Yoshida, Kitaoka, Nishimura
Jointing of Pipes # 1998 Gothenburg
Because dirt ( sand, mud, etc. ) on the fusion interface causes a decrease in the strength of fusion joints, it is necessary to scrape and clean the pipe surface before fusion jointing. We have determined the degree of dirt that causes a decrease in the strength of fusion joints by experiments on peeling off at the fusion interface. Our work procedure provides for the necessity of scraping and cleaning the pipe surface before fusion jointing. In order to maintain high and uniform quality of EF jointing work, we have developed an electric scraper for saddle fusion and an ethanol-saturated bottlecontained wet wiper for cleaning. If we fuse an EF joint with water, mud, or sand left on the fusion interface, its strenbqh decreases. Particularly, if we fuse an EF joint with water or mud left on the fusion interface, vaporized water on the fusion interface becomes bubbles by electrofusion. These bubbles on the fusion interface can cause serious faults. Therefore, a point-focused polymer transducer of a narrow frequency band to detect bubbles 0.5 mm in diameter on the fusion interface after electrofusion at work site has been developed. This transducer has excellent resolution and sensitivity; it is possible to observe bubble faults in a B-Scan image.
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