Common knowledge of lubricants

Generally the product of fractional distillation of petroleum, but also from animal and vegetable oils. Also known as "grease". It is a non-volatile, oily lubricant. According to its source of animal and vegetable oils, petroleum lubricants and synthetic lubricants three categories. The amount of petroleum lubricants accounted for more than 97% of the total amount of lubricants, so lubricants often refer to petroleum lubricants. Mainly used to reduce the friction between the surfaces of moving parts, and at the same time on machinery and equipment with cooling, sealing, corrosion, rust, insulation, power transmission, cleaning impurities and so on. Mainly from the crude oil distillation unit of the lubricating oil fraction and residual oil fraction as raw materials, through the solvent deasphalting, solvent dewaxing, solvent refining, hydrogenation refining or acid and alkali refining, clay refining and other processes, to remove or reduce the formation of free carbon substances, low-viscosity index of the material, oxidation stability of the material is poor, paraffin waxes, as well as affect the color of the finished product of the chemical substances and other components, to obtain qualified lubricating oil base stock oils, after the mixing and adding additives, it becomes a lubricant. After combining and adding additives, it becomes lubricating oil products. The most important properties of lubricants are viscosity, oxidative stability and lubricity, which are closely related to the composition of lubricant fractions. Viscosity is an important quality indicator reflecting the fluidity of the lubricant. Different conditions of use have different viscosity requirements. Heavy load and low speed machinery should use high viscosity lubricants. Oxidation stability indicates that the oil in the use of the environment, due to temperature, air oxygen and metal catalytic effect of the performance of the antioxidant capacity. After oxidization, the oil will generate fine asphaltene-based carbonaceous substances, sticky varnish or varnish film, or sticky water-containing substances according to the conditions of use, thus reducing or losing its performance. Lubricity indicates the lubricant's wear-reducing properties.

The role of lubricants

Lubricants are used in various types of machinery to reduce friction, to protect the machinery and processed parts of the liquid lubricant, mainly lubrication, cooling, rust, cleaning, sealing and cushioning and so on. Lubricants account for 85% of all lubricating materials, a wide range of types of grades, now the world's annual consumption of about 38 million tons. The total requirements of the lubricant is:

(1) anti-motor anti-wear, reduce frictional resistance to save energy, reduce wear and tear in order to extend the life of machinery, improve economic efficiency;

(2) cooling, the requirements of the friction at any time to discharge the heat out of the machine;

(3) sealing, the requirements of the anti-leakage, anti-dust, anti-stringing gas;

(4) corrosion and rust, the requirements of the friction to protect the friction Surface from oil deterioration or foreign erosion;

(5) cleaning and flushing, the requirements of the friction area scale cleaning and exclusion;

(6) Stress dispersion cushioning, dispersal of loads and moderating the impact and vibration damping;

(7) kinetic energy transfer, hydraulic systems and remote control motors and friction stepless speed change, etc..

Lubricant composition

Lubricants are generally composed of two parts: base oil and additives. Base oil is the main component of the lubricant, determines the basic properties of the lubricant, additives can make up and improve the base oil performance deficiencies, give some new performance, is an important part of the lubricant.

Storage of lubricants

Barrels and cans of lubricants should be stored in warehouses where possible to avoid the effects of climate, and open barrels of lubricants must be stored in the warehouse. The drums should be placed in a lying position, and the ends of the drums should be wedged tightly with wooden wedges to prevent them from rolling. In addition, the drums should be checked regularly for leaks and for the clarity of the markings on the drum surface. If the drum must be placed in a straight position, it should be inverted with the lid down or slightly tilted to prevent rainwater from collecting on the surface and flooding the drum. Water has an adverse effect on any lubricant.

On the surface, water is not likely to penetrate a full drum lid and enter the drum, however, a drum stored outdoors, exposed to the sun during the day and cooler at night, will affect the pressure of the air inside the drum; slightly above atmospheric during the day and close to a vacuum at night. This day and night pressure shift will produce a "breathing" effect, daytime part of the air is "exhaled" outside the barrel, the night air is "inhaled" in the barrel, if the barrel lid is immersed in water, then the water will inevitably be removed with the air at night. If the lid is immersed in water, then the water will inevitably enter the barrel with the air at night, and the water mixed in the oil will naturally be quite substantial as the days and months accumulate.

Take the oil, should be lying on a height of the barrel on a wooden frame, in the barrel surface of the cover mouth with a faucet to release the oil, and in the faucet under a container, to prevent dripping and splashing. Or put the barrel straight from the barrel lid mouth inserted into the oil pipe through the hand pump to get oil.

Bulk oil stored in tanks inevitably condensed water and dirt mixed in, and eventually gathered in the bottom of the tank to form a layer of sludge-like substances, so that the lubricating oil is contaminated. So the tank bottom design to nest butterfly or tilt is appropriate, and the installation of drainage plug, in order to discharge the residue on time. Within the possible range, the tank interior should be cleaned regularly.

The impact of temperature on grease is greater than on lubricants, long-term exposure to high temperatures (eg: sun exposure), can make the grease in the oil component separation, so the grease barrel should be prioritized for storage in warehouses, the barrel mouth upward vertical put is appropriate. The mouth of the grease pail is larger, so dirt and water can penetrate more easily, and the lid should be tightened immediately after use. Too low or too high a temperature has a negative impact on the lubricant, so it is not advisable to store the lubricant for a long time in a place that is too cold or too hot.　

Lubricant base oil

Lubricant base oil is mainly divided into two categories: mineral base oil and synthetic base oil. Mineral base oils are widely used, the amount of (about 95%), but some applications must use synthetic base oils formulated products, thus making the rapid development of synthetic base oils.

Mineral base oils are refined from crude oil. The main production process of lubricant base oils are: atmospheric decompression distillation, solvent deasphalting, solvent refining, solvent dewaxing, white earth or hydrogenated supplemental refining. 1995 revised China's existing standards for lubricant base oils, the main modification of the classification method, and the addition of a low condensate and depth of refinement of two categories of special base oil standards. The most important thing in the production of mineral-based lubricants is the selection of the best crude oil.

The chemical composition of mineral base oils includes a mixture of high boiling point, high molecular weight hydrocarbons and non-hydrocarbons. Its composition is generally alkanes (straight chain, branched chain, multi-branched chain), cycloalkanes (monocyclic, bicyclic, polycyclic), aromatic hydrocarbons (monocyclic aromatics, polycyclic aromatics), cycloalkyl aromatic hydrocarbons, as well as oxygen-containing, nitrogen-containing, sulfur-containing organic compounds and gums, asphaltene and other non-hydrocarbon compounds.

Foreign oil companies used to be based on the nature of the crude oil and processing technology base oils are divided into paraffin-based base oils, intermediate base oils, naphthenic base oils, etc. Since the 1980s, the development of engine oil as a precursor to the lubricating oil tends to be low-viscosity, multigrade, generalized, the viscosity index of the base oil put forward a higher demand for the original method of classification of base oils can not be adapted to this trend of change. The original base oil classification method can no longer adapt to this trend of change. Therefore, the major foreign oil companies are generally based on the size of the viscosity index classification, but there has been no strict standards. API in 1993, the base oil is divided into five categories (API-1509), and will be and such as the EOLCS (API engine oil licensing certification system), the classification method is shown in Table 1

(Table 1) API-1509 Base Oil Classification Criteria < /p>

Test Methods: ASTM D2007, ASTM D2270, ASTM D2622/D4294/D4927/D3120

Category: Saturated Hydrocarbon Content/%, Viscosity Index VI, Sulfur Content/% (Mass Fraction)

Class I: <90%, 80~120, >0.3

Class II: >90%, 80~120, <0.3

Class III: >90%, >120, <0.3

Class IV: Polyalphaolefin (PAO)

Class V: All base oils that are not Class I, II, III, or IV

Class I base oils are usually made from the same old "old three sets". The traditional "old three sets" of production process, from the production process, the production process of I base oils is basically a physical process, does not change the structure of hydrocarbons, the production of base oil quality depends on the content and nature of the ideal components of the raw material. Therefore, this type of base oil is limited in performance.

Type II base oils are produced through a combination of processes (solvent process and hydrogenation process combined), the process is mainly based on chemical processes, not restricted by raw materials, and can change the original hydrocarbon structure. As a result, II base oils have fewer impurities (aromatic content less than 10%), higher saturated hydrocarbon content, better thermal stability and oxygen resistance, and better low-temperature and soot dispersion properties than I base oils.

Type III base oils are produced by the full hydrogenation process, and compared with Type II base oils, they are high viscosity index hydrogenated base oils, also known as unconventional base oils (UCBO).Type III base oils are far superior to Type I and Type II base oils in terms of their performance, especially in terms of their high viscosity index and low volatility. Some Group III oils are comparable in performance to polyalphaolefins (PAO) and are much less expensive than synthetic oils.

Class IV base oils refer to polyalphaolefin (PAO) synthetic oils. Commonly used production methods include paraffin decomposition and ethylene polymerization. PAO can be divided into low polymerization, medium polymerization and high polymerization according to the different degrees of polymerization, which are used to modulate different oils. This kind of base oil compared with mineral oil, no S, P and metal, because it does not contain wax, so the pour point is very low, usually below -40 ℃, viscosity index is generally more than 140. but PAO boundary lubricity is poor. In addition, because of its own polarity is small, the ability to dissolve polar additives is poor, and there is a certain degree of contraction of the rubber seal, but these problems can be overcome by adding a certain amount of esters. In addition to I ~ IV base oil other synthetic oils (synthetic hydrocarbons, esters, silicone oil, etc.), vegetable oils, recycled base oils, etc. collectively referred to as V base oil.

The main technical requirements for lubricant base oils in the 21st century are: good thermal and oxidative stability, low volatility, high viscosity index, low sulfur/sulfur-free, low viscosity, and environmental friendliness. The traditional "old three sets" process of production of class I lubricant base oils can not meet the future of lubricants such requirements, hydrogenation method of production of class II or III base oils will become the mainstream of the market. China's lubricant base oil standard was established in 1983, in order to adapt to the modulation of high-grade lubricants, the original standard was revised in 1995, the implementation of the lubricant base oil classification methods and specifications standard QSHR 001-95, see Table 2 for details. this classification method and the international classification of the essential difference.

(Table 2) China's classification of base oils

Class: Viscosity Index VI

Ultra-high viscosity index: IV ≥ 140

Very high viscosity index: 120 ≤ VI & lt; 140

High viscosity index: 90 ≤ VI & lt; 120

Medium viscosity index: 40 ≤ VI & lt; 90

Medium viscosity index: 40 ≤ VI & lt. 90

Viscosity index: VI<40

Universal base oils: UHVI VHVI HVI MVI LVI

Specialized base oils Low condensate: UHV IW V HVIW HVIW MVIW

Deeply refined: UHVIS VHVIS HVIS MVIS

The standard classifies base oils into low viscosity indices according to viscosity index. The base oils are categorized into 5 grades: Low Viscosity Index (LVI), Medium Viscosity Index (MVI), High Viscosity Index (HVI), Very High Viscosity Index (VHVI) and Ultra High Viscosity Index (UHVI) base oils. According to the scope of use, base oils are divided into general-purpose base oils and specialized base oils. Specialized base oils are further divided into low condensation base oils (add W to the code) which are suitable for products such as multigrade engine oils, low-temperature hydraulic oils and hydraulic transmission fluids, etc., and y refined base oils (add S to the code) which are suitable for products such as turbine oils and extreme-pressure industrial gear oils. Among them, HVI oil and VI>80's MVI oil belong to Class I base oil of international classification; while VI<80's MVI base oil and LVI base oil are not included in the class at all; VHVI and UHVI are classified as Class II and III base oils according to the international classification but there are no clear regulations on sulfur content and saturated hydrocarbons.