Sonya Pemberton, David Chrystie-Lowe, Sabah Rafiq, Karolina Modelska, Edward Ingham
Papers # 2014 Chicago
A room temperature tensile test using thin films taken from the outside and inside surface of polymer pipes has been developed to study the slow crack growth resistance of ageing PE pipelines via analysis of their strain hardening behaviour. A range of PE materials in service since the early 1970s and 80s are studied, focussing on MDPE gas pipeline materials. The aim of this work is to allow prediction of the remaining lifetime of ageing PE pipes or to give a risk ranking of ageing materials to assist with network management. The advantages of testing thin films are the small amount of material required, which could potentially be taken as scrapings or coupons from live material in the field, the short test time of 20 minutes to 8 hours required compared to potentially thousands of hours for NPT or other slow crack growth tests, the fact that testing is undertaken at room temperature, avoiding the necessity for heat treatment of the samples, and the none-specialised equipment required in the form of a tensometer, contact extensometer and ISO 37 stamp. However, as yet no correlation has been found between the strain hardening response of various PE pipeline materials and their expected slow crack growth resistance.
