Section 52.01-3 - Definitions of terms used in this partFor primary definitions associated with power boiler design, see Section I of the ASME BPVC (incorporated by reference; see § 52.01-1 ).
(a)Types of boilers - (1)Main power boiler. A main power boiler is a steam boiler used for generating steam for main propulsion.(2)Auxiliary or donkey boiler. An auxiliary or donkey boiler is a steam boiler used for general purposes other than main propulsion.(3)Watertube boiler. A watertube boiler is a steam boiler in which the boiler tubes contain water and steam. The heat is applied to the outside surface of the tubes.(4)Internally fired firetube boiler (scotch boiler). An internally fired firetube boiler is a steam boiler containing furnaces, one or more combustion chambers and tubes or flues, which are surrounded by water and through which the products of combustion pass from the furnace to the uptake.(5)Externally fired firetube or flue boiler (horizontal return tubular). An externally fired firetube or flue boiler is a steam boiler, part of the outer shell of which is exposed to fire or to the products of combustion, and containing flues through which such products pass from the furnace to the uptake.(6)Unfired steam boiler. A pressure vessel in which steam is generated by means other than fuel combustion is classed as an unfired steam boiler. (See § 54.01-10 of this subchapter.)(b)Parts of boilers - (1)Superheater. A superheater is an appliance, normally consisting of tube rows, for the purpose of increasing the temperature of steam above the saturation temperature.(2)Economizer. An economizer is a feed-water heater usually located in the uptake or casing of a boiler to absorb heat from the waste gases.(3)Furnace. A furnace is a firebox or a large flue in which the fuel is burned.(4)Flues. Flues are cylindrical shells made of seamless or welded tubing, or with a riveted longitudinal joint, the ends being attached by riveting or welding. Their purpose is to provide additional heating surface and to form a path for the products of combustion.(5)Tubes. Tubes are cylindrical shells of comparatively small diameter constituting the main part of the heating surface of a boiler or superheater.(c)Pressure relief devices. For boilers, pressure vessels, and pressure piping, a pressure relief device is designed to open to prevent a rise of internal pressure in excess of a specified value due to emergency or abnormal conditions. It may be a pressure relief valve or a nonreclosing pressure relief device. (1)Pressure relief valve. A pressure relief valve is a pressure relief device, which is designed to reclose and prevent the further flow of fluid after normal conditions have been restored.(i)Safety valve. A safety valve is a pressure relief valve actuated by inlet static pressure and characterized by rapid opening or pop action. Examples of types used on boilers include: (A)Spring-loaded safety valve. A spring-loaded safety valve is a safety valve fitted with a spring, which normally holds the valve disk in a closed position against the seat and allows it to open or close at predetermined pressures. Spring-loaded safety valves are characterized by pop action.(ii)Pilot operated pressure relief valve. A pilot operated pressure relief valve is a pressure relief valve in which the major relieving device is combined with and is controlled by a self-actuated auxiliary pressure relief pilot valve.(iii)Temperature actuated pressure relief valve. A temperature actuated pressure relief valve is a dual-function relief device designed to protect against both excessive pressure and temperature.(2)Nonreclosing pressure relief device. A nonreclosing pressure relief device is a pressure relief device not designed to reclose after operation. (i)Rupture disk device. A rupture disk device is a device actuated by inlet static pressure and designed to function by the bursting of a pressure-retaining disk.(ii)Explosion rupture disk device. An explosion rupture disk device is a rupture disk device designed for use at high rates of pressure rise.(iii)Fusible plug device. A fusible plug device is a device designed to function by the yielding or melting of a plug of suitable melting temperature.(3)Vacuum relief valve. A vacuum relief valve is a valve designed to admit fluid or gas to prevent an excessive internal vacuum. (d)Other boiler attachments -(1)Mountings. Mountings are nozzle connections, distance pieces, valves, or fittings attached directly to the boiler. (2)Main steam stop valve. A main steam stop valve is a valve usually connected directly to the boiler for the purpose of shutting off the steam to/from the main steam line.(3)Auxiliary steam stop valve. An auxiliary steam stop valve is a valve usually connected directly to the boiler for the purpose of shutting off the steam to/from the auxiliary lines.(4)Manifold. A manifold is a fitting with two or more branches having valves either attached by bolting or integral with the fitting.(5)Blowoff valve. A blowoff valve is a valve connected directly to the boiler for the purpose of blowing out water, scum or sediment.(6)Dry pipe. A dry pipe is a perforated or slotted pipe placed in the highest part of the steam space of a boiler to prevent priming (water carryover).(7)Water column. A water column is a fitting or tube equipped with a water glass attached to a boiler for the purpose of indicating the water level.(8)Test cocks. Test cocks are small valves on a boiler for indicating the water level or water sampling.(9)Fusible plugs. Fusible plugs are plugs made with a bronze casing and a tin filling, which melts at a temperature of 445 to 450 °F. They are intended to melt in the event of low water level.(e)Boiler fabrication - (1)Repair. Repair is the restoration of any damaged or impaired part to an effective and safe condition.(2)Alteration. Alteration is a structural modification to or departure from an approved design or existing construction.(3)Access or inspection openings. Access or inspection openings are holes cut in the shells or heads of boilers or boiler pressure parts for the purpose of inspection and cleaning.(f)Gage (or gauge) pressure. Gage pressure is the difference between the pressure at the point being measured and the ambient pressure for the gage. It is measured in units such as pounds per square inch gage (psig).(g)Maximum allowable working pressure. For a definition of maximum allowable working pressure, see PG-21 of Section I of the ASME BPVC.CGFR 68-82, 33 FR 18815, Dec. 18, 1968, as amended by CGFR 69-127, 35 FR 9976, June 17, 1970; CGD 81-79, 50 FR 9431, Mar. 8, 1985; CGD 83-043, 60 FR 24772, May 10, 1995