| 摘要 |
The tube is composed of a number of similar flat strips bent into an L- or U-shape, each forming a lengthwise rib and a strip of outside wall between this and the next rib. They are welded together so that the bend in one is joined to the edge of the next one. In welding the seams (6) the operations are carried in a sequence running in the opposite direction to that in which the strip portions (5') forming the outside wall extend. Each weld can be made at the same height and along the next seam in the same direction, working round the tube until all welds are complete. |
