Principles of Lifetime Analysis for Plastic Pipes

摘要

Almost six decades ago, plastic pipes were for the first time introduced on a large industrial scale. Since that time they have gained strong significance and are used today especially in the areas of drinking water and gas supply, sewage engineering, sanitary and heating installations as well as industrial pipe systems. Causative for this development are not least their low manufacturing costs, the low placement and installation effort required and the long lifetime verified on the basis of international standards. Depending on the area of application and the connected operating conditions, pipes are exposed to a multitude of different loads. These are reflected in a complex stress collective with predominantly static and/or quasi-static, but also cyclic portions in addition. Internal pressure and internal pressure surges as well as outer loads cause mechanical stress, which find expression in a tri-axial state of stress in the pipe wall. Both the ambient temperature and the temperature of the flow medium lead to thermal stress. Chemical stress is caused for example by the flow medium. The aforementioned stresses influence the usability of the pipe over the intended lifetime to different degrees, whereas the stress resulting from internal pressure and temperature are of prominent importance.