The new gasholder which has been erected by Messrs. C. and W. Walker for the Imperial Continental Gas Company at Erdberg, near Vienna, has been graphically described by Herr E.R. Leonhardt in a paper which he read before the Austrian Society of Engineers. The enormous dimensions and elegant construction of the holder - being the largest out of England - as well as the work of putting up the new gasholder, are of special interest to English engineers, as Erdberg contains the largest and best appointed works in Austria. The dimensions of the holder are - inner lift, 195 feet diameter, 40 feet deep; middle lift, 197½ feet diameter, 40 feet deep; outer lift, 200 feet diameter, 40 feet deep. The diameter over all is about 230 feet. The impression produced upon the members of the Austrian Society by their visit to Erdberg was altogether most favorable; and not only did the inspection of the large gasholder justify every expectation, but the visitors were convinced that all the buildings were in excellent condition and well adapted for their purpose, that the machinery was of the latest and most approved type, and that the management was in experienced hands.
is contained in a building consisting of a circular wall covered with a wrought iron roof. The holder itself is telescopic, and is capable of holding 3½ million cubic feet of gas. The accompanying illustrations (Figs. 1 and 3) are a sectional elevation of the holder and its house and a sectional plan of the roof and holder crown. Having a capacity of close upon 3,200,000 Austrian cubic feet, this gasholder is the largest of its kind on the Continent, and is surpassed in size by only a few in England and America. By way of comparison, Hamburg possesses a holder of 50,000 cubic meters (1,765,000 cubic feet) capacity; and there is one in Berlin which is expected to hold 75,000 cubic meters (2,647,500 cubic feet) of gas.
The gasholder house at Erdberg is perfectly circular, and has an internal diameter of 63.410 meters. It is constructed, in three stories, with forty piers projecting on the outside, and with four rows of windows between the piers - one in each of the top and bottom stories, and two rows in the middle. These windows have a height of 1.40 meters in the lowest circle, where the wall is 1.40 meters thick, and of 2.90 meters in the two top stories, where it is respectively 1.11 meters and 0.90 meter thick. The top edge of the wall is 35.35 meters above the base of the building, and 44.39 meters from the bottom of the tank; the piers rising 1.60 meters beyond the top of the wall. The highest point of the lantern on the roof will thus be 48.95 meters above the ground.
The tank in which the gasholder floats has an internal diameter of 61.57 meters, and therefore a superficial area of 3,000 square meters; and since the coping is 12.31 meters above the floor, it follows that the tank is capable of holding 35,500 cubic meters (7,800,000 gallons) of water. The bottom consists of brickwork 1.10 meters thick, rendered with Portland cement, and resting on a layer of concrete 1 meter thick. The walls are likewise of brick and cement, of a thickness of 3.30 meters up to the ground level, and 2.40 meters thick to the height of 3.44 meters above the surface. Altogether, 2,988,680 kilos. of cement and 5,570,000 bricks were used in its construction. In fact, from the bottom of tank to top of roof, it reaches as high as the monument at London Bridge.
FIG. 1. - SECTION OF GASHOLDER AND HOUSE.
The construction of the tank offered many and serious difficulties. The bottom of the tank is fully 3 meters below the level of the Danube Canal, which passes close by, and it was not until twelve large pulsometer pumps were set up, and worked continually night and day, that it was possible to reach the necessary depth to allow of the commencement of the foundations of the boundary wall.
The wrought iron cupola-shaped roof of the gasholder house was designed by Herr W. Brenner, and consists of 40 radiating rafters, each weighing about 25 cwt., and joined together by 8 polygonal circles of angle iron (90×90×10 mm.). The highest middle circle is uncovered, and carries a round lantern (Fig. 1). These radiating rafters consist of flat iron bars 7 mm. thick, and of a height which diminishes gradually, from one interval to another on the inside, from 252 to 188 mm. At the outside ends (varying from 80×80×9 mm. in the lowest to 60×60×7 mm. in the last polygon but one) these rafters are strengthened, at least as far as the five lowest ones are concerned, by flat irons tightly riveted on. At their respective places of support, the ends of all the spars are screwed on by means of a washer 250 mm. high and 31 mm. thick, and surmounted by a gutter supported by angle irons. From every junction between the radial rafters and the polygonal circle, diagonal bars are made to run to the center of the corresponding interval, where they meet, and are there firmly held together by means of a tongue ring.
The roof is 64.520 meters wide and 14.628 meters high; and its total weight is 103.300 kilos. for the ironwork - representing a weight of 31.6 kilos. per square meter of surface. It is proposed to employ for its covering wooden purlins and tin plates. The whole construction has a light, pleasing, and yet thoroughly solid appearance.
Herr Brenner, the engineer of the Erdberg Works, gives a description of how the roof of a house, 54.6 meters wide, for a gasholder in Berlin, was raised to a height of 22 meters. In that instance the iron structure was put together at the bottom of the tank, leaving the rafter ends and the mural ring. The hoisting itself was effected by means of levers - one to each rafter - connected with the ironwork below by means of iron chains. At the top there were apertures at distances of about 26 mm. from each other, and through these the hoisting was proceeded with. With every lift, the iron structure was raised a distance of 26 mm.
Herr Brenner had considerable hesitation in raising in the same way the structure at Erdberg, which was much larger and heavier than that in Berlin. The simultaneous elevation to 48 meters above the level, proposed to be effected at forty different points, did not appear to him to offer sufficient security. He therefore proposed to put the roof together on the ground, and to raise it simultaneously with the building of the wall; stating that this mode would be perfectly safe, and would not involve any additional cost. The suggestion was adopted, and it was found to possess, in addition, the important advantage that the structure could be made to rest on the masonry at any moment; whereas this had been impossible in the case at the Berlin Gasworks.
At a given signal from the foreman, two operatives, stationed at each of the forty lifting points, with crowbars inserted in the holes provided for the purpose, give the screws a simultaneous turn in the same direction. The bars are then inserted in another hole higher up. The hoisting screws are connected with the structure of the roof, and rise therewith. All that is requisite for the hoisting from the next cross beam is to give a forward turn to the screws. When the workmen had become accustomed to their task, the hoisting to a distance of 1 meter occupied only about half to three-quarters of an hour. At the outset, and merely by way of a trial, the roof was lifted to a height of fully 2 meters, and left for some time suspended in the air. The eighty men engaged in the operation carry on the work with great regularity and steadiness, obeying the signal of the foreman as soon as it was given.
The holder, which was supplied by the well-known firm of Messrs. C. and W. Walker, of Finsbury Circus, London, and Donnington, Salop, was in an outer courtyard. It is a three-lift telescopic one; the lowest lift being 200 feet, the middle lift 197 ft. 6 in., and the top lift 195 ft. in diameter. The height of each lift is 40 feet. The several lifts are raised in the usual way; and they all work in a circle of 24 vertical U-shaped channel irons, fixed in the wall of the house by means of 13 supports placed at equal distances from the base to the summit (as shown in Fig. 2). When the gasholder is perfectly empty, the three lifts are inclosed, one in the other, and rest with their lower edges upon the bottom of the tank. In this case the roof of the top lift rests upon a wooden framework. Fixed in the floor of the tank are 144 posts, 9 inches thick at the bottom and 6 inches thick at the top, to support the crown of the holder in such a way that the tops are fixed in a kind of socket, each of them being provided with four horizontal bars, which decrease in thickness from 305 by 100 mm. to 150 by 50 mm., and represent 16 parallel polygons, which in their turn are fastened diagonally by means of iron rails 63 by 100 mm. thick, arranged crosswise.
The top of this framework is perfectly contiguous with the inside of the crown of the gasholder. The crown itself is made up of iron plates, the outer rows having a thickness of 11 mm., decreasing to 5 mm. toward the middle, and to 3 mm. at the top. The plates used for the side sheets of the holder are: For the top and bottom rows, 6.4 mm.; and for the other plates, 2.6 mm.
A new bleaching compound has been discovered, consisting of three parts by measure of mustard-seed oil, four of melted paraffin, three of caustic soda 20° Baume, well mixed to form a soapy compound. Of this one part of weight and two of pure tallow soap are mixed, and of this mixture one ounce for each gallon of water is used for the bleaching bath, and one ounce caustic soda 20° Baume for each gallon is added, when the bath is heated in a close vessel, the goods entered, and boiled till sufficiently bleached.