Development of ASME Section VIII Division 1 Code Case 3078 on Electrochemical Cell Stacks for Electrolysis

Abstract Electrochemical Cell Stacks (ECS) are a critical component in electrolysis and fuel cell systems. The design of ECS typically consists of multiple layered cell packs that are secured by end plates and tie rods to achieve a leak tight construction. To achieve better efficiency and reduce operating cost, the development of ECS has evolved to larger sizes and higher operating pressures. It is not uncommon for ECS to have hundreds of stacked unit cells with a design pressure exceeding 500 psi (3.5 MPa) and maximum cross section diagonal exceeding several feet. ISO 22734 and ANSI/CSA B22734 provide some performance-based design guidelines for mechanical integrity of ECS. However, the detailed pressure stress design and material requirements are lacking. Having recognized that the construction of ECS is very similar to plate heat exchangers, ASME BPVC Section VIII Division 1 has developed specific code rules for ECS based on Mandatory Appendix 45 for plate exchangers. The rules are first introduced in a newly approved Section VIII Division 1 Code Case 3078, considering the metallic components such as end plates, tie rod and nozzles as pressure boundary. Due to the special electrochemical functionality of the cell pack, the cell pack itself is exempted from code rules provided that it meets certain performance-based requirements. This paper documents the technical basis and the development of Code Case 3078. As future development, considerations are being given to incorporate the Code Case as Mandatory Appendix in Section VIII Division 1.