Agenda - Public Works Committee - 05/18/2010

Home

Changes in the HDPE Service Tubing Market ThatAre Critical to Your Municipal Utility's Standards and Specifications By Richard G. Iuaft* Presented September I8, 2007 Abstract Over the past 5 years new HDPE (High Density Polyethylene) materials have been introduced into the North American pipe and tubing market. These materials are known as bi-modal resins. Bi-modal resins originated in Europe over 20 years ago and have been in use in Europe with excellent results. Bi-modal resins are commonly known as PE-80 or PE-100 in Europe using the ISO designations. In the USA where the ASTM standards are used the designation for bi- modal resins is PE 4710. Older uni-modal resins were designated as PE-3408. density PE) reactor and a HDPE (high density PE) reactor have their processes merged about 1 /3 of the way through the process. The final product produced has properties that are far superior to either the original MDPE or the HDPE products alone. For example the density of the final product is in the range of .949 to .959 g/cc. This is higher than the older PE- 3408 resin which had a density range of .943 to .954 g/cc. This looks like a small change, but it is significant. The increase results in higher tensile strength and pressure ratings of pipe and service tubing made from bi-modal resins. These new bi-modal resins have created opportunity and challenges for the America water utilities. The opportunity is the availability of pipe and tubing with a service life of over I00 years (vs. 50 years for older HDPE resins) and pressure ratings that are 25% higher than older HDPE resins. The challenges are these new materials have created a need to revise standards and material designations at the municipal level. These new material designations will obsolete the current standards and specifications of many utilities. First -What is a Bi-Modal Resin? Bi-modal resins are made in reactors that combine the production of two different types of resin in one reactor. In the simplest form a MDPE (medium *Vice President Sales & Marketing, Endot Industries, Inc., Rockaway, NJ The pressure rating for service tubing produced from PE4710 is 25% higher than tubing produced from PE-3408, i.e. 250 PSI vs. 200 PSI. The resistance to environmental stress cracking increases over 100%. The older PE-3408 had a PENT rating of 500 to 1000 hours to failure. PE- 4710 materials have PE1~TT ratings of 4,000 to 25,000 hours to failure. This means the service tubing made from PE-4710 has little likelihood of failing due to environmental stress cracking. The extrapolated life expectanry of the PE- 4710 resin from DOW Chemical that Endot Industries uses is 100 years vs. 50 years for older PE-3408 resin. Rapid Crack Propagation (RCP), a performance standard critical to the gas piping market, is reduced significantly. RCP is the Journal NEWWA June 2008 l37 B