Article Index

Sludge- Accumulation residue produced from impurities.

Smoke- Tiny particles of carbon or soot resulted from incomplete combustion.

Softening- Is the removal of calcium, magnesium, and certain other metal atoms in hard water.

Soft water- Is water which has relatively low concentration of calcium carbonate and other ions.

Solenoid valve- An electromagnetic valve positioned open or closed.

Solution- Is a mixture of one substance dissolved in another so the properties are the same throughout such as boiler water.

Soot- Impure carbon particles resulting from the incomplete combustion of hydrocarbons.

Soot blower- A mechanical device for removing the soot that is deposited on the furnace tubes of a boiler during combustion.

Spalling- Hairline cracks in boiler brickwork (refractory) due to changes in furnace temperature.

Spark Arrester- Any device which prevents the emission of flammable debris to protect large dust particles flow or sparks from a stack, usually screening at the top.

Specific heat- The quantity of heat, expressed in Btu, required to raise the temperature of 1 lb. of a substance 1°F.

Specific humidity- The weight of water vapor in a gas water-vapor mixture per unit weight of dry gas.

Spontaneous combustion- Occurs when combustible materials self-ignite.

Spray nozzle- A nozzle from which a liquid fuel is discharged in the form of a spray.

Stack- A vertical conduit, which due to the difference in density between internal and external gases, creates a draft at its base.

Stack draft- The magnitude of the draft measured at the inlet to the stack.

Stack effect- That portion of a pressure differential resulting from difference in elevation of the points of measurement.

Stagnation- The condition of being free from movement or lacking circulation.

Standard air- Dry air weighing 0.075 lb. per cu ft. at sea level (29.92 in. Barometric Pressure) and 70 °F.

Standard flue gas- Gas weighing 0.078 lb. per cu ft. at sea level (29.92 in. Barometric Pressure) and 70 °F.

Static pressure- The measure of potential energy of a fluid.

Steam- The vapor phase of water, unmixed with other gases.

Steam boiler- A closed pressure vessel in which water is converted to steam by the application

Steam bound- Condition that occurs when the temperature in the open feedwater heater gets too high and the feedwater pump cannot deliver water to the boiler of heat.

Stem gauge- A gauge for indicating the pressure of steam.

Steam generating unit- A unit to which water, fuel, and air are supplied and in which steam is generated. It consists of a boiler furnace, and fuel burning equipment, and may include as component parts water walls, superheater, reheater, economizer, air heater, or any combination thereof.

Steam pressure gauge- Indicates the steam pressure in the boiler in pound per square inch.

Steam purity- The degree of contamination. Contamination is expressed in ppm.

Steam quality- The percent by weight of vapor in a steam and water mixture.