NO. 1. So much has been said and written on this highly important subj ect, that it may seem a superfluous task to attempt a further elucidation of it; but, as even at this late date many men, scientific and practical, differ materially in their appreciation of the causes and extent of loss of heat, both in the production of steam and in the artsand manufactures, we have thought that a short summary of _the best ascertained and most recent facts in relation to this mattermight prove valuable to many persons who have no spare time for study, and also to a large class of men, who, holding responsible positions such as managers, directors, or superintendents of steamboat, lines, railroad companies, or of manufacturing establishments, have not received that preliminary tuition which would lead them to discover " waste of fuel" and the correctives to be applied to the same in their special cases. Economy of fuel is of much more consequence than is generally realized, so much so indeed, that many companies whose shares ought to be paying splendid dividends, have proved unprofitable and ruinous investments, simply because of a waste of perhaps twenty or thirty per cent of coal, caused by the incapacity or negligence of some one man whose duty it ought to have been to prevent this loss. It is, especially in the case of ocean steam navigation and in metallurgical operations, carried on where fuel is expensive (as it is in many of our Western Territories), that many catastrophes attributable to this cause have been recorded. Desiring in the following notes to be concise and practical, we commence with the enumeration of the principal remediable causes of waste of fuel in our steam engines, stationary, locomotive, and marine, all of which, notwithstanding their admirable recent improvements, are to be considered as very imperfect apparatus as regards their power of converting heat into motion. The causes of waste depend either on the mode of working and treatment of the engine and boilers, or on the construction of the same. In the first category we class: 1. Inefficient stoking; 2. Blowing off or brine extraction ; 3. Incrustations ; 4. Urging of fires; 5. Leaks ; 6. Carelessness before stopping; 7. Imperfect vacuum; 8. Radiation of heat; 9. Priming; 10. Use of bad coal, etc. In the second series we will enumerate : 1. Imperfections in the relative parts of the engine; 2. Defective boilers ; 3. Misconstruction of fireplaces smoke boxes, flues, and chimneys, and their effects on combustion. We shall now briefly review in succession these various sources of loss and state how best they can be remedied. INEFFICIENT STOKING Every stoker who presents himself for hire, if his skin be only sufficiently thick, cracked, and carbonized, is supposed to be competent to take care of the fires of an engine; work of this nature being considered of the simple kind which any able-bodied man can properly perform without previous schooling. This, however, is a radical mistake, as a really good and "careful" stoker, who thoroughly understands his business, is by no means common, and when found is always much valued by any competent engineer placed over him. A change in stokers, has in very many instances been im- mediately followed by a reduction of as much as one quarter in the amount of fuel consumed, which proves that one of the first things to be investigated where " waste of fuel " is suspected, is into the competency of the man who has the actual handling of it. An inefficient stoker will, independently of his extravagant use of coal, be very apt to cause damage to fire grates and boilers which will lead to their early destruction. Such a man ought to be discharged without any hesitation. As, however, it is not always possible to obtain perfect help in this line, much may be done by watching and instructing such as are willing to learn. The principal rules to be followed in firing (the air being supposed to be properly introduced into the furnace), as given by the best authority on this subj ect, W. Wye Williams, C. E., are the following: " 1. Begin to charge the furnace at the bridge end, and keep firing to within a few inches of the dead plate. "2. Neverallow thefire to be so low before a fresh charge is thrown in that there shall not be at least four or five inches of clear, incandescent fuel on the bars, and equally spread over the whole. " 3. Keep the bars constantly and equally covered, particularly at the sides and bridge end, where the fuel burns away most rapidly. " 4. If the fuel burns unequally, or into holes, it must be leveled and the vacant spaces filled. " 5. The large coals must be broken into pieces not bigger than a man's fist. " 6. Where the ash-pit is shallow it must be frequently cleared out. A body of hot cinders overheat and burn the bars." BLOWING OFF AND BRINE EXTRACTION The employment in boilers of salt, calcareous, or muddy waters, is the cause of a very considerable waste of fuel, as these various substances would soon form dangerous incrustations on the interior surfaces were they not eliminated before their deposition or solidification. The ordinary mode of doing this is by blowing off or " pumping out," a certain proportion of the hot water before its complete saturation and the cousequent formation of solid precipitates. In the British navy one-half, o'r near that quantity, of the total amount of water is extracted from the boilers by means of brine pumps, and although this immense loss of heat is equivalent to nearly three-fourths of the whole consumption j of fuel on the grates, it has been found that incrustations of variable thickness will invariably form after a voyage of a few weeks' duration. In the French navy the blow-off is continuous, the water in the boilers being kept at 0'10 of total concentration, so that one-half pound is blown off for every one pound transformed into steam, or one-half pound is blown off for every one and one-half pounds of feed water, corresponding to three degrees (observed while hot) of the standard saturometer adopted by by the service. In the Dutch navy the blow-off is effected by hand, periodically, according to the_ indications of the saljnometer, care being taken to allow the water to rise three or four inches above its normal level in the boiler before opening the blow-off cocks. The quantity of fuel wasted (that is heat lost) by " blowing off," varies according to the proportion of hot water extracted, the temperature pf the same, and the heat of the feed water supplied to replace it. The theoretical figures given in relation to this subject vary considerably in various authors, according to their caloric estimate of one pound of coal and to the quantity of water blown off, relatively to the whole quantity consumed. These figures will be found in most manuals intended for the use of officers cf the navy, and in many treatises on the steam engine. We shall, however, confine ourselves here to a purely practical mode of investigating the matter, and simply state that from careful long-contumed experiments, under the management of experienced engineers and the direction of Mr. Thos. Halliday, one of the managers of the works of the celebrated marine-building firm of John Penn & Sons, of Greenwich, England, the results of which have been kindly communicated to us by a friend, the actual loss by blowing off under careful management, may be put down at thirty-three per cent of the total amount of fuel used. This is a rather startling figure but facts are stubborn witnesses, as is shown by Mr. Halliday's conclusions which we give in his own words: "If we take" says he, "a marine steam engine of the most modern construction, with the ordinary condenser, by one of the best makers, and working with moderately superheated steam at a pressure of twenty to twenty-five pounds on the square inch, we obtain an indicated horse power by the consumption of from three and one-half to four pounds of good Welsh coals per hour. This would be the mean average of twelve months working. " Now if we take an engine with surface condensers (also by one of our best makers), and also working steam moderately superheated, we obtain an indicated horse power by the consumption of two and one-fourth to two and three-fourth pounds of similar coals per hour. Therefore we may fairly estimate the loss of heat sustained by 'blowing off' of marine boilers to be equal to thirty-three per cent. The generally received idea that the salts in sea water or in water containing lime, only form sediments after the point of saturation has been reached, is proved by recent important researches to be fallacious. In the case of bicarbonate of lime in the water, a comparatively low temperature will produce the elimination of the ex. cess of carbonic acid which caused its solubility, and the consequence will be the deposition of crusts of insoluble carbon- ate of lime. Water containing gypsum, or sulphate of lime, according to the experiments of Mr. Couste, will give up this earthy salt in a solid form when heated to about 802 Pah., equivalent to about 71 pounds of steam pressure on the square inch in the boiler. In the same manner the whole of the salts contained in sea-water, may as first stated by Delacour (and irrespectively of the degree of saturation), be mechanically precipitated if the heat of the water be raised to 320 Pah., which will take place with a boiler pressure of about 94 pounds per square inch. The above facts clearly show the causes of the great danger attending the use of high pressure boilers in connection with waters containing mineral salts in solution or suspension; even in presence of the best salinometers, brine pumps, blow-offs, or the most careful engineers. The only way of avoiding the waste of heat caused by blowing off, is by using none but pure, clear, fresh water in the production of steam. This is practically effected by the employment of surface, condensers, many different models of which are constructed. These surface condensers collect the steam escaping from the engines and cool it, until it resolves itself again into water which is run back into the boiler, so that the same fresh water used at the start, maybe indefinite ly reconverted into steam, allowance being simply made for leakage. Unfortunately, however, surface condensers are cumbrous, complicated, expensive, and liable to get out of order, so much so, indeed, that in many cases the saving of fuel has not compensated for the increased amount of repairs. Beside, the condensed water seems to have a rapidly-corroding action on iron and copper, which makes the question of durability of boilers and tubes a matter of very serious consideration. Several substitutes for surface condensers have at different times been proposed, such as the use of special accessory boilers in which to collect the sediments, or the ingenious contrivance of E. Martin, for causing the deposition of all impurities on perforated plates by the action of superheated steam on the feed water, but all of these have practically been found wanting in some respect or other. A really good surface condenser, or a substitute for it, is to this day a desideratum which urgently claims the prompt attention of inventors.
This article was originally published with the title "“Waste” and “Economy” of Fuel"