The outer trunnion bearing is open, so that by slightly raising and lowering the ram of the crane, the converter may be left suspended to a weighing machine in front of the furnace, if it is required to determine the weight of the charge.  When the converter is filled, it is borne by the crane into a convenient position for blowing, and if the basic method is followed for removing the slag, the converted metal is cast into ingot moulds, which are manipulated by a small ingot crane of the ordinary pattern.  In the case of small existing blast-furnaces, which usually have their tap holes near to the ground, it may be necessary to have a shallow ingot pit (20 to 24 inches deep); but with cupolas this will not generally be necessary, and the whole of the operations may be carried on at the ground level.  Each crane is intended to be supplied with two or three converters, so that operations may be carried on continuously.  The weight of charge proposed is 15 cwt., which should under ordinary conditions give 12 cwt. of ingots.  Taking the time of a single converting operation at half an hour it will be easy to obtain fifty blows per day, or a production of 30 tons.  This may be easily increased by placing a second converting crane on the other side of the furnace, for which the same blowing engine will be sufficient, as the actual blowing time will not exceed twelve minutes.  The labor required for each converter will be about six men per shift.

The blast required has been experimentally determined at 40-50 cubic meters per minute at 15 lb. pressure.  This will be supplied by a single cylinder engine of 900 millimeters blast, and 786 millimeters steam piston, diameter 786 millimeters, stroke making fifty revolutions per minute, which is also to work a Root blower and the accumulator pumps.  Having regard to these very different demands upon the power of the engine, it will be provided with expansion gear, allowing a considerable variation in the cut-off.  A single boiler of 70 to 75 square meters heating surface will be sufficient.  The accumulator is intended to work at 300 lb. pressure.

The cost of the plant, including one of each of the following items, converter, converter truck, blowing engine, accumulator, ingot crane, centesimal weighing machine, and accumulator pump, is estimated at L2,050 to L2,100; and that of the steam boiler, L325.  The buildings may be of the simplest and cheapest possible character.  As the productive power of such a plant contrasts very favorably with its cost, the author considers that it may be fairly expected to meet the competition of large works, especially in the manufacture of a high-class product.—­Stahl und Eisen, vol. iv., page 524; through Proc.  Inst.  Civ.  Eng.

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TRIPLE COMPOUND ENGINES.

[Footnote:  Paper read before the Institution of Naval Architects, March 27, 1885.]