Natural gas networks have the potential to flow blended hydrogen and to be re-purposed to 100% hydrogen to provide low carbon energy to help meet future emissions targets. However, hydrogen does not contain the same energy by volume as natural gas, so the flowrate supplied to consumers would have to increase by over 3 times for a 100% hydrogen network to deliver energy at an equivalent rate. Without network reinforcement this requirement could dictate a significant increase in the pressure and/or velocity of the gas. Currently, UK gas industry standards specify a maximum velocity of 20 m/s, primarily to avoid the risk of debris being picked up by the flow and causing wear to components, whereas a velocity limit of 40 m/s is prescribed where the network is assumed to be clean.

Hydrogen has different properties to natural gas, so it is unknown whether debris may be picked up to the same degree, or if other factors such as noise or vibration may constrain the design velocity. The limits need to be defined as they will impact the investment required to transition the system to hydrogen service. To provide this understanding, a multi-partner project is in progress, supported by UK energy regulator funding.

Initial phases of the project concluded that there are several constraints which could potentially limit any increase in gas velocity, and that full-scale testing would be required to investigate the erosion, vibration and noise behaviour associated with transportation of hydrogen / hydrogen blends. Conceptual test facility designs were developed, progressing to a detailed test programme aiming to investigate particle transportation phenomena and erosion risks, together with validation of models for vibration and noise. Ultimately this knowledge will be used to validate the key limitations relating to gas velocity and input to the development of updated velocity limits.