Among the signs of the times in the world of steam engineering is the wonderful growth during the past decade of mechanical stoking. Not merely is this scientific method of firing being adopted for isolated steam plants of moderate capacity, but it is safe to say that mechanical stoking has come to be regarded as a sine qua non in the equipment of a large modern power station. Just how extensive has been the growth of this industry may be judged from the fact that one firm alone in this city, who handle what is probably the most successful form of stoker in existence, are now installing at the power houses of the Metropolitan Street Railway Company of this city, mechanical stokers for a total of 66.000 horse power of boilers, while they are, furthermore, equipping over 225,000 horse power of boilers in various parts of the United States. These figures are particularly striking when we bear in mind that the era of the rapid growth of the industry in this country has been confined almost exclusively to the decade which is now drawing to a close. As a matter of fact, at the commencement of this decade there were only three mechanical stokers manufactured in this country, and the activity which is now manifest in the invention and improvement of existing forms is due to the stimulus offered by the excellent results achieved by the Murphy, the Brighman, and the Roney types. The later forms are almost entirely improvements upon designs which had been patented either here or abroad previous to 1885. Equally curious is the fact that although the application of this industry on a large scale in this country is of such recent date, mechanical stoking, as such, is as old as the steam engine itself. The earliest records of this subject show that the first mechanical stoker to be patented was one designed by the inventor of the steaui engine himself, and it is to the credit of James Watt that the design, crude as it may have been, embodies the essential features of any good mechanical stoker. The coal was fed at the furnace door,.and as it became coked was pushed back over two sets of horizontal grate bars. At the front of the furnace it became coked, and the gases from the coking fuel passed over tbe, partially coked and live fuel in the middle and at the back of the grate, where they were completely consumed. Such, in principle at least, is the mechanical stoker of to-day. The.popularity of mechanical stoking is to be set down to the relative obvious advantages over stoking by hand. In the first place, the feeding of the fuel is constant and even. The fresh fuel being introduced only at the front of the furnace is very gradually coked, the liberated gases meeting with a supply of fresh air led in by special ducts to provide the necessary oxygen for combustion, and the bed of incandescent fuel over which the gases pass serves to raise their temperature to the ignition point and secure their perfect combustion. A further advantage is the ease with which a bed of fuel of uniform thickness may be maintained over the whole grate surface. Furthermore, there is the prevention of a serious loss of beat due to the necessarily frequent opening of the fire doors in hand firing, which not only reduces the temperature of the furnace by allowing streams of cold air to impinge on the tube sheets, but subjects the latter to serious strain, and is a fruitful source of leaking tube ends. Other advantages are the great saving in labor in plants which require more than one fireman in firing by hand, and the abatement of the smoke nuisance, due to the very perfect combustion. A further improvement, which is readily appreciated in the engine room, is the uniformity of the steam pressure, rendering the boiler better able to respond to heavy demands for steam. It is stated by an inventor who has had more to do with the modern development of mechanical stoking in this country than any other man, that a well designed stoker, as compared with a hand-fired furnace, will save ten per cent in the fuel, while one man operating a stoker will do as much as two men engaged in hand firing ; this last estimate referring to the smaller plants. Where the boiler plant is of such a size as to warrant the installation of coal and ash handling machinery, the reduction of labor is estimated by the same authority to be about seventy-five per cent. In view of the remarkable growth of the industry we are publishing in the SUPPLEMENT a series of illustrated articles, commencing with the issue of last week, in which some of the most representative forms of mechanical stokers will be fully illustrated and described.
This article was originally published with the title "Mechanical Stoking" in SA Supplements 50, 1290supp, 178 (September 1900)