N.V. Nederlandse Gasunie has converted an existing natural gas pipeline to an gaseous transportation line. The pipeline currently is transporting 70% hydrogen and 30% syngas. this paper will describe all steps taken to convert the existing line and include all elements from material assessment, valve operation, maintenance issues, emergency response control and external safety risk assessment.  The paper will review the various hydrogen embrittlement/corrosion mechanisms and will review their applicability in this situation. Based on the review the applicable mechanism, increased fatigue growth rate, will be discussed. Based on the outcome of this review the integrity of the actual pipeline was evaluated. A parallel step was the review of existing guidelines and standards such as EIGA 121/14 hydrogen pipeline systems and ASME B31.12.  Since a number of deviations of these standards were found from the requirements of these documents a review was performed of papers on the transportation and use of gaseous hydrogen. This to be able to support the allowance of the deviations found based on research.  For the conversion a new part of the pipeline had to be constructed and it was decided to exchange the existing valve stations, this based on uncertainty for their operation and leak tightness under hydrogen service. But to evaluate the necessity for exchange in the future, one of the existing valve station was used for experimental purposes. It has been leak tested and operated under 100% hydrogen conditions. The results of the tests will be discussed in the paper. External safety rules in the Netherlands are more stringent for gaseous hydrogen transportation as for natural gas, these rules where evaluated and any changes in the external safety was addressed. Operation safety was evaluated and subsequent changes in operational procedures where implemented for the involved personal. Safety and emergency procedures where evaluated for the change from natural gas to hydrogen, this resulted in a number of procedures and instructions to be amended to include the new hydrogen pipeline. Currently the line is almost a year in service and the exchange of the valve station seems to be an overly conservative measure. The outlook is in the future a large part of the existing natural gas transmission network will be converted to the transport of hydrogen gas. This to create a hydrogen backbone for industry, transportation and an alternative for other current natural gas use.


H2 in an Exisiting Natural Gas Pipeline

Division / Sponsors: 
Pipeline Systems Division

Paper Proceedings: https://asmedigitalcollection.asme.org/IPC/IPC2020/volume/84447

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