Flange joints are those which are made with flanges forming bearings for bolts or clamps, by means of which the pipes are secured together. Our first example is:
(a) The Spigot and Socket flange joint represented in Figs. 463 and 464. The pipes are here made with circular flanges, one having an annular groove on one end, and the other a corresponding annular projection or spigot, both being slightly beveled. The flanges have four or more slots in their periphery at uniform distances apart. A suitable packing ring, usually of lead, is placed in the groove and compressed by screwing up the bolts which pass through the slots. The ordinary steam-fitters' flanged joint differs from this in having plain level surfaces without groove or spigot. The steam-fitters' packing consists of paper, leather, rubber, or composition rings with or without putty, red lead or other filling. The surface of the flanges is for the best work, planed off, to give proper tightness, and instead of slots, holes are usually used to take the bolts. These kinds of joints are unsuitable for plumbing purposes, because they are not adjustable and do not admit of slight variation in direction of the piping, as is absolutely necessary in plumbing work. The machine planing of the steam-fitters' flanged pipes, moreover, involves too great an expense to render the joint practicable for plumbing purposes.
Figs. 465, 466 and 467 show a joint devised with a view to overcoming the first of the above-mentioned objections to the ordinary flange-joint. On each side of the pipe are cast curved projections or collars extending only partially round its circumference. A flanged collar, recessed to correspond with the curved projections, is slipped over the end of each pipe and turned partly round behind the projections. The flanges are thus held securely on the pipe, which may be adjusted in a variety of positions. An annular connecting piece, recessed to receive packing rings, is placed between the pipes to be joined. These connecting pieces are made with one or both faces at any desired angle to the bore of the pipes. A short portion at each end of the pipes is made somewhat thicker than the main length, so that at the extreme ends a wider surface of metal is obtained for the packing ring to rest against. Fig. 467 shows the same joint with the bevelled connecting pieces to give a change of direction to the piping.
There are several objections to this form of joint. The slotted collars occupy too much space and are liable to be easily broken in screwing the pipes together, especially at those points where the flange is weakened by the bolt hole and yet has no support immediately below. Moreover, the arrangement, though allowing a certain amount of play of the pipes in adjusting them, still limits their movement and would cause considerable annoyance in handling. The very long bolts are expensive and awkward. The heads and nuts do not rest square on their bearings when the bevelled connecting rings are used. The bolts are, therefore, easily broken in screwing up, as I have found in experimenting upon them in this connection, unless bevelled washers are used, which still further increases the cost.
Moreover, lead for packing is entirely unsuitable, since longitudinal expansion of the pipes will compress the lead, and subsequent contraction will then leave an annular opening for the escape of air or water.
Fig. 468 gives another form of flange joint devised with the same end in view. At one end of each length of pipe is a cone-shaped socket, having at opposite sides two lateral projecting lugs with bolt holes. On the other end of the pipe, which is plain, is placed a loose flanged collar which has bolt holes to coincide with the holes in the lugs of the socket, into which the end or neck of the collar is free to enter. A packing ring of India-rubber, hemp, or other elastic compressible substance, is placed on the end. The neck of the collar is then slid forward into the socket, and is brought to bear upon the packing by means of bolts, which are passed through the bolt holes. The joint is neither permanent nor tight under pressure. Moreover, it offers no resistance to longitudinal strain under which the two pipes might be drawn apart. If lead is used as a packing it would be compressed by both longitudinal and lateral expansion by heat and upon cooling again leakage is caused.
(b) The Spherical Flange Joint.
Figs. 469, 470 and 471 show another device for variable adjustment of the pipes. The parts at the points of junction are of spherical form, and the parts of the spheres where the junction takes place are inclined, by preference, to an angle of 45 degrees with the axis of the pipes, and are fitted with suitable packing and bolted as shown. This form of joint is evidently unsuitable for plumbing purposes. Should the bolt be made to pass through the center of the pipes, as shown in the last four figures, it would form an obstruction to the flow of the sewage. If, on the other hand, the bolts are made to pass through the flanges, the amount of possible variation of adjustment would be limited to the number of holes made in the flanges, and the piercing of these holes would not only add to the expense in proportion to their number, but also weaken the flange. Another serious objection lies in the sewage fouling caused by the spherical sockets.