1 Scope of Section I, Organization, and Service Limits

Section I applies to several types of boilers and components of boilers, such as economizers, superheaters, reheaters, and, in some circumstances, feedwater heaters. Although its title is Rules for Construction of Power Boilers, its scope is somewhat broader. The Preamble to Section I explains that it covers electric boilers, miniature boilers, high-temperature water boilers, heat recovery steam generators, certain fired pressure vessels, and organic fluid vaporizers. Since the precise definitions of these various types of boilers are not generally known, the following definitions, found in footnotes to the Preamble, are helpful:

Power boiler—a boiler in which steam or other vapor is generated at a pressure of more than 15 psi (100 kPa) for use external to itself.

Electric boiler—a power boiler or a high-temperature water boiler in which the source of heat is electricity.

Miniature boiler—a power boiler or high-temperature water boiler in which the limits in PMB-2 are not exceeded. (PMB-2 establishes limits on shell diameter, heating surface, gross volume, and maximum allowable working pressure. See further discussion under Part PMB later in this chapter.)

High-temperature water boiler—a water boiler intended for operation at either pressures in excess of 160 psi (1.1 MPa) or temperatures in excess of 250° F (120°C), or both.

Heat recovery steam generator (HRSG)—a boiler that has as its principal source of thermal energy a hot gas stream having high-ramp rates and temperatures such as the exhaust of a gas turbine.

Fired pressure vessel—reheater, isolable superheaters, and nonintegral separately fired superheaters.