CLAY WORKING INDUSTRIES. 209 



III. THE MANUFACTURE OF PIPE AND HOLLOW GOODS, 



The manufacture of pipe and hollow goods is made to include the 

 following general divisions : 



1. Sewer pipe. 



2. Fire proofing. 



3. Terra cotta chimneys and flue linings. 



4. Building tiles. 



5. Drain tiles. 



Of these, the first four are frequently worked all together in the 

 same factory. The fireproofing and terra cotta work is managed entirely 

 in connection with sewer pipe plants. The manufacture of building tiles 

 or hollow T foundation blocks of heavy cross section is now carried on in a 

 few factories as a separate business, entirely apart from the sewer pipe 

 manufacture. Great expansion is sure to take place in this direction in 

 the future; the use of vitrified clay products in this class of work has 

 scarcely begun and it cannot fail to become a constantly increasing source 

 of wealth to the state. 



The manufacture of sewer pipe and building material demands the 

 use of vitrifying clays; terra cotta and fireproofing, though not vitrified, 

 are as a fact produced from the same clays; the difference in their ap- 

 pearance is due to the comparatively low temperatures used in burning. 



The clays used in the manufacture of the first four kinds of hollow 

 ware have already received general notice under the description of clays 

 suited to the manufacture of vitrified wares. 



The processes of preparation of these clays has also been described 

 in connection with paving material; there is nothing about the prepara- 

 tion which is characteristic of this particular use except that the temper- 

 ing has to be much more prolonged and thorough, on account of the 

 difficult shapes and sections of ware which are produced. The shapes 

 required in fireproofing ire especially difficult and troublesome to manu- 

 facture, and they require very thorough tempering of the clays. 



The manufacture of the various kinds of pipe and hollow goods is 

 almost wholly accomplished on one machine, the sewer pipe press; this 

 machine has had brief description in connection with brickmaking ma- 

 chinery. It consists of two vertical cylinders separated by a heavy, cast 

 iron frame to which the cylinder heads are bolted; the upper or steam 

 cylinder is usually forty inches in diameter. The piston rod is made 

 either single or triple and connects the steam and clay pistons. The clay 

 piston is a cast iron head, which can be renewed easily and it is not usu- 

 ally provided with any means of taking up wear. It is rapidly cut away 

 around its edges by the flow of the clay past it when under great press- 

 ure. It is sometimes bushed with a wrought iron ring shrunk on, which 

 can be replaced easily as it wears out. The clay cylinder should be a 



14 G. O. 



