Modern Gasworks Practice

246 MODERN GASWORKS PRACTICE the retort, extending about 8 inches backwards. In this case the end of the retort is not thickened up, the lengths as laid having 3-inch. walls throughout; and as a fairly tight fit is arranged for (slight chipping of the fireclay end often being necessary), ao rust joint is employed, but the retort is given a wash. of fireclay before the socket is fitted. Bolts, countersunk on the inside of the socket, form the attachment for the ordinary mouthpiece flange. The chief merits of the method are that the retort mouthpiece can be easily removed for repairs, the holding bolts are far less liable to bum or break away than with the common type of attachment, and, if properly fitted, a tighter, and at the same time more elastic, joint is obtained. The third method. (Fig. 148) is comparatively rare in this country, but possesses the advantage that no retort bolts whatever are required. It is really an.oth.er means of carrying out the socket principle described above, with the difference that some initial expense is saved by casting the socket and mouthpiece in one. Its disadvantage, however, lies in the fact that the security of the mouthpiece is entirely dependent upon the cross bracing employed (although the latter can. be made more effec-tive owing to the absence of protruding bolts) and the socket portion has a tendency to crack. Once such, a crack develops it is difficult to prevent a certain amount of gas leakage when the retort is under pressure. Pro. 149. Figs. 149 and 150 show a method of fastening which has been adopted in Continental gasworks. The retort is made up in two parts, the heads, and the retort proper. With the more common types of fastening it is occasionally found that a rupture occurs in the retort a dj acent to the mouthpiece, particularly during the starting up of the beuch. This is due to the fact that the body of the retort, being directly above the producer arch, is exposed to the full effect of the heat, whereas the ends are still moderately cold. As a result, inferior stresses are set up, which. are followed by cracking, and it is claimed that in the system shown this defect is eliminated. In addition to the bolt attachment, all retort mouthpieces must be stayed up by means of bracing attached to the main buckstays, and passing outside the front wall of the setting across the flanges of the mouthpieces. There are several means of attaching such bracing, the most common being shown in Figs. 151 and 152. In Fig. 151 a double bull-headed rail is carried in. cast-iron brackets attached to the buckstays as shown. In many cases the rail is carried across vertically (as shown