The gas industry has an excellent safety record in operating high-pressure transmission pipelines. Nevertheless, it is important that pipeline operators have an understanding of the consequences of possible accidental gas releases, in order to help manage the risks involved. This paper presents a programme of full scale experiments, undertaken by an international collaboration of gas companies, to study the consequences of both unignited and ignited releases of natural gas from simulated punctures and rips in a 900mm diameter above-ground transmission pipeline. Experimental parameters varied during the programme included release orifice size and shape, release pressure, release height, release direction, wind speed and wind direction. Instrumentation was deployed to obtain detailed data on the dispersion of gas, the ignitability of the gas cloud produced, the levels of incident thermal radiation and the resulting fire size and shape, following ignition. The results provide important data for the validation of mathematical models, used in developing risk assessment methodologies for gas pipelines, and in establishing those standards and design codes that are risk based.

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