| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem of a conventional fire resisting double tube consisting of an inner tube and a fire resisting outer tube put thereon that the workability in cutting is good while the workability in connection is poor since the whole outer tube is movable in the tube axial direction to the inner pipe and to provide a fire resisting double tube capable of reconciling both the workability in cutting and the workability in connection. SOLUTION: The outer tube 22 is divided into a fixed outer tube 22A not movable in the tube axial direction to the inner tube 21 and a movable outer tube 22B movable in the tube axial direction to the inner tube 21. The movable outer tube 22B is moved and cut, and the fixed outer tube 22A is grasped to perform the connection work, whereby the working property in cutting and the workability in connection can be reconciled.
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