Article Index

Through stay- A brace used in fire-tube boilers between the heads or tube sheets.

Tile- A preformed refractory, usually applied to shapes other than standard brick.

Total air- The total quantity of air supplied to the fuel and products of combustion. Percent total air is the ratio of total air to theoretical air, expressed as percent.

Total pressure- The sum of the static and velocity pressures.

Total solid concentration- The weight of dissolved and suspended impurities in a unit weight of boiler water, usually expressed in ppm.

Trap- A receptacle for the collection of undesirable material.

Treated water- Water which has been chemically treated to make it suitable for boiler feed.

Trim- Ancillary boiler components, like water level controls, pressure controls, and temperature controls.

Tube- A hollow cylinder for conveying fluids.

Tube brushes- Used in fire tube boilers to remove soot from inside of tubes.

Tube hole- A hole in a drum, heater, or tube sheet to accommodate a tube.

Tube sheets- Tubes are rolled, expanded and beaded into front and rear tube sheets of HRT and scotch marine boilers and upper and lower tube sheets of vertical fire tube boilers.

Tubular gauge glass- Round gauge glass used for pressures up to and including 250 psi.

Turbulence- Movement of water in the steam and water drum.

Turbulent burner- A burner in which fuel and air are mixed and discharged into the furnace in such a manner as to produce turbulent flow from the burner.

Turndown ratio- Ratio of maximum to minimum fuel or steam input or boiler output.

UL LISTED- Product certification that indicates the product meets safety standards determined by Underwriters Laboratories. (ULC and cUL indicate Canadian requirements.

Unfired pressure vessel- A vessel designed to withstand internal pressure, neither subjected to heat from products of combustion nor an integral part of a fired pressure vessel system.

Use factor- The ratio of hours in operation to the total hours in that period.

VA- Volt amperes.

Vapor- The gaseous product of evaporation.

Vaporization- The change from liquid or solid phase to the vapor phase.

Velocity pressure- The measure of the kinetic energy of a fluid.

Vent- An opening in a vessel or other enclosed space for the removal of gas or vapor.

Vent condenser- Removes oxygen and other non-condensable gases in a deaerating feedwater heater.

Vertical firing- An arrangement of a burner such that air and fuel are discharged into the furnace in practically a vertical direction.

Viscosity- Measure of the internal friction of a fluid or its resistance to flow.

Volume of air- The number of cu ft. of air per min expressed at fan outlet conditions.