Fatigue analysis of metallic-plastic-valve pipeline systems: a numerical case study

Metallic and plastic pipe sections are often mixed in use in water distribution systems. The interface between metallic and plastic pipe sections is typically associated with a significant change in hydraulic impedance. Multiple impedance changes in a pipeline system may induce repeated pressure reflections during hydraulic transient events, which may accelerate the fatigue process. This research simulates the hydraulic transient pressure response of a metallic-plastic series pipeline system using the method of characteristics. The impact on the fatigue lifetime of the plastic section is then investigated by adopting a fatigue analysis model based on the stress-life method. The results show that the plastic section in a metallic-plastic-valve pipeline configuration can have a significantly reduced fatigue lifetime relative to the corresponding plastic-valve configuration (a plastic pipe with a valve at one end).