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Bridging -- a condition of filter element loading in which contaminant spans
the space between adjacent sections of a filter element, thus blocking a portion
of the useful filtration.
Bright stock -- a heavy residual lubricant stock with low pour point, used
in finished blends to provide good bearing film strength, prevent scuffing,
and reduce oil consumption. Usually identified by its viscosity, SUS at 210°F
or cSt at 100°C.
Brinelling -- permanent deformation of the bearing surfaces where the rollers
(or balls) contact the races. Brinelling results from excessive load or impact
on stationary bearings. It is a form of mechanical damage in which metal is
displaced or upset without attrition.
Brookfield viscosity -- apparent viscosity in cP determined by Brookfield viscometer,
which measures the torque required to rotate a spindle at constant speed in
oil of a given temperature. Basis for ASTM Method D 2983; used for measuring
low temperature viscosity of lubricants.
BTU -- British thermal unit. The amount of heat required to raise the temperature
of 1 pound of water 1 degree Fahrenheit.
Bubble point -- the differential gas pressure at which the first steady stream
of gas bubbles is emitted from a wetted filter element under specified test
conditions.
Built-in-dirt -- Material passed into the effluent stream composed of foreign
materials incorporated into the filter medium.
Bulk modulus (of elasticity) -- a ratio of normal stress to a change in volume.
A term used in determining the compressibility of a fluid.
Burst pressure rating -- the maximum specified inside-out differential pressure
that can be applied to a filter element without outward structural or filter-medium
failure.
Buna-N -- (Nitrile Rubber-NBR) synthetic rubber made by the copolymerization of butadiene
and acrylonitrile. It resists heat, oil and fuels and is often used in the manufacture of o-rings and fluid seals.
Bushing -- a short, externally threaded connector with a smaller size internal
thread.
Bypass Filtration -- a system of filtration in which only a portion of the
total flow of a circulating fluid system passes through a filter at any instant
or in which a filter having its own circulating pump operates in parallel to
the main flow.
Bypass valve (Relief valve) -- a valve mechanism that assures system fluid
flow when a preselected differential pressure across the filter element is exceeded;
the valve allows all or part of the flow to bypass the filter element.
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