This section is from the book "A Practical Treatise On The Joints Made And Used By Builders", by Wyvill J. Christy. Also available from Amazon: Practical treatise on the joints made and used by builders.
A wiped soldered joint between a pipe and union, effected by rolling the pipe, with the union temporarily attached to it with small wedges or any other equally effective contrivance, whilst the cloth or solder is held under the junction with the right hand.
This is the common egg-shaped wiped pipe joint, as shown in Fig. 150.
The form of joint about to be described is, perhaps, most frequently made by main layers, but it is sufficiently appropriate to be included in this section. It is a lead joint in piping between two cast iron socket pipes, and is made by inserting a spigot end into the socket of an already laid pipe and caulking the cavity between them with tarred gaskets of spun yarn, or else with white spun yarn if for water, until it is filled to about half its depth. Molten lead is then poured in, which requires great care so as to insure the joint being full enough but not too full, for in setting up there is almost equal danger of fracturing the socket if too much or too little lead be used, the caulking iron in the one case being perhaps applied too vigorously, and in the other running the chance of being driven too far in under the socket. A belt of plastic well-tempered clay is first passed round the pipe close to the edge of the socket, working it up from the bottom, leaving enough room for the lead and an opening or gate for the molten metal to enter. When the lead is cold the excrescences are cut off with a chisel, and then with a steel "set," or stout cranked caulking iron and heavy square faced hammer, the workman sets up the lead, by which means it is tightly wedged, all pin holes arising from air bubbles closed up, and the joint rendered air-tight. In some instances when large pipes have to be united the luting or band of clay is superseded by a flat metal ring, about ¼ in.
thick and 2 in. wide, made in two pieces to suit the diameter of the pipe and with the necessary gate. It is hinged in the middle and flanged for bolting at the free ends. This is passed round the pipe close to the socket, bolted, and made tight with clay, and is then ready for pouring in the lead. This contrivance admits of ready application and quick removal for the next joint, and a similar treble jointed iron collar is sometimes used for small pipes. To prevent the dampness of the clay, etc, blowing out some of the lead in spray through the vapour caused by the hot metal it is advisable to drop a small quantity of resin through the gate. Salt and grease are said to have a similar effect. In every case the ladles should follow one another sufficiently quickly or be large enough to hold more than the joint requires, so that there may be no risk of not filling it at one running. Pipes laid and united in this manner can be deviated considerably from a straight line, but a sound and durable joint cannot be made if the spigot be much smaller than the socket. To give an idea of the dimensions of the joint and of the trifling variation in its size caused by the increased diameter of the pipes, it may be stated that for pipes of the respective diameters of 1½ in. and 12 in. inside measurement, the corresponding depths of socket are 3 in. and 4½ in., whilst the thickness of the lead joint is respectively ¼ in. and ⅜ in., and its depth 1½ in. and 2¾ in. Thus, although the diameter of one pipe is eight times that of the other, the thickness of the lead joint is only half as much again, and its depth not double that of the smaller one, whilst the depth left in the socket for the caulking of spun yarn is about 1¾ in. for both and all intermediate sizes. All lead joints between iron pipes are very easily ruptured unless the pipes are bedded so as to be uninfluenced by superincumbent pressure and protected from shocks. The beds of drums or frusta of stone pillars already plumbed true and kept in proper position by wedges of lead, iron. etc, were occasionally in mediaeval times run with lead to a thickness in some places of ½ in., the joints "being very rough tooled and the lead affording the requisite uniform bearing. There are reasons for supposing that the practice may have arisen from a wish to avoid the delay that waiting for the setting of the mortar would cause. However this may be, it is not even now quite obsolete with respect to tracery and the shafts of pillars, though there are several existing instances where splits and fissures owe their origin to the holes through which the lead was poured. Raglets, cramp holes, holes for lewis bolts, holes in hook stones for crooks, and in sills for guard bars, mortise holes for railings, lead plugs for screws, etc, are run in the same manner, the clay luting being in each case round or under the hole, or placed to the best advantage for conducting the molten metal all over the joint. Care is always necessary that iron embedded in stonework is completely surrounded so that moisture cannot reach it, otherwise the formation of hydrous oxide will certainly corrode, exfoliate, and swell it, and burst or blow the work. Cast iron resists oxidation perhaps much better than wrought if not denuded of its so-called skin (p. 145), but so far as concerns the efficacy of lead as a protective coating, its value is diminished if by any means the lime in the stone or mortar succeeds in oxidising the lead and dissolving the oxide.