| 摘要 |
A liner or other elongated duct is made by joining lengths of thin-walled polyethylene fusion. Typical thickness 2-4 mm, diameter 200 mm. Pipe ends are clamped in clamps which restore circularity. The ends are trimmed leaving aligned ends normal to pipe length. The clamps force the ends against a heated body, which is retracted and the ends are then forced together. The total heating period, say 15 seconds, and the periord between separation from the body and engagement of the ends, say 1 second, are very short. Good joint strengths and small beads result. The liner can be pulled into burst cast-iron gas main before a new main is passed through the liner; or the liner is a seal in a pipe. The method is applicable to other polyolefins e.g. polyropylene.
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