# 2006 Washington DC
After the discovery of the low-pressure process for the production of polyethylene with the aid of Ziegler catalysts, only another year went by before pipes were being extruded in highdensity polyethylene. In the same year, at the end of 1954, Hoechst had already begun to carry out long-term failure tests on HDPE pipes under internal hydrostatic pressure at temperatures of between 20 and 80 °C. Consistent continuation of the long term test has shown that even the first pipes to be made of HDPE more than exceeded the former design service life of 50 years. Through intensive material developments, the long term hydrostatic strength ascertained in long-term failure tests on HDPE pipes rated for 50 years' service meanwhile exceeds 10 MPa.