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Steam Basics – Definitions

Boiler Horsepower (BHP). The amount of energy needed to produce 34.5 pounds of steam, per hour, at a pressure and temperature of 0 Psig and 212 ºF, with feedwater at 0 Psig and 212 ºF. This is equivalent to 33,475 BTU/Hr / 8430 Kcal/Hr or 9.8095 kW.

Calorie (C). The amount of heat required, at a pressure of one atmosphere, to raise the temperature of one gram of water one degree Celsius.

Enthalpy (H or h). Thermodynamically, Enthalpy is defined as the sum of the internal energy of a body and the product of its volume multiplied by its pressure. For the sake of boiler calculations, Enthalpy can be defined as the amount of heat in a fluid, usually expressed as BTU/lb or kcal/gm. In these cases, Enthalpy is considered to be zero at 32 ºF (0 ºC).

From and at 212 ºF. A term used to qualify the amount of steam produced by a boiler (see the article on Steaming Rate). The qualification indicates that the amount of steam produced is at a pressure of 0 Psig and 212 ºF, with feedwater at 0 Psig and 212 ºF. (0 barg and 100°C).

Gross Steaming Rate. The amount of steam produced by a boiler at the outlet flange of the boiler. This is the amount of steam produced before steam is removed to heat the water in the feedwater receiver (deaerator or hotwell).

Heat of Vaporisation. For boiler calculation purposes, the amount of heat required to convert water, at saturated conditions, to vapour (steam) at the same saturated conditions. Same as Latent Heat.

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