LEAD PIPES are known to have heen used at Babylon. Home, and Pompeii, and, like all lead pipe until recent times, were made from sheets of lead bent to a pear-shaped section. with the horizontal joint welded or soldered. About, the beginning of the sixteenth century the casting of lead pipes was begun in Eng land, the prneess having been invented by Robert Brooke. In 1791) an English patent fin• draw ing lead pipe was granted. and a machine was built for pressing lead pipe through dies. As the larger sizes of lead pipe have to be very thick to retain their shape and withstand high pressures. and on account of the high cost of lead pipe and for other reasons, such pipe is but little used now in diameters of over 2 inches or so. but it is made np to 4 inches, and, though rarely, to 6 or S inches. At the other extreme, it is made as small as inch, inside diameter. Modern lead pipe is pressed through dies in a continuous length. The molten lead is poured into a cylindrical hole in a hydraulie press. T11 the centre of the hole is a metal rod or core the same diameter as the pipe. When the metal begins to solidify the press rises and forces the soft, hot lead through a (lie. the diameter of
which corresponds with the interior diameter of the pipe. total pressure used is about 400 tons. distributed over a 14- or 16-inch cylinder.
Block-tin pipes arc made in the same way as lead, except that they are cold-pressed. Nost of the block-tin pipe is used in soda fountain-, or to convey beer, or in chemical works.
CAST !nos PIPES. The general process of cast ing iron is described under ForNDING. It may be said here that in some of the foundries the core is made by winding a spindle with a ma chine-made hay rope. Over the rope two or three layers of clay are packed, successively. after which the clay is shaped in a lathe, then dried in an oven. This Core shapes the interior of the pipe. For the exterior a pattern is placed in a compartment known as a flask. Around the pattern tempered clay and sand are rammed to form a mold for the exterior of the pipe. The flask is then placed in an oven to dry the sand and clay, after which it is placed in a known as sewer pipe. A machine for the manu facture of clay pipe was built at Ottweiler, Rhenish Prussia, about 1858.