ABSOLUTE PRESSURE – Pressure above zero pressure; the sum of the gauge and atmospheric pressures.
ACCUMULATOR – (STEAM) A pressure vessel containing water and/or steam, which is used to store the heat of steam for use at a late period and at some lower pressure.
ACID CLEANING – The process of cleaning the interior surfaces of steam generating units by filling the unit with dilute acid accompanied by an inhibitor to prevent corrosion, and subsequently draining, washing and neutralizing the acid by a further wash of alkaline water.
ACIDITY – Represents the amount of free carbon dioxide, mineral acids and salts (especially sulphates of iron and aluminum) which hydrolyze to give hydrogen ions in water and is reported as milliequivalents per liter of acid, or ppm acidity as calcium carbonate, or pH the measure of hydrogen ions concentration.
ADIABATIC FLAME TEMPERATURE – The theoretical temperature that would be attained by the products of combustion provided the entire chemical energy of the fuel, the sensible heat content of the fuel and combustion above the datum temperature were transferred to the products of combustion. This assumes: No heat loss to surroundings and no dissociation.
AIR – The mixture of oxygen, nitrogen, and other gases, which with varying amounts of water vapor, forms the atmosphere of the earth.
AIR ATOMIZING OIL BURNER – A burner for firing oil in which the oil is atomized by compressed air, which is forced into and through one or more streams of oil which results in the breaking of the oil into a fine spray.
AIR DEFICIENCY – Insufficient air, in an air-fuel mixture, to supply the oxygen required for complete oxidation of the fuel.
AIR-FREE – The descriptive characteristic of a substance from which air has been removed.
AIR-FUEL RATIO – The ratio of the weight, or volume, of air to fuel.
AIR INFILTRATION – The leakage of air into a setting or duct.
AIR, SATURATED – Air which contains the maximum amount of water vapor that it can hold at its temperature and pressure.
AIR VENT – A valved opening in the top of the highest drum of a boiler or pressure vessel for venting air.
ALARM – A suitable horn, bell, light or other device which when operated will give notice of malfunction or off normal condition.
ALKALINITY – Represents the amount of carbonates, bicarbonates, hydroxides and silicates or phosphates in the water and is reported as grains per gallon, or ppm as calcium carbonate.
ALLOWABLE WORKING PRESSURE – See design pressure.
AMBIENT AIR – The air that surrounds the equipment. The standard ambient air for performance calculations is air at 80 °F, 60% relative humidity, and a barometric pressure of 29.921 in. Hg, giving a specific humidity of 0.013 lb of water vapor per lb of dry air.
AMBIENT TEMPERATURE – The temperature of the air surrounding the equipment.
ANALYSIS – Quantitative determination of the constituent parts.
ANALYSIS, ULTIMATE – Chemical analysis of solid, liquid or gaseous fuels. In the case of coal or coke, determination of carbon, hydrogen, sulfur, nitrogen, oxygen, and ash.
AQUASTAT – Water limit temperature control, a safety device often used on boilers.
ARRESTER – A device to impede the flow of large dust particles or sparks from a stack, usually screening at the top.
AS-FIRED FUEL – Fuel in the condition as fed to the fuel burning equipment.
ASH – The incombustible inorganic matter in the fuel.
ASH-FREE BASIS – The method of reporting fuel analysis, whereby ash is deducted and other constituents are recalculated to total 100%.
ASH PIT – A pit or hopper located below a furnace where refuse is accumulated and from which refuse is removed at intervals.
ASME – The American Society of Mechanical Engineers.
ASPIRATING BURNER – A burner in which the fuel in a gaseous or finely divided form is burned in suspension, the air for combustion being supplied by bringing into contact with the fuel, air drawn through one or more openings by the lower static pressure created by the velocity of the fuel stream.
AS-RECEIVED FUEL – Fuel in the condition as received at the plant.
ATMOSPHERIC AIR – Air under the prevailing atmospheric conditions.
ATMOSPHERIC PRESSURE – The barometric reading of pressure exerted by the atmosphere. At sea level 14.7 lb per sq in. or 29.92 in. of mercury.
ATOMIZER – A device by means of which a liquid is reduced to a very fine spray.
AVAILABLE DRAFT – The draft which may be utilized to cause the flow of air for combustion or the flow of products of combustion.
AVAILABILITY FACTOR – The fraction of time during which the unit is in operable condition.
AXIAL FAN – Consists of a propeller or disc type of wheel within a cylinder that discharges air parallel to the axis of the wheel.
BAFFLE – A plate or wall for deflecting gases or liquids.
BAFFLE TILE – A tile for deflecting gases.
BAFFLE-TYPE COLLECTOR – A device in gas paths utilizing baffles so arranged as to deflect dust particles out of the gas stream.
BAG FILTER – A device containing one or more cloth bags for recovering particles from the dust laden gas or air which is blown through it.
BAG-TYPE COLLECTOR – A filter in which the cloth filtering medium is made in the form of cylindrical bags.
BAROMETRIC PRESSURE – Atmospheric pressure as determined by a barometer usually expressed in inches of mercury.
BASE LOAD – Base load is the term applied to that portion of a station or boiler load that is practically constant for long periods.
BEADED TUBE END – The rounded exposed end of a rolled tube when the tube metal is formed over against the sheet in which the tube is rolled.
BLIND NIPPLE – A nipple, or a short piece of pipe or tube, closed at one end.
BLOWDOWN – Boiler water that is removed from the boiler in order to maintain the desired concentration levels of suspended and dissolved solids in the boiler and removal of sludge.
BLOWDOWNÐSAFETY VALVE – The difference between the pressure at which a safety valve opens and at which it closes.
BLOWDOWN VALVE – A valve generally used to continuously regulate concentration of solids in the boiler, not a drain valve. (Often called continuous blowdown.)
BLOW-OFF VALVE – A specially designed, manually operated, valve that connects to the boiler for the purpose of reducing the concentration of solids in the boiler or for draining purposes. (Often called bottom blowdown.)
BLOWER – A fan used to force air under pressure.
BOILER – A closed vessel in which water is heated, steam is generated, steam is superheated, or any combination thereof, under pressure or vacuum by the application of heat from combustible fuels, electricity or nuclear energy.
BOILER EFFICIENCY – The term Òboiler efficiencyÓ is often substituted for combustion or thermal efficiency. True boiler efficiency is the measure of fuel-to-steam efficiency.
BOILER HORSEPOWER – The evaporation of 34-1/2 lbs of water per hour from a temperature of 212 °F into dry saturated steam at the same temperature. Equivalent to 33,475 Btu/hr.
BOILER RATING – The heating capacity of a boiler expressed in boiler horsepower, Btu/hour, or pounds of steam/hour.
BOILER SHELL– The outer cylindrical portion of a pressure vessel.
BOILER WATER – A term construed to mean a representative sample of the circulating boiler water, after the generated steam has been separated and before the incoming feed water or added chemical becomes mixed with it so that its composition is affected.
BOILING – The conversion of a liquid into vapor with the formation of bubbles.
BOILING OUT – The boiling of highly alkaline water in boiler pressure parts for the removal of oils, greases, etc.
BOOSTER FAN – A device for increasing the pressure or flow of a gas.
BREECHING – A duct that transports the products of combustion between parts of a steam generating unit or to the stack.
BRIDGEWALL – A wall in a furnace over which the products of combustion pass.
BRITISH THERMAL UNIT (Btu) – The mean British Thermal Unit is 1/180 of the heat required to raise the temperature of 1 lb of water from 32 °F to 212 °F at a constant atmospheric pressure. A Btu is essentially 252 calories.
BUCKSTAY – A structural member placed against a furnace or boiler wall to restrain the motion of the wall.
BUNKER C OIL – Residual fuel oil of high viscosity commonly used in marine and stationary steam power plants. (No. 6 fuel oil)
BURNER – A device for the introduction of fuel and air into a furnace at the desired velocities, turbulence and concentration.
BURNER WINDBOX – A plenum chamber around a burner that maintains an air pressure sufficient for proper distribution and discharge of secondary air.
BURNER WINDBOX PRESSURE – The air pressure maintained in the windbox or plenum chamber measured above atmospheric pressure.
BY-PASS – A passage for a fluid, permitting a portion of the fluid to flow around its normal pass flow channel.
C – Carbon element, the principal combustible constituent of all fuels.
CaCO3 – Calcium Carbonate.
CALORIE – The mean calorie is 1/100 of the heat required to raise the temperature of 1 gram of water from Zero C to 100 °C at a constant atmospheric pressure. It is about equal to the quantity of heat required to raise one gram of water 1 °C. Another definition is: A calorie is 3600/860 joules.
CALORIMETER – Apparatus for determining the calorific value of a fuel.
CAPACITY FACTOR – The ratio of the average load carried to the maximum design capacity.
CARBON – Element. The principal combustible constituent of all fuels.
CARRYOVER – The chemical solids and liquid entrained with the steam from a boiler.
CASING – A covering of sheets of metal or other material such as fire resistant composition board used to enclose all or a portion of a steam generating unit.
CENTRAL STATION – A power plant or steam heating plant that generates power or steam.
CENTRIFUGAL FAN – Consists of a fan rotor or wheel within a housing that discharges air at a right angle to the axis of the wheel.
CHEMICAL ANALYSIS – Determination of the principal chemical constituents.
CHEMICAL FEED PIPE – A pipe inside a boiler drum through which chemicals for treating the boiler water are introduced.
CHIMNEY – A brick, metal or concrete stack.
CIRCULATION – The movement of water and steam within a steam generating unit.
CIRCULATION RATIO – The ratio of water entering a circuit to the steam generated by that passes that circuit in a unit of time.
CIRCULATOR – A pipe or tube to pass steam or water between upper boiler drums usually located where the heat absorption is low. Also used to apply to tubes connecting headers of horizontal water tube boilers with drums.
CLEANOUT DOOR – A door placed so that accumulated refuse may be removed room a boiler setting.
CO – Carbon monoxide.
CO2 – Carbon dioxide.
COLLECTOR – A device used for removing gas borne solids from flue gas.
COLLOID – A finely divided organic substance which tends to inhibit the formation of dense scale and results in the deposition of sludge, or causes it to remain in suspension, so that it may be blown from the boiler.
COMBUSTIBLE LOSS – The loss representing the unliberated thermal energy occasioned by failure to oxidize completely some of the combustible matter in the fuel.
COMBUSTIBLES – The heat producing constituents of a fuel.
COMBUSTION – The rapid chemical combination of oxygen with the combustible elements of a fuel resulting in the release of heat.
COMBUSTION AIR – Air used in the combustion process. Air contains oxygen which is required to combust fuel.
COMBUSTION CHAMBER – See Furnace.
COMBUSTION EFFICIENCY – The effectiveness of the burner to completely burn the fuel. A well designed burner will operate with as little as 10 to 20% excess air, while converting all combustibles in the fuel to useful energy.
COMPLETE COMBUSTION – The complete oxidation of all the combustible constituents of a fuel.
CONCENTRATION – (1) The weight of solids contained in a unit weight of boiler or feed water. (2) The number of times that the dissolved solids have increased from the original amount in the feedwater to that in the boiler water due to evaporation in generating steam.
CONDENSATE – Condensed water resulting from the removal of latent heat from steam.
CONDUCTION – The transmission of heat through and by means of matter unaccompanied by any obvious motion of the matter.
CONDUCTIVITY – (1) A material property relating heat flux (heat transferred per unit area per unit time) to a temperature difference. In American units, it is typically defined as the amount of heat (Btu) transmitted in one hour through one square foot of material 1 inch thick, with a temperature difference of 1°F between the two surfaces of the material. (2) The property of a water sample to transmit electric current under a set of standard conditions. Usually expressed as microhms conductance.
CONTINUOUS BLOWDOWN – The uninterrupted removal of concentrated boiler water from a boiler to control total solids concentration in the remaining water.
CONTROL – Any manual or automatic device for the regulation of a machine to keep it at normal operation. If automatic, the device is motivated by variations in temperature, pressure, water level, time, light, or other influences.
CONTROL VALVE – A valve used to control the flow of air, gas, water, steam or other substance.
CONVECTION – The transmission of heat by the circulation of a liquid or gas. It may be natural, with the circulation caused by buoyancy affects due to temperature differences, or forced with circulation caused by a mechanical device such as a fan or pump.
CORROSION – The wasting away of metal due to chemical action. In a boiler, usually caused by the presence of O2, CO2, or an acid.
CROWN SHEET – In a firebox boiler, the plate forming the top of the furnace.
CRUDE OIL – Unrefined petroleum.
CSD-1 – Abbreviation for the ASME standard for Controls and Safety Devices.
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