Failure analysis of steel wire reinforced thermoplastics composite pipe

Incident involving failures of steel wire reinforced thermoplastic composite pipes (SRTP) which transport saline wastewater had caused serious burst after several months of usage from July 2009. Investigations were performed to identify the most probable causes of the pipe failures. The study was conducted by reviewing the background of the incident, visual physical inspection, mechanical property test and thermal analysis. Results revealed that the failure of this pipe was mainly caused by a typical environmental stress cracking (ESC) of its basal resin. The basic reason for crazing of the resin was that the oxidation induction time (OIT) of utilized HDPE 63 (4801EX) in the composite pipes was only 4.7 min, which was largely lower than that stated in standard (⩾20 min). The worse thermal oxidation stability of the resin gave a hidden peril of ESC to result in the final failure of the pipes.