HANDHOLE – An access opening in a pressure part usually not exceeding 6Ó in its longest dimension.
HANDHOLE COVER – A handhole closure.
HARDNESS – A measure of the amount of calcium and magnesium salts in water. Usually expressed as grains per gallon or ppm as CaCO3.
HARD WATER – Water which contains calcium or magnesium in an amount which require an excessive amount of soap to form a lather.
HEAT AVAILABLE – The thermal energy above a fixed datum that is capable of being absorbed for useful work.
HEAT BALANCE – An accounting of the distribution of the heat input, output and losses.
HEAT EXCHANGER – A vessel in which heat is transferred from one medium to another.
HEAT RELEASE RATE – Rate that describes the heat available per square foot of heat-absorbing surface in the furnace or per cubic foot of volume.
HEATING SURFACE – Those surfaces which are exposed to products of
combustion on one side and water on the other. This surface is measured on the side receiving the heat.
HEATING VALUE – The quantity of heat released by a fuel through complete combustion. It is commonly expressed in Btu per lb, per gallon, or cu-ft.
HIGH GAS PRESSURE CONTROL – A control to stop the burner if the gas pressure is too high.
HIGH OIL TEMPERATURE CONTROL – A control to stop the burner if the oil temperature is too high.
HYDROCARBON – A chemical compound of hydrogen and carbon.
HYDROSTATIC TEST – A strength and tightness test of a closed pressure vessel by water pressure.
IGNITION – The initiation of combustion.
IGNITION TEMPERATURE – Lowest temperature of a fuel at which combustion becomes self-sustaining.
ILLUMINANTS – Light oil or coal compounds that readily burn with a luminous flame, such as ethylene, propylene and benzene.
INCOMPLETE COMBUSTION – The partial oxidation of the combustible constituents of a fuel.
INDUCED DRAFT FAN– A fan exhausting hot gases from the heat absorbing equipment.
INERT GASEOUS CONSTITUENTS – Incombustible gases such as nitrogen which may be present in a fuel.
INHIBITOR – A substance which selectively retards a chemical action. An example in boiler work is the use of an inhibitor, when using acid to remove scale, to prevent the acid from attacking the boiler metal.
INJECTOR – A device utilizing a steam jet to entrain and deliver feed water into a boiler.
INSULATION – A material of low thermal conductivity used to reduce heat losses.
INTEGRAL BLOWER – A blower built as an integral part of a device to supply air thereto.
INTEGRAL-BLOWER BURNER – A burner of which the blower is an integral part.
INTERLOCK – A device to prove the physical state of a required condition, and to furnish that proof to the primary safety control circuit.
INTERMITTENT BLOWDOWN – the blowing down of boiler water at intervals.
INTERNAL TREATMENT – The treatment of boiler water by introducing chemicals directly into the boiler.
ION – A charged atom or radical which may be positive or negative.
IRI – Industrial Risk Insurers.
LAGGING – A light gauge steel covering used over a boiler, usually combined with insulation, to provide a low temperature outer surface.
LEAKAGE – The uncontrolled quantity of fluid which enters or leaves through the enclosure of air or gas passages.
LIBERATION – See ÒHeat Release.Ó
LIMIT CONTROL – A switching device that completes or breaks an electrical circuit at predetermined pressures or temperatures. Also known as an interlock. See interlock.
LINING – The material used on the furnace side of a furnace wall. It is usually of high grade refractory tile or brick or plastic refractory material.
LOAD – The rate of output required; also the weight carried.
LOAD FACTOR – The ratio of the average load in a given period to the maximum load carried during that period.
LOW GAS PRESSURE CONTROL – A control to stop the burner if gas pressure is too low.
LOW OIL TEMPERATURE CONTROL – (Cold Oil Switch) A control to prevent burner operation if the temperature of the oil is too low.
LOW WATER CUTOFF – Safety device that shuts off the boiler/burner in the event of low water, preventing pressure vessel failure.
LUG – Any projection, like an ear, used for supporting or grasping.
MAKE-UP – The water added to boiler feed to compensate for that lost through exhaust, blowdown, leakage, etc.
MANHOLE – The opening in a pressure vessel of sufficient size to permit a man to enter.
MANIFOLD – A pipe or header for collection of a fluid from, or the distribution of a fluid to a number of pipes or tubes.
MANUAL GAS SHUTOFF VALVE – A manually operated valve in a gas line for the purpose of completely turning on or shutting off the gas supply.
MANUFACTURED GAS – Fuel gas manufactured from coal, oil, etc., as differentiated from natural gas.
MAXIMUM ALLOWABLE WORKING PRESSURE – The maximum gauge pressure permissible in a completed boiler. The MAWP of the completed boiler shall be less than or equal to the lowest design pressure determined for any of its parts. This pressure is based upon either proof tests or calculations for every pressure part of the boiler using nominal thickness exclusive of allowances for corrosion and thickness required for loadings other than pressure. It is the basis for the pressure setting of the pressure relieving devices protecting the boiler.
MAXIMUM CONTINUOUS LOAD – The maximum load which can be maintained for a specified period.
MAXIMUM INSTANTANEOUS DEMAND – The sudden load demand on a boiler beyond which an unbalanced condition may be established in the boilerÕs internal flow pattern and/or surface release conditions.
MECHANICAL ATOMIZING OIL BURNER – A burner which uses the pressure of the oil for atomization.
MECHANICAL DRAFT – The negative pressure created by mechanical means.
MICRON – One millionth of a meter, or 0.000039 in. or 1/25400 in. The diameter of dust particles is often expressed in microns.
MINIATURE BOILER – Fire pressure vessels which do not exceed the following limits:
16 in. inside diameter of shell; 42 in., overall length to outside of heads at center; 20 sq ft water heating surface; or 100 psi maximum allowable working pressure.
MMBtu – Millions of Btus (British Thermal Units).
MOISTURE – Water in the liquid or vapor phase.
MOISTURE IN STEAM – Particles of water carried in steam, expressed as the percentage by weight.
MOISTURE LOSS – The boiler flue gas loss representing the difference in the heat content of the moisture in the exit gases and that at the temperature of the ambient air.
MULTIFUEL BURNER – A burner by means of which more than one fuel can be burned.
MULTIPORT BURNER – A burner having a number of nozzles from which fuel and air are discharged.
NATURAL CIRCULATION – The circulation of water in a boiler caused by differences in density.
NATURAL GAS – Gaseous fuel occurring in nature.
NET POSITIVE SUCTION HEAT (NPSH) – The liquid pressure that exists at the suction end of a pump. If the NPSH is insufficient, the pump can cavitate.
NOx – Abbreviation for all of the family of oxides of nitrogen.
NOZZLE – a short flanged or welded neck connection on a drum or shell for the outlet or inlet of fluids; also a projecting spout through which a fluid flows.
OIL BURNER – A burner for firing oil.
OIL HEATING AND PUMPING SET – A group of apparatus consisting of a heater for raising the temperature of the oil to produce the desired viscosity, and a pump for delivering the oil at the desired pressure.
OPERATING CONTROL – A control to start and stop the burner – must be in addition to the high limit control.
OPERATING PRESSURE – The pressure at which a boiler is operated.
ORGANIC MATTER – Compounds containing carbon often derived from living organisms.
ORIFICE – (1) The opening from the whirling chamber of a mechanical atomizer or the mixing chamber of a steam atomizer through which the liquid fuel is discharged. (2) A calibrated opening in a plate, inserted in a gas stream for measure velocity of flow.
ORSAT – a gas-analysis apparatus in which certain gaseous constituents are measured by absorption in separate chemical solution.
OVERPRESSURE – Minimum operating pressure of a hot water boiler sufficient to prevent the water from steaming.
OXIDATION – chemical combination with oxygen.
OXIDIZING ATMOSPHERE – An atmosphere which tends to promote the oxidation of immersed materials.
OXYGEN ATTACK – Corrosion or pitting in a boiler caused by oxygen.
PACKAGED BOILER – A boiler supplied with all of its components – burner, controls and auxiliary equipment, designed as a single engineered package, and ready for on-site installation.
PACKAGED STEAM GENERATOR – See Packaged Boiler.
PARTICLE SIZE – A measure of dust size, expressed in microns or per cent passing through a standard mesh screen. PASS – A confined passageway, containing heating surface, through which a fluid flows in essentially one direction.
PERFECT COMBUSTION – The complete oxidation of all the combustible constituents of a fuel, utilizing all the oxygen supplied.
PETROLEUM – Naturally occurring mineral oil consisting predominately of hydrocarbons.
pH – The hydrogen ion concentration of a water to denote Acidity or Alkalinity. A pH of 7 is neutral. A pH above 7 denotes alkalinity while one below 7 denotes acidity. This pH number is the negative exponent of 10 representing hydrogen ion concentration in grams per liter. For instance a pH of 7 represent 10-7 grams per liter.
PILOT – (See also ÒIgnitor.Ó) A flame which is utilized to ignite the fuel at the main burner or burners.
PITOT TUBE – An instrument which will register total pressure and static pressure in a gas stream, used to determine its velocity.
PITTING – A concentrated attack by oxygen or other corrosive chemicals in a boiler, producing a localized depression in the metal surface.
PORT – An opening through which fluid passes.
POST PURGE – A method of scavenging the furnace and boiler passes to remove all combustible gases after flame failure controls have sensed pilot and main burner shutdown and safety shut-off valves are closed.
ppm – Abbreviation for parts per million. Used in chemical determinations as one part per million parts by weight.
PRECIPITATE – To separate materials from a solution by the formation of insoluble matter by chemical reaction. The material which is removed.
PRECIPITATION – The removal of solid or liquid particles from a fluid.
PREHEATED AIR – Air at a temperature exceeding that of the ambient air. PRESSURE – Force per unit of area.
PRESSURE DROP – The difference in pressure between two points in a system, caused by resistance to flow.
PRESSURE VESSEL – A closed vessel or container designed to confine a fluid at a pressure above atmospheric.
PRIMARY AIR – Air introduced with the fuel at the burner.
PRIMING – The discharge of steam containing excessive quantities of water in suspension from a boiler, due to violent ebullition.
PROCESS STEAM – Steam used for industrial purposes other than for producing power.
PRODUCTS OF COMBUSTION – The gases, vapors, and solids resulting form the combustion of fuel.
PULSATION – Rapid fluctuations in pressure.
PURGE – To introduce air into the furnace and the boiler flue passages in such volume and manner as to completely replace the air or gas-air mixture contained therein.
RADIATION LOSS – A comprehensive term used in a boiler-unit heat balance to account for the conduction, radiation, and convection heat losses from the boiler to the ambient air.
RATED CAPACITY – The manufacturerÕs stated capacity rating for mechanical equipment; for instance, the maximum continuous capacity in pounds of steam per hour for which a boiler is designed.
RATE OF BLOWDOWN – A rate normally expressed as a percentage of the water fed.
RATING – See “Load.”
RAW WATER – Water supplied to the plant before any treatment.
REACTION – A chemical transformation or change brought about by the interaction of two substances.
REASSOCIATION – The recombination of the products of dissociation.
RECIRCULATION – The reintroduction of part of the flowing fluid to repeat the cycle of circulation.
REDUCING ATMOSPHERE – An atmosphere which tends to 1) promote the removal of oxygen from a chemical compound; 2) promote the reduction of immersed materials.
REDUCTION – Removal of oxygen from a chemical compound.
REFRACTORY – Brickwork or castable used in boilers to protect metal surfaces and for boiler baffles.
RELATIVE HUMIDITY – The ratio of the mass of water vapor present in a unit volume of gas to the maximum possible mass of water vapor in unit volume of the same gas at the same temperature and pressure.
RELIEF VALVE (Safety Relief Valve) – An automatic pressure relieving device actuated by the pressure upstream of the valve and characterized by opening pop action with further increase in lift with an increase in pressure over popping pressure.
RESIDUAL FUELS – Products remaining from crude petroleum by removal of some of the water and an appreciable percentage of the more volatile hydrocarbons.
RESIN – A bead-like material used in chemical exchange for softeners and dealkalizers.
RESISTANCE – Impediment to gas flow, such as pressure drop or draft loss through a dust collector. Usually measured in inches water column (“wc).
RETURN FLOW OIL BURNER – A mechanical atomizing oil burner in which part of the oil supplied to the atomizer is withdrawn and returned to storage or to the oil line supplying the atomizer.
RINGELMANN CHART – A series of four rectangular grids of black lines of varying widths printed on a white background, and used as a criterion of blackness for determining smoke density in stack gas streams.
ROTARY OIL BURNER – A burner in which atomization is accomplished by feeding oil to the inside of a rapidly rotating cup.