API 5L DSAW PIPE
DOUBLE SUBMERGED ARC WELD 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, hence the word “double.”
These separate welds consume a portion of the other resulting in a single high quality weld nugget.
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Two different processes are used to manufacture DSAW pipe;
1. The pyramid rolls method, and the
2. U-O-E method.
The difference in the processes is found only in the method of forming the cylinder.
a. In the pyramid rolls process the cylinder is formed between 3 rolls arranged in a pyramidal fashion.
b. 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.
vBoth processes use flat steel plate as the raw material.
DSAW pipe mayor may not be cold expanded. Cold expansion is a process where the pipe is expanded (up to 1.5%) to
obtain its final 00 dimension. In the process, a gain of yield strength results.
Expansion is most often utilized in a U-O-E mill due to the need to recover the yield strength lost during forming in the “0
DSAW Pipe is available in the following specifications:
– ASTM A134,
– A139, A252,
– A671, A672, A690, A691,
– A500, A515.
– CSA (Canadian) –Z245.1 and custom specifications.
– API 2B, 5LB, 5LX-42 thru 5LX-80
SPIRAL WELDED. -Is a steel pipe having a DSAW seam the entire length of the pipe in a spiral form. The outside diameter is determined by the angle of the de-coiled steel against the forming head. The more acute the angle, the greater the diameter.
The production of large, hot rolled coils of sufficient width and the development of dependable non-destructive testing methods has enabled this product to be placed in more demanding service.
Spiral weld pipe can be rolled in exact lengths up to 115 feet in either ID or OD dimensions up to 144 inches. There is a minimum tonnage required for rolling. Because the manufacturing process is slow, it gives the contractor an advantage of short term changes to the order. This same slow production can also be a disadvantage when large tonnages are needed with a short lead time.
Spiral weld pipe is produced to limited specifications. Now, if this is confusing to you, don’t get discouraged. Steel pipe is a complex world to understand. A few charts might help.