OEM --
Original Equipment
Manufacturer. Confusingly manufacturers who resell another
company's product under their own name and offering its own support and
warranty.
OHM -- The SI unit of
electrical resistance, such that 1 ampere through it produces a potential
difference across it of 1 volt. Symbol
OMNIBUS-BAR-- The original term from which the commonly used
expression bus-bar is derived.
ONCE-THROUGH BOILER -- A monotube boiler in which
the feed water evaporates to steam immediately in the tube. Also referred to as
Flash Boiler.
OPPOSED-CYLINDER ENGINE-- An engine with cylinders, or banks
of cylinders, on opposite sides of the crankcase in the same plane, their
connection-rods working on a common crankshaft placed between them.
ORIFICE -- The opening from the whirling chamber of a
mechanical atomizer or the mixing chamber of a steam atomizer through which the
liquid fuel is discharged.
ORIFICE GAUGE -- A flow gauge consisting of a thin orifice
plate clamped between pipe flanges, with pressure take-offs drilled into the
adjacent pipes, or of a thick orifice plate similarly, clamped but containing
its own pressure take-offs.
OSMOSIS -- Diffusion of a solvent through a semipermeable
membrane into a more concentrated solution, tending to equalize the
concentrations on both sides of the membrane.
OSMOTIC PRESSURE -- The pressure exerted by a dissolved
substance in virtue of the motion of its molecules. It may be measured by the
pressure that must be applied to a solution in order just to prevent osmosis
into the solution.
OUTSIDE LAP -- The amount by which the slide-valve of a
reciprocating steam-engine overlaps the edge of the steam ports when in
mid-position. Also called Steam lap.
OZONE -- O3 A
bluish, toxic gas produced by the action of ultraviolet radiation or electric
corona discharge on oxygen or air. Powerful oxidizing agent.
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