Analysis of ultimate pressure of corroded subsea pipe repaired with composite considering temperature and material degradation

Corroded subsea pipe repaired with composite material is more and more used because of its low cost, simple process and short time, but the repair effect will be affected by factors such as temperature and material degradation. To study the law of the effect, the finite element method is used to analyze ultimate loads on repaired pipe by considering the factors of temperature and material degradation. The results show that the ultimate yielding and bursting pressure decreases with the increase in temperature for both the defect pipe and repaired pipe under temperature and internal pressure. The ultimate pressures are larger when both ends of the pipe are fixed comparing with one end is free, but they also decrease faster as the temperature increases. Experiments show that elastic modulus and glass transition temperature of composite will decrease when exposed to prolonged seawater and high temperature. The degradation of composite repair layer performance has a great effect on the ultimate pressure of pipe, and the failure of the repair area will be caused under long-time harsh environment. In this paper, the design repair thickness of composite is obtained, which could improve the repair efficiency of corroded pipes and reduce cost as well.