BACK PRESSURE - Pressure in low side of refrigerating system; also called
suction pressure or low-side pressure.
BACK PRESSURE TURBINE -
BACK SEATING - Fluid opening/closing such as a gauge opening or to seal
the joint where the valve stem goes through the valve body.
BACK WORK RATIO - Is the fraction of the gas turbine work used to drive
BACKGROUND NOISE - Sound other than the wanted signal. In room acoustics,
the irreducible noise level measured in the absence of any building occupants.
BACKING RING - Backing in a form of a ring, generally used in welding of
BACKWASH - The counter-current flow of water through a resin bed (that
is, in at the bottom of the exchange unit, out at the top) to clean and
regenerate the bed after exhaustion (water treatment). Also, the process whereby
a filtering mechanism is cleaned by reversing the flow through the
BACTERIA - Microscopic unicellular living organisms.
BAFFLE - Plate or vane used to direct or control movement of fluid or air
within confined area.
BAG HOUSE - A chamber containing bags for filtering solids out of
BALLAST GAS - Are the nonflammable portion of the gas, such as carbon
BAROMETER - Instrument for measuring atmospheric pressure. It may be
calibrated in pounds per square inch, in inches of mercury in a column in
millimeters or kPa.
BASE - An alkaline substance.
BASE METAL - The metal present in the largest proportion in an alloy.
(Copper is the base metal in brass)
BASICITY - The ability of a substance to boost the pH after neutralizing
all the acid species.
BATCH OPERATION - The utilization of ion-exchange resins to treat a
solution in a container wherein the removal of ions is accomplished by agitation
of the solution and subsequent decanting of the treated liquid.
BAUDELOT COOLER - Heat exchanger in which water flows by gravity over the
outside of the tubes or plates.
BEARING, AIR - A bearing using air as a lubricant.
BEARING, ALIGNING - A bearing with an external spherical seat surface
that provides a compensation for shaft or housing deflection or
BEARING, ANNULAR - Usually a rolling bearing of short cylindrical form
supporting a shaft carrying a radial load.
- A bearing containing a solid lubricant.
BEARING, AXIAL LOAD (see bearing, thrust)
BEARING, BABBITT - A bearing metal of non-ferrous material, containing
several tin-based alloys, mainly copper, antimony, tin and lead.
BEARING, BALL - A rolling element bearing in which the rolling elements
BEARING, BIG END - A bearing at the larger (crankshaft) end of a
connecting rod in an engine.
BEARING, BIMETAL - A bearing consisting of two layers.
BEARING, BOTTOM END
- (see bearing, big end)
BEARING, BUSH - A plain bearing in which the lining is closely fitted
into the housing in the form of a bush, usually surfaced with a bearing
BEARING, CIRCULAR STEP - A flat circular hydrostatic bearing with a
central circular recess.
BEARING, FIXED PAD
- An axial or radial load bearing equipped with fixed
pads, the surface of which a are contoured to promote hydrodynamic
BEARING, FLOATING - A bearing designed or mounted to permit axial
displacement between shaft and housing.
BEARING, FLOATING RING
- A type of journal bearing that includes a thin
ring between the journal and the bearing. The ring floats and rotates at a
fraction of the journal rotational speed.
BEARING, FLUID - (see hydrostatic bearing)
BEARING, FULL JOURNAL
- A journal bearing that surrounds the journal by a
BEARING, GAS - A journal or thrust bearing lubricated with gas.
BEARING, HALF JOURNAL
- A bearing extending 180° around a journal.
BEARING, JOURNAL - A machine part in which a rotating shaft revolves or
The predominant thrust bearing used in hydroelectric
generators is the Kingsbury thrust bearing. It consist of a annular
arrangement of babbit covered, pie shaped, stationary, shoes. The shoes form a
circle around the rotating shaft. A cylindrical thrust block with a highly
polished end is pressed onto the shaft and held to the shaft with half moon
collars. The polished end of the shaft rests on the surfaces of the babbitted,
stationary shoes. The shoes are mounted on spherical studs that allows them to
tilt. As the hydraulic turbine spins the shaft, the collar turns on the shoes.
BEARING, MAGNETIC - A type of bearing in which the force that separates
the relatively moving surfaces is produced be a magnetic field.
BEARING, MAIN - A bearing supporting the main power-transmitting
BEARING, MITCHELL -(see tilting pad bearing).
BEARING, NEEDLE - A bearing in which the relatively moving parts are
separated by long thin rollers that have a length-to-diameter ratio exceeding
BEARING, NONCONTACT - A bearing in which no solid contact occurs between
relatively moving surfaces.
BEARING, PEDESTAL - A bearing that is supported on a column or pedestal
rather than on the main body of the machine.
BEARING, PIVOT - An axial load bearing, radial-load-type bearing which
supports the end of a shaft or pivot.
BEARING, POROUS - Made from porous material, such as compressed metal
powders, the pores acting either as reservoirs for holding or passages for
BEARING, ROLLER - A bearing in which the relatively moving parts are
separated by rollers.
BEARING, RUBBING - A bearing in which the relatively moving parts slide
without deliberate lubrication.
BEARING, SELF-ALIGNING - A roller-element bearing with one spherical
raceway that automatically provides compensation for shaft or housing deflection
- A bearing independent of external
lubrication. These bearings may be sealed for life after packing with grease or
may contain self-lubricating material.
BEARING, SLEEVE - A cylindrical plain bearing used to provide radial
location for a shat, which moves axially. Sleeve bearings consist of one or more
layers of bearing alloys, bonded to a steel backing.
BEARING, SLIDE - A bearing used or positioning a slide or for axial
alignment of a long rotating shaft.
BEARING, STEP - A plane surface bearing that supports the lower end of a
BEARING, THRUST - A bearing in which the load acts in the direction of
the axis of rotation.
BEARING, TILTING PAD
- A pad bearing in which the pads are free to take
up a position at an angle to the opposing surface according to the hydrodynamic
pressure distribution over its surface.
BEARING, TRUNNION - A bearing used as a pivot to swivel or turn an
BED - A mass of ion-exchange resin particles contained in a
BED DEPTH - The height of the resinous material in the column after the
ion exchanger has been properly conditioned for effective operation.
BED EXPANSION - The effect produced during backwashing when the resin
particles become separated and rise in the column. The expansion of the bed due
to the increase in the space between resin particles may be controlled by
regulating backwash flow (typical with water treatment).
BELLOWS - Corrugated cylindrical container which moves as pressures
change, or provides a seal during movement of parts.
BELLOWS SEAL - A type of mechanical seal that utilizes a bellows for
providing secondary sealing.
BENDING MOMENT - The algebraic sum of the couples or the moments of the
external forces, or both, to the left or right of any section on a member
subjected to bending by couples or transverse forces, or both.
- In stream of liquid, the sum of elevation head,
pressure head and velocity remains constant along any line of flow provided no
work is done by or upon liquid in course of its flow, and decreases in
proportion to energy lost in flow.
- The presence in a solution of hydroxyl (OH-)
ions resulting from the hydrolysis of carbonates or bicarbonates. When these
salts react with water, a strong base and a weak acid are produced, and the
solution is alkaline.
BICARBONATE - An ion or salt of carbonic acid, containing hydrogen,
carbon, and oxygen (HC03), such as sodium bicarbonate,
BIMETAL STRIP - Temperature regulating or indicating device which works
on principle that two dissimilar metals with unequal expansion rates, welded
together, will bend as temperatures change.
- A joint or union of two dissimilar metals.
BIOCIDE - A chemical used to control the population of troublesome
BLACK LIQUOR - The liquid material remaining from pulpwood cooking in the
soda or sulfate papermaking process.
BLADE CLEARANCE (STEAM TURBINE) - Reaction turbine - the gap between blade
and casing. Impulse turbine - the gap between the stationary and moving
BLAST FREEZER - Low-temperature evaporator which uses a fan to force air
rapidly over the evaporator surface.
BLAST FURNACE GAS
- Is the waste product from furnaces used to smelt iron
BLEEDER VALVE - A valve designed to slowly relief a liquid or gas form
BLEEDING - Slowly reducing the pressure of liquid or gas from a system or
cylinder by slightly opening a valve.
BLEEDOFF - The continuous removal of water from a re-circulating water
BLEEDOFF RATE - The rate at which water is continuously removed from a
BLOWDOWN - In connection with boilers or cooling towers, the process of
discharging a significant portion of the aqueous solution in order to remove
accumulated salts, deposits and other impurities.
BOILER - Closed container in which a liquid may be heated and
BOILER FEED WATER
- The total water fed to a boiler producing steam. This
water is the mixture of return steam condensate and makeup water.
- The work required to evaporate 34.5 lb of water per
hour into steam from and at 100°C.
BOILER LAY-UP - Storing and protecting the boiler when not in use.
BOILING OUT - The boiling of high alkaline water in boiler pressure parts
for the removal of oil, greases, prior to normal operation or after major
BOILING POINT - The temperature at which the vapor pressure of a liquid
equals the absolute external pressure at the liquid-vapor interface.
- Temperature at which a fluid changes from a liquid
to a gas.
BORE - Inside diameter of a cylinder.
BOURDON TUBE - Thin-walled tube of elastic metal flattened and bent into
circular shape, which tends to straighten as pressure inside is increased. Used
in pressure gauges.
BOYLES' LAW - If the temperature on a gas is constant, the volume is
inversely proportional to the pressure. By formula - VP =
BRANCH CIRCUIT - Wiring between the last over current device and the
branch circuit outlets.
BRASS - A copper-zinc alloy containing up to 40% zinc and some smaller
amounts of other metals.
BRAYTON CYCLE (also referred to as the Joule Cycle) - A rotating machine
in which compression and expansion take place. Gas turbine are such an
BRAZE - A weld produced by heating an assembly to suitable temperatures
and by using a filler metal having a liquid us above 450°C. The filler metal is
distributed between the closely fitted facing surface of the joint by capillary
BRAZING, BLOCK - A brazing process in which the heat required is obtained
from heated blocks applied to the parts to be joined.
BREAKTHROUGH - The first appearance in the solution flowing from an
ion-exchange unit of unabsorbed ions similar to those which are depleting the
activity of the resin bed. Breakthrough is an indication that regeneration of
the resin is necessary.
BRINE - Water saturated with a chemical such as salt.
BRITISH THERMAL UNIT, (BTU) - The Btu is defined as the heat required to
raise the temperature of a pound of water from 59° to 60°F.
BRITTLENESS - The tendency of a material to fracture without first
undergoing significant plastic deformation.
BRONZE - A copper-rich copper tin alloy with or without small proportions
of other elements.
BTU - British Thermal Unit. Is the measure of heat energy.
BUFFER - A substance used in solution, which accepts hydrogen ions or
hydroxyl ions, added to the solution as acids or alkali’s, minimizing a change
BULB - The name given to the temperature-sensing device located in the
fluid for which control or indication is provided. The bulb may be
liquid-filled, gas filled, or gas-and-liquid filled. Changes in temperature
produce pressure changes within the bulb which are transmitted to the
BULGE - A local distortion or swelling outward caused
by internal pressure on a tube wall or boiler shell due to overheating.
BUS BAR - A heavy, rigid metallic conductor which carries a large current
and makes a common connection between several circuits. Bus bars are usually uninsulated and located where the electrical service enters a building; that is,
in the main distribution cabinet.
BYPASS - A pipe or duct, usually controlled by valve or damper, for
conveying a fluid around an element of a system.
BYPASS - Passage at one side of, or around, a regular passage.
BYPASS FEEDER - A closed tank that is installed in a system in "bypass,"
that is, in a side stream taken off the system and leading back to the system
rather than directly in-line.