Third-Party Validation of a Protocol to Qualify the Performance of Materials for Subsea Pipelines Transporting Hydrogen

Abstract The primary objective of this paper is to describe the process adopted by a third-party to validate the methodology proposed by an Offshore Contractor for assessing the performance of materials of offshore pipelines intended for gaseous hydrogen transportation, with a specific focus on hydrogen embrittlement. Indeed, while offshore natural gas pipelines are a well-established technology, the unique challenges posed by hydrogen service need to be addressed through a formal Technology Qualification (TQ) process. The validation process involves two subsequent phases: (1) Approval In Principle (AIP) and (2) Technology Qualification (TQ). The main objective of AIP phase is to assess the methodology before its application to a real project. The proposed approach consists of two tasks: Performing a dedicated material testing campaign according to a protocol specifically designed for offshore hydrogen pipelines. Executing an Engineering Critical Assessment (ECA) considering the outcomes from the testing campaign and typical applied loads for an offshore pipeline. Afterwards, the application of the methodology to a real project / case study is reviewed to verify its adequacy and soundness. The work describes the results of the two key phases of the technology qualification process. The initial AIP phase assessed the adequacy of the proposed testing protocol and the ECA methodology before their application to a real project. In the subsequent TQ phase, the case study presented by Offshore Contractor has been thoroughly reviewed to verify its compliance with the methodology stated in AIP stage and the soundness of any technical assumption and calculation detail not previously explicitly stated. The selected case study has been developed to demonstrate the proper and conservative design for an offshore pipeline destined to hydrogen service. The ECA study is based on fracture mechanics principles and take advantage of the laboratory testing campaign conducted as per the Contractor protocol, which provides quantitative information about the material properties in the hydrogen environment. The third-party review concludes that the proposed methodology is suitable for assessing materials of offshore pipelines for hydrogen transportation and verified Contractor's compliance and proficiency in applying the methodology issuing a final Technology Qualification Statement. The Approval in Principle and Technology Qualification paves the way for large-scale deployment of Saipem's protocol for qualifying the performance of materials used in the construction of subsea pipelines transporting hydrogen, a key solution for the energy transition.