Boiler

An ingenious attempt to expose water in thin sheets over an extended surface of metal, was made by Mr. John M'Curdy, from the United States, who patented it in this country.. It consisted of a series of cylinders, with spherical ends, arranged horizontally like retorts, in a pyramidal form, in a &mace, so as to cause the heat as much as possible to impinge against their surfaces, in its ascent amongst them to the flue above. Each of these cylinders contained within it another cylinder, of so much less diameter than the outer, as to leave between them throughout a very narrow space, the uniformity of which space was preserved by coiling a spiral band upon the outside of the inner cylinder, or other suitable contrivance. These latter cylinders were hermetically closed at each of their ends, and were placed inside the former to produce between them hollow cylindrical sheets of water. The water was forced into one of the lower cylinders, and made, by the action of the pump, to circulate through the others of the series. By this arrangement of disposing the water in thin sheets, it was pre sumed that steam of a very high pressure would be generated with extraordinary rapidity. We have, however, never been informed of the cause of this boiler not having been brought into practical operation, and are therefore left to con jecture that it was probably owing to the great expense of construction ; the liability to deposits and incrustations in the narrow spaces between the internal and external cylinders ; the difficulty of cleansing them; and, by the neglect of the latter operation, causing an irregular generation of steam, the heatmg red hot the incrusted parts, and, as a consequence, the blowing out of the water, and the rapid destruction of the metal. To these causes may be added the waste of fuel by the shortness of the flue. The contrivance is, nevertheless, not devoid of merit, and may afford a useful hint to succeeding inventors. The superior strength and safety of boilers made of small tubes have within the last few years led to their introduction in almost every possible variety of form, a great many of which have been the subjects of unproductive patents. Those which most distinct character from each other, and have been more or less brought into public use, we shall proceed to notice. The first we shall describe is the invention of Mr. W. H. James, patented in 1823. It consisted of a series of annular tubes of equal capacity and diameter, placed side by side, and bolted together, so as to form by their union a long cylindrical boiler, in the centre of which, at one end, the fire-place was situated. The tubes were made of the toughest wrought iron, three sixteenths of an inch thick ; and being of only one inch in diameter, they were capable, as was proved, of sustaining a pressure of several thousand pounds per inch. In some of these boilers, the tubes were made square in their transverse section, consequently, when their flat sides were placed together as described, there were no open spaces between them ; and the annular tubes were connected together by means of long bolts passing through the endplates of the cylinder, where they were screwed up firmly by nuts on the outside. Communications from tube to tube were made by making two perforations in them lengthways of the cylinder; one on the upper side, for the free passage of the steam, and one on the lower, for the flow of the water. When it was desired to construct a boiler of greater power in a compact form, to adapt it more particularly to loco motion, Mr. James preferred making two concentric cylinders, each composed of a series of annular tubes, like those described, and as delineated in the annexed diagram, which exhibits a transverse section of such a boiler. The annular tubes are distinguished by the water drawn therein. The upper per forations or steam passages are shown at b b, and the lower, or water passages, at c c. The water was maintained at the desired level by the action of a float, in an adjoining vessel, not shown in the figure. The furnace bars formed two inclined planes, as shewn, at one end of the cylinders, and the flue descended at the other end. These latter parts were made so as to be easily detached at pleasure. The entire boiler turned upon an axis, and rested upon rollers, fixed in a circular stand; every tube was furnished with some shot, mixed with angular pieces of metal, so that when it was desired to cleanse the boiler of deposit, the furnace and chimney tube were drawn out, the con necting pipes unscrewed, when the cylinder was turned round by a winch, in the manner of the common scouring barrel, used for brightening metallic articles. To prevent the loss of heat by radiation, the boiler was surrounded by a double case, the spaces between which were filled up with a mixture of clay and char coal. We have repeatedly seen a boiler of Mr. James's construction, on the principle of the last described, but consisting of only one cylinder of annular tubes, 3 feet 6 inches long, and 20 inches diameter, effectively working a very small high pressure engine, (having only a 3 inch piston of 12 inch stroke,) up to three horses power. This boiler had circular tubes, and each annulus was made out of two semicircular pieces, connected at their extremities to an upper and a lower transverse horizontal tube, the length of the cylinder; the upper one forming the principal and the connecting steam tube, and the lower one the water tube. Into these horizontal tubes, conical perforations were drilled, to receive the extremities of the semicircular tubes to which they were united, steam and water tight, by means of bolts and rivetted keys. However firm this mode of uniting appeared to the eye, and however accurate the workman ship, when the fire came to act upon the joints they often became leaky, and were the source of great trouble and inconvenience. Since the period alluded to, Mr. James has invented another boiler, to which he gives the preference, and will be described under the article STEAM. Before, however, we quit this

part of the subject, we would draw the reader's attention to the circumstance of the steam chambers in Mr. James's boiler, as shewn in the preceding engraving, by which it is evident that the surfaces of the water are pressed upon by the steam, and that the latter derives an increase of heat and of elasticity to its formation, by the action of the most intense part of the fire ; consequently it would appear that this arrangement is eminently calculated to prevent the water rising, or being forced over into the engine ; an inconvenience which had been experienced in most boilers made of small tubes. Although the in convenience never occurred in Mr. James's boilers whilst the fire was kept steady, the supply of water regular, and the tubes clean ; yet from the neglect or failure of some one of these conditions, the water did occasionally come over. The observations we have been enabled to make upon these facts, incline us to the opinion that it would be better not to make boilers of tubes of a less diameter than two inches; because the much larger body of water such contain are not so suddenly and violently affected by ordinary variations of temperature occasioned by unskilful firing, or by the irregular supply of water; nor are the tubes so liable to become choked, as the joints can be made with greater accuracy without filling up the water or steam way, to the danger of the tubes becoming red-hot, and the destruction of the boiler. Tubes of two inches can be much more easily cleansed; and as respects safety, it is scarcely possible to burst them, if only a quarter of an inch thick, by any pressure of steam that can be beneficially applied.

The contrivance we shall next notice is the invention of Mr. Goldsworthy Gurney, a gentleman of the medical profession, but more generally known to the public by his persevering attempts for the establishment of steam carriages on the common road; and the boiler we shall describe is especially designed for that purpose. Fig. 1 shows a vertical section of the boiler. Fig. 2, an ex ternal end view of the same. Fig. 3, the manner in which the series of pipes composing the boiler are fixed, and open into horizontal chambers. Fig. 4, a portion of one of the horizontal chambers, partly broken away to exhibit the apertures of the pipes, and their arrangement. The same letters on each figure refer to corresponding parts. In the section Fig. 1 the semi-elliptical form in which the pipes are bent, and the manner in which they respectively cross each other, is seen ; the ends of these pipes have screw threads on the outside, to receive nuts, which secure them to the horizontal chambers b, as shown in Fig. 3; a packing composed of pounded asbestos, mixed with red lead and litharge, in about equal parts, is interposed between the nuts and the end plate, applied in hollow washers of a saucer-like form, which it is said makes perfectly steam, water-tight, as well as fire-proof joints. The chambers b have direct communication one with another, by means of the vertical pipes c; d d, are two bent tubes, leading from b b into the steam vessels or " separators " e e (as Mr. Gurney calls them.) From thirty to fifty, (according to the size of the apparatus) of the small pipes a, are arranged in the manner shown in Figs. 1 and 4, in which the fuel is placed as at h, the heated air and flames being directed by a bridge i, to take the course delineated before entering the chimney k ; but a considerable portion of the heat passes freely between and round about the pipes, the whole of them being exposed to the powerful effects of a furnace so circumstanced; o is the furnace door, and i the ash-pit. During the working of the engine, the steam chambers e are by the usual means kept sup plied with water up to the level shewn, which being higher than the pipes in the furnace, the latter are always kept full of water, as judiciously recommended by Woolf in his specification, quoted in the preceding part of this article. The steam generated in the small pipes ascends by its superior levity through the water in the steam vessels e, or it may be, transmits its caloric to other particles of water, which escape at the surface of the fluid in the form of vapour, which passes off through the branches f f into a common pipe g, that leads to the engine. In fixed engines the iron casing represented as surrounding the boiler is dispensed with, the apparatus being set in the usual manner in brick-work. To obviate a com mon objection to tubular boilers, of their becoming choked with a deposition of earthy matter, Mr. Gurney purposes to clean them out when they become foul, by the following chemical treatment. If the tubes are of iron, one part of muriatic acid, with 100 parts of water, are to be left in the boiler, a sufficient time to dissolve the incrustations ; if of copper, the following solution is to be used in a similar way, one pound of common salt, half a pound of sulphuric acid, in four gallons of water. To expedite the operation of cleansing, a small fire may be made in the boiler, and the steam be employed to blow the contents out of the tubes. One of the most prominent advantages attending the use of this boiler, is the great facility with which repairs are executed ; when a tube is injured or burned, the removal of it or the substitution of a new one are only the work of an hour. Like other tubular boilers, it is safe from the effects of rup ture ; but the " separator " being in fact a steam reservoir, that part is as liable to explosion as other boilers of the same capacity and thickness of metal. The small tubes exposed to the fire, if always kept full of water, are not likely to be soon burned out. The merit of this arrangement is however, due to Mr. Woolf, (see page 201,) and were Mr. Gurney's steam reservoirs defended like that gentleman's, from the cooling influence of the atmosphere, the effect of their contents upon the engine would be improved.