Failure analysis of a reinforced thermoplastic pipe used in an oil transportation system

A burst failure occurred in a reinforced thermoplastic pipe used in an oil transportation system for 5 years. Visual inspection, tensile test, FTIR, TGA, VST, DSC, and pressure test were conducted to find out the failure cause. The results show that the damage to sealing rings led to the leakage of conveying medium in the joint. The fibers in the reinforcement layer were contaminated by the leaked conveying medium, resulting in performance degradation. The tensile strength and elongation at break of the fiber all decreased by 60 similar to 80%. The burst pressure of the contaminated pipe is only 6 similar to 7 MPa, far lower than its PN. According to the operating record, the highest working pressure ever reached 5.2 MPa during the operation, which approached its burst pressure. Meanwhile, there were pressure fluctuations during the operation. When the transient pressure was higher than the burst pressure of the contaminated pipes, burst failure occurred.