Determination of deflagration venting requirements in chemical/process plants is usually carried out using well established standards employing an empirically based formula. However, this formula is shown to have severe shortcomings, especially in the range of low KG-values, where either negative or inconceivably large venting areas can be predicted. Due to these shortcomings a method has been developed using the efflux function for gases as a basis to predict the mass flow through a vent opening in a vessel during an internal explosion. The simulated rise in pressure due to the internal explosion is quantitatively determined from the KG-value, with the mass flow through the vent opening in the vessel resulting from the pressure difference between the vessel and its surroundings. This enables the maximum overpressure as a function of the pressure relief surface area to be predicted. The method takes into account the temperature of the efflux gases and turbulence enhancement brought about by the venting process. In the following paper explosion pressure relief experiments are described and the results from these experiments are compared to predictions from the efflux method. It is shown that by adjusting the assumed turbulence which evolves during the venting process, the reduced explosion pressure can be reasonably well reproduced.
The explosion of hydrogen gas storage cylinders on May 25, 1894, represents one of the most spectacular failure cases during the late industrialization period in Germany. With respect to modern applications to hydrogen storage as energy carrier, it has several times been referred to as precedent failure case for the whole industrial sector. The detailed investigation reports by Martens have thus gained interest in the last years, but also, because the publications in 1896 about his expertise already provided in September 1894 document one of the first and most comprehensive investigations which can be regarded as a nucleus for modern failure analysis.
After summarizing the newspaper reports in the introduction, the present contribution provides a review of Martens' reports targeted at the development of failure analyses and materials testing procedures as well as potential failure origins.
Preventing the explosion of acetylene cylinders involved in fire with help of numerical modeling
(2012)
The current paper describes a mathematical model, which was developed to simulate the heat transfer in acetylene cylinders during exposure to a fire. The cases of a direct engulfment of the cylinder in the flames and of exposure to a distant fire were considered. Furthermore, the model was also applied to the prediction of the heat transfer during the cooling with water of heated acetylene cylinders, in order to assess the effectiveness of this procedure as a measure to prevent the burst of the cylinder. To provide data for the definition and validation of the model a total of 13 bonfire tests with 8.9-, 10- and 50-dm³-cylinders were performed, where pressure and temperature measurements in the samples were performed. During 5 experiments the fire was extinguished before the expected cylinder burst and a cooling with water was applied. In the paper a short description of the experimental set-up and of the test results is given. Finally, a comparison with the model predictions is provided, showing reasonable agreement.
Self-ignition behavior of mixtures of methane and oxygen was investigated in a temperature range from 600 to 800°C. Variations of mixture composition, inert gas content, temperature and filling rate of the ignition autoclave were carried out in order to establish process boundaries for high temperature partial oxidation processes. The tests show that considerably high methane contents are needed to avoid an ignition. Heating-up tests show that ignition is possible at surprisingly low temperatures. This can be attributed to pre-ignition reactions that produce more instable intermediates.
Die BAM hält mit dem TTS umfangreiche Möglichkeiten für Großversuche im Bereich Brand- und Explosionsschutz. Neben dem Themenfeld-Projekt CoFi-ABV werden andere Projekte des Fachbereichs 2.4 kurz vorgestellt. Außerdem werden die Möglichkeiten der BAM dargestellt, Behörden und Organisationen mit Sicherheitsaufgaben mit wissenschaftlich-technischer Expertise zu unterstützen.
In der Prozesstechnik kommt es immer wieder zu Zündungen durch Druckstöße mit Gasen. Bekannt ist dieses Phänomen vom Umgang mit Sauerstoff im Kontakt mit nicht geeigneten Materialien. Aber auch andere Gase, z. B. Acetylen, können durch schnelle Kompression gezündet werden. In der vorliegenden Arbeit werden, in Fortführung früherer Untersuchungen in Rohren, solche Zündvorgänge mit Hilfe von Zündtemperaturen abgeschätzt.