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Sipila J.,Helsingin Energia | Auerkari P.,VTT Technical Research Center of Finland | Malmen Y.,VTT Technical Research Center of Finland | Heikkila A.-M.,VTT Technical Research Center of Finland | And 2 more authors.
Journal of Risk Research | Year: 2013

Observed autoignition events and extinguishing the resulting smouldering fires in an underground storage system of a coal-fired power plant have provided insight into the array of contributing variables, and some experience on quantifying the risk with alternative scenarios of event initiation, progress and potential mitigation. Although the first attempts to quantify the risk suggest high sensitivity to the sequence of action taken after fire alarm, and no similar storage sites really exist, some recommended preventive, corrective and other mitigating activities can be at least partly defined and improved by using the cumulative experience and parallel efforts in other closed or underground storage sites. However, there are also so-called black (or at least grey) swans: unexpected events for which the facility may be poorly prepared for. In the case of the underground storage silos, such an event was experienced when incoming cold coal during a harsh winter season froze the sewer system that normally protects the stored coal from seepage water. With blocked normal bypass, the seepage water found its way to the coal silos and created large clumps of icy coal that blocked the coal conveyors. Although freezing weather is not unusual at high-latitude power plants, the common methods to combat freezing of coal are mainly useful for open storage sites and above-ground transport. Options for mitigation are discussed, as well as the event chain leading to an event that had never previously occurred. The case is discussed from the point of view of options to prepare for rare or unforeseen events. © 2013 Taylor and Francis Group, LLC.

Oesterle W.,BAM | Dmitriev A.I.,Tomsk State University
SAE International Journal of Passenger Cars - Mechanical Systems | Year: 2014

Third bodies, also termed friction layers, tribofilms or secondary contact patches, are layers of more or less compacted wear debris between pads and rotor of a disc brake. Our approach of assessing the sliding behavior and friction properties induced by third bodies has been: i) structural characterization after AK-master test procedure, ii) sliding simulation of model structures similar to the observed ones but with simpler and well defined compositions, and iii) verification of simulation results by pin-on-disc tests with artificial third bodies showing the same microstructures and compositions as the model structures. The idea was to simulate structure formation during real braking conditions by high energy ball milling of appropriate powder blends. The final outcome of numerous parameter studies was that a third body containing 15 vol% soft ingredients and 0-20 vol % hard ingredients, both distributed homogeneously in a nanocrystalline iron oxide matrix, should be most desirable for braking. This general description of the optimum third body structure and several parameter studies performed by modelling enabled us to interpret a number of features of the AK-master test procedure, such as i) friction evolution during bedding, ii) the role of solid lubricants in respect to the initiation of smooth sliding behavior, and iii) friction evolution during a single braking event (in-stop behavior). © 2014 SAE International.

Niederleithinger E.,BAM | Tronicke J.,University of Potsdam
Near Surface 2010 - 16th European Meeting of Environmental and Engineering Geophysics | Year: 2010

The parallel-seismic method for foundation length estimation has proven to be one of the most reliable and versatile methods for foundation (mostly piles) length estimation. The interpretation is mainly based on simple graphical interpretation of the seismograms or first arrival travel-time curves. Recently introduced methods lead to better estimation but still contain several approximations. Intensive paramter studies have been carried out using the CEFIT simulation technique. The influence of certain geometry parameters as well as material changes in pile and soil have been studied. Based on theses studies improved algorithms have been developed to predict first arrival times. They are used as forward operator in inversion schemes based on the Levenberg-Marquardt method and Simulated Annealing. The advantages and limitations of both methods have been tested by simulated and field data. The developed methodology and software programs are currently used in field studies leading to improved foundation length estimations.

Schroeder V.,BAM Federal Institute of Materials Research and Testing | Schalau B.,BAM Federal Institute of Materials Research and Testing | Molnarne M.,BAM | Molnarne M.,Texas A&M University
Procedia Engineering | Year: 2014

Renewable energies became more and more important in the last years. The production of biogas using agricultural waste and the use of wind and solar energy in combination with water electrolysis is one way to substitute natural gas. Therefore the number of biogas plants is growing very fast in Germany. In the meantime, the operation of such plants is responsible for a significant number of accidents. New safety regulations on biogas plants and a short statistical summary of accidents in Germany are presented in the first part of this presentation. The main focus of the paper is the principle hazards arising from the substances and materials in biogas and hybrid power plants. Primarily, these are the hazards of fire and explosion induced by flammable methane gas. However, further hazards are the dangers of asphyxiation and poisoning by gases such as carbon dioxide, hydrogen sulphide and ammonia. Furthermore, hydrogen is produced by water electrolysis in hybrid power plants and mixed with bio methane in some cases. In order to prevent explosions when handling biogas and hydrogen it is necessary to know the explosion limits of gas and gas mixtures in mixture with air. However, biogas from agricultural plants can vary significantly in its composition. Therefore, for each gas composition the explosion limits would have to be determined. This would require a considerable amount of time and effort. Due to this fact, the explosion limits of biogas are frequently referred to only by the methane fraction of the gas mixture in the safety-relevant literature. In reality as biogas can consist of methane, carbon dioxide and further residual gases the explosion limits are generally over or underestimated. A calculation method for explosion limits was developed by means of explosion diagrams to avoid such errors. In a last topic methods are shown for the calculation of gas spreading in case of leakages in gas buffers for risk evaluation and land use planning. For this purpose the German directive VDI 3783 was evaluated. © 2014 The Authors. Published by Elsevier Ltd.

Molnarne M.,BAM | Molnarne M.,Texas A&M University | Seifert A.,BAM Federal Institute of Materials Research and Testing | Schroeder V.,BAM Federal Institute of Materials Research and Testing
Procedia Engineering | Year: 2014

For international trade and production of machinery used in potentially explosive atmospheres it is important to know about the regulations within the European Union. This paper presents an application of CHEMSAFE flammability data for fulfilling the requirements of the EU explosion protection directives. Most of the published data for flammability of substances are measured under atmospheric conditions although chemical processes operate often under non-atmospheric conditions. A couple of R&D projects were initiated in Germany to get more knowledge on explosion characteristics for non-atmospheric conditions. The explosion protection for machinery operated under non-atmospheric conditions is defined in the 2006/42/EU Directive. CHEMSAFE fulfills this requirement while it contains data of flammable compounds measured under non-atmospheric conditions and with other oxidizers than air. Furthermore it includes flammability data for gas mixtures consisting of flammable, inert, and different oxidizing components and most of the data are measured according to international standards. Safety data on flammable dusts - such as minimum ignition energy, maximum explosion pressure, ignition temperatures - represents also an important part of the database. The potentially explosive atmospheres are defined in revised Directive 2014/34/EU. For preparing risk assessment documents the following data for flammable gases and vapors, relating to the use of equipment, among others are necessary: Flammability limit, flash point, temperature class - auto-ignition temperature, maximum experimental safe gap. CHEMSAFE'2013 includes not only these data but also more than 200 triangular explosion diagrams, e.g. the newly measured methane/nitrogen/oxygen system under pressures up to 50 bars. The international standard Draft of IEC 80079-1-1 publishes data tables for flammable substances originated from CHEMSAFE which represents the international acceptance of these data. © 2014 The Authors. Published by Elsevier Ltd.

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