This subclass covers general aspects of, or methods for, generating superheated steam. Methods of steam superheating characterised by the form of heating method and by location, arrangement and disposition, constructional features of steam superheaters, control systems for controlling superheat temperature and all component parts or details of steam superheaters are covered. Thereby this subclass is limited in only methods of, or apparatus for, the generation of superheated steam for heating or power purposes.

Methods of steam generation and steam boilers are classified in F22B, economisers and all aspect concerning feed water supply and circulation of feed water in boilers are classified in F22D, engine plants where engine aspects predominate are classified in F01K, domestic central heating systems using steam are classified in F24D, heat exchange or heat transfer in general is classified in F28 and the generation of vapour in cores of nuclear reactors is classified in G21.

Attention is drawn to the definition of superheated "steam" and superheated "vapour". In cases where a specific entry for vapour is missing, documents related to special superheated vapours are classified in groups where only superheated "steam" is explicitly mentioned.

Superheaters and methods of generation of superheated steam characterised by the heating method, such as the heat being supplied by steam, by hot flue gases from a furnace or a steam boiler, by radiation, by chemical radiation or by a separate heat source independent from heat supply of the steam boiler, including electrically heated superheaters. Furthermore methods of creating superheated steam by throttling such as reducing the pressure or direct superheaters such as devices and methods for mixing steam with furnace gases or other combustion products are classified in this main group

Methods of steam generation, where there is not mentioned, that the generated steam is superheated and characterised by form of heating method are classified in F22B 1/00.

When superheated steam is created only by the exothermic combustion of oxygen and hydrogen, then the groups F22B 1/003 and F01K 25/005 should also be considered.

Constructional features and details of component parts of steam superheaters such as steam tube arrangements, superheater drain arrangements, steam tubes with steam flowing in opposite direction in one pipe, annular steam tubes, steam superheaters with heating tubes, headers and collectors of superheaters. Furthermore arrangements for the protection of superheater elements and connecting or sealing of superheater tubes are covered.

Component parts or details of steam boilers are classified in F22B 37/00, which contains much more entries than F22G 3/00.

Methods and devices for controlling superheat steam by regulating flue gas flow, by circulating flue gases, by displacing superheater sections, by attemperating the superheated steam (i. e. spraying water into steam), by indirectly cooling or heating the superheated steam in auxiliary enclosed heat-exchangers, by by-passing steam around superheater sections. Furthermore applications of combustion-control devices and combined control procedures for controlling superheat temperature are covered.

Control of steam boilers in general are covered by the group F22B 35/00

Steam superheaters, which are characterised by their location, arrangement or disposition, like superheaters being located in locomotive boilers, in fire tubes, in jackets around fire tubes, in furnace tubes, in fire boxes, in smoke boxes, in flues or in water-tube boilers.

Methods of steam generation and steam boilers are classified in F22B