Oil mist lubrication - a lubrication system in which oil mist is produce by
atomization in an auxiliary unit and transported to the bearing housing by
compressed air to lubricate the bearing, or bearings. It is usually used in high
speed application. See pure oil mist lubrication and purge oil mist lubrication.
Oil whirl - the turbulent flow of oil in a bearing that can cause instabilities such as
elevated vibration level. It usually occurs in plain journal bearings (or sleeve
bearings) that are lubricated hydrodynamically. The instabilities usually occur at
half the pump running speed.
Open impeller - an impeller with vanes attached to the hub with no front or back
shrouds; the impeller may have small web in-between vanes for structural
Operating region - a range in the pump performance curve over which the pump
Outboard - the state of being farther away from the pump coupling as opposed to
the inboard which is nearer the coupling. Thus, an outboard impeller, outboard
cover, or outboard bearing housing, is farther away from the coupling whereas an
inboard impeller, inboard cover, or inboard bearing housing, is on the opposite
side or is nearer to the coupling. (Same term as outboard side, or outboard end).
Overhung pump - a pump whose impeller is cantilevered from its bearing
assembly, or a pump with only one bearing housing assembly as opposed to a
"between-bearing" pump which has two bearing housing assemblies mounted
on opposite sides of the pump casing. An overhung pump, which typically is also
a radially split pump, can be either a horizontal or a vertical pump. Also known as
Overrunning clutch - clutch that transmits torque in one direction and freewheels
in opposite direction. An example is a clutch between an HPRT and a driven
equipment to prevent the HPRT from being a drag to the driven equipment in an
upset condition of insufficient flow to the HPRT.
F: glossary O1