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LUBRICATION
LUBRICANT TERMS AND DEFINITIONS
TERM DEFINITION
ADHESIVE
The ability of grease, gear lubricant or oil to cling to
metal.
ANTI WEAR AGENTS
Used to help combat metal-to-metal contact, thus
reducing wear.
COHESIVE
The ability of grease, gear lube or oil to cling to itself,
thus resisting tearing apart.
CONSISTENCY
Consistency of grease is its hardness or firmness. It is
determined by the depth in millimeters to which the cone
of a penetrometer sinks into a sample under specified
conditions. Consistency of grease may be influenced by
the type and amount of thickener, viscosity of oil, working
and other factors.
CONTAMINATION
Foreign material that could damage a part.
DROPPING POINT
The minimum temperature at which the oil in grease
subjected to heat begins to actually drip and breakdown.
EXTREME PRESSURE
AGENTS
Additives that under extreme pressure form an adherent
film on metal surfaces, thus forming a film of protection.
FILM STRENGTH
Film strength is defined as the tendency of oil molecules
to cling together. It is the ability of those molecules to
resist separation under pressure between two metals and
to hold these metal surfaces apart.
FRICTION
The resistance to fluid flow in a hydraulic system. (An
energy loss in terms of power output.)
GALLING
Surface damage on mating, moving metal parts due to
friction. A severe form of adhesive wear.
LUBRICATION
Use of a substance (grease, oil, etc.) to reduce friction
between parts or objects that move against each other.
NLGI
A rating given to grease from the National Lubricating
Grease Institute. This rating determines the hardness of
the grease and goes on from a 000 to a 6 rating. Most
different brands of grease are NLGI #2 rated.
OILINESS
Oiliness is measured of the coefficient of friction of a
lubricant. Oiliness or lubricity depends on the adhering
characteristics of the oil. It is determined by the attraction
between the molecules of the oil and the molecules of
another material. Of two oils having the same viscosity
but different degrees of fluid friction, the one with the
lower friction index has the higher degree of oiliness.
PUMP
A device which converts mechanical force into hydraulic
fluid power. Basic design types are gear, vane, and
piston units.
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