H2 in an Existing Natural Gas Pipeline

N.V. Nederlandse Gasunie (Gasunie) has converted an existing gas transmission line from transporting natural gas to transporting a mixture of gaseous hydrogen and 30% to 0% methane. To enable this, an assessment was carried out on technical safety, process safety, work safety and external safety. The pipeline, with two valve stations, was constructed in 1996 according to applicable Dutch regulations and actively managed in accordance with Gasunie company standards. The pipeline was evaluated for hydrogen transportation and, based on the following measures, this was seen as being feasible: - The water dew point of the feed must not exceed −8° C; - The pipeline must be separated from the natural gas transport system; - Blowdown must be performed either at the site of the supplier or the user of the hydrogen; - Gas measurement equipment, personal safety and leak detection must be suitable for hydrogen; - Due to the assignment of hydrogen as a chemical agent, the safety contour was reduced by performing extra measures, such as additional communication to landowners, additional requirements for the pressure-regulating system and verification of additional settlement and stresses. The operational changes consist of a number of maintenance and management issues: • In-service welding and hot tapping are not allowed; • Equipment suitable for use in gas group IIC (ATEX) must be used; • Emergency and maintenance procedures must be updated to those applicable for pipeline and valve stations containing hydrogen.