What is a Grease?

A grease is best thought of as a sponge full of oil, with the sponge being the “base“ or thickener. It holds the oil and additives in place and gives the grease the basic characteristics such as drop point and water resistance. The oil content, typically 80-90% of the grease, provides most of the lubrication performance. To achieve the desired characteristics of a grease, careful selection of base lubricating oil viscosity, base type additives and fillers is essential.

When Are Greases Used

Greases are generally used in place of oil in the following situations:

  • The manufacturer specifies a grease and a lubricant is not required for cooling.
  • Where the grease acts as a seal to prevent entry of contaminants or loss of lubricant.
  • Soft grease can be used in place of oils in gearboxes with worn or ineffective seal or where oils would be thrown off the bearing surfaces or leak past seals.
  • Lubrication points can only be reached during maintenance shutdowns.
  • It is important to maintain lubricant in the bearing area during periods of prolonged shutdowns or frequent stop-start operations (oil drains away when a machine is stopped but a grease does not).
  • Where noise reduction is important.
  • To decrease the frequency of lubrication.
  • In worn bearings previously lubricated by oil to reduce noise and extend useful life.
  • Resists leakage, dripping or undesirable throw off.
  • The main advantage of grease over a fluid are its potentially longer life convenience and ease of application.

Lubricating Oil

This is usually a mineral oil although synthetic oils are used for extreme temperature applications. Careful selection is required to suit the applications for high speed light loads. A light oil should be selected for heavy loads and slower speeds might be necessary if prolonged high temperatures are likely to be experienced. A light oil may evaporate too readily for good load carrying capacity.

Grease Base

The base of a grease is the thickener used to produce the grease structure .It solidifies the liquid to make into a grease.

Thickeners 

A wide range of materials are used as thickeners such as:-

  • Metallic soaps
  • Calcium, Sodium, Lithium , Aluminium and others
  • Metalic soaps plus  complexing agents
  • Clacium complex, Lithium complex, Aluminium complex .
  • Non Soap Greases
  • Organo Clay, Polyurea, Silica, Carbon Black , Dyes and Organic Polymers.

Additives and Fillers

A variety of compounds maybe added to improve specific properties such as

  • Oxidation inhibitors
  • Corrosion Inhibitors
  • Extreme Pressure additivies
  • Adhesive or tacky agents
  • Solid additives such as Molybdenum disulphide and graphite flakes

Types Of Castrol Grease

  • Spheerol
  • Tribol Range of high performance greases
  • Optimol Range of high performance greases

This information has been sourced, reviewed and adapted from materials provided by Castrol.

For more information on this source, please visit Castrol.

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