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Double submerged arc welded pipe (DSAW) derives its name from the welding process wherein the welding arc is submerged in flux while the welding takes place. Both inside and outside welds are required and are usually accomplished in separate processes. These separate welds consume a portion of the other resulting in a single high quality weld nugget. DSAW pipe is produced in sizes from 18 inch through 72 inch and wall thicknesses from 0.250 inch through 1.5 inch.
Two different processes are used to manufacture DSAW pipe: the pyramid rolls method, and the U-O-E method. The difference in the processes is found only in the method of forming the cylinder. In the pyramid rolls process the cylinder is formed between 3 rolls arranged in a pyramidal fashion. As the name implies, the U-O-E method uses a "U" press, and "0" press for forming. Other parts of the process such as finishing and inspection are similar. Both processes use flat steel plate as the raw material.
DSAW pipe is normally produced in double random lengths with square or beveled end for welding. It is usually furnished barely but varnish is also offered. A wide range of external coatings and internal linings are available with DSAW pipe. DSAW pipe is used in high pressure gas and oil transmission lines (both onshore and offshore), structural members and pipe piles.
