II. SPIRALLY WELDED TUBING.—The manufacture of spirally welded tubing, as carried on at the works of the Spiral Weld Tube Co., Orange, N. J., is thus described: The raw material of the industry is the sheet-iron or steel of commerce, of such lengths and widths as it is convenient to roll. The range of the gauges of the metal which can be employed has not yet been determined. The lightest metal thus far successfully made into pipe is No. 29 iron, and the heaviest a steel gauging •105 of an inch in thickness, or No. 8 of the Birmingham gauge.
The first step in the process of manufacture is to slit the sheets into bands of the width most convenient for the production of the desired diameter of pipe. The wider the skelp, the faster the pipe is made. For convenience, all diameters are made from four widths of skelp, 6. 12, 18, and 24 ins. To make a 6-in. pipe 30 ft. long from 12-in. skelp, it is neces sary to have a ribbon of metal about 49 ft. long. The ends of the strips of skelp are united by a machine known as a cross welder. The sheets are so placed as to give about fin. lap, and in this position they are firmly clamped. Heat is then applied by furnaces above and below, which move along the seam. As they recede, the hot edges are welded between a hammer moving vertically and an anvil of reciprocal motion. To place and clamp the skelp, heat the overlapping edges and weld them, consumes about one minute to each cross seam of 12 ins. A pressure of the foot of the operator upon a treadle engages a worm-wheel and worm, which rotates a reel upon which the skelp is wound. As it is drawn from the reel, it passes between pressure-rolls, which smooth out any buckling or other irregularity in the still hot metal, and rotary shears trim off the burr at the ends of the welded seam. In case the weld is defective or the sheets have not been clamped in line, the weld is cut by a shear held suspended when not in use, and the ends are welded again. As a rule, the weld is smooth and perfect, and the extra thickness of metal at the weld occasions no inconvenience in forming the pipe.
The pipe-machine (Fig. 7) is chiefly made of heavy castings, requiring but little finish.
It occupies about 3 x 0 ft. of floor space. The reel carrying the ribbon of skelp is put in position, and one end of the metal is placed upon the guide table, which is set at the angle due to the width of the skelp and the diameter of the pipe into which it is to be made. The metal is carried into the machine between feed rolls geared together, which are actuated by a ratchet, giving them an intermittent rotation, and a rate of feed variable between and K of an inch at each impulse, at the pleasure of the operator. This carries it into the
forming jaws, which bend it to the desired curvature—the forming being effected by pinching the metal in curved jaws. The essential features of the pipe-machine are a guide table for the skelp, adjustable to the desired angle; feed rolls, to pass it forward with an intermittent progress, so that it shall advance when the hammer is raised and be at rest when the hammer falls; a former, to curve the metal to the desired radius, also adjustable; a furnace, to heat the metal ; a hammer, to weld it, and an anvil to support the pipe, and receive:the shocks of the hammer. No mandrel is used. The pipe in the forming process is held in place by a pipe-mould, which is a cylindrical shell, within which the pipe rotates as the stock is fed in. The anvil is of considerable mass, steel-faced, and extends the entire width of the skelp. The hammer is light, and at normal speed strikes 100 blows per minute. The heating is done in a furnace so constructed as to heat both the edges to be united for the space of several inches ahead of the point at which the welding is effected. A 6-in. pipe made of No. 14 gauge iron of good average quality, showing under test 33.000 lbs. elastic limit, and 50,000 lbs. ultimate strength, has a proof strength of 913 lbs. per sq. and an ultimate strength of 1,383 lbs. per sq, in. A 12-in. pipe of the same stock has a proof strength of 456 lbs., and an ultimate strength of 691 lbs. Using the same diameters and gauges of stock for comparison, the 6-in, spirally welded pipe weighs 5.2 lbs. per ft. against lbs. per ft. for standard lap-welded pipe. and 28.28 lbs. for medium cast-iron pipe: the 12-in, spirally welded pipe weighs 10'46 against 54.05 lbs. for lap-welded, anti 77-36 for medium cast-iron. The question of durability in service is one when naturally suggests itself when light steel ar iron pipes are discussed. Experience on the Pacific Coast seems to have settled this question, as the cheap expedients adopted for water-conveyance during the days when hydraulic mining was most extensively conducted have been followed ever since in engineering works. Data on this subject, are presented in a paper read by amilton Smith, Jr., before the British Iron and Steel Institute, and printed in Vol. 1. of the Journal for 1886.