Boiler System Terminology

Alkalinity: a measure of the ability to neutralize hydrogen ion (acidity). In most cases the alkalinity is equal to the bicarbonate, carbonate, and hydroxide content of the water; it may also include phosphate species. Bicarbonate alkalinity breaks down in a boiler to carbonate, carbon dioxide, and hydroxide.

Amine: a chemical characterized by having its primary functional group a nitrogen atom attached to a least one carbon atom; used for neutralizing acidity, especially carbon dioxide from the breakdown of alkalinity.

Blowdown: that portion of the boiler water which is periodically removed to maintain boiler cycles; blowdown is a continuous and/or intermittent, often to a blowdown flash tank for heat recovery.

Boiler: in general a piece of equipment consisting of a combustion chamber and a water-containing chamber for the purpose of converting water to steam and for its control and conditioning for a specific service.

Boiler feed pump: the feed pump that pressurizes the preheated feedwater for entry into the boiler section.

Carryover: liquid water which exits the boiler; it carries all the dissolved solids that are present in the boiler water; generally undesirable; it is produced by poor water/steam separation in the steam drum due to any of a variety of causes.

Condensate: condensed steam that may be returned to the feedwater loop of the boiler circuit.

Condensate Return: that fraction of steam that is returned as a condensate to the boiler, including extraction steam.

Cycles: the ratio of the concentration of a non-volatile dissolved species in the boiler liquid to that in the feedwater liquid; a measure of the degree of concentration.

Deaerator: a device for the mechanical removal of dissolved gases, especially oxygen, in boiler feedwater; functioning on the principle of reduced solubity of most dissolved gases as temperature increases, and providing for a mechanical means of removing the gases from the system.

Density: the mass of substance divided by its volume, expressed in the units of the measurement.

Dissolved solids: non-volatile components (solutes) in a liquid phase which do not exist as a separate phase.

Drum Steam: the steam contained in the drum i.e. saturated steam, also containing physically entrained water.

Expansion tank: a ballast tank which allows for volume changes in the water contained in a hot water heater (boiler) so as to prevent water hammer, and allow for the controlled flow of hot water.

Feedwater: water which has been conditioned for entry into a boiler; usually chemically treated and heated to near boiling temperature at the throttle pressure of the boiler.

Hardness: ions of polyvalent metal atoms which form insoluble species with carbonate usually expressed as CaCO3 equivalent.

Heat Exchanger: a mechanical device for the transfer of heat energy form one phase to another, usually a shell and tube container in which both process and working liquids are circulated in separate spaces separated by metallic conductor.

HVAC: Heating Ventilation and Air Conditioning

Internal Treatment: Chemical treatment added to the boiler as opposed to the feedwater or condensate; usually a precipitating treatment, chelant, all polymer, combination, or coordinated phosphate.

Makeup: any fresh water added to the boiler circuit to make up for losses due to blowdown or non-returned steam; usually added to the steam drum.

Oxygen Scavenger: a chemical substance that is capable of reacting with oxygen under feedwater conditions so as to reduce the level of dissolved oxygen below that achievable by mechanical deaeration.

Passivation: the process whereby a metal is converted to a passive phase; such as iron into magnetite.

Polymer: a chemical substance characterized by the presence of a large number of repeating units; in water treatment polymers are used for desperation or flocculation.

Steam: the gaseous phase of water

Steam Drum: the boiler element consisting of a horizontal metal tube with risers, a downcomer, internal elements for chemical treatment addition, makeup water addition, level control, and a steam exit; used to promote efficient separation of the steam from the water in the boiler.

Steam Generator: a vessel in which steam is produced by a liquid/liquid of gas/liquid heat exchange as opposed to direct firing.

Steam Quality: the attribute of steam that expresses the fraction of liquid moisture in the steam.