Holographic investigation of brittle crack propagation in plastic pipes

Abstract

Plastic pipes dominated the low pressure gas distribution piping market during the last decade. Research on steel pipes has long since indicated that the susceptibility to rapid crack propagation (RCP) increases with increasing diameter. Although most plastic pipes used in gas distribution systems are of small diameter (<200mm), there is a tendency to use larger diameter piping, with increasing wall thickness. Based on simple physical principles it is reasonable to expect that susceptibility to RCP in plastic gas distribution piping will also increase with increasing pipe diameter and wall thickness. Although installed pipe sizes seem to be safe, it is imperative to obtain an understanding of the various factors that affect RCP in plastics. Some recent incidents show it is necessary to find criteria to assess the safety of larger diameter piping before such piping is installed in distribution systems. In particular, the newly developed third generation polyethylene materials, of which large diameters are already produced, need extended RCP evaluation.