CONFIRMATION OF LONG SERVICE LIVES OF PE-PIPES UNDER HIGHER TEMPERATURES APPLYING CONVENTIONAL OVEN TESTS AND MODERN HIGH-PRESSURE AUTOCLAVE TESTS

Januari 17, 2022 by admin in Industry News, Uncategorized

Anja Armani, Helmut Zanzinger

# 2021 Amsterdam

PE-pipes are used in applications at temperatures higher than 40°C and long service lives like drainage pipes in landfill basal lining systems, drainage pipes in tunnels with high cover heights, geothermal applications, power plant technology, mining, underground cable protection pipes for power lines for renewable energy and underground pipes in hot climatic zones. For such demands PE-pipes must provide evidence of a high thermo-oxidative resistance. A PE-pipe was subjected to a very extensive test program to compare the oven aging method with the high-pressure autoclave test (HPAT) method regarding lifetime estimation. Oven tests had been carried out at four temperatures between 85°C and 100°C in a laboratory oven with air inlet for more than five years. Oxidation induction time (OIT) had decreased steadily. OIT described the thermo-oxidative stabilization of the polymer at measurement temperature in molten state. The significantly decrease showed that the stabilizer was consumed. Nevertheless, after even more than five years the mechanical properties changed only slightly.

In HPAT specimens were immersed in an aqueous medium in pressure vessel with O 2 gas phase. During the test elevated oxygen pressures and elevated temperatures were applied and the medium was steadily stirred. HPAT was performed at test temperatures between 60°C and 90°C and oxygen pressures between 165 kPa and 5,100 kPa. Additionally leaching in an alkaline solution was also considered in the HPAT. The estimation of lifetime at a service temperature of 40°C and atmospheric pressure were lying in the range of at least 280 years with activation energy found of around 94 kJ/mol. These HPAT results were achieved within a year. For modern PE-materials, the oven aging method was already reaching its limits for practicability, as the performance of the PE-material was so high that no results were achieved in acceptable times whereas the HPAT method could answer the lifetime question of the PE-pipe even for the highest performance.

Article source: https://www.pe100plus.com/PPCA/CONFIRMATION-OF-LONG-SERVICE-LIVES-OF-PE-PIPES-UNDER-HIGHER-TEMPERATURES-APPLYING-CONVENTIONAL-OVEN-TESTS-AND-MODERN-HIGH-PRESSURE-AUTOCLAVE-TESTS-p1781.html
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