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Boiler glossary C |
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| 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. 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). 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) 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 expansion of the steam from the boiler pressure to the exhaust pressure is carried out in two stages, necessitating the use of high- pressure and low-pressure cylinders in series. In some cases, especially for dynamo-engines, with two low-pressure cylinders. Consequently three cylinders but expansion in two steps. 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 CROWN SHEET -- The plate over the furnace in a Locomotive type, or the plate over the combustion chamber in a Scotch marine steam boiler. |
© 2007 Lars Josefsson Boilers