John Fishburne
Papers # 2016 Berlin
The United States water industry relies heavily on American Water Works Association (AWWA) Standards publications for product ratings, design parameters, and guidance on installation methodologies. In September 2015, AWWA published Standard C906-15 covering 4” – 65” polyethylene pressure pipe for waterworks applications. The previous standard was significantly revised in response to the global prevalence of PE4710/PE100 HDPE pipe compounds. Publication of AWWA C906-15 completed an unusually exhaustive standard development process that was initiated at AWWA in 2005 and taken up in earnest by the full Polyolefin Pressure Pipe & Fittings Committee during 2008.
The improved performance capabilities of the latest generation of polyethylene pipe compounds particularly challenged the US water industry’s understanding of the relevance of the ratio between the Hydrostatic Design Basis (HDB) and the Hydrostatic Design Strength (HDS) as a single proportional measure of safety for pressure pipelines. Work at AWWA addressed tenacious US perceptions that the safety factor for thermoplastic pipe is simply the inverse of the “design factor” (HDS:HDB) and established that PE4710/PE100 compounds rated to AWWA 906-15 are more resistant to sustained static loads than their predecessors. Work to establish AWWA requirements for the latest generation of polyethylene pipe compounds revealed the US water industry’s educational legacy in rigid, elastic materials, and relied upon European experience with PE100, the ISO designation for the latest generation of PE pipe compounds.
The Chair of the AWWA Standards Committee responsible for AWWA C906 reviewed the expert rationale that quantified inherent minimum safety factors for HDPE piping against failure due to surge, fatigue oxidation, and sustained load that supported the approval of the standard. Organizations that participate in the US water market will be interested to fully understand the points debated during the formal development cycle, as the exhaustive process to approve AWWA C906 revealed much about the state of sustainable pipeline engineering and construction thought in the United States and the implications for water main break and leakage rate trends for pressure water pipelines.
