| 摘要 |
<p>The sheath is formed by rolling a strip of thermoplastic insulating material into a tube, and joining its longitudinal edges together by welding. The joint may be formed by heat welding, or ultrasonic welding, pref. spot welding with a distance of 2 mm between spots, or HF welding. The joint may be a flange weld, a lap weld or a butt weld. When fitted over the pipe, the sheath forms a continuous water-tight covering, as long as, in the case of spot welded sheaths, the distance between spots is reduced sufficiently. The welding operation and the presence of a welded joint in no way diminish the initial properties of the plastic material with respect to thermal and sound insulation and protection against corrosion of the pipes.</p> |
