Copy of `Lubrication and Oil Analysis Dictionary`

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Lubrication and Oil Analysis Dictionary Category: General technical and industrial > Oil terms Date & country: 25/09/2008, USA Words: 421

Viscosity
measurement of a fluid's resistance to flow. The common metric unit of absolute viscosity is the poise, which is defined as the force in dynes required to move a surface one square centimeter in area past a parallel surface at a speed of one centimeter per second, with the surfaces separated by a fluid film one centimeter thick. In addition to kinematic viscosity, there are other methods for dete...

Viscosity grade
any of a number of systems which characterize lubricants according to viscosity for particular applications, such as industrial oils, gear oils, automotive engine oils, automotive gear oils, and aircraft piston engine oils.

Viscosity index
a commonly used measure of a fluid's change of viscosity with temperature. The higher the viscosity index, the smaller the relative change in viscosity with temperature.

Viscosity index improvers
additives that increase the viscosity of the fluid throughout its useful temperature range. Such additives are polymers that possess thickening power as a result of their high molecular weight and are necessary for formulation of multi-grade engine oils.

Viscosity modifier
lubricant additive, usually a high molecular weight polymer, that reduces the tendency of an oil's viscosity to change with temperature.

Viscosity-temperature relationship
The manner in which the viscosity of a given fluid varies inversely with temperature. Because of the mathematical relationship that exists between these two variables, it is possible to predict graphically the viscosity of a petroleum fluid at any temperature within a limited range if the viscosities at two other temperatures are known. The charts used for this purpose are the ASTM Standard Viscos...

Viscosity, absolute
the ration of the shearing stress to the shear rate of a fluid. It is usually expressed in centipoise.

Viscosity, kinematic
the absolute viscosity divided by the density of the fluid. It is usually expressed in centistokes.

Viscosity, SUS
Saybolt Universal Seconds (SUS), which is the time in seconds for 60 milliliters of oil to flow through a standard orifice at a given temperature. (ASTM Designation D88-56.)

Viscous
possessing viscosity. Frequently used to imply high viscosity.

Volatility
this property describes the degree and rate at which a liquid will vaporize under given conditions of temperature and pressure. When liquid stability changes, this property is often reduced in value.

Water-Glycol fluid
A fluid whose major constituents are water and one or more glycols or polyglycols.

Way
Longitudinal surface that guides the reciprocal movement of a machine part.

Way lubricant
Lubricant for the sliding ways of machine tools such as planers, grinders, horizontal boring machines, shapers, jig borers, and milling machines. A good way lubricant is formulated with special frictional characteristics designed to overcome the stick-slip motion associated with slow-moving machine parts.

Wear
the attrition or rubbing away of the surface of a material as a result of mechanical action.

Wear debris
Particles that are detached from machine surfaces as a result of wear and corrosion. Also known as wear particles.

Wear inhibitor
An additive which protects the rubbing surfaces against wear, particularly from scuffing, if the hydrodynamic film is ruptured.

Weld point
The lowest applied load in kilograms at which the rotating ball in the Four Ball EP test either seizes and welds to the three stationary balls, or at which extreme scoring of the three balls results

Wicking
the vertical absorption of a liquid into a porous material by capillary forces.

Work penetration
The penetration of a sample of lubricating grease immediately after it has been brought to 77F and then subjected to 60 stokes in a standard grease worker. This procedure and the standard grease worker are described in ASTM Method D 217.

ZDDP
an antiwear additive found in many types of hydraulic and lubricating fluids. Zinc dialkyldithiophosphate.