Free Span Dynamics Versus Global Buckling of the High Pressure And High Temperature Pipeline

According to the design codes, the pipeline free spans dynamics/fatigue can be screened and analyzed as isolated single span with single mode or multi-mode response and interactive multi-spans with single mode or multi-mode response. The common practice is to analysis the thermal expansion/global buckling and free span independently while DNVRP-F105 recommended considering the interactive effects. The longitudinal loads under the thermal expansion are provided for the free span analysis but the spans are assumed not going to change from isolate to interactive. Since the pipeline responses due to the thermal expansion will be most likely a displacement control at the span locations, flowline global buckling in a downhill manner will not be as severe as the lateral or upheaval buckling but it may change the free span behavior, such as a single free span to a multi-span. The purpose of this work is to use “Simulator”, an in-house finite element analysis tool based on ABAQUS, to establish the relationship between the pipeline free span dynamics and the thermal expansion/global buckling under the high pressure and high temperature conditions. Both single pipeline and Pipe-in-Pipe flowline are considered. The analysis focused on the conditions that may enhance the pipeline “Feed-In” into the span and the variations of effective axial load at the free span locations. As a unique lateral buckling and free span interactive case, the dynamics of sleeper span was also investigated. This work intends to realistically analyze the free span behavior with the involvements of global buckling under the high pressure and high temperature condition and to degrade the uncertainty during the free span analysis.