Mechanical stokers, including their mechanical grates,

84.16 Furnace burners for liquid fuel, for pulverised solid fuel or for gas; mechanical stokers, including their mechanical grates, mechanical ash dischargers and similar appliances. 8416.10 - Furnace burners for liquid fuel 8416.20 - Other furnace burners, including combination burners 8416.30 - Mechanical stokers, including their mechanical grates, mechanical ash 8416.90 - Parts dischargers and similar appliances This heading covers a ran e of apparatus for the mechanical or automatic firing and stoking of furnaces of all kinds, and or evacuating the ash and cinders. f (A) FURNACE BURNERS These project a flame directly into the furnace, and dispense with the need for a grate and for ash removal. They include the following types : (1) Heavy oil burners (atomisers). In these the hea fuel is atomised in the air stream, in some cases by compressed air and in others by hig pressure steam or mechanically (the latter types of apparatus usually incorporate a motor, a pump and an air blower). y (2) Pulverised coal burners. These are often of lar e size. A 'et of pulverised coal is forced into the furnace by means of an air blast which a so provi es the prima air supply. The burners may sometimes incorporate a coal conveyor and a grinmng mi?. In another type, soft coal is pulverised and injected intermittently by the alternate achon of high or low pressure steam. f d (3) Gas burners. These include both high pressure types for use with forced draught, and low pressure types for use with atmospheric air. The air and gas is in either case fed through concentric or converging tubes. (4) Combination burners. These provide for the simultaneous combustion of oil, gas and powdered coal, or any two of them. @) MECHANICAL STOKERS, MECHANICAL GRATES, MECHANICAL ASH DISCHARGERS AND SIMILAR APPLIANCES These are various mechanical appliances for feeding solid fuels to furnaces, or for forming the fire bed. Mechanical stokers and mechanical grates are fie uently combined and also equipped with devices for the automatic removal of the slag and as after combustion, thus forming a full automatic installation. In other cases a mechanical or automatic element may be combined wit i a non-mechanical element. II (I) Mechanical stokers. These are of wide1 differing t es. They usually corn rise a coal hopper together with various devices suc as Archtme ean screws, mechanics shovels, sliding trays, propelling ? pistons, operated b hand or by power, for regulatin the su ply of coal and conveying it to the furnace bed. hese appliances are often fittef with greakers for reducing the coal supply to uniform size. The heading covers mechanical stokers for central heating (including domestic) boilers. f (2) Mechanical grates. These are ap liances of varying design by which the coal is distributed over the fire-bed and moved onvard through the furnace to secure even combustion. The most common systems are based on the principle of the cate illar band, or take the form of oscillating inclined steps. These grates often terminate wit appliances for removing the slag and ash. In other systems the slag and ash removal is effected by separate mechanical units; these are also classified in this heading. 'f 'R PARTS Sub'ect to the general provisions regardin the classification of parts (see the General Exp anatory Note to Section XVI), parts of tfe goods of this heading are also classified here (e.g., burner nozzles, thrust pistons and tra s for mechanical stokers; chassis for mechanical grates, link sections and links, guides and rol s for mechanical grates). T The heading does not cover non-mechanical fire-bars or grates, industrial or other. Fire-boxes consisting of fixed grates in a metal body designed to be fitted as an integral art into certain typespf boilers are excluded d are regarded as pats of boilen and fall in heading 8i.n.Similarly, certam other types of nonmechanical grates whlch are identifiable as specialised for particular machines or appliances are classified as arts for such machines and appliances (e-g., for gas generators - heading 84.05 . On the other hand, iron Le-bars and grates of general use, for fitting into brickwork, are classified m he. 'ng 73.21,73.22 or 73.26 according to type. d, -