Chapter 2

Against these advantages are to be set the greater first cost of the automatic engine, and the consequent annual charge due to capital sunk. These several items should all be fairly estimated when an engine is to be bought, and the kind chosen accordingly. Let us take the item of fuel, for instance, and let us suppose this fuel to cost four dollars per ton at the place where the engine is run. Suppose the engine to be capable of developing one hundred horse-power, and that it consumes five pounds of coal per hour per horse-power, and runs ten hours per day: this would necessitate the supply of two and one-half tons per day at a cost of ten dollars per day. To be really economical, therefore, any improvement which would effect a saving of one pound of coal per hour per horse-power must not cost a greater sum per horse-power than that on which the cost of the difference of the coal saved (one pound of coal per hour per horse-power, which would be 1,000 pounds per day) for, say, three hundred days, three hundred thousand (300,000) pounds, or one hundred and fifty tons (or six hundred dollars), would pay a fair interest.

Assuming that the mill owner estimates his capital as worth to him ten per cent, per annum, then the improvement which would effect the above mentioned saving must not cost more than six thousand dollars, and so on. If, instead of being run only ten hours per day, the engine is run night and day, then the outlay which it would be justifiable to make to effect a certain saving per hour would be doubled; while, on the other hand, if an engine is run less than the usual time per day a given saving per hour would justify a correspondingly less outlay.

It has been found that for grain and other elevators, which are not run constantly, gas engines, although costing more for the same power, are cheaper than steam engines for elevating purposes where only occasionally used.

For this reason it is impossible without considerable investigation to say what is really the most economical engine to adopt in any particular case; and as comparatively few users of steam power care to make this investigation a vast amount of wasteful expenditure results. Although, however, no absolute rule can be given, we may state that the number of instances in which an engine which is wasteful of fuel can be used profitably is exceedingly small. As a rule, in fact, it may generally be assumed that an engine employed for driving a manufactory of any kind cannot be of too high a class, the saving effected by the economical working of such engines in the vast majority of cases enormously outweighing the interest on their extra first cost. So few people appear to have a clear idea of the vast importance of economy of fuel in mills and factories that I perhaps cannot better conclude than by giving an example showing the saving to be effected in a large establishment by an economical engine.

I will take the case of a flouring mill in this city which employed two engines that required forty pounds of water to be converted into steam per hour per indicated horse-power. This, at the time, was considered a moderate amount and the engines were considered "good."

These engines indicated seventy horse power each, and ran twenty-four hours per day on an average of three hundred days each year, requiring as per indicator diagrams forty million three hundred and twenty thousand pounds (40 x 70 x 24 x 300 x 2 = 40,320,000) of feed water to be evaporated per annum, which, in Philadelphia, costs three dollars per horse-power per annum, amounting to (70 x 2 x 300 = $420.00) four hundred and twenty dollars.

The coal consumed averaged five and one-half pounds per hour per horse-power, which, at four dollars per ton, costs

((70 x 2 x 5.5 x 24 x 300) / 2,000) x 4.00= $11,088

Eleven thousand and eighty-eight dollars.

Cost of coal for 300 days. $11,088 Cost of water for 300 days. 420 ------- Total cost of coal and water. $11,503

These engines were replaced by one first-class automatic engine, which developed one hundred and forty-two horse-power per hour with a consumption of _three pounds_ of coal per hour per horse-power, and the indicator diagrams showed a consumption of _thirty_ pounds of water per hour per horse-power. Coal cost

((142 x 3 x 24 x 300) / 2,000) x 4.00 = $6,134

Six thousand one hundred and thirty-four dollars. Water cost (142 x 3.00= $426.00) four hundred and twenty-six dollars.

Cost of coal for 300 days. $6,134 Cost of water for 300 days. 426 ------ Total cost of coal and water. $6,560

The water evaporated in the latter case to perform the same work was (142 x 30 x 24 x 300 = 30,672,000) thirty million six hundred and seventy-two thousand pounds of feed water against (40,320,000) forty million three hundred and twenty thousand pounds in the former, a saving of (9,648,000) nine million six hundred and forty-eight thousand pounds per annum; or,

(40,320,000 - 30,672,000) / 9,648,000 = 31.4 per cent.

--_thirty-one and four-tenths per cent_.

And a saving in coal consumption of

(11,088 - 6,134) / 4,954 = 87.5 per cent.

--_eighty-seven and one-half per cent_., or a saving in dollars and cents of four thousand nine hundred and fifty-four dollars ($4,954).

In this city, Philadelphia, no allowance for the consumption of water is made in the case of first class engines, such engines being charged the same rate per annum per horse-power as an inferior engine, while, as shown by the above example, a saving in water of _thirty-one and four-tenths per cent_. has been attained by the employment of a first-class engine. The builders of such engines will always give a guarantee of their consumption of water, so that the purchaser can be able in advance to estimate this as accurately as he can the amount of fuel he will use.

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RIVER IMPROVEMENTS NEAR ST. LOUIS.

The improvement of the Mississippi River near St. Louis progresses satisfactorily. The efficacy of the jetty system is illustrated in the lines of mattresses which showed accumulations of sand deposits ranging from the surface of the river to nearly sixteen feet in height. At Twin Hollow, thirteen miles from St. Louis and six miles from Horse-Tail Bar, there was found a sand bar extending over the widest portion of the river on which the engineering forces were engaged. Hurdles are built out from the shore to concentrate the stream on the obstruction, and then to protect the river from widening willows are interwoven between the piles. At Carroll's Island mattresses 125 feet wide have been placed, and the banks revetted with stone from ordinary low water to a 16 foot stage. There is plenty of water over the bar, and at the most shallow points the lead showed a depth of twelve feet. Beard's Island, a short distance further, is also being improved, the largest force of men at any one place being here engaged. Four thousand feet of mattresses have been begun, and in placing them work will be vigorously prosecuted until operations are suspended by floating ice. The different sections are under the direction of W. F. Fries, resident engineer, and E. M. Currie, superintending engineer. There are now employed about 1,200 men, thirty barges and scows, two steam launches, and the stern-wheel steamer A. A. Humphreys. The improvements have cost, in actual money expended, about $200,000, and as the appropriation for the ensuing year approximates $600,000, the prospect of a clear channel is gratifying to those interested in the river.

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BUNTE'S BURETTE FOR THE ANALYSIS OF FURNACE GASES.

For analyzing the gases of blast-furnaces the various apparatus of Orsat have long been employed; but, by reason of its simplicity, the burette devised by Dr. Bünte, and shown in the accompanying figures, is much easier to use. Besides, it permits of a much better and more rapid absorption of the oxide of carbon; and yet, for the lost fractions of the latter, it is necessary to replace a part of the absorbing liquid three or four times. The absorbing liquid is prepared by making a saturated solution of chloride of copper in hydrochloric acid, and adding thereto a small quantity of dissolved chloride of tin. Afterward, there are added to the decanted mixture a few spirals of red copper, and the mixture is then carefully kept from contact with the air.

To fill the burette with gas, the three-way cock, _a_, is so placed that the axial aperture shall be in communication with the graduated part, A, of the burette. After this, water is poured into the funnel, t, and the burette is put in communication with the gas reservoir by means of a rubber tube. The lower point of the burette is put in communication with a rubber pump, V (Fig. 2), on an aspirator (the cock, _b_, being left open), and the gas is sucked in until all the air that was in the apparatus has been expelled from it. The cocks, _a_ and _b_, are turned 90 degrees. The water in the funnel prevents the gases communicating with the top. The point of the three-way cock is afterward closed with a rubber tube and glass rod.

If the gas happens to be in the reservoir of an aspirator, it is made to pass into the apparatus in the following manner: The burette is completely filled with water, and the point of the three-way cock is put in communication with a reservoir. If the gas is under pressure, a portion of it is allowed to escape through the capillary tube into the water in the funnel, by turning the cock, _a_, properly, and thus all the water in the conduit is entirely expelled. Afterward _a_ is turned 180°, and the lower cock, _b_, is opened. While the water is flowing through _b_, the burette becomes filled with gas.

_Mode of Measuring the Gases and Absorption_.--The tube that communicates with the vessel, F, is put in communication, after the latter has been completely filled with water, with the point of the cock, _b_ (Fig. 2). Then the latter is opened, as is also the pinch cock on the rubber tubing, and water is allowed to enter the burette through the bottom until the level is at the zero of the graduation. There are then 100 cubic centimeters in the burette. The superfluous gas has escaped through the cock, _a_, and passed through the water in the funnel. The cock, _a_, is afterward closed by turning it 90°. To cause the absorbing liquid to pass into the burette, the water in the graduated cylinder is made to flow by connecting the rubber tube, s, of the bottle, S, with the point of the burette. The cock is opened, and suction is effected with the mouth of the tube, r. When the water has flowed out to nearly the last drop, _b_ is closed and the suction bottle is removed. The absorbing liquid (caustic potassa or pyrogallate of potassa) is poured into a porcelain capsule, P, and the point of the burette is dipped into the liquid. If the cock, _b_, be opened, the absorbing liquid will be sucked into the burette. In order to hasten the absorption, the cock, _b_, is closed, and the burette is shaken horizontally, the aperture of the funnel being closed by the hand during the operation.

If not enough absorbing liquid has entered, there may be sucked into the burette, by the process described above, a new quantity of liquid. The reaction finished, the graduated cylinder is put in communication with the funnel by turning the cock, _a_. The water is allowed to run from the funnel, and the latter is filled again with water up to the mark. The gas is then again under the same pressure as at the beginning.

After the level has become constant, the quantity of gas remaining is measured. The contraction that has taken place gives, in hundredths of the total volume, the volume of the gas absorbed.

When it is desired to make an analysis of smoke due to combustion, caustic potassa is first sucked into the burette. After complete absorption, and after putting the gas at the same pressure, the diminution gives the volume of carbonic acid.

To determine the oxygen in the remaining gas, a portion of the caustic potash is allowed to flow out, and an aqueous solution of pyrogallic acid and potash is allowed to enter. The presence of oxygen is revealed by the color of the liquid, which becomes darker.

The gas is then agitated with the absorbing liquid until, upon opening the cock, _a_, the liquid remains in the capillary tube, that is to say, until no more water runs from the funnel into the burette. To make a quantitative analysis of the carbon contained in gas, the pyrogallate of potash must be entirely removed from the burette. To do this, the liquid is sucked out by means of the flask, S, until there remain only a few drops; then the cock, _a_, is opened and water is allowed to flow from the funnel along the sides of the burette. Then _a_ is closed, and the washing water is sucked in the same manner. By repeating this manipulation several times, the absorbing liquid is completely removed. The acid solution of chloride of copper is then allowed to enter.

As the absorbing liquids adhere to the glass, it is better, before noting the level, to replace these liquids by water. The cocks, _a_ and _b_, are opened, and water is allowed to enter from the funnel, the absorbing liquid being made to flow at the same time through the cock, _b_.

When an acid solution of chloride of copper is employed, dilute hydrochloric acid is used instead of water.

Fig. 2 shows the arrangement of the apparatus for the quantitative analysis of oxide of carbon and hydrogen by combustion. The gas in the burette is first mixed with atmospheric air, by allowing the liquid to flow through _b_, and causing air to enter through the axial aperture of the three way cock, _a_, after cutting off communication at v. Then, as shown in the figure, the burette is connected with the tube, B, which is filled with water up to the narrow curved part, and the interior of the burette is made to communicate with the combustion tube, v, by turning the cock, a. The combustion tube is heated by means of a Bunsen burner or alcohol lamp, L. It is necessary to proceed, so that all the water shall be driven from the cock and the capillary tube, and that it shall be sent into the burette. The combustion is effected by causing the mixture of gas to pass from the burette into the tube, B, through the tube, v, heated to redness, into which there passes a palladium wire. Water is allowed to flow through the point of the tube, B, while from the flask, F, it enters through the bottom into the burette, so as to drive out the gas. The water is allowed to rise into the burette as far as the cock, and the cocks, _b_ and _b¹_, are afterward closed.

By a contrary operation, the gas is made to pass from B into the burette. It is then allowed to cool, and, after the pressure has been established again, the contraction is measured. If the gas burned is hydrogen, the contraction multiplied by two-thirds gives the original volume of the hydrogen gas burned. If the gas burned is oxide of carbon, there forms an equal volume of carbonic acid, and the contraction is the half of CO. Thus, to analyze CO, a portion of the liquid is removed from the burette, then caustic potash is allowed to enter, and the process goes on as explained above.

The total contraction resulting from combustion and absorption, multiplied by two-thirds, gives the volume of the oxide of carbon.

The hydrogen and oxide carbon may thus be quantitatively analyzed together or separately.--_Revue Industrielle_.

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THE "UNIVERSAL" GAS ENGINE.

The accompanying engravings illustrate a new and very simple form of gas engine, the invention of J. A. Ewins and H. Newman, and made by Mr. T. B. Barker, of Scholefield-street, Bloomsbury, Birmingham. It is known as the "Universal" engine, and is at present constructed in sizes varying from one-eighth horse-power--one man power--to one horse-power, though larger sizes are being made. The essentially new feature of the engine is, says the _Engineer_, the simple rotary ignition valve consisting of a ratchet plate or flat disk with a number of small radial slots which successively pass a small slot in the end of the cylinder, and through which the flame is drawn to ignite the charge. In our illustrations Fig. 1 is a side elevation; Fig. 2 an end view of same; Fig. 3 a plan; Fig. 4 is a sectional view of the chamber in which the gas and air are mixed, with the valves appertaining thereto; Fig. 5 is a detail view of the ratchet plate, with pawl and levers and valve gear shaft; Fig. 6 is a sectional view of a pump employed in some cases to circulate water through the jacket; Fig. 7 is a sectional view of arrangement for lighting, and ratchet plate, j, with central spindle and igniting apertures, and the spiral spring, k, and fly nut, showing the attachment to the end of the working cylinder, f1; b5, b5, bevel wheels driving the valve gear shaft; e, the valve gear driving shaft; e2, eccentric to drive pump; e³, eccentric or cam to drive exhaust valve; e4, crank to drive ratchet plate; e5, connecting rod to ratchet pawl; f, cylinder jacket; f1, internal or working cylinder; f2, back cylinder cover; g, igniting chamber; h, mixing chamber; h1, flap valve; h2, gas inlet valve, the motion of which is regulated by a governor; h3, gas inlet valve seat; h4, cover, also forming stop for gas inlet valve; h5, gas inlet pipe; h6, an inlet valve; h8, cover, also forming stop for air inlet valve; h9, inlet pipe for air with grating; i, exhaust chamber; i2, exhaust valve spindle; i7, exhaust pipe; j6, lighting aperture through cylinder end; l, igniting gas jet; m, regulating and stop valve for gas.

The engine, it will be seen, is single-acting, and no compression of the explosive charge is employed. An explosive mixture of combustible gas and air is drawn through the valves, h2 and h6, and exploded behind the piston once in a revolution; but by a duplication of the valve and igniting apparatus, placed also at the front end of the cylinder, the engine may be constructed double-acting. At the proper time, when the piston has proceeded far enough to draw in through the mixing chamber, h, into the igniting chamber, g, the requisite amount of gas and air, the ratchet plate, j, is pushed into such a position by the pawl, j3, that the flame from the igniting jet, l, passes through one of the slots or holes, j1, and explodes the charge when opposite j6, which is the only aperture in the end of the working cylinder (see Fig. 7 and Fig. 2), thus driving the piston on to the end of its forward stroke. The exhaust valve, Fig. 9, though not exactly of the form shown, is kept open during the whole of this return stroke by means of the eccentric, e3, on the shaft working the ratchet, and thus allowing the products of combustion to escape through the exhaust pipe, i7, in the direction of the arrow. Between the ratchet disk and the igniting flame a small plate not shown is affixed to the pipe, its edge being just above the burner top. The flame is thus not blown out by the inrushing air when the slots in ratchet plate and valve face are opposite. This ratchet plate or ignition valve, the most important in any engine, has so very small a range of motion per revolution of the engine that it cannot get out of order, and it appears to require no lubrication or attention whatever. The engines are working very successfully, and their simplicity enables them to be made at low cost. They cost for gas from ½d. to 1½d. per hour for the sizes mentioned.

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GAS FURNACE FOR BAKING REFRACTORY PRODUCTS.

In order that small establishments may put to profit the advantages derived from the use of annular furnaces heated with gas, smaller dimensions have been given the baking chambers of such furnaces. The accompanying figure gives a section of a furnace of this kind, set into the ground, and the height of whose baking chamber is only one and a half meters. The chamber is not vaulted, but is covered by slabs of refractory clay, D, that may be displaced by the aid of a small car running on a movable track. This car is drawn over the compartment that is to be emptied, and the slab or cover, D, is taken off and carried over the newly filled compartment and deposited thereon.

The gas passes from the channel through the pipe, a, into the vertical conduits, b, and is afterward disengaged through the tuyeres into the chamber. In order that the gas may be equally applied for preliminary heating or smoking, a small smoking furnace, S, has been added to the apparatus. The upper part of this consists of a wide cylinder of refractory clay, in the center of whose cover there is placed an internal tube of refractory clay, which communicates with the channel, G, through a pipe, d. This latter leads the gas into the tube, t, of the smoking furnace, which is perforated with a large number of small holes. The air requisite for combustion enters through the apertures, o, in the cover of the furnace, and brings about in the latter a high temperature. The very hot gases descend into the lower iron portion of this small furnace and pass through a tube, e, into the smoking chamber by the aid of vertical conduits, b', which serve at the same time as gas tuyeres for the extremity of the furnace that is exposed to the fire.

In the lower part of the smoking furnace, which is made of boiler plate and can be put in communication with the tube, e, there are large apertures that may be wholly or partially closed by means of registers so as to carry to the hot gas derived from combustion any quantity whatever of cold and dry air, and thus cause a variation at will of the temperature of the gases which are disengaged from the tube, e.

The use of these smoking apparatus heated by gas does away also with the inconveniences of the ordinary system, in which the products are soiled by cinders or dust, and which render the gradual heating of objects to be baked difficult. At the beginning, there is allowed to enter the lower part of the small furnace, S, through the apertures, a very considerable quantity of cold air, so as to lower the temperature of the smoke gas that escapes from the tube, e, to 30 or 50 degrees. Afterward, these secondary air entrances are gradually closed so as to increase the temperature of the gases at will.

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THE EFFICIENCY OF FANS.

Air, like every other gas or combination of gases, possesses weight; some persons who have been taught that the air exerts a pressure of 14.7 lb. per square inch, cannot, however, be got to realize the fact that a cubit foot of air at the same pressure and at a temperature of 62 deg. weighs the thirteenth part of a pound, or over one ounce; 13.141 cubic feet of air weigh one pound. In round numbers 30,000 cubic feet of air weigh one ton; this is a useful figure to remember, and it is easily carried in the mind. A hall 61 feet long, 30 feet wide, and 17 feet high will contain one ton of air.