Failure analysis of polytetrafluoroethylene lined pipe under thermal shock

In the process of fluid transportation, polytetrafluoroethylene (PTFE) lined pipe is subject to constant thermal stress caused by constant temperature fluid and alternating thermal stress caused by alternate flow of cold and hot fluid, making it susceptible to progressive plastic strain accumulation, namely the ratcheting. In this paper, cold and hot shock tests of PTFE lined pipe at different temperatures were carried out. Ohno-Wang II model was used to predict the ratcheting of PTFE lined pipe under cyclic temperature loading. The simulation result shows that the ratcheting strains occur in the same position as the test result. The equivalent plastic strain control method was used to determine the ratcheting boundary temperature as 145 °C and 90 °C for PTFE lined pipes under cold and hot shock respectively. The ratcheting boundaries of lined pipe with different PTFE lining thickness were given to obtain the influence of lining thickness on ratcheting boundary.