Every Industry has its own unique terminology. Sometimes these terms can be confusing so we thought a boiler dictionary would be helpful. The following definitions can be found in a number of texts.
Glossary of Boiler Terms and Definitions
R
Radiant – As applied to heat, having the property that permits heat to be transmitted by rays similar to those of light. To absorb radiant heat, an object must be in the “light” of the fire.
Radiant section – The part of a process heater into which the burners fire. Tubes mounted in this area of the furnace receive heat principally via direct radiation from both burner flames and furnace refractory. Physical volume arrangement of the radiant section has a great effect on burner choice and required flame patterns.
Radiation – All warm bodies emit light (electromagnetic radiation – mostly infrared). When this radiation is absorbed or emitted by a body, heat is transferred and termed “heat transfer by radiation”. Such heat transfer requires a line of sight (view factor) and is proportional to the fourth power of the absolute temperature difference between bodies and the emissivity of the bodies.
Rated capacity – The manufacturer’s stated capacity rating for mechanical equipment, for instance, the maximum continuous capacity in pounds of steam per hour for which a boiler is designed.
Ratio of specific heats (k) – Also known as isentropic coefficient. Is equal to the quotient of the heat capacity at constant pressure and the heat capacity at constant volume. (Cp/Cv). This parameter is tabulated for many pure components at standard conditions, but is technically dependent on the gas composition and temperature. The values are dimensionless and range from 1.0 to 1.6.
Raw water – Untreated feedwater.
Recycle – The process of sequencing a normal burner start-up following shutdown.
Refractory – A heat-insulating material, such as firebrick or plastic fire clay, used for purposes as lining combustion chambers.
Reheater – A device using highly superheated steam or high-temperature flue gases as a medium serving to restore superheat to partly expanded steam; used often between high – and low-pressure turbines.
Relay – A device that is operative by a variation in the conditions of one electric circuit to start the operation of other devices in the same or another electric circuit (such as pressure or temperature relay).
Return trap – A trap designed to discharge its condensate against boiler pressure and feed to the boiler without additional mechanical equipment.
Ringlemann chart – A series of four rectangular grids of black lines of varying widths printed on white background, used in criterion of blackness for determining smoke density from chimneys.
Riser tube – A tube through which steam and water pass from an upper waterwall header to a drum.
Regulator, gas pressure – A spring loaded, dead weighted or pressure balanced device which will maintain the gas pressure to the burner supply line.
Sources:Sources for this listing were found in the ASME Boiler Codes, American Society of Mechanical Engineers, New York; ABMA; Metals Handbook, American Society for Metals; ASHRAE Handbooks; and Boiler Operator’s Guide by Anthony L. Kohan, The John Zink Combustion Handbook, Charles E. Baukal, Jr., editor.
