PIPE, a circular or square artificial channel for the conveyance of watery fluids, either under pressure, or flowing freely, or for the passage of wriform fluids, or of sound. According to the almost endless varieties of uses to which pipes may be converted, and to the positions in which they may be placed, the materials of which they are formed may be modified in an equally varied manner. A few of the more prominent uses, and of the more generally adopted materials, aro therefore all it will be possible here to allude to, under the general name of pipes.
For the purpose of removing rain-water from buildings the ancients, and even occasionally the moderns also, have resorted to the use of earthenware pipes of ordinary clay baked in kilns, but of late years lead, zinc, or iron pipes have been used in preference either to the earthen, or the stoneware pipes. Copper pipes are commonly used for the ascending pipes from force pumps ; but the distribution of water horizontally is almost always effected through cast or wrought iron, lead, or tin pipes. Gas is distributed through cast iron mains, wrought iron service-pipes, or through small pipes of tin, or of mixed metal with a tin base. The foul waters from modern houses are removed through glazed stoneware drains, whilst land drainage waters are removed by means of red earthenware pipes. Until within a very few years the whole of the water supply of our towns was carried through elm pipes ; and at the present day wood is still used for conveying water in agricultural districts, whilst that material is considered to be the most fitted for the .conveyance of such fluids as tan liquor, or the bilge waters of ships. Indian rubber and gutta percha pipes are some times used for garden and irrigation purposes ; and leather pipes are almost universally used for fire engines, or for moveable pumps, of any kind.
Smoke, hot air, and hot water are conducted through pipes or channels formed, as the case may require, of ordinary bricks ; of moulded bricks, of glazed brick, or stoneware pipes ; or of cast or wrought iron, or of copper, zinc, lead, or tin ; and in the construction of boiler furnaces, of drawn brass. Sound is conveyed through metal pipes, or through Indian rubber, or gutta percha tubes.
The stoneware and cast iron pipes certainly are the most durable under ground ; but the chemical natures of the fluids conveyed, and of the ground itself, vary within so wide a range as to render it necessary to exercise great circumspection in the choice of the materials to be used. Every case must in fact be regarded on its own merits ; observing simply that metals are peculiarly liable to decay under the continuous action of dilute acids ; and that such decay will be accele. rated if any galvanic action should be superinduced. In earth, it may be taken as a general rule that stoneware pipes will last longer than metal ones ; that lead will last longer than cast iron, and much longer than wrought iron or wood; and that both on the score of their rapid decay in such positions, and of their compressibility, the pipes made from vegetable substances, such as gutta percha or Indian rubber, ire very objectionable for use in the ground. [SEWERAGE; WATER
S0rrtT.) Cast iron pipes are cast vertically in loam moulds; wrought iron pipes are either lapwelded or brazed ; lead pipes are either soldered on their longitudinal seams, or they are forced by hydraulic pressure upon a mandril, so as to ensure their perfectly homogeneous character ; tin pipes, and copper or composition pipes are usually brazed, but in j unimportant works their longitudinal joints may be soldered like those of the lead pipes. The end joints of cast iron pipes are either made with a spigot and faucet joint, which may be either turned so as to fit quite tight, or be left large enough to receive a packing of yarn, white lead, and melted pig lead ; or they are made with flange joints connected by means of bolts and Washers. The ends of wrought iron pipes may be connected by means of screw couplings, or by flanges ; and the end joints of the more easily soldered materials are made by that process, taking care of course to provide against the irregularities of contraction, or of expansion in the pipes. It is precisely on account of the play afforded by the spigot and faucet joints of cast iron pipes, that they are adopted when any danger of changes of temperature exists. As it is not possible to make a screwed joint with any description of earthen pipes, those articles are always made with spigot and faucet joints. The end joints of gutta perches and of Indian rubber tubes are melted, and both the longitudinal or the end joints of leather pipes are 10%11 or riveted ; wood pipes have turned and bored joints fitting into each other, which are sometimes screwed together.
The strength of a pipe must be such as to ensure its resiatance to the external and Internal pressures it Is likely to be exposed to; but, if it should work under pressure, the intoned force will be, generally speaking, so much in excess of the external one, that it will suffice to cdnsider the former condition to the exclusion of the Litter. The usual formula for calculating the thickness of pipes is as follows : calling p, the pressure per square inch ; r, the radius in inches of the interior diameter; and c, the cohesive strength of the metal per car square inch ; then x = : Mr. Ilawksley adopts a rather simpler formula, namely : x = 0.18 ; in which d = the diameter in inches.
In practice, however, the theoretical thicknesses attained by either of these f ormuhe are exceeded, on account of the difficulty of securing good sound pipes, when the thickness is very small. Stone and earthen ware pipes being usually made of large diameters, and being exposed to greet external pressures and jars, seem to require greater thicknesses than are usually given to them ; perhaps when their diameter exceeds 9 inches they ought, in the present state of the arts, to be made of such a thickness that tho latter dimension should be equal to Ath of the diameter at least.
Rain-water, or other metal descent-pipes are made with projecting ears upon the socket ends, for the purpose of receiving the nails by which they are to be fixed one above another. In these cases the end joints are not required to be fitted hermetically.