BOILERS AND PIPES. 



247 



their joints with what is called a " loose 

 collar," namely, hemp, white lead, brown 

 paper, Dorking lime, and boiled oil. 

 This mode of joining has the advantage 

 of being readily taken to pieces when 

 alterations are required ; and also that 

 the pipes can be jointed by any handy 

 labourer. 



" The thimble-joint is not only a strong, 

 but also a neat connection. It has the 

 advantage over the flange-joint of being 

 much neater ; while, like it, it may be 

 taken to pieces for repairs or otherwise 

 without disturbing the other joints. It 

 has been recommended to make the 

 thimble of thin wrought iron, leaving but 

 a small space for the cement, that the 

 expansion may be equalised, and the risk 

 of an unsound joint avoided. 



"The saddle-joint is composed of two 

 pieces, forming a thimble, which are em- 

 braced by two hoops, the ends of which 

 are secured and tightened by screws. 

 This is a convenient joining when a 

 branch has to be made from the main 

 pipe. The branch ought, however, always 

 to be cast upon the main, with its proper 

 flange or faucet. When the pipes are 

 vertical, the ends are ground to fit each 

 other ; and the iron cement being placed 

 between them, the weight is sufficient to 

 unite the joint. Where the exterior 

 of the pipes must be flush at the joint, 

 the projection is made inside of the 



" In small wrought-iron pipes used in 

 some hot- water apparatuses, the joint is 

 formed by placing the ends of the tubes 

 within a socket, forming a right and left 

 hand screw : the edge of the one pipe 

 being flattened, and the other sharpened, 

 they are screwed so tight that the edge of 

 the one is indented into the flattened sur- 

 face of the other. The wrought-iron 

 pipes of small diameter that are occasion- 

 ally used as branch-pipes, or to carry off 

 the water of condensation, are screwed 

 into the cast-iron pipe. By whatever 

 method the joints are made, the space 

 between the joined ends should be as 

 small as possible, to prevent the lodg- 

 ment of water in the lower part." — Ber- 

 nan's Hist, of the Art of Warming and 

 Ventilating. 



All metallic bodies expand by heat; 

 and hence pipes heated by hot water or 

 steam expand and contract by change of 



temperature. This has been noticed in 

 another part of this work. Engineers, to 

 provide against danger from this expan- 

 sion, have adopted rollers placed under 

 the pipes, which latter, being kept clear 

 of the building, admit of the pipes stretch- 

 ing out, when heated, to their full expan- 

 sion, and also of returning to their origi- 

 nal length when contracted. In ordinary 

 cases, such as in hothouse-heating, unless 

 upon a very extensive scale, this provision 

 is unimportant ; but where the pipes are 

 carried to a great length horizontally, it 

 is useful. 



Expansion-joints are also used to 

 correct expansion 

 and contraction ; 

 as, for example, in 

 the case of the 

 flange-joint, fig. 329, 

 where Count Rum- 

 ford's expansion- 

 drum, b, is made of 

 thin copper : as the 

 pipes a i elongate, 

 they press on the thin sides, b, of the 

 drum, inwards ; and as they cool, they 

 draw the sides out. 



The thimble-joint, fig. 330, is often 

 formed to admit of this 

 expansion, by having 

 the adjoining ends of 

 the pipes a b turned 

 true on the outside, 

 and having a thimble, 

 as in the common 

 joint : a piece of tin, c, or inner thimble, 

 is interposed, and made to fit nicely to 

 the turned parts of the pipes, which 

 w T orks backwards and forwards like a 

 piston in a cylinder, as expansion and 

 contraction goes on. 



Spigot-and-faucet joints are similarly 

 made, and, in a range of pipes 120 feet 

 in length, permit a movement of three- 

 quarters of an inch upon the whole 

 length. 



The cone-joint, fig. 331, is employed 

 by Mr Parkins in his 

 high - pressure mode 

 of circulation : it is a 

 strong joint, and easily 

 made. The cone is 

 inserted into the ends 

 | of the pipes, in the same 

 way as connecting gas- 

 pipes, and is made tight by two screw- 



Fig. 331. 



H 



