MACHINES positive displacement rotary or oscillating piston liquid and elastic fluid or elastic fluid liquid only reciprocating piston or other liquid and elastic fluid or elastic fluid liquid only non-positive displacement liquid and elastic fluid or elastic fluid liquid only ENGINES positive displacement rotary or oscillating piston liquid and elastic fluid or elastic fluid liquid only reciprocating piston or other liquid and elastic fluid or elastic fluid liquid only non-positive displacement liquid and elastic fluid or elastic fluid liquid only PUMPS positive displacement rotary or oscillating piston reciprocating piston or other non-positive displacement In this class, the following terms or expressions are used with the meanings indicated: "combustion" means the direct combination of oxygen gas, e.g. in air, and a burnable substance. Any other heat-producing combination of chemical substances, e.g. hydrogen peroxide and methane, iron oxide and aluminium, is covered by section C or by subclass ; "combustion chamber" means a chamber in which fuel is burned to establish a self-supporting fire or flame and which surrounds that fire or flame; "burner" means a device by which fluent fuel is passed to a combustion space where it burns to produce a self-supporting flame; "air" means a mixture of gases containing free oxygen and able to promote or support combustion. This subclass only covers combustion wherein the main body of fuel is either essentially stationary during combustion or mechanically transported, as opposed to pneumatically transported or suspended in air, during combustion. In this subclass, the first place priority rule is applied, i.e. at each hierarchical level, classification is made in the first appropriate place. In this subclass, methods are classified in the groups that cover the apparatus used. Methods that are not related to a particular type of apparatus are classified in group . In this subclass, it is desirable to add the indexing codes of groups . COMBUSTION APPARATUS Combinations of two or more combustion chambers Specially adapted for portability or transportability Functional types Returning solid combustion residues to the combustion chamber Creating a distinct flow path for flue gases or for non-combusted gases given off by the fuel COMBUSTION METHODS NOT RELATED TO A PARTICULAR TYPE OF APPARATUS SUBJECT MATTER NOT PROVIDED FOR IN OTHER GROUPS OF THIS SUBCLASS In this subclass, methods are classified in the groups that cover the apparatus used. COMBUSTION APPARATUS SPECIALLY ADAPTED FOR COMBUSTION OF TWO OR MORE TYPES OF FUEL COMBINATIONS OF TWO OR MORE COMBUSTION CHAMBERS FUNCTIONAL TYPES OF COMBUSTION APPARATUS Fluidised bed combustion Catalytic combustion Resonant combustion COMBUSTION APPARATUS CHARACTERISED BY SUBSYSTEMS Combustion chambers Arrangement or mounting of burners Air supply Arrangements for returning flue gases or combustion products SUBJECT MATTER NOT PROVIDED FOR IN OTHER GROUPS OF THIS SUBCLASS BURNERS FOR PULVERULENT FUEL BURNERS FOR COMBUSTION OF A LIQUID Using capillary action Using fuel evaporation; direct spraying action ; Using fuel impingement on a surface , BURNERS FOR COMBUSTION OF A GAS BURNERS FOR COMBUSTION OF GASEOUS OR LIQUID OR PULVERULENT FUEL OTHER BURNERS ASSEMBLIES OF TWO OR MORE BURNERS This subclass covers also the burning of low-grade fuel of solid, liquid, or gaseous nature. CREMATION FURNACES CONSUMING WASTE BY COMBUSTION Processes; Functional types of apparatus Adaptation for specific waste or fuels Details; Accessories Control or safety arrangements GRATES With solid bars; with hollow bars ; Double; inclined; revolving or rocking; travelling ; ; ; Other types Details CLEANING ARRANGEMENTS FOR GRATES, MOVING FUEL ALONG GRATE This subclass covers also the cleaning of surfaces of furnace tubes, flame tubes, water tubes, flues or the like of boilers, heat-exchange or heat-transfer conduits, which surfaces are contaminated by combustion products or combustion residues. This subclass does not cover the cleaning of surfaces of boilers, heat exchange or heat-transfer conduits contaminated by other than combustion products or combustion residues, which is covered by subclass . REMOVAL OF SOLID COMBUSTION PRODUCTS OR RESIDUES From combustion chamber From places beyond the fire TREATMENT OF COMBUSTION PRODUCTS OR RESIDUES Supply of chemicals; preventing solidification; Treating smoke or fumes ; ; FLUES, FITTINGS FOR CHIMNEYS OR FLUES , SUBJECT MATTER NOT PROVIDED FOR IN OTHER GROUPS OF THIS SUBCLASS AIR SUPPLY Passages for: primary air; secondary air ; Valves or dampers construction arrangements: before the fire; after the fire ; Blast-producing apparatus before the fire; heating of air for combustion ; SUPPLYING NON-COMBUSTIBLE LIQUIDS OR GASES, OTHER THAN AIR, TO THE FIRE DRAUGHT-INDUCING SUBJECT MATTER NOT PROVIDED FOR IN OTHER GROUPS OF THIS SUBCLASS IGNITERS Mechanical Using electric sparks , Incandescent With pilot flame By catalysis Other REMOTE IGNITION TESTING LIGHTERS CONTAINING FUEL , , EXTINGUISHING DEVICES