POLYTHEYLENE FABRICATED FLANGE FAILURES

摘要

Large diameter fabricated high density polyethylene (HDPE) flanges have been used successfully in a variety of industriesand applications. However, fabricated flange failures at two DuPont Gulf Coast plants resulted in expensive field repairs andone failure caused a significant production loss. Both HDPE lines were in cooling water service and both failures occurred ina flange-to-stub-end weld made in seemingly ideal conditions at a shop (as contrasted to the difficulty of making field welds).The failed components are 36' (914 mm) diameter, one flange is 13.5 SDR and the other is 11 SDR. One flange failedbecause of thermal degradation during welding, while the second flange failed due to a cold weld. This paper describes thefield assessment, field repair and failure analysis for each flange.