Vapor degreasing: cleaning procedure to remove oil, grease and lightly attached
solids from metals. An appropriate solvent, e.g., hexane or cleaners solvent, is
boiled; as the vapors condense on the metal surfaces, contaminants fall into the
Vapor phase corrosion inhibitors: fine, volatile powders made from stable
nitrites of organic amines that prevent rusting; after vaporizing, they are
adsorbed by metal surfaces. They are also marketed as treated papers; see VCI
Vapor pressure: measure of the volatility of a liquid at specified temperatures
and pressures (or vacuum).
Variable displacement pumps: pumps that can be adjusted to deliver a variable
volume while the speed remains constant.
Varnish: in lubrication, a deposit resulting from oxidation and polymerization
of fuels and lubricants; like lacquer, but softer.
Volatile corrosion-inhibiting (VCI) paper: corrosion-inhibiting papers and
films impregnated with vapor phase corrosion inhibitors to prevent corrosion of
ferrous and non-ferrous metals; may be used to wrap new parts to prevent
corrosion during storage or shipping (see vapor phase corrosion inhibitors).
Vegetable oils: oily fluids with varying percentages of fatty acids, obtained from
vegetable sources; examples are coconut oil, rapeseed oil, sunflower oil, crambe
Vent valve (lube systems): device for relieving supply line pressure.
Venturi: tube, constricted at the middle and flared at both ends, in the pathway
of a fluid, to reduce fluid pressure in the constricted area.
Venturi meter: a form of flow measuring device containing no moving parts
that operates on the principle of velocity to pressure conversion with values
taken on each side of the venturi tube.
VI: see viscosity index.
Vibrational analysis: analytical method used to monitor bearing conditions
Virgin oil: a fresh oil product not recycled or reclaimed.
Viscometer/viscosimeter: an apparatus for determining the viscosity of a fluid.
Viscosity: the property of a fluid, semi-fluid or semi-solid substance that causes
it to resist flow. Its numerical value is based on the ratio of shear stress to the
rate of shear during flow. The standard unit of absolute viscosity in the English
system is the reyn, expressed as lb-s/in.2. The standard unit of viscosity in the
cgs and ISO system is the poise, expressed as dyne-s/cm2. Conversion from one
system to the other is as follows:
reyn = poise X 1.45 X 10-5
poise = reyn X 6.895 X 104
centipoise = poise X 10-2
microreyn = reyn X 10-6
For Saybolt seconds, convert to centistokes, then to centipoise before converting
to reyns. Specific calculations are:
cp = cSt X specific gravity
SUS – 180
cSt = 0.22 X
(see absolute viscosity, kinematic viscosity).
Viscosity Index/VI: common measure of changes in viscosity with temperature;
the higher the viscosity index, the smaller the relative change in viscosity with
Volatile organic/VOC: as potential hazard or pollutant, applies to any carbon
compound that can be evaporated using standard test methods, except for
carbon monoxide, carbon dioxide, carbonic acid, metallic carbides or carbonates
and ammonium carbonate. Because of the complexities involved in measuring
VOC, no universal definition has been formulated. VOC control is often
enforced by local government agencies.
Volatility – the tendency of a fluid to evaporate. High evaporation rate means
Vapor phase inhibitor/VPI: corrosion inhibitor in the form of vapor, also
referred to as a vapor corrosion inhibitor (see VCI).