Agenda - Public Works Committee - 05/18/2010

Home

Changes in the HDPE Service Tubing Market That Are Critical to Your Municipal Utility's Standards and Specifications catastrophic failure of PE tubing which results in the pipe splitting open longitudinally. It is a rare occurrence, but one that might happen. Increasing the RCP resistance is critical to the gas utility market and gas utilities are switching to PE-4710 materials because of this property alone. 95% of the gas pipe installed in the USA is MDPE or HDPE. The materials designations for pipe resin changed as a result of the changes to ASTM D3350 and PPI TR-4. What we used to call PE-3408 is now known is PE-3608. There is no change to the material, only its designation. New designations have also resulted such as PE-3708, PE-3710 and PE-4710. Beginning in 2002 the NorthAmerican HDPE pipe industry, through the Plastic Pipe Institute (PPI), initiated efforts to integrate the bi-modal resins into the ASTM standards and specification system. The initial difficulty was the existing standards .provided no basis for differentiation of the new bi-modal resins vs. the then current PE-3408 uni-modal resins in use throughout the North American market. Basically the pressure rating and environmental stress crack ratings did not have a wide enough range to handle the superior properties of PE-4710 resins. Over the next few years the following changes occurred: 1) ASTM D3350 was revised to expand the cell classification of HDPE resins and this revision was completed in 2005. 2) PPI Technical Report 4 (TR-4) was revised to include the bi-modal resin properties and this was completed in 2006. 3) Revisions to ASTM D3035, F714, D2737 and D2239 were undertaken. ASTM D3035 and F714 revisions were completed in 2006. ASTM D2737 and D2239 are still being reviewed and we expect this process to be complete by the end of 2007. These changes were necessary to incorporate the new materials into the ASTM system, but unfortunately they also will create some confusion and will obsolete the standards and specifications of water utilities across the country. 13R Journal NEW WA June 2(10A Over the course of time and reaction to market demands the materials that will be available will be limited to a few resins. Most likely the water pipe resins that will be used will be PE-3608 and PE- 4710. Resin producers will not make any more variations than they have to for economic reasons. Pipe producers will not make available multiple resins, again for economic reasons. Even the new ranges created do not fully differentiate resins from various producers. Variations in cell classification andhigh temperature Hydrostatic Design Basis (HDB) are key items to review when writing your utilities specification for HDPE water pipe and tubing. Some PE-4710 resins have PENT test ratings of greater than 4000 hours and others that exceed 25,000 hours without failure. ASTM D3350 only rates materials up to 10,000 hours so the specifier should ask the pipe producer what resin is used and what PENT test results are for this resin. Some resins are rated as much as 20% higher for HDB at elevated temperatures. Again this is not reflected in the ASTM D3350 cell class and must be investigated by the specifier to be sure that you are getting the best product available. This information should be readily available from your pipe supplier or directly from resin suppliers. For the short term most producers are now dual marking their HDPE pipe and tubing as follows: