Fatigue of Plastic Water Pipe: A Technical Review with Recommendations for PE4710 Pipe Design Fatigue

Abstract

The PE design practices for preventing pressure surge fatigue failures in water pipe have a long and very successful history. These practices were developed based on the older generation PE materials. Since this time there has been considerable evolution in the performance of PE pipe and the introduction of a new classification of high performance PE4710 materials. This study conducted an assessment of the current design approaches to determine their continued suitability with the introduction PE4710 materials. Comparison was also made with the current US fatigue design approaches for PVC along with an examination of other international design practices. The fatigue resistance of PE4710 materials is seen to be excellent, and shows these materials are capable of providing for essentially unlimited fatigue resistance under the operating conditions of water transmission and distribution systems. The current design approaches for both occasional (short-term) surge resistance and repetitive (long-term) fatigue resistance for PE4710 materials are conservative and appear justified based on available data. The US design approach for PE4710 materials is also seen to more conservative than that of the UK for both occasional and repetitive surge events. Background The cyclic fatigue resistance of PE piping materials has not been a design issue or concern 1, 2 . The high fatigue resistance of PE materials in general allowed some simple fatigue design rules-of-thumb to be developed during the introduction of PE piping. The general adequacy and utility of these practices, to some extent, has limited the need and the motivation to develop more detailed or precise practices for PE fatigue design. This is particularly so for the effects of internal pressure surges on PE water pipe. While these design practices for preventing pressure surge fatigue failures in water pipe have a long and very successful history, they were developed based on the older generation PE materials. Since this time there has been considerable evolution in the performance of PE pipe and the introduction of a new classification of high performance PE4710 materials. This study conducted an assessment of the current design approaches to determine their continued suitability with the introduction PE4710 materials. Comparison was also made with the current US fatigue design approaches for PVC along with an examination of other international design practices.