CALCIUM CARBONATE -- Calcium is found in nearly all
natural water supplies. Calcium oxide, known as quicklime, combines with water
to form calcium hydroxide, or hydrate, known also as caustic lime or slaked
lime, and soluble in water to form lime water. If there is an excess of the
hydrate, the mixture is known as milk of lime, or white-wash. Calcium oxide
combines with carbon dioxide to form calcium monocarbonate, which occurs in
nature as calcite, marble or limestone. This substance by itself is only'
slightly soluble in pure water, but with the addition of another molecule of
carbon dioxide and one molecule of water, it forms calcium bicarbonate, which
is highly soluble, and is the form in which calcium is taken up from calcium
carbonate rocks by rain water, which contains carbon dioxide in solution.
CALCIUM SULPHATE -- Soleplate of lime, or calcium soleplate,
occurs in nature with the addition of seven molecules of water as gypsum, or
alabaster, which when heated dry, gives up some of the water of crystallization
and becomes a fine, white powder known as plaster of Paris. Calcium sulphate is
soluble in water. When concentration occurs in the boiler, the calcium sulphate
crystallizes out as a hard, porcelain-like scale, which is both very resistant
to the passage of heat and difficult of removal, differing in this respect from
the carbonate, which forms a soft porous scale in the boiler.
CALCULATED CARBON AROMATICITY INDEX -- A measure of the Fuel
Oils Ignition Quality. The value can be calculated using the following, ISO
8217 Ann.C, formula:
CCAI = D-81-141 Log10 Log10( VK+0. 85)-483 Log10((T+273)/323)
where
D = density (kg/m³) at 15°C
VK = kinematic viscosity (mm²/s) at temperature T (°C)
CAPSTAN -- Used to wind up a rope or wire. Placed upright on the deck
and revolved by means of a twin cylinder steam engine or, in newer ship, by
means of an electric engine.
CARBONIC ACID -- A week, unstable acid, H2CO3, existing only in solution.
Carbonic acid is formed as carbon dioxide in steam dissolves in condensate.
This is the primary cause of condensate system corrosion.
CARRY-OVER -- Chemical solids and liquid entrained with the
steam from a boiler. Carry-over is caused by poor water condition within the
boiler.
CAUSTIC EMBRITTLEMENT-- The intergranular corrosion of steal
in hot alkaline solotions (boiler water).
CCAI -- Abbreviation for Calculated
Carbon Aromaticity Index.
CHECK VALVE -- A nonreturn valve, closed automatically by
fluid pressure; fitted in a pipe to prevent return flow of the fluid pumped
through it.
CHLORIDES -- Both calcium and magnesium chlorides are found in
boiler feed water, the magnesium chloride being particularly undesirable, as it
breaks down, when heated to boiler temperature, probably forming magnesia and
hydrochloric acid, thus producing corrosion, Calcium and magnesium chlorides
are converted to insoluble salts by the same reagents ordinarily employed to
treat sulphates.
CLINKER -- The incombustible residue, fused into an irregular
lump that remains after the combustion of coal.
COMBUSTION CHAMBER -- A chamber or space adjacent
to the furnace in a boiler designed for the purpose of completing the
combustion of the gases from the fuel.
COMBUSTION EFFICIENCY -- Defined as the energy input minus
stack loss, divided by the energy input. Sometimes referred to as thermal
efficiency.
COMPOUND ENGINE -- A steam engine in which the
steam expands in two cylinders of increasing size, both on the same
crankshaft.
COMPOSITE BOILER -- A combination of an oil-fired
steam boiler and an exhaust gas economizer.
CONDENSATE -- Condensed steam, usually recirculated back to
the boiler again.
CONDENSER -- A device which cools exhaust steam back into
water, either to conserve water or to lower the back pressure by creating a
partial vacuum in the exhaust.
CONDUCTIVITY -- Represents the electrical current carrying
capacity of a water. It is used as a means of indirectly measuring the total
dissolved solids concentration of a water.
CONTINUOUS BLOWDOWN -- The uninterrupted removal of
concentrated boiler water from a boiler to control total solids concentration
in the remaining water.
CONVECTION OF HEAT -- The transfer of heat from one part of a
fluid to another by flow of the fluid from the hotter parts to the colder. Thus
if heat is applied to the bottom of a vessel containing a liquid, the hot
liquid, being less dense than the cold, will rise, its place being taken by
cold liquid moving down. There is thus set up a circulation of liquid (known
as a convection current), which keeps the temperature more uniform than if
the liquid were stagnant.
CORROSION -- Corrosion of all interior surfaces of the boiler
is caused by the chlorides of magnesium and sodium, and by mineral and organic
acids, and appears to be largely conditional upon the presence of free oxygen.
CRITICAL PRESSUR -- The pressure at which a gas may just be
liquefied at its critical temperature. Critical pressure for water is 221.287bar
CRITICAL TEMPERATURE -- The temperature above which a given
gas cannot be liquefied. Critical temperature for steam is 374.15°C
CROSSHEAD
-- A reciprocating block, usually sliding between guides, forming the
junction piece between the piston-rod and connecting-rod of an engine.
CROWN SHEET -- The plate over the furnace in a Locomotive
type, or the plate over the
combustion chamber in a Scotch marine steam boiler.
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