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MODERN GASWORKS PRACTICE
Fig. 120.—The Wooden Strip Mbthod.
ging action of the dust •carried forward by the furnace gases ; and, for this reason, th.e block illustrated in Fig. 122 has in some cases been adopted. This shield is made wholly from Stourbridge clay, of the same material as the retorts, and will frequently be found to out-last the retorts themselves. The main body of the block is 3 inch.es in thick-ness, and it is made of such a length as to run from centre to centre of the cross
division walls from which it is supported.
Another successful idea, which has been introduced with a view both to economy and the protection of the retort, is that shown in Fig. 123. In the majority of cases of “ through ” retort
settings it is customary to insert a 9-incli cross-wall here and there in the setting, and particu-larly where the retort joints occur. By adopt-i n g the arrangement shown in the sketch, the •expen.se of the heavier wall is obviated, and 4J-inch brickwork (o r certainly 6-inch) can be run up instead. A '9-inch. ring of brickwork (usually silica or siliceous) is carried. completely round the retort, and the 4|-inch wall carried direct from this. In
Owing to the liability of retorts immediately sur-rounding the combustion chamber to sufEer from the severe and sometimes local he a t i n g at this point, it has for some-time been the practice to insert special silica pro-tection shields (as shown in Fig. 121) around the bottom corners. At the same time the silica material is ' liable to be afEected by the slag-
Fig. 121.—Segmental Retokt, 21 inches x 15 inches, with Round Spkisger and Shield on Combustion Chambbk, Side and Sqttabe Springer on External Side. The Length of the Segments varies from 1 foot 3 inches to 2 fest.