Page 156 - Wurth Total Catalogue

gloSSary of tHe moSt important tribological termS

Terms Explanation
Additive Substances added to lubricants in small quantities to improve their performance.
Emergency Running Property Ability of lubricants to counteract wear and high friction in case of insufficient lubrication.
Emergency running properties are often achieved with solid lubricants like PTFE.
OMC 2 Liquid organometallic compound that offers advantages of molybdenum sulphide (reduced friction values,
decreased wear) without having the disadvantages of a solid lubricant
(poor stabilisation in an oil).
Consistency Consistency is a measure of the character of lubricants. It is measured as the un- worked or the worked
penetration. The consistency is specified according to the NLGI (National Lubricating Grease Institute).
For simpler description of the consistency of lubricating greases, the entire consistency range is divided into
9 classes - measured as the worked penetration.
Viscosity The viscosity of a liquid is understood as the resistance which the molecules of a liquid put up against their
movement. This resistance is also called internal friction.
Drop Point The lubricating grease to be tested is heated in a standardised crucible at a defined speed until liquefaction
occurs, i.e. until the first drop of the lubricating grease falls.
The temperature measured in the process is specified.
Wear Factor Wear results through friction and contact of the sliding partners after the lubricating film is broken through.
The wear factor is a measure of the degree of wear.
Degree of Corrosion The corrosion is judged by evaluating test plates. The degree of corrosion indicates the amount of corrosion.
The evaluation scale ranges from 0 (no corrosion) to 3. (heavy corrosion)
Low-viscosity Grease Lubricating greases with a semi-liquid consistency for lubricating slowly running gearboxes, and gearboxes
which are difficult to seal off for design reasons.
NLGI Class See Consistency.
Density Density is the weight of a lubricant in g per ml at room temperature (20°C).
Flash Point The flash point is a variable which enables the fire danger of a substance to be estimated.
The substance to be tested is slowly heated in an open (ISO 2592) or closed (DIN 51755) crucible, and a
small defined flame is moved over it until the resulting gases over the substance to be tested flare up briefly.
Base Oil Base oil is the main component of lubricating greases and oils.
Oxidation Chemical reaction which leads to ageing of lubricants.
Synthetic Oils In contrast to mineral oils, these are synthetically produced oils. Synthetic oils usually have a good viscosity
to temperature behaviour, a low coking tendency, a low pour-point, high thermal stability and good chemical
resistance.
Thickener Lubricating greases consist of an oil component, which is contained in the thickener like in a sponge.
Common thickeners include soaps like lithium, calcium and sodium soaps, or complex soaps like calcium,
barium and lithium complex soaps, as well as polycarbamide and bentonite.
Coking Residue Residues form when oils are subject to high thermal loading.
SKF-Emcor method Standardised tester for evaluating corrosion protection properties of lubricants, in rolling
PTFE Polytetrafluor ethylene, the chemical name of Teflon ®.
SRV Test (DIN 51834) Model tester for lubricants and materials in a vibration-friction system. The load, temperature and geometry
can be adjusted in accordance with the requirements.

AUS. pub. 09/10 ©

04 1008