ICP (inductively coupled plasma): quantitative analytical technique for
measuring metal contents of fluids.
Idler gear (gears): gear placed between two other gears to change a mechanism’s
direction of rotation.
Inboard bearing (bearings): the bearing supporting a shaft nearest the coupling
or drive mechanism.
Indicator (lube systems): device that shows movement of discharge piston.
Inhibitor: additive that prevents or retards undesired chemical changes,
especially to metal surfaces; common inhibitors prevent oxidation, corrosion and
Injector (lube systems): part that dispenses a measured amount of lubricant to a
point of lubrication.
Injector body (lube systems): steel cylinder that serves as a container for
lubricant passage, valve port, line connections and grease fitting assembly.
Inlet disc (lube systems): channel-lipped disc that directs lubricant through the
Inlet section (lube systems): top section of divider valve that contains the inlet
connection, internal porting, tie rod holes and mounting holes.
Insolubles (oil): (ASTM D-893) a term used in the analysis of used oil,
especially when determining the presence of oxidation products. The procedure
dilutes the sample with pentane, causing the precipitation of oxidized material
and other contaminants, collectively known as pentane insolubles. These
insolubles are then treated with toluene to dissolve the oxidation products. The
difference in weight between the pentane and toluene insolubles is called
insoluble resins or oxidation products.
Insolubles (grease): (ASTM D-128) components of a lubricating grease that are
insoluble in the prescribed reagents; generally denotes fillers, additives and
certain types of thickeners as well as impurities.
Insulating oil/transformer oil: clean, dry, high-quality, oxidation-resistant oil of
low viscosity and high dielectric strength, designed for extended service in
circuit breakers, transformers, switches and other electrical apparatus; most
commonly utilized for cooling in transformers.
Intensifier (hydraulics): device that converts low-pressure hydraulic or
pneumatic power to high-pressure hydraulic power.
Interfacial tension (IFT): the energy per unit area existing at the boundary of
two immiscible liquids, like water and oil; obtained by measuring the force
required to rupture the interface. ASTM D-971 measures the force required to
draw a platinum ring through the interface in dynes/cm. A lowered IFT
promotes emulsification and indicates that oxidized products are forming in the
Intermediate base crude: see mixed base crude.
Invert emulsion: water-in-oil emulsion, typically containing 40% water, utilized
as a fire- resistant fluid; oil is the outer or continuous phase of an invert
emulsion, in contrast to the normal (oil-in-water) emulsion, where water is the
Involute tooth form: profile of a tooth face generated by unwinding a line from
a base circle where the end of the line scribes the involute shape.
Iodine number: the amount of iodine absorbed by an oil under prescribed
conditions; like the bromine number, it measures the percentage of unsaturates
in an oil.
ISO: International Standards Organization
ISO viscosity classification system: internationally accepted system, in which
each viscosity grade (VG) corresponds to the midpoint of the viscosity range
expressed in centistokes at 40°C; originated with a Saybolt (SUS) system
developed jointly by ASTM and STLE, later changed to centistokes to gain
international acceptance. The original Saybolt system rated viscosity at 100°F;
the ISO system rates viscosity at 104° (40°C).