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 hot water 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
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.
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.
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.
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.
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.
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.
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.
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 normal operating water level (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.
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.
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.
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 through 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.
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.
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
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.
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.
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.
