| 摘要 |
PROBLEM TO BE SOLVED: To provide an internal perimeter sealing system of pipe for electron beam welding, which seals each pipe of two pipes to be welded together when they are welded, and lets a welding carriage readily go through inside the pipe when no welding is performed. SOLUTION: When welding a butt joint 58 of each pipe 1, 2, compressed air is supplied inside the first sealing member 28. This makes the first sealing member 28 expand, the second sealing member 29 expand and protruded strips 43 of the third sealing member 30 contact internal perimeter of each pipe 1, 2. This shuts airtightly an internal space 24 of the butt joint 58 against atmosphere. After welding the sealed butt joint 58, the compressed air inside the first sealing member is exhausted. This makes the first sealing member 28 shrink, the second sealing member 29 be folded to external perimeters of each base member 18, 19. Also the third sealing member 30 returns, with its own resilient force, to the external perimeter side of each base member 18, 19, releasing seals at each pipe 1, 2. This makes the welding carriage 7 travel readily inside the pipe.
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