Design and Finite Element Analysis (FEA) of Bulkheads for a Pipe-in-Pipe Flowline: Application of ASME Boiler and Pressure Vessel Code

Evaluating a pipe-in-pipe (PIP) system with bulkheads is not explicitly covered by the Canadian Standards Association (CSA) Z662 for oil & gas pipeline systems and refers to the rules in the ASME Boiler and Pressure Vessel Code (BPVC Section VIII, Division 2) as alternative reference code. However, the BPVC does not specifically address the pipeline design. Due to the nonlinear nature of the PIP and bulkhead geometry and loading condition, careful modeling and an appropriate interpretation and application of design criteria by BPVC code are required. The current paper addresses the challenges and recommendations for geometric design of the bulkheads, the appropriate modeling of the problem using FEA method, as well as analysis and accurate interpretation of the results based on the BPVC rules. The bulkhead design was checked per ASME B&PV VIII.2, design-by-analysis, and showed that the assembly has met the criteria for protection against 1) plastic collapse, 2) local failure and 3) failure from ratcheting.