The Unique Field Experiments on the Assessment of Accident Consequences at Industrial Enterprises of Gas-Chemical Complexes. Nikolai S. Belov, Senior Researcher of Gas Research Institute (VNIIGAS); I. Trebin, Deputy Director of Gas Research Institute; and O. Sorokovikova, Senior Researcher of Nuclear Safety Institute (IBRAE), VNIIGAS, Razvilka, Moscow Region, 142717, RUSSIA, fax (095) 399 16-77, e-mail edigarov@nv.vniigaz.gazprom.ru
Safety of gas transport systems is a very complicated scientific and technological problem. It must be investigated and comprehensively solved. Transportation of natural and liquefied gases by pipelines brings more dangerous and harmful factors for the biosphere. Emergency situations followed by pipelines break-down are ones of the most dangerous. Development of mathematical forecast models for assessment of accidents progression and consequences is one of the main elements of works on safety analysis and risk evaluation. The critical step in development of such models is their validation using the experimental material. It is very important to plan these experiments and to collect the data so that they could be used for comparison with theoretical models.
Such full-scale experiments have been conducted by the Russian Gas Research Institute (VNIIGAS) for grounding of sizes of hazard zones in case of the severe accidents with the gas pipelines. The source of emergency gas release was the working gas pipeline with 1000 mm diameter and 110 km length. This pipeline was used for transportation of natural gas with significant amount of hydrogen sulphide (H2S). During these experiments significant quantities of the gas including H2S were released into atmosphere and then concentrations of gas and H2S were measured in the accident region.
Methodology and conditions of experimental investigations are described in the report. The experiments were conducted during seven years in different seasons and different times of day. Special experimental series was conducted in extremely unfavourable meteorological conditions, when accident consequences became catastrophic. Maximum volume of released gas was 22 mln. m3/day. Measurement of H2S concentration field was performed at different distances from the source (from 1 to 30 km).
During the experiments dynamics and size of gas cloud and meteorological parameters were detected. Some experiments were conducted over the complex terrain. It allowed to find the influence of relief (especially the influence of the large ravines) on the propagation of the released gas. Some experiments were conducted in conditions of absence of the fluctuation of the wind direction and in calm conditions. These data allowed to make scientific and practical conclusions. Comparison of the experimental data with the results of the calculations by generally accepted methods showed their poor applicability for the stable atmosphere and calm. The mentioned above experimental data are used for validation of the new Lagrangian trace stochastic model of atmospheric dispersion that takes into account a wide range of meteorological factors. This model was developed as a part of computer system for decision making support in case of accident release of toxic gases into atmosphere at the enterprises of Russian gas industry.
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