| CAUTION: When using the term, always clarify the way the term is being used. |
Absolute Pressure - The sum of gauge pressure and atmospheric pressure.
Accumulation Test - Test used to establish the relieving capacity of boiler safety relief valves.
Acid Dew Point - Temperature at which acids begin to settle out of flue gases.
Alkalinity - Determined by boiler water analysis. Boiler water with a pH over 7 is considered alkaline.
Ambient Temperature - Temperature of the surrounding area.
Ampere - Unit of measure of electrical current.
Anion - Ion that has a negative electrical charge.
Area - The number of unit squares equal to the surface of an object.
ASME Code - Code written by the American Society of Mechanical Engineers that controls the construction, repairs and operation of boilers and their related equipment.
Atmospheric Pressure - Pressure at sea level (14.7 PSI).
Atomization - Process of breaking a liquid fuel stream into a mist of tiny droplets.
Atomize - To break up fluids into a fine mist.
Boiler - Closed vessel in which water under pressure is transformed into steam by application of heat.
Boiler Capacity - Pounds of steam of BTU=s of hotwater a boiler is capable of producing.
Boiler Horsepower - The evaporation of 34.5 pounds of water per hour from and at a feedwater temperature of 212°F.
Boiler Lay-Up - Removing a boiler from service for a period of time. A boiler can be laid-up wet or dry.
Boiler Room Log - A data sheet to record pressures, temperatures of other operating conditions of a boiler on a continuous basis.
Boiler Shutdown - A sequence of operation completed when taking a boiler off line.
Boiler Startup - A sequence of operations completed when preparing a boiler for service.
Boiler Vent - Valved port coming off highest part of the waterside of the boiler that is used to vent air from the boiler when it is filled. Also used to prevent a vacuum from forming when the boiler is drained.
Boiling Point - Temperature at which water changes into steam.
Bottom Blowdown - Periodic draining of part of the water in the boiler to remove the heavy sludge that settle to the bottom of a vessel.
Breeching - Ducting from boiler flue gas outlet to stack (or chimney).
British Thermal Unit - (BTU) Amount of heat necessary to raise the temperature of 1 lb. Of water 1°F.
By-Pass Line - A pipeline that passes around a control. Used so a boiler can operate manually without use of the control.
Calibrate - Adjusting a gauge, control or piece of equipment to conform with a test gauge, control or piece of equipment.
Carryover - Particles of water that flow with steam into the system piping.
Cavitation - Condition caused when a portion of water or other liquid entering the eye of a pump impeller flashes into steam bubbles. Causes pitting of pump impellers.
Celsius (Centigrade) - Temperature scale commonly used with the metric system of measurements. The freezing point of water on this scale is 0° and the boiling point of water is 100° at normal atmospheric pressure.
Centrifugal Force Force - caused by a rotating impeller that builds up in a centrifugal pump.
Check Valve -One-way flow valve for fluids.
Combustible Material - Any material that burns when it is exposed to oxygen and heat.
Combustion - The rapid union of oxygen with an element or compound that results in the release of heat.
Complete Combustion - The burning of all supplied fuel using the minimum amount of excess air.
Compound Gauge - Combination pressure gauge and vacuum gauge.
Condensate - Steam that has lost its heat and returned to water.
Condense - Process whereby steam turns back to water after the removal of heat.
Conduction - A method of heat transfer in which heat moves from molecule to molecule.
Continuous Blowdown - Small stream of water that constantly drains from a boiler to control the quantities of impurities in a boiler on a continuous basis.
Convection - A method of heat transfer that occurs as heat moves through a fluid.
Cracking Open - Slowly opening a valve, generally to allow equalization.
Cross AT@ - Used in water column piping for inspection for being clean and clear.
Cut-In Pressure - Automatic pressure control setting at which the boiler turns on.
Cut-Out Pressure - Automatic pressure control setting at which the boiler turns off.
Cycle of Concentration - Number of times solids in a particular volume of water are concentrated as compared to concentration of the solids in the original volume of water.
Deaerator - Pressure vessel that removes oxygen from the feedwater before going into the boiler.
Dealkalizer - Ion - Exchange unit that works exactly like a sodium zeolite water softener, but removes anions and replaces them with chloride.
Differential Pressure - Difference between two pressures at different points.
Differential Setting - Difference between the pressure at which the automatic pressure control turns the burner on, and the pressure at which the automatic pressure control turns the burner off.
Dissolved Solids - Impurities that have passed into solution.
Draft - The difference in pressures between two points that cause air or gases to flow.
Economizer - Uses the gases of combustion to heat boiler feedwater.
Element - A basic substance consisting of atoms.
Enthalpy - Total heat in steam.
Erosion - Wearing away of metal.
Excess Air - Air more than the theoretical amount needed for combustion.
Factor of Evaporation - Heat added to water in an actual boiler in BTU per pound and divided by 970.3.
Fahrenheit - Temperature scale commonly used with the U.S. system of measurements. The freezing point of water on this scale is 32° and the boiling point of water is 212° at normal atmospheric pressure.
Feedwater - Water that is supplied to a boiler.
Feedwater Treatment - Using softwater and chemicals in the boiler feedwater. Protects against scale and corrosion.
Fire Point - Temperature at which fuel oil burns continuously when exposed to an open flame.
Firetube Boiler - Has heat and gases of combustion passing through the furnace and boiler tubes surrounded by water.
Firing Rate - Amount of fuel the burner is capable of burning in a given unit of time.
Flame Failure - When the burner pilot or main flame goes out on its own.
Flame Scanner - Device that confirms that the pilot and main burner flame exists.
Flash Point - Temperature at which fuel oil, when heated produces a vapor that flashes when exposed to an open flame.
Flash Steam - Created when water at a high temperature has a sudden drop in pressure.
Foaming - Rapid fluctuations of the boiler water level that can lead to priming or carryover. Caused by impurities on the surface of the boiler water.
Foot Pound - Unit of measure that equals the movement of an object by a constant force (in pounds) to a specific distance (in feet).
Force - Energy exerted or brought to bear on.
Forced Draft - Mechanical draft produced by a fan.
Furnace Volume - Amount of space available in a boiler furnace to complete combustion.
Gate Valve - Valve used to shutoff or admit flow.
Gauge Glass - Glass connected to a water column or directly to a boiler that allows an operator to see the water level inside a boiler.
Gauge Pressure - Pressure above atmospheric pressure. Assumes atmospheric pressure being zero.
Gas Analyzer - Used to analyze the gases of combustion to determine combustion efficiency.
Gas Leak Detector - A device to locate gas leaks in the boiler room.
Gases of Combustion - Gases produced by the combustion process.
Globe Valve - Valve having a tapered rounded or flat disc held horizontally on the stem.
Gravity - Natural force that makes objects on earth fall to the lowest point possible.
Handhole - Small access hole, smaller than a manhole (manway), used for looking and reaching into the boiler shell during inspections.
Header - Manifold that feeds several branch pipes or takes in steam or water from several smaller pipes.
Heat Exchanger - Any piece of equipment where heat is transferred from one substance to another.
Heating Surface - Any part of a boiler metal that has hot gases or combustion on one side and water on the other.
Heat Recovery System - Equipment that is installed to reclaim heat that is normally lost.
Heat Transfer - Movement of heat from one substance to another that can be accomplished by radiation conduction or convection.
Heating Value - Expressed in BTU=s. Heating value of fuel varies with the type.
High Pressure Boiler - A boiler that operates over a steam pressure of 15 PSI.
Hot Water Boiler - Boiler that is completely full of water that produces only hot water, not steam.
Hydrostatic Pressure - Water pressure per vertical foot (.433) exerted at the base of a column of water.
Inches of Mercury (IN.Hg) - Unit of measure for vacuum.
Incomplete Combustion - Occurs when all the fuel is not burned, resulting in the formation of smoke or soot.
Infrared - Invisible light rays produced by the combustion process and detected by a flame scanner.
Latent Heat - Heat in BTU that is added so boiling water at a given temperature will change into steam at the same temperature.
Laying Up - Taking a boiler out of service for longer than a normal period of time.
Low Pressure Boiler - A boiler that operates at a steam pressure of not more than 15 PSI.
Low Water - Lower than acceptable water level in a boiler that is dangerous because it can cause over heating of a boiler.
Low Water Fuel Cutoff - Device located slightly below the NOWL of a boiler that shuts off the boiler burner in the event of low water.
Main Steam Stop Valve - Gate valve in the main steam line between the boiler and the steam header.
Makeup Water - Water that must be added to the boiler to make up for condensate that was dumped, lost through boiler blowdowns or leaks in the system.
Manhole (Manway) - Hole on the steam and waterside of a boiler used to clean, inspect and repair a boiler.
Maximum Allowable (MAWP) - Highest legal pressure at which a pressure vessel may be working pressure operated.
Modulating Pressure - Control device that regulates the burner for a higher or lower fuel Control burning rate depending on steam pressure in the boiler.
Multiple-Pass Boiler - Boilers that are equipped with a means to direct the flow of the gases of combustion so that the gases make more than one pass over the heating surfaces.
Natural Draft - Caused by the difference in weight between a column of hot gases of combustion inside the chimney (stack) and a column of cold air of the same height outside the chimney.
Non-Condensable Gas - Any gas that will not change into a liquid when its temperature is reduced.
Non-Return Valve - Combustion shutoff and check valve that allows steam to pass out of the boiler, but a back flow of steam from a drop in pressure causes the valve to close.
Normal Operating Water Level (NOWL) - Level of the boiler water at normal operation.
Overfiring - Forcing a boiler beyond its designed steam producing capacity.
Package Boiler - Boiler that comes completely factory assembled, with exception of those items that have to be removed from the boiler for shipment.
Passes - Number of times gases or combustion flow the length of the pressure vessel as they transfer heat to the water.
Perfect Combustion - Burning of all the fuel with the theoretical amount of air. Can only be achieved in a laboratory.
PH - Value representing how acidic or alkaline water is.
Phosphates - Chemicals that cause hardness particles to settle out as a heavy sludge.
Power - Unit of measure that equals the amount of foot pounds of work in a given period of time.
Pneumatic System - A system of control that uses air as the operating medium.
Pounds of Steam Per Hour (LB/HR) - Unit of measure that expresses the amount of steam produced by a boiler in one hour.
Popping Pressure - Predetermined pressure at which a safety relief valve opens and remains open until the pressure drops.
Post-Purge - The passing of air through the boiler fireside after normal burner shutdown.
Pour Point - The lowest temperature at which a fuel oil flows as a liquid.
Pre-Purge - The passing of air throught the boiler fireside prior to pilot and main burner flame lightoff.
Pressure - Application of force commonly measured in PSI.
Pressure Reducing Station - Where higher pressure steam is reduced in pressure for lower pressure needs.
Primary Air - Air supplied to the burner that regulates the rate of combustion.
Priming - Severe form of carryover in which large slugs of water leave the boiler with the steam.
Process Steam - Steam used in a plant for manufacturing or processing purposes.
Products of Combustion - Gases that are formed as a fuel is burned in a furnace.
Programmer - Device that controls the burner sequence of operation.
Proving Pilot - Sighting the pilot through a flame scanner to verify that the pilot is lit.
Pounds Per Square Inch (PSI) - Number of pounds of pressure exerted on one square inch of a given area.
Purge Period - Before ignition and after burner shutdown when explosive combustibles are removed.
Quality of Steam - Term used to express the moisture content present in saturated steam. Quality of steam effects the BTU content of the steam.
Rate of Combustion - The amount of fuel that is being burned in the furnace per unit of time.
Raw Water - Untreated water.
Reseat Pressure - The pressure at which a safety valve will reseat. It will pop above the pressure.
Ringlemann Chart - Chart used as a measure of determining smoke density.
Safety Valve - Valve that keeps the boiler from exceeding its maximum allowable working pressure.
Safety Valve Capacity - Measured in pounds of steam per hour safety valves can discharge.
Sample Cooler - Closed heat exchanger that cools a sample before it enters a sample container.
Saturated Steam - Steam at a temperature that corresponds with its pressure.
Scale - Deposits in the boiler waterside caused by improper boiler water treatment.
Scotch Marine Boiler - A firetube boiler with an internal furnace.
Secondary Air - Air that is needed to complete the combustion process.
Sediment - Particles of foreign matter present in the boiler water.
Sensible Heat -Heat that can be measured by a change in temperature.
Sludge - Accumulated residue produced from impurities in water.
Smoke Density - Varies from clear to dark. Determined by the amount of light that passes through the smoke as it leaves the boiler.
Sodium Zeolite Water Ion Softener - Exchange water softener that uses a bronze solution and resin
Softener beads to soften water.
Solid State - An electronic system using transistors in place of electronic tubes.
Soot - Fine powder consisting primarily of carbon that results from incomplete combustion.
Spalling - Hairline cracks in boiler refractory due to changes in fireside temperatures.
Specific Gravity - Weight of a given volume of a material divided by the weight of an equal volume of water measured at 60°F.
Spontaneous Combustion - Occurs when combustible materials self-ignite.
Stack - Outlet to the atmosphere for the gases of combustion. Used to create a draft.
Static Head Pressure (SHP) - Pressure at the bottom, or at some specified point, of a column of still liquid.
Steam - Gaseous form of water. Steam is odorless, colorless and tasteless.
Steam Boiler - A closed pressure vessel in which water is converted to steam by the application of heat.
Steambound - Condition that occurs when the temperature in the open feedwater heater gets too high and the feedwater pump cannot deliver water to the boiler.
Steam Space - The space above the water line in a steam boiler.
Steam Trap - Mechanical device used to remove condensate from steam piping.
Sulfur - A combustion element found in coal and fuel oil.
Superheated Steam - Steam at a temperature above its corresponding pressure.
Surface Tension - Caused by impurities on the top of the water in a steam boiler.
Tensile Stress - Occurs when two forces of equal intensity act on an object, pulling in opposite directions. Affects boiler plates and staybolts.
Therm - Unit used to measure BTU content of natural gas. A therm has 100,000 BTU.
Thermal Efficiency - The ratio of heat absorbed by the boiler to the heat available in the fuel per unit of time.
Thermal Shock - Stress imposed on boiler metal by a sudden and drastic change in temperature.
Total Force - Total pressure that is acting on an area, determined by diameter and pressure.
Total Heat - Sum of sensible heat and latent heat.
Turbulence - Movement of water in the boiler.
Ultraviolet - A form of light that is produced during combustion.
Vacuum - A pressure below atmospheric pressure.
Vacuum Breaker - Vent on top of vessel that allows air to be pulled into the tank to prevent formation of a vacuum.
Vacuum Gauge - Pressure gauge used to measure pressures below atmospheric pressure.
Valve - Mechanical device that starts, stops or regulates flow of a liquid, gas or loose bulk material.
Vapor - Diffused matter in a gaseous state.
Vertical Firetube Boiler - One pass boiler that has firetubes in a vertical position.
Viscosity - Ability of a liquid or semi-liquid to resist flow.
Waste Heat Recovery Boiler - Boiler in which heat that would otherwise be discarded is used to make steam.
Water Column - Metal vessel installed on the outside of a boiler shell or drum at the NOWL that helps an operator determine the water level in a boiler.
Water Hammer - A banging condition that is caused by steam and water mixing in a steam line.
Wet-Lay-Up - Method of short term boiler storage that keeps the boiler free from oxygen on the inside, which prevents damage from corrosion.
Working Pressure - Maximum allowable working pressure or the pressure at which the boiler is normally operated.
