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Results
H2Pipe JIP – Development of Guidelines for Design of Offshore Hydrogen Pipelines
Østby, Erling (DNV) | Thodla, Ramgopal (DNV Columbus) | Helgaker, Jan Fredrik (DNV) | Collberg, Leif (DNV) | Horn, Agnes Marie (DNV)
ABSTRACT The potential role of hydrogen as an important energy carrier in the new energy mix is receiving a lot of attention. The option of transporting hydrogen in pipelines is highly relevant in this respect. At the same time, it is known that hydrogen may have a detrimental effect on steel properties, which could pose restrictions in design of such pipelines. Currently, some experience exists when it comes to transporting hydrogen in onshore pipelines, and some codes (e.g. ASME B31.12) have been developed to provide guidelines on design. There is an interest to also develop projects including offshore pipelines for H2 transport. Offshore pipelines pose some new design challenges, e.g. higher axial loads (both cyclic and static) and typically higher pressures. As a response to these challenges DNV has launched the H2Pipe Joint Industry Project with an objective to develop a guideline for design and potential re-purposing of offshore pipelines for H2 transport. This paper gives a status summary of the guideline work in the JIP and presents results from mechanical testing performed in Phase 1 of the JIP. INTRODUCTION Hydrogen is assumed to be an important part of tomorrow's energy mix. C-Mn pipelines are considered a highly relevant means of transporting H2 gas in this respect. The recently increased interest is likely due to that it in addition to transporting energy may also be used for storing energy. Both design of new and re-purposing of existing pipelines are relevant scenarios. At the same time, it is well known that hydrogen may have a detrimental effect on the properties of steels, resulting in what is often termed "hydrogen embrittlement" (HE). HE might lead to significantly reduced ductility in steels. In addition to reduction in ductility, it is also likely that hydrogen leads to increased susceptibility under fatigue loading as well as a decrease in fracture resistance. It is necessary to have a sufficiently detailed knowledge on the magnitude of these effects in order to allow for safe yet cost-effective pipeline solution for transport of H2. Despite having been known for about 150 years, there are still significant uncertainties regarding the actual mechanisms controlling HE. There is already some experience with H2 transport in onshore pipelines. Further, guidance regarding design of such can be found in ASME B31.12 and IGEM/TD/1. However, offshore transport of H2 is also a relevant scenario, and no experience exists in this respect. Offshore pipelines offer some additional challenges like more cyclic loading, larger operational loads, and special accidental loading scenarios. In order to address these challenges DNV has launched the H2Pipe JIP with the ambition to provide guidelines for design and re-purposing of C-Mn pipelines for offshore H2 transport. The focus of the paper will be towards structural integrity issues of H2 pipelines while flow and transport capacity issues will not be addressed. First limit states and special challenges for offshore pipelines are discussed. Then a brief outline of HE is presented together with a short summary of existing codes for design of H2 pipelines. This is followed by a presentation of key experimental findings from Phase 1 of the JIP and an outline of the current status of the Guideline document. The paper is concluded with a general discussion and key conclusions. Phase 1 of the JIP was concluded early in 2023 and a Phase 2 of the JIP was kicked off in early 2023 with the objective to close some of the main gaps identified in this paper.
Robust Material Qualification For Arctic Applications
Horn, Agnes Marie (Det Norske Veritas, and SINTEF, and Statoil) | Østby, Erling (Det Norske Veritas, and SINTEF, and Statoil) | Hauge, Mons (Det Norske Veritas, and SINTEF, and Statoil) | Aubert, Jean-Michel (Det Norske Veritas, and SINTEF, and Statoil)
ABSTRACT Oil and gas exploration and production is moving into arctic areas. The reduction in ice-covered areas has rendered northern routes more advantages and in addition it is anticipated that as much as 25% of the undiscovered oil and gas resources can be found in the Arctic. There is a lack of rules and standards that provide guidelines for material selection and qualification of materials for offshore and onshore structures in Arctic areas. Some actions have been taken to develop new standards e.g. ISO19906 Arctic Structure, however the guideline does not specify material requirements except for the statement that material shall have adequate toughness in order to behave ductile at low temperature. Material related standards like EN10225, API 2W and Norsok are not developed for low temperature applications and are generally applied for service temperatures down to -10°C (Norsok covers down to -14°C). For lower temperature, it is up to the designer to show fit for purpose of the selected material. Hence, one major challenge for designers is to specify adequate toughness requirements at an early stage of the design process for low temperature applications. This paper will discuss factors that influence the required CTOD toughness value at an early stage of a design process by discussing the following topics: required qualification and testing, utilization/robustness of a structure, weld defect size, residual stress, constraint effect and tensile properties. INTRODUCTION There is a lack of rules and standards that provide guidelines for material selection and qualification of materials for offshore and onshore structures in Arctic areas. Most of the offshore construction steels are purchased according to EN 10225 "Weldable structural steels for fixed offshore structures technical delivery conditions" which only provide requirements for Charpy values. No guidelines on CTOD toughness values are provided. For designers it can be challenging to decide the adequate CTOD requirements at an early stage when material is ordered, since limited design analyses have been carried out.