Lubricant

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Lubricants are an essential part of modern machinery. From computer hard disk drives to the space shuttle, virtually every moving part requires lubrication.

 'Purpose '

Lubricants perform the following key functions. Keep moving parts apart Reduce friction Transfer heat Carry away contaminants & debris Transmit power Protect against wear Prevent corrosion

 'History '

Romans used rags dipped in animal fat to lubricate wagon wheels however the science of lubrication (tribology) really only took off with the industrial revolution in the 19th century.

 'General composition '

Lubricants are generally composed of a majority of base oil and a minority of additives to impart desirable characteristics.

 'Types of lubricants '

Liquid including emulsions and suspensions Solid Greases Pastes  'Liquid Lubricants ' Liquid lubricants may be characterized in many different ways. One of the most common ways is by the type of base oil used. Following are the most common types. Water Mineral oils Vegetable (natural oil) Synthetic oils Others Note that although generally lubricants are based on one type of base oil or another it is quite possible to use mixtures of the base oils to meet performance requirements.    'Water   ' Water can be used on its own or as a major component in combination with one of the other base oils.    'Mineral Oil   ' This term is used to encompass lubricating base oil derived from crude oil. API designates several types of lubricant base oil identified as: Group I - Saturates < 90% and/or Sulphur >0.03% and Viscosity Index > 80 to <120 Group II – Saturates >= 90% and Sulphur <0.03% and Viscosity Index >= 80 to <=120 Group III – Saturates >= 90% Sulphur <0.03% and Viscosity Index >= 120 The lubricant industry commonly extends this group terminology to include Group I+ with a Viscosity Index of 100 -105 Group II+ with a Viscosity Index of 110 - 120 Group III+ with a Viscosity Index of >= 140 Group IV – Poly alpha olefins (PAO) Group V – All others not included above    'Vegetable (natural) oils   ' These are primarily triglyceride esters derived from plants and animals. For lubricant base oil use the vegetable derived materials are preferred. Common ones include high oleic canola oil, palm oil, sunflower seed oil and rapeseed oil from vegetable and Tall oil from animal sources. Many vegetable oils are often hydrolyzed to yield the acids which are subsequently combined selectively to form specialist synthetic esters.     Synthetic Oils     Poly alpha olefins (PAO) see polyolefin Synthetic Esters Polyalkylene glycols (PAG) Phosphate Esters Alkylated Naphthalenes (AN) Silicate esters Ionic fluids Note: In USA certain Group III base stocks may be designated as synthetic.     Solid lubricants     Graphite Molybdenum disulphide Teflon Boron nitride (http://www.advceramics.com/geac/downloads/documents/81503.pdf)

Additives

A large number of additives are used to impart performance characteristics to the lubricants. The main families of additives are: Anti-oxidants Anti-wear Metal Deactivators Corrosion inhibitors Rust inhibitors Friction modifiers Extreme Pressure Anti-foaming Demulsifying / Emulsifying

Application by fluid types

Automotive Engine oils Petrol (Gas) engine oils Diesel engine oils 2-stroke engine oils Automatic transmission fluids Gearbox fluids Brake fluids Hydraulic fluids Industrial Hydraulic fluids Compressor oils Gear oils Aviation Gas Turbine engine oils Piston engine oils Marine Top engine oil Crankcase fluids Stern tube lubricants

Disposal and Environmental issues

Societies and Industry Bodies

API – American Petroleum Institute STLE – Society of Tribologists and Lubrication Engineers NLGI – National Lubricating Grease institute SAE – Society of Automotive Engineers ILMA – Independent lubricant manufacturer association

Major Publications

 'Peer reviewed ' Tribology Transactions Journal of Synthetic Lubricants  'Trade periodicals ' Tribology and Lubrication Technology Lubes n’ Greases Compoundings Chemical Market Review Machinery lubrication  Prior text below: It has several errors in it that I hope will get corrected in due course.  A  'lubricant ' (colloquially,  'lube ', although this usually refers to personal lubricants) is a substance (usually a liquid) introduced between two moving surfaces to reduce the friction and wear between them. An understanding of how lubricating systems work is crucial to the selection of a lubricant for a particular application. Any surface contains irregularities, even when polished to a mirror finish. These irregularities may not be visible, except under a microscope. A lubricant provides a protective film which allows for two touching surfaces to be separated, thus lessening the friction between them. Typically lubricants contain 90% base oil (most often petroleum fractions, called mineral oils) and less than 10% additives. Vegetable oils or synthetic liquids such as hydrogenated polyolefins, esters, silicone, fluorocarbons and many others are sometimes used as base oils. Additives deliver reduced friction and wear, increased viscosity, resistance to corrosion and oxidation, aging or contamination, etc. Non-liquid lubricants include grease (lubricant) , powders (dry graphite, Teflon, Molybdenum disulfide, etc.), teflon tape used in plumbing, air cushion and others. Alternative way to reduce friction and wear is to use bearings such as ball bearings, roller bearings or foil bearings or to use sound, in the case of acoustic lubrication. Lubricants are also added to some fuels. Sulfur impurities in fuels also provide some lubrication properties, which has to be taken in account when switching to a low-sulfur diesel; biodiesel is a popular diesel fuel additive providing additional lubricity. In addition to automotive and industrial applications, lubricants are used for many other purposes, including personal hygiene, e.g. K-Y Jelly, often used as a sexual lubricant, bio-medical applications (e.g. lubricants for Replacement joints) and others.

Reference

1 Boughton and Horvath, 2003, Environmental Assessment of Used Oil Management Methods, California Environmental Protection Agency, Department of Toxic Substances Control

This article is licensed under the GNU Free Documentation License.It uses material from the Wikipedia article 'Lubricant' (click for full Wikipedia text) Hide