Engineering Wonders of the World
Volume III

342 ENGINEERING WONDERS OF THE WORLD. A DRILLING RIG AT WORK. One of the men is seen turning the rods by means of a tiller. Other salvage operations that the well- sinker must be prepared to undertake are the unscrewing of rod's while in the bore, the re- covery of the pipes, and the cutting off of pipes below ground. For the first of these he uses a tool with a bell-shaped end, in the inside of which is chased a left-handed screw thread. This tool is attached to rods—which also have left- handed screw joints—lowered to embrace the top of the uppermost rod, and rotated in an anti-clockwise direction. The bell works its way on to the rod, and when the resistance has increased to a certain point the rod un- screws from that next to it, or some other joint lower down gives, and the released rods can be drawn up. The operation is repeated until all the rods have been retrieved. Instead of a bell a “ latch box, ’ with spring catches which take hold of a joint, may be used. The same tool also serves, in some cases, for rescuing pipes. An alternative is a somewhat similar instrument which grips the pipe on the inside. It sometimes happens that the well-sinker is in doubt as to what Rescuing Pipes. kind of an end there is to take hold of. He therefore lets down on th© encl of a rod a socket filled with stiff clay or putty, in which an impression of the obstruction is obtained to guide the devising of a special tool to deal with the case. To sever a pipe below ground requires the use of a pipe-cutter. This consists of a piece of piping with three or four slots cut in the at right angles Through each a sharp-edged circumference to the axis, slot projects Cutting Pipes below ground. disc of very hard steel, carried on a spring which can be forced outwards by means of a long tapered bar pushed down inside the pipe. Th© principle is the same as that of the ordi- nary pipe expander. The discs are gradually forced outwards by the tapered bar as the tool revolves, and eat their way into the pipe until the latter has been completely severed, and can be raised by a latch too]. Occasionally a drill crown is cut through by the fragments of some hard substance which fall into the bore. As an instance of such an occurrence, we may quote what hap- pened in a well being sunk by Messrs. C. Isler and Co. At a depth of 848 feet sharp flints dropped out of the chalk through which they were boring, and cut away the crown as cleanly as if it had been turned off in a lathe. Tho detached crown was nearly 18" in diameter, and I" thick. When the obstruction had been removed—this operation gave a great deal of trouble—boring was resumed. The same mis- hap was repeated three times, and in one case a string of tools over 20 feet long was severed by the flints, which were finally checkmated by means of a temporary lining driven down to keep them in their natural positions.