Modern Gasworks Practice

248 MODERN GASWORKS PRACTICE the prevention of stoppage will ensue. Fürther, precaution must be taken to see that the jointing material used in the pipe sockets is not allowed to get past the spigot end, and thus be responsible for projections which. partly stop the pipe and provide a lodgment for tlie formation of pitchy deposits. It is a good practice to make all ascension pipes slightly bell-mouthed. at the spigot end so that there is no possibility of a ridge forming on which the auger may catch. So far as the general arrangement is concerned, as many of the pipes as conveniently possible should be carried up on the sides of the main arch nearest its springings, and it is necessary to avoid running up two pipes between any two mouthpieces, otherwise the retorts will have to be spaced wider apart in order to give sufficient room, this tending to spoil the heating arrangements of the interior. The joints in ascension pipes must on no account be made with lead. Although xust joints of iron borings are not essential, they are to be preferred to any other material, in spite of the additional labour entailed in cutting thern out du ring dis-mantling. For ascension-pipe, bridge-pipe, and dip-pipe joints the following material may be used :—■ Cast-iron borings damped down with. gas liquor, rammed well into the joint, and left. When the bench is got to work, the heat from the setting quickly hardens off the joint. Many engineers prefer not to use gas liquor, and in cases where a particularly durable joint is required it should be made up as follows To 2 cwt. of iron borings adel 2|- Ib. of sal ammoniae, and 1 Ib. 2 oz. of flowers of sulpliur. This should be mixed to a stiff paste with water, and should preferably be kept for two days before use. If kept under water the material may be stored for several months. Where borings are oiily obtained with difficulty, or to save expense, a very serviceable joint can be made from the following mixture:— Ewell brick dust ........... 1 part. Slaked lime.........2 parts. This is rammed into the joint dry, no moistening whatever (beyond the slaking of the lime) being necessary. In cases where a cast-iron foul main is used, lead joints may safely be used in the sockets, and are desirable. STOPPED PIPES The introduction into the larger works of the mass system of carbonization has proved the most effeetive deterrent to the old-time trouble of continually stopped ascension pipes. The absence of deposits may be chiefly attributed to the lower temperature of the escaping gases and the inereased velocity with which they travel through the pipe. In addition, the elimination of an excessive “ free space ” in the retort accounts for less degradation of the hydrocarbons, with the result that a minimum quantity of free carbon is carried forward in suspension by the gas. It is such solid particles (also those drawn up from the cloud of coal dust inseparable