Polymer Competence Center Leoben GmbH, Austria
Buried pipes, especially pressurized plastic pipes, have been used successfully for several decades, and pipe systems made of polyethylene (PE) have been employed widely in fuel gas and water supply and in sewage systems for more than 50 years. As a result of improvements in the raw materials, an increase in minimum service life to possibly 100 years has been proposed, most recently for latest-generation PE materials of the PE 100 type. Thus the reliability of these pipe systems is of major significance, and reliable lifetime prediction with modern methods is essential.
Crack initiation and slow crack growth (SCG) are the critical failure mechanisms in long-term applications of pressurized PE pipes. For a fracture mechanics lifetime and safety assessment, knowledge of material-specific SCG kinetics is crucial. As testing of SCG with common test methods is not possible in real time, an accelerated extrapolation test procedure based on cyclic tests with cracked round bar (CRB) specimens was developed.
This webinar will introduce the fracture mechanics approach and the testing procedure for lifetime predictions of PE pressure pipes, specifically, of modern PE 80 and PE 100 pipe grades. The advantages of using the CRB specimen will be explained. Validation of the procedure at elevated temperatures of 60°C will be shown, where real failure times of high-density PE pipes correlate to predicted failure times.