The Butt-Weld Process
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Early Water Pipes
How Butt-weld Pipes Are Made
From the double refined puddled iron, in the case of wrought iron, or from billets of soft Bessemer or open-hearth steel, long narrow plates are rolled. The width and thickness of these plates, which are known as “skelps,” are exactly such as will give pipe of the desired diameter and gauge. In order that the weld may be solid all along, the skelp as it leaves the rolls has edges not exactly square but very slightly beveled, so that the surface which is to form the interior of the pipe is slightly narrower than the other.
After trimming the pieces of skelp so that each has one end with a sort of point where the tongs are to take hold, they are laid side by side in a heating furnace and left there until they have become white-hot.
Just in front of the furnace is the “bell,” with a second and slightly smaller one in front. With strong tongs the workman reaches into the furnace and fastens onto the pointed end of a piece of the white-hot skelp. Hooking the handle of his tongs into the draw chain the skelp is drawn through the first and second bell, the first bending it almost into tube shape, the second completing the operation and pressing together the edges of the plate in the top of the bell so tightly that they weld.
Plates Called “Skelp” Are First Rolled
The pipe now goes through what are known as cross rolls, the axes of which are somewhere near parallel with the axis of the pipe. In these the pipe is rapidly spun around, surface-cleaned and straightened. Going up a cooling incline it goes to tables where the ends are cut off and the product inspected.
A very important part of the inspection is the hydrostatic or water test. One at a time the pieces are tightly fitted in between two water-tight caps, water is turned into the pipe and gradually brought up to the testing pressure of 600 pounds or more per square inch according to specifications.
Charging Skelp into the Heating Furnace
Drawing Butt-weld Pipe
Pipes of diameters between ⅛″ and 3″ are usually made by the butt-weld process.