Lubricity

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Lubricity is the measure of the reduction in friction and or wear by a lubricant. The study of lubrication and wear mechanisms is called tribology.

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Measurement of lubricity

The lubricity of a substance is not a material property, and cannot be measured directly. Tests are performed to quantify a lubricant's performance for a specific system. This is often done by determining how much wear is caused to a surface by a given wear-inducing object in a given amount of time. Other factors such as surface size, temperature, and pressure are also specified. For two fluids with the same viscosity, the one that results in a smaller wear scar is considered to have higher lubricity. For this reason, lubricity is also termed a substance's anti-wear property.

Examples of test setups include "Ball-on-cylinder" and "Ball-on-three-discs" tests.

Lubricity in diesel engines

In a modern diesel engine, the fuel is part of the engine lubrication process. Diesel fuel naturally contains compounds that provide lubricity, but because of regulations in many countries (such as the US and the EU countries), sulphur must be removed from the fuel before it can be sold. The hydrotreatment of diesel fuel to remove sulphur also removes the compounds that provide lubricity. Reformulated diesel fuel that does not have biodiesel added has a lower lubricity and requires lubricity improving additives to prevent excessive engine wear. [1] [2] [3]

See also

Related Research Articles

A lubricant is a substance, usually organic, introduced to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. It may also have the function of transmitting forces, transporting foreign particles, or heating or cooling the surfaces. The property of reducing friction is known as lubricity.

Diesel fuel Liquid fuel used in diesel engines

Diesel fuel in general is any liquid fuel used in diesel engines, whose fuel ignition takes place, without any spark, as a result of compression of the inlet air mixture and then injection of fuel. Diesel engines have found broad use as a result of higher thermodynamic efficiency and thus fuel efficiency. This is particularly noted where diesel engines are run at part-load; as their air supply is not throttled as in a gasoline (petrol) engine, their efficiency still remains very high.

Biodiesel vegetable oil- or animal fat-based diesel fuel

Biodiesel is a form of diesel fuel derived from plants or animals and consisting of long-chain fatty acid esters. It is typically made by chemically reacting lipids such as animal fat (tallow), soybean oil, or some other vegetable oil with an alcohol, producing a methyl, ethyl or propyl ester.

Motor oil Lubricant used for lubrication of internal combustion engines

Motor oil, engine oil, or engine lubricant is any one of various substances that consist of base oils enhanced with various additives, particularly antiwear additives, detergents, dispersants, and, for multi-grade oils, viscosity index improvers. Motor oil is used for lubrication of internal combustion engines. The main function of motor oil is to reduce friction and wear on moving parts and to clean the engine from sludge and varnish (detergents). It also neutralizes acids that originate from fuel and from oxidation of the lubricant (detergents), improves sealing of piston rings, and cools the engine by carrying heat away from moving parts.

Lubrication The presence of a material to reduce friction between two surfaces.

Lubrication is the process or technique of using a lubricant to reduce friction and wear and tear in a contact between two surfaces. The study of lubrication is a discipline in the field of tribology.

Wear Damaging, gradual removal or deformation of material at solid surfaces

Wear is the damaging, gradual removal or deformation of material at solid surfaces. Causes of wear can be mechanical or chemical. The study of wear and related processes is referred to as tribology.

Tribology is the science and engineering of interacting surfaces in relative motion. It includes the study and application of the principles of friction, lubrication, and wear. Tribology is highly interdisciplinary. It draws on many academic fields, including physics, chemistry, materials science, mathematics, biology, and engineering. People who work in the field of tribology are referred to as tribologists.

Synthetic oil lubricant consisting of chemical compounds that are artificially made

Synthetic oil is a lubricant consisting of chemical compounds that are artificially made. Synthetic lubricants can be manufactured using chemically modified petroleum components rather than whole crude oil, but can also be synthesized from other raw materials. The base material, however, is still overwhelmingly crude oil that is distilled and then modified physically and chemically. The actual synthesis process and composition of additives is generally a commercial trade secret and will vary among producers.

Cetane number is an indicator of the combustion speed of diesel fuel and compression needed for ignition. It plays a similar role for diesel as octane rating does for gasoline. The CN is an important factor in determining the quality of diesel fuel, but not the only one; other measurements of diesel fuel's quality include energy content, density, lubricity, cold-flow properties and sulphur content.

Ultra-low-sulfur diesel (ULSD) is diesel fuel with substantially lowered sulfur content. Since 2006, almost all of the petroleum-based diesel fuel available in Europe and North America has been of a ULSD type.

Oil analysis (OA) is the laboratory analysis of a lubricant's properties, suspended contaminants, and wear debris. OA is performed during routine predictive maintenance to provide meaningful and accurate information on lubricant and machine condition. By tracking oil analysis sample results over the life of a particular machine, trends can be established which can help eliminate costly repairs. The study of wear in machinery is called tribology. Tribologists often perform or interpret oil analysis data.

Tribometer An instrument that measures tribological quantities

A tribometer is an instrument that measures tribological quantities, such as coefficient of friction, friction force, and wear volume, between two surfaces in contact. It was invented by the 18th century Dutch scientist Musschenbroek

Friction modifiers are added to lubricants in order to reduce friction and wear in machine components. They are particularly important in the boundary lubrication regime, where they can prevent solid surfaces from coming into direct contact, substantially reducing friction and wear.

Oil additives are chemical compounds that improve the lubricant performance of base oil. The manufacturer of many different oils can utilize the same base stock for each formulation and can choose different additives for each specific application. Additives comprise up to 5% by weight of some oils.

Dry lubricants or solid lubricants are materials that, despite being in the solid phase, are able to reduce friction between two surfaces sliding against each other without the need for a liquid oil medium.

Crankcase dilution is a phenomenon of internal combustion engines in which unburned diesel or gasoline accumulates in the crankcase. Excessively rich fuel mixture or incomplete combustion allows a certain amount of fuel to pass down between the pistons and cylinder walls and dilute the engine oil. It is more common in situations where fuel is injected at a very high pressure, such as in a direct-injected diesel engine.

Koehler Instrument Company, Inc.

Koehler Instrument, or Koehler, is a US company which provides petroleum and petrochemical testing equipment and technical support services to testing laboratories worldwide. The company’s corporate headquarters is in Holtsville, NY and the manufacturing headquarters is in Bohemia, NY.

Internal combustion engines come in a wide variety of types, but have certain family resemblances, and thus share many common types of components.

Internal combustion engine Engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber

An internal combustion engine (ICE) is a heat engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combustion engine, the expansion of the high-temperature and high-pressure gases produced by combustion applies direct force to some component of the engine. The force is applied typically to pistons, turbine blades, rotor or a nozzle. This force moves the component over a distance, transforming chemical energy into useful work.

HFRR Lubrication measurement

HFRR is a measurement for lubrication of Diesel or heating oil and stands for high frequency reciprocating rig. The value is given in μm, lower is better. The measured value is the diameter of the flattening of the ball after the test.

References

  1. Reformulated Diesel Fuels and Fuel Injection Equipment; Author: Hugh C. Grigg (Lucas Powertrain Systems) Presented at the New Fuels and Vehicles for Cleaner Air Conference, January 11-12, 1994, Phoenix, Arizona. (Retrieved via Google from a publication of the National Biodiesel Board, entitled Lubrication)
  2. Fuels for Diesel Engines — Diesel Fuel Injection Equipment Manufacturers Common Position Statement, Signed by: Delphi Diesel Systems, Stanadyne Automotive Corp., Denso Corporation, and Robert Bosch GmbH, issued June, 2000 (Retrieved via Google from a publication of the National Biodiesel Board, entitled Lubrication)
  3. Diesel Fuel Lubricity Authors: Paul Lacey and Steve Westbrook (Southwest Research Institute) SAE paper 950248, International Congress and Exposition, Detroit, Michigan, February 27-March 2, 1995 (Retrieved via Google from a publication of the National Biodiesel Board, entitled Lubrication)