| 摘要 |
PURPOSE:To enable the wall thickness of each original pipe to be thickened by a method wherein the pipes are arranged in such a manner as a plane containing a central line of a single U-pipe is not at a right angle in respect to central line of an arrangement of pipes. CONSTITUTION:U-pipes 1 are arranged across a central line 2 of an arrangement of pipes. A plane 3a containing a central line of a single U-pipe is inclined in respect to the central line 2 of the arrangement of pipes and crossed (at a no-right angle theta) therewith. In this case, a bending radius Ra of a U-pipe 1a can be set larger than the shortest distance Ha from the central line 2 of the arrangement of pipes to a position of the arrangement of U-pipe 1a. For example, if an internal pressure of a pipe is 415 atg, an outer diameter of a pipe is 19mm and the shortest distance from the central line of the arrangement of pipes to the position of the arrangement of pipes is 40mm, a required wall thickness of the original pipe before its U-bending operation is 3.12mm in the prior art. To the contrary, the wall thickness of the pipe in accordance with the present invention is a small value of 2.90mm and so a reduction of 8% can be attained.
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