Article Index

Steam separator- Device used to increase the quality of steam. Found in the steam and water drum.

Steam space- The space above the water line in the steam and water drum.

Steam strainer- Used before steam traps and turbine throttle valves to remove solid impurities.

Steam supply stop valve- The valve installed at the steam outlet of the boiler to shut off the flow of steam

Steam trap- An automatic device that removes gases and condensate from steam lines and heat

exchangers without the loss of steam.

Steam turbine - Used to drive boiler auxiliaries or generators in large plants.

Stopcock- A quick-opening or closing valve usually found on gas lines.

Stud- A projecting pin serving as a support or means of attachment.

Suction pressure- Pressure on the liquid at the suction side of a pump

Sulfur- A combustible element found in coal and fuel oil.

Superheated steam- Steam at a temperature above it’s correspond pressure.

Superheater- Used to increase the amount of heat in the steam.

Superheater drain- Valve found on the superheater header outlet. Used to maintain flow throughout the superheater during start-up and shutdown.

Surface blowdown valve- Used to remove impurities from the surface of the water in a steam and water drum.

Surface blowoff- Removal of water, foam, etc. from the surface at the water level in a boiler. The equipment for such removal.

Surface condenser- A shell-and-tube vessel used to reduce the exhaust pressure on the outlet end of turbines or engines.

Surface tension- Caused by impurities on the top of the water in the steam and water drum.

Surge- The sudden displacement or movement of water in a closed vessel or drum.

Suspended solids- Undissolved solids in boiler water.

Swinging load- A load that changes at relatively short intervals.

Tertiary air- Air for combustion supplied to the furnace to supplement the primary and secondary air.

Theoretical air- The quantity of air required for perfect combustion.

Theoretical draft- The draft which would be available at the base of a stack if there were no friction or acceleration losses in the stack.

Therm- Unit used to measure BTU content of natural gas. One Therm = 100,000 Btu.

Thermal efficiency- The ratio of the heat absorbed by the boiler to the heat available in the fuel per unit of time.    

Thermocouple- Used to measure temperatures in the system and send them back to a recording chart.

Thermometer- Instrument used to measure temperature (degree of heat). Calibrated in degrees Celsius or degrees Fahrenheit.

Thermal shock- A cycle of temperature swings that result in failure of metal due to expansion and contraction.