Lifetime expectations play a major role when selecting materials for pressure pipes. Information on the service life of a piping system made of polyethylene can be gained from creep rupture tests at various temperatures being evaluated by standardised extrapolation methods (ISO/TR 9080). With the help of test results on modern bimodal pipe resins the different failure mechanisms will be explained and differences to the second-generation PE material demonstrated. One can conclude that the durability of modern pipe systems is only limited by the thermo oxidative ageing of the material. Practical experience for 45 years show quite clearly that plastic pipe systems do not fade away after the end of the service life guaranteed in the relevant standards. There are three influencing factors governing the functional properties and service life of pipeline systems: Material, Mechanical load, Environment influences. The result of long-term failure tests carried out on pipes under internal hydrostatic pressure and the extrapolation of these results using the SEM laid down in ISO/TR 9080 show that the high-quality plastic pipe materials available today have a reliable service of more than 100 years. This means in practical terms that such pipes are capable of lasting much longer because: the safety factors used by designer when rating the pipeline mechanically permit a considerable longer life service; the rated load is much higher than the load which occurs during the actual operation of the pipeline; Pipelines are usually laid underground and are better protected against environmental influences than the test specimens.
Pipeline systems made of plastics: - unlimited working life?
2001
11 Seiten, 8 Bilder, 1 Tabelle, 9 Quellen
Conference paper
English
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