not store oil vertically outdoors to avoid contamination by water and debris.
The oil can be stored upright indoors with the top facing up for easy extraction.
Tighten the sealing cap to maintain the oil drum seal.
Keep the drum surface clean and clearly marked.
Keep floors clean to facilitate timely discovery of oil spills.
Record inventory and use the first-in, first-out method.
For frequently used oil, use a switch to control the flow from an oil barrel holder.
Keep new oil separate from used oil and do not use a container containing used oil to store new oil to avoid contamination.
Oil Security:
Store the oil separately and do not place flammable materials around it.
Smoking is not permitted and open flames are not permitted in the oil storage area.
Equip with at least two fire extinguishers.
Do not accumulate oily rags or cleaning oil after cleaning the machinery to avoid combustion.
Store flammable special oils or chemical solvents separately and mark them with a flammable label.
Usage precautions:
Consult a lubrication specialist and use lubricants with appropriate specifications, minimizing the number of types of oil used.
Indicate the parts that need to be lubricated, the name of the oil, the lubrication cycle, etc. with simple diagrams for each machine and designate someone responsible to avoid using the wrong type of oil.
Clean and clean the oil suction pump, oil container and other containers and tools before adding oil each time.
Use dedicated containers for each type of oil and label them with the name of the oil to avoid contamination.
Before changing the oil, wash the machinery with solvents and do not use water-soluble cleaning products.
Keep a record of machinery maintenance after each addition or replacement of lubricating oil.
If abnormal conditions are found in the oil or if the oil reaches the oil change cycle, samples must be collected and sent to a professional company for chemical testing.
Environmental Protection and Health:
Do not dispose of used oil directly into the sewer or soil to avoid polluting the environment.
Collect waste oil and waste liquids in dedicated barrels and then deliver them to government-authorized recyclers. Don't discard them indiscriminately.
People with allergies or skin irritations should avoid direct contact with lubricating oil.
Do not wear oil-stained clothing or place oil-stained rags in a bag.
Do not use dirty rags to wipe oil from your skin to prevent metal fragments on the rags from scratching your skin and causing infection.
Glossary of technical terms
Abrasive Wear: Mechanical wear caused by the relative sliding of two surfaces in contact.
Additive: A small amount of material added to improve lubricating properties.
Adhesion Improver: An additive added to oils and greases to improve adhesion (e.g., polyisobutene).
Adhesive Lubricant: A lubricant with an adhesion enhancer added to prevent the lubricant from being expelled due to centrifugal force.
Antifriction Coating (AF), Anti-Wear Coating (AW): Widely used dry film solid lubricants, including room temperature curing and heat curing types.
The formula contains solid lubricating materials (called “raw materials”) and binding materials. See “binder.”
Anti-aging: Aging of the material caused by oxidation, overheating or the presence of certain metals (such as copper, lead, silver, etc.), which can be improved with the addition of certain additives (such as antioxidants).
ASTM: American Society for Testing and Materials.
Base Oil: Basic component of lubricating oil and grease.
Binder: Non-volatile medium or modeling agent used to increase the bond strength between solid lubricant particles or the degree of adhesion between a solid lubricant film and a friction surface.
Breaking torque: The torque required to break a bolt connection.
Chemical Inertness: (lubricant) and some substances do not react chemically.
Friction coefficient: The ratio between the friction force between two surfaces in contact and the normal force.
Low temperature performance: Indicated by cloud point, pour point and solidification point for lubricating oil, and by Kesternich flow pressure and low temperature torque tests for lubricating grease.
Colloid: A stable liquid suspension of particles (particle size 10^-5~10^-7cm) as solute (no particle sedimentation).
Complex Grease: A lubricating grease made from metallic soap and various acids as thickeners, particularly suitable for high temperatures and long-term use.
Consistency: Parameter of the lubricating grease, divided into gross penetration and worked penetration, measured according to the NLGI (National Lubricating Grease Institute) standard. Consistency is simply classified into nine grades, such as:
| Consistency level | Working taper (1/10mm) |
| 00 | No.: 400-430 |
| 0 | No.: 350-385 |
| 1 | No.: 310-340 |
| two | No.: 265-295 |
Density: the mass (in g) of lubricant per unit volume (in cm3) at 20°C.
Cleaner: Surfactant used to remove residual and sedimentary materials from surfaces.
Dispersion: ability of a liquid to disperse insoluble substances.
DN value: reference value for the grease used in bearings which is calculated by multiplying the bearing diameter (in mm) by the rotation speed (in revolutions per minute).
Dropping point: The temperature at which a lubricating grease changes from a semi-solid to a liquid state and is an indication of the heat resistance of the grease.
Dynamic viscosity: also known as absolute viscosity, this property reflects the internal resistance between fluid molecules when lubricating oil flows through a pipe or slot.
EP additive (extreme pressure): chemical substance that improves the lubricant's ability to withstand heavy loads and high temperatures, thus increasing the wear resistance of oils and greases.
Emcor Test: a corrosion resistance test for water-resistant greases that involves operating at least two grease-lubricated bearings in water for about a week, with a corrosion resistance value ranging from 0 to 5 (0 indicating no of corrosion and 5 indicating severe corrosion).
Ester oil: composed of acid and alcohol used as a lubricating material and in the production of lubricating greases.
Flash Point: The lowest temperature at which a mixture of oil vapor and air can ignite when exposed to a flame.
Fluorosilicone oil: silicone oil that contains fluorine atoms in its molecular structure.
Friction wear: type of mechanical-chemical wear caused by micromovements between two contact surfaces, resulting in corrosion and accumulation of oxides on the friction surface.
Friction: a resistance to tangential motion that occurs when two objects move relative to each other at their contact interface.
Grease: lubricating medium composed of base oil and a thickener.
Inhibitor: additive used in lubricants to delay aging and corrosion.
Pour Point: The highest temperature at which an oil sample does not move under specified test conditions, expressed in degrees Celsius.
Tipping Point: The lowest temperature at which an oil sample can flow under specified test conditions, expressed in degrees Celsius. It is a standard indicator used to measure the fluidity of lubricating oils at low temperature and is generally slightly higher than the pour point.
Perspectives for the Development of Lubricants
Over the next 10 years, demand for lubricants in the Asia-Pacific region will reach 15.5 million tons, with China responsible for 40% of regional demand.
By 2020, demand for lubricants in the Chinese market will double and consumption could surpass that in the United States.
The rapid growth in demand for automobile oils and the trend towards high-end automobile oils will lead the lubricant industry into a period of rapid development.
As the demand for automotive lubricants continues to increase year after year, the quality of lubricants will also achieve a breakthrough, with high-quality lubricants directly aligned with international standards.
Does high viscosity lubricant indicate good quality?
Generally, when the operating speed of parts is high, the load on the surface of parts may be lower and the viscosity of the corresponding lubricant is lower (for example, spindle oil).
On the other hand, the viscosity of the corresponding lubricant will be higher (e.g. gear oil). Of course, lubricant selection must ultimately follow the supplier's requirements for lubricant selection.
However, the quality of lubricants includes many indicators in addition to viscosity, so viscosity alone cannot be used to evaluate the quality of lubricants.
Lubricant
Lubricating oil, also known as lubricating grease, is a non-volatile oily lubricant usually derived from petroleum or extracted from animal and vegetable oils.
There are three main types of lubricating oil based on their origin: animal and vegetable oil, petroleum lubricating oil, and synthetic lubricating oil.
Petroleum lubricating oil accounts for more than 97% of total consumption, therefore lubricating oil generally refers to petroleum lubricating oil.
It is mainly used to reduce friction between moving parts and has other functions such as cooling, sealing, anti-corrosion, rust prevention, insulation, power transmission and impurity removal in machinery equipment.
Lubricating oil is produced using lubricating oil fractions and residual fractions from crude oil distillation units as raw materials, and then subjected to processes such as solvent deasphalting, solvent dewaxing, solvent refining, hydrogen refining or refining acid-base, bleaching, etc. , to remove or reduce components such as substances that form free carbon, substances with a low viscosity index, substances with low oxidation stability, paraffin and chemical substances that affect the color of the finished product.
Qualified lubricating oil base oil is obtained, and after mixing and adding additives, it becomes a lubricating oil product.
The main performance of lubricating oil is viscosity, oxidation stability and lubricity, which are closely related to the composition of lubricating oil fractions. Viscosity is an important quality indicator that reflects the fluidity of the lubricating oil.
Different usage conditions have different viscosity requirements. High viscosity lubricating oil should be selected for machines with heavy loads and low speeds.
Oxidation stability indicates the ability of petroleum products to resist oxidation in the environment of use due to temperature, air oxygen and metal catalysis.
After oxidation, the petroleum product will generate carbon-like substances mainly composed of small asphaltenes, viscous lacquer-like substances or films or viscous substances containing water according to the conditions of use, thereby reducing or losing its usability.
Lubricity indicates the anti-wear performance of the lubricating oil.
Functions of lubricating oil
Lubricating oil is a liquid lubricant used in various types of machines to reduce friction, protect machines and work parts, and mainly serves for lubrication, cooling, rust prevention, cleaning, sealing and plugging.
Lubricating oil represents 85% of all lubricants and there are many types and classes. Annual global use is about 38 million tons. The general requirements for lubricating oil are:
(1) Anti-friction and anti-wear, reducing friction resistance to save energy, reducing wear to extend mechanical life and improving economic efficiency;
(2) Cooling, requiring frictional heat to be discharged from the machine at any time;
(3) Sealing, requiring leak prevention, dust prevention and gas leak prevention;
(4) Anti-corrosion and rust prevention, requiring protection of the friction surface against oil deterioration or external corrosion;
(5) Clean washing, requiring the removal of dirt from the friction area;
(6) Stress dispersion and damping, dispersing loads, cushioning and reducing impact and shock;
(7) Kinetic energy transmission, such as hydraulic systems, remote control motors, and continuously variable transmissions.
Lubricating oil composition
Lubricating oil generally consists of two parts: base oil and additives. The base oil is the main component of the lubricating oil, determining its basic properties.
Additives can compensate and improve the performance deficiencies of the base oil, impart some new properties, and are an important component of the lubricating oil.
Lube oil storage
Lubricating oil from barrels and cans should be stored in warehouses as much as possible to avoid the impact of weather.
Opened barrels of lubricating oil must be stored inside the warehouse. Oil barrels should be placed horizontally and both ends of the barrel should be wedged with wooden wedges to prevent them from rolling.
Additionally, oil barrels should be checked regularly for leaks and that the markings on the surface of the barrel are clear.
If the barrel needs to be stored upright, it is recommended to invert the barrel so that the barrel lid is facing downwards or tilt the barrel slightly to prevent rainwater from accumulating on the surface of the barrel and flooding the lid. Water has adverse effects on any lubricating oil.
On the surface, it may appear that water cannot penetrate the intact barrel lid and enter the oil barrel, but oil barrels stored outdoors are exposed to intense sunlight during the day and cooler weather at night.
This thermal expansion and contraction can affect the air pressure inside the pipe.
During the day, the air pressure inside the barrel is slightly higher than atmospheric pressure, while at night it approaches a vacuum.
This pressure change between day and night can cause a “breathing” effect. Some of the air inside the barrel is “breathed out” during the day and the air is “breathed in” at night.
If the barrel lid is immersed in water, the water will inevitably enter the barrel with the air, and over time the amount of water mixed into the oil will be considerable.
When removing the oil, the oil barrel must be placed horizontally on a wooden support of suitable height, a tap must be installed on the lid of the barrel to drain the oil and a container must be placed under the tap to prevent drips.
Alternatively, the oil barrel can be placed vertically and a hand pump can be used to extract the oil through a tube inserted into the barrel lid.
Bulk oil stored in oil tanks is inevitably contaminated with condensed water and impurities, which eventually accumulate at the bottom of the tank, forming a layer of sludge-like material, which contaminates the lubricating oil.
Therefore, the bottom of the tank must be designed to be concave or inclined, and a drain plug must be installed for timely discharge of waste. As far as possible, the inside of the oil tank should be cleaned regularly.
Temperature has a greater impact on lubricating grease than lubricating oil. Prolonged exposure to high temperatures (e.g. sunlight) can cause the oil components in the lubricating grease to separate.
Therefore, lubricating grease barrels must be stored inside the warehouse, with the barrel mouth facing upwards.
The opening of the barrel for storing lubricating grease is larger, facilitating the entry of impurities and water.
After use, the barrel cap must be closed tightly immediately.
Storing lubricating oil in very cold or very hot places should be avoided as it may cause adverse effects to the oil.
Lubricating Oil Base Oil
Lubricating oil base oil can be classified into two main categories: mineral base oil and synthetic base oil. Mineral base oil is widely used and accounts for a large proportion (more than 95%) of lubricating oil consumption, but in some specific applications synthetic base oil lubricants are required, which has led to the rapid development of synthetic base oil.
Mineral base oil is extracted from crude oil. The main production processes of lubricating oil base oil include atmospheric distillation, solvent deasphalting, solvent refining, solvent dewaxing and clay finishing or hydrogenation.
China revised its lubricating oil base oil standard in 1995, mainly modifying the classification method and adding two special base oil standards for low pour point and deep refining. The most important aspect of mineral lubricating oil production is choosing the best crude oil.
The chemical composition of mineral base oil includes a mixture of high-boiling point, high-molecular-weight hydrocarbons and non-hydrocarbon mixtures.
Its composition generally includes alkanes (straight chain, branched chain and multi-branched chain), cycloalkanes (single ring, double ring and multiple ring), aromatics (single ring aromatics, multiple ring aromatics), cycloalkyl aromatics and non-hydrocarbon compounds such as oxygen, nitrogen, organic sulfur compounds and colloidal compounds and asphaltenes.
In the past, major foreign oil companies classified base oil into paraffin base oil, naphthene base oil and intermediate base oil according to the properties of crude oil and processing technology.
Since the 1980s, with the development of engine oil, lubricating oil tends to be low viscosity, multigrade and universal.
Higher requirements have been put forward for the base oil viscosity index, and the previous base oil classification method cannot adapt to this trend.
Therefore, major foreign oil companies now generally classify base oil according to viscosity index, but there is no strict standard.
In 1993, API classified base oil into five categories (API-1509) and included it in the EOLCS (API Engine Oil Licensing and Certification System).
