Lubricants

Overview

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AUTHOR

Jean AYEL: Engineer from the École nationale supérieure des arts et industries de Strasbourg and the École nationale supérieure du pétrole et des moteurs - Doctor-Engineer - Head of the Petroleum and Energy Applications program at the École nationale supérieure du pétrole et des moteurs

INTRODUCTION

Depending on their physical state, lubricants can be classified into three groups:

liquid lubricants: of vegetable and animal origin (fatty oils), mineral (petroleum oils) and synthetic;
Semi-solid or plastic lubricants, which mainly include lubricating greases, but also waxes, kerosenes and petroleum jelly for lubricating applications;
solid lubricants: lamellar, polymeric, soft metals, salts, oxides, etc.

These different lubricants can be used in the form of dispersions, emulsions or solutions in water, whenever high cooling power (high-speed metalworking) or fire resistance (HF-type hydraulic fluids) is required.

The first two categories of lubricants (oils and greases) contain a variable quantity of additives (up to 25% by mass) depending on the application and severity of service.

To situate the relative importance of each lubricant group, it should be remembered that liquid lubricants account for 96% of the market, greases for 3% and solid lubricants for around 1%.