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ACCOUNT OF VINCOTTE'S EXPERIMENTS MADE AT WILLEBROEK, BELGIUM, ON A TUBULOUS BOILER, WITH SEMI-BITUMINOUS COAL.

By Chief-Engineer ISHERWOOD, United States Navy.

During the session of the third Congress of the Engineers-in-Chief of the Associations of the Proprietors of Steam Apparatus, held in Paris on the 7th, 8th, 9th and 10th of July, 1878, at the rooms of the Parisian Association, Mr. Vincotte, the Engineer-in-Chief of the Belgian Association, presented a paper on some experiments he had made with a tubulous boiler in the establishment of Mr. Denaeyer, at Willebroek, for the purpose of ascertaining its economic vaporization with semi-bituminous coal.

As this boiler is of a type not much used, and with which but very few experiments have been made, presenting, also, wide differences in its principles of design and construction from those commonly employed, I considered the subject of sufficient engineering interest to the readers of the JOURNAL to take from Mr. Vincotte's paper all the observed data, and from them to re-calculate, independently, the results in the manner found by English-speaking engineers the most convenient for practical purposes. I have given, likewise, a description of the boiler WHOLE NO. VOL. CX.-(THIRD SERIES, Vol. lxxx.)

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and a calculation of its elements not in the original paper, and I have added my own remarks.

BOILER.

The boiler is composed of an assemblage of inclined water-tubes placed along the sides of and above the fire-grate, together with their

connections; the whole being enclosed in a rectangular casing of brick masonry. The entire heating surface consists of the tubes and the

inmost sides of their connecting boxes, all of which are completely filled with water. There is no steam-superheating surface.

The steam-room is contained in a large horizontal cylinder lying immediately over the tubes and separated from them by a vaulting of brick masonry sustained on H iron girders. This cylinder is also enclosed by a rectangular casing of brick masonry; and, upon its upper side, at the front end, is a small steam-drum in the form of a vertical cylinder. The interiors of the large horizontal and the small vertical cylinders are in common, and the steam-pipe is carried from the top of the latter to the engine.

There is one furnace with a rectangular grate, and it is fired through two doors in the front, the opening for each of which is 8 inches high and 14 inches wide. The thickness of the wall through which these openings are made is 15 inches. The grate is 6·562 feet long and 6.168 feet broad, with the grate-bars in two equal lengths. The top of the grate inclines downwards 8 inches at the back, where the bridgewall of brick masonry, 9 inches thick, rises 7 inches above it.

The bottom of the ashpit at the front of the furnace is 2 feet 8 inches, and at the back of the furnace 2 feet, below the top of the grate. The back, sides and bottom of the ashpit are of brick masonry; the side walls are 18 inches thick and the back wall is 9 inches thick. The front of the ashpit is closed by cast iron doors.

Between the back of the bridge-wall and the back wall of the boiler is an enclosed space 6.168 feet broad and 17 inches long lengthwise the boiler.

The height from the top of the grate to the lower side of the lower row of tubes above it is, at the front of the grate 37 inches, and at the back 30 inches.

At each side of the grate, and extending from its top to the top of the assemblage of tubes lying over it, is a vertical row of 18 inclined wrought iron water-tubes, making 36 tubes for the two sides, 5 inches in outer diameter and 5 inches in inner diameter. These tubes are placed one upon the other without any intervening spaces, so that they touch along their whole length. The lower 6 of these tubes on each side are 7 feet long, and the remaining 12 are 93 feet long. They rest on a 5 inches offset in the brick wall at the side of the furnace, which wall is thence carried up 12 inches thick to the top of the boiler, the inside face of the wall and the outer ends of the horizontal diameter of the tubes touching, so that the tubes are in contact with

the wall and form a lining for it, which leaves only their inner semicircumferences to act as heating surface. These tubes are united in pairs, alternately, at both ends, by connecting boxes of ordinary cast

which traverses in succession all the remaining 17 tubes beneath it, and is delivered at the back end of the lowest tube into a lower cast iron box of rectangular cross section lying horizontally across the whole breadth of the boiler at its back. This box is 10 inches square on the outside, 7 inches square on the inside, and of 9 feet 2 inches extreme length; it is supported upon the 10 inches thick back brick wall of the boiler.

Immediately over the fire-grate, and lying between the two vertical rows of tubes just described, are 144 inclined wrought iron water-tubes of 4 inches outer diameter, 4 inches inner diameter and 9 feet length. All these tubes are parallel to each other and to the tubes at the sides of the furnace. The declination from the front to the back ends of the tubes is 22 inches in a horizontal length of 110 inches, or 1 in 5. The tubes are arranged in twelve rows horizontally and twelve rows vertically. The centres of the tubes of each of the horizontal rows are in the same straight line, but the tubes of the vertical rows are zig-zagged, the centres of the tubes of each of these rows being over the centres of the spaces between the tubes of the horizontal rows immediately above and below. The least distance between the tubes horizontally in the clear is 15 inches. The distance from the bottom of the tubes of the lower row to the top of the tubes of the upper row, measured at right angles to the axes of the tubes, is 5 feet.

The back ends of all the tubes of the lower horizontal row are secured into the inner side of the lower cast iron box already described of 10 inches square cross section and 9 feet 2 inches extreme length, whence they receive the feed-water, each tube of this row receiving the water simultaneously, which thence ascends, by suitable connections, the tubes of each vertical row in succession, passing alternately from back to front and from front to back until it emerges simultaneously from all the tubes of the upper horizontal row into an upper horizontal cast iron box of exactly the same dimensions as the lower one already described, which upper box is supported on the top of the front wall of the boiler.

The tubes of each horizontal row are secured in pairs-two adjacent tubes constituting a pair-into the inner side of a rectangular box of ordinary cast iron or malleable cast iron. The outside dimensions of each of these boxes are 11.81 inches wide, 5.91 inches high and 5.04 inches long lengthwise the boiler; least thickness of metal, & inch.