The energy transition from hydrocarbon-based energy to renewable is progressing rapidly. The transition speed has experienced ups and downs but has recently seen a boost and there are clear indications that the speed will accelerate considerably over the next 5-10 years.
This transition and a possible future change in the European gas market has triggered several stakeholders to investigate the possibility for export of hydrogen gas as an addition or replacement for natural gas. In this context, both the design, fabrication and installation of new pipelines as well as utilisation of existing gas export infrastructure is on the agenda.
A large-scale deployment of pipelines for hydrogen transport, however, requires that the best possible balance between safety and cost-effectiveness can be established to allow for optimal design of new pipelines, or possibly assessment of the use of existing pipeline infrastructures.
There is today no offshore pipeline code covering hydrogen transport or mix of hydrogen. A new revision of ASME B31.12 [1] design code was issued in 2019. This new revision may reduce the conservatism for transporting hydrogen, however, it lacks offshore specific design issues.
A study has been performed on behalf of Equinor and Gassco to evaluate and identify gaps for offshore applications as reflected in DNVGL-ST-F101 [2] that either needs to be updated or re-formulated in case of hydrogen transport.
The focus of this paper will be on the structural side, but considerations on flow (pressure, speed, impurities), safety (leakage, dispersion, accidents), materials and operation (repair, inspections) are also covered. The main impact from hydrogen is assumed to be on fracture propagation and toughness. The main limit states were evaluated on this basis and modifications proposed.
The intention is to publish the results in a recommended practice as complement to the already existing DNVGL-ST-F101 [2] for offshore pipelines.
As recently as three years ago, clean hydrogen energy was on the fringes of the energy-transition conversation – an outlier solution, at least for the short or medium term. Today, it is rapidly moving into the mainstream and, for many, it is essential to a net-zero energy future.
