Transient thermal hazards from gas pipeline ruptures: From large scale testing to lab-scale investigative techniques

Although natural gas transmission pipelines are one of the safest forms of transporting gas, the average number of gas pipeline rupture incidents per year is 2 in Europe and 13 in the US (2015 to 2019). Such incidents can cause property and environmental damage as well as injuries/fatalities.
This thesis examines the hazards associated with natural gas pipeline ruptures, focusing on fireballs ensuing from immediate gas releases. The study leverages both large scale rupture tests (1.2 m diameter pipeline and 90-ton release) and laboratory scale experiments to advance the understanding of thermal radiation effects and material responses in such scenarios. The large scale tests, in line with other data confirmed that the fraction of heat radiated for natural gas is 0.3, much lower than 0.6 derived from the recently proposed correlation by Wang and co-workers.
Innovatively, a laboratory setup was designed based on the bench scale cone calorimeter, achieving a high coefficient of determination (0.97) when comparing thermal doses from both scales. This setup enabled the examination of materials (plastics and man-made and natural cellulosic substances) response under varying heat fluxes, to better predict ignition risks for common materials like paper, card and plastics.
The research extends the concept of thermal dose that is used for human exposure to different levels of material response (first onset of smoke, piloted ignition, spontaneous ignition). Empirical correlations were established for the materials tested, achieving a coefficient of determination of 0.88. Statistical analysis was conducted providing confidence in the derived correlations.
The versatile laboratory setup was used to evaluate material behaviour in a high-risk scenarios where the exposure to a heat a flux is variable and transient. Consequently this approach could be utilised to other scenarios, such as deflagrations and military applications.
The results have relevance for the risk management of gas pipelines, potentially influencing the analysis currently undertaken.