Impact Assessment of Hydrogen Transmission on TD1 Parallel Pipeline Separation Distances

The recommended minimum separation distances in IGEM/TD/1 were based on a research programme that studied the different ways in which a failure of one buried natural gas transmission pipeline can affect another similar pipeline installed adjacent to the first, taking account of the initial pressure wave propagating through the ground, the size of the ground crater produced and the threat of escalation from fire if the second pipeline is exposed. The methodology developed from the research was first published in 2010 and is implemented in a software program (“PROPHET”). The distances in IGEM/TD/1 are generally cautious and are essentially determined by the size of the ground crater produced by pipeline ruptures, as predicted by the methodology.
To assess the impact of hydrogen transmission on the recommended separation distances, the possibility of one pipeline transporting natural gas and the other transporting hydrogen was considered, as well as both pipelines transporting hydrogen. The following steps were carried out to assess the impact of hydrogen transmission on parallel pipeline separation distances, drawing on existing knowledge only:

• Estimate the ground pressure loading predicted from a hydrogen pipeline rupture.
• Consider the ground pressure effect on a parallel natural gas or hydrogen pipeline.
• Evaluate available ground crater formation models and assess if existing natural gas model is cautious for hydrogen.
• Consider effects of thermal loading due to hydrogen fires where recommended natural gas separation distances are not met.

The following conclusions were made as to whether the current methodology for natural gas is cautious when applied to hydrogen:

• Ground pressure loading: The current natural gas methodology is cautious.
• Ground pressure effects: The current natural gas methodology is applicable (no change for hydrogen).
• Ground crater formation: The current natural gas methodology is cautious for ruptures and applicable for punctures (almost no change for hydrogen).
• Thermal loading: The current natural gas methodology is cautious for the thermal loading from ruptures but not necessarily cautious for punctures. Calculations of the minimum flow velocity required to prevent failure of a natural gas pipeline are not cautious for hydrogen.

In summary, the recommended minimum separation distances in IGEM/TD/1 for parallel natural gas pipelines should be cautious when applied to parallel hydrogen pipelines. However, in cases where the recommended minimum separation distances are not met, the calculations to predict the thermal loading and response of the exposed pipeline should take account of the properties of hydrogen, as the natural gas results will not necessarily be cautious.