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Organisationseinheit der BAM
Eingeladener Vortrag
- nein (34)
Mechanical stress often accelerates the failure of polymer materials. The aim of this research is to study the interaction between the sealing material FKM and biofuels B10 (heating oil with 10% biodiesel). The mechanical stress test was carried out in a special apparatus. Both mechanical and non-mechanical stress tests were conducted on specimens at 20, 40, and 70 °C for 28 days to document changes in mass, volume, and tensile properties. Both increasing temperature and mechanical stress have a significant effect on the tensile strength of the FKM polymer when exposed to B10. The combination of increasing temperature and mechanical stress induced rupture within 2 h. It was also established that FKM polymer with pre-exposure in B10 survived longer during mechanical stress compared to specimens exposed only to air. With the support of infrared (IR) spectroscopy, we were able to confirm the penetration of B10 into the FKM polymer.
In der Vergangenheit führte die Bundesanstalt für Materialforschung und -prüfung (BAM) zahlreiche Tankbrandversuche mit und ohne Sicherheitseinrichtungen durch. Dabei stellte sich heraus, dass Gastanks mit nicht ausreichend dimensionierten Sicherheitseinrichtungen bei einer äußeren thermischen Belastung innerhalb von 6 bis 10 min in Form eines BLEVE (Boiling Liquid Expanding Vapour Explosion) versagen können. Um die Feuerwiderstandsdauer eines Tanks zu erhöhen, besteht die Möglichkeit, den Tank u. a. mit einer sog. reaktiven Brandschutzbeschichtung zu versehen. Bei einer Temperatureinwirkung ab ca. 200 °C (produktabhängig) beginnt die Schicht aufgrund einer thermochemischen Reaktion aufzuschäumen. Die Tankwand wird dabei temporär vor einer weiteren schnellen Erwärmung geschützt.
Die BAM – Bundesanstalt für Materialforschung und -prüfung führt schon seit vielen Jahren auf zwei Brand- prüfständen Brandprüfungen z.B. an Transport- und Lagerbehältern für radioaktive Stoffe oder zur Prüfung von Brandschutzbeschichtungen durch. Als Brandmedium wird auf diesen Prüfständen Flüssiggas (Propan- Butan-Gemisch C) eingesetzt, mit dem die Prüfobjekte simulierten Unfallfeuern ausgesetzt werden. Mit dem neuen Jetfire – Prüfstand der BAM können seit Anfang 2018 diverse Belastungsszenarien nach den Anforde- rungen der ISO22899-1:2007 [1] simuliert werden.
Seit zehn Jahren führt die Bundesanstalt für Materialforschung und -prüfung (kurz: BAM) auf zwei Prüfständen Brandprüfungen z. B. an Transport-und Lagerbehältern für radioaktive Stoffe oder zur Prüfung von Brandschutzbeschichtungen durch. Als Brandmedium wird Flüssiggas (Propan-Butan-Gemisch C) eingesetzt, mit dem die Prüfobjekte simulierten Unfallfeuern ausgesetzt werden. Seit Anfang 2018 verfügt die BAM darüber hinaus auch über einen Jetfire-Prüfstand, der die Anforderungen der ISO 22899-1:2007 1) erfüllt.
Neben herkömmlichen Stahlflaschen, die seit Jahrzehnten in fast unveränderter Bauform für Flüssiggase (Propan-Butan-Gemische) eingesetzt werden, etablieren sich immer mehr Flaschen aus Faserverbundwerkstoffen (GFK) mit einer geringeren Masse. Die Bundesanstalt für Materialforschung und -prüfung (BAM) wurde beauftragt, das Verhalten dieser Gasflaschen unter den extremen Bedingungen eines Unfallfeuers zu untersuchen. In einem Brandprüfstand der BAM auf dem Testgelände Technische Sicherheit (TTS) in Horstwalde wurden deshalb beide Typen von Propangasflaschen einem simulierten Unfallfeuer ausgesetzt.
The US Department of Transportation, Federal Railroad Administration (FRA) current regulations for rail tank cars in the United States stipulate that, for certain hazardous materials, tank cars shall have a thermal protection system capable of preventing rupture of the tank for 100 minutes when exposed to an engulfing fire with a blackbody equivalent flame temperature of 871 °C (+/- 56°C), and that tanks shall have a pressure relief device set at an appropriate level (depending on the type of tank car and contents). Pressure relief devices are a source of non-accident releases, and hence may cause serious incidents when tanks are transporting hazardous materials. Industry in North America would therefore benefit from removal of pressure relief devices on tanks transporting certain hazardous materials. Such an approach is known as full Containment, and is standard practice in Europe. In 2014 the FRA commissioned an experimental study to investigate the ability of a specific design of rail tank to resist rupture without incorporating a pressure release valve. As a precursor to tests on tanks there was a need to develop and characterise a simulated pool fire capable of reliably exposing large-scale tanks to repeatable, uniform conditions. This paper describes such a fire test setup, developed using a burner array system fuelled by liquid propane and designed to produce luminous, low velocity flames representative of those found in large hydrocarbon pool fires. The experimental set-up is described, along with the Instrumentation (directional flame thermometers, infra-red camera, and thermally massive calorimeter) and methodology used to characterise the fire. Comparisons are made against previous fire tests on vessels to assess the suitability of the experimental set-up for future vessel testing.
Pressurisation of full-containment pressure vessels in fire is known to be driven by thermal stratification. The predominant mode of heat transfer to the contents (convection from the shell to the liquid phase) results in formation of „hot“ boundary layers. Sub-cooled boiling may also be present. The warm layer rises to the surface through buoyancy and bubble flow, increasing the surface of the liquid above that of the bulk temperature, and hence driving a pressure rise.
For reliable prediction of the complex effects governing vessel pressurization a three-dimensional numerical model is required. Work is being undertaken on such a model by other institutions in cooperation with this project.
A novel deign of test equipment has been commissioned to investigate thermal stratification and boiling during fire exposure of pressure vessels. Extensive temperature measurements and video of the internal conditions during fire exposure are possible, and the equipment has been designed for future compatibility with laser-based velocity measurement techniques. It is expected to generate data large quantities of data that will be of use in validation of two- and three-dimensional CFD models for the prediction of pressure vessel behaviour in fire. Future work will seek to characterize the boundary layer conditions in detail for a range of test fluids, fill levels and fire-induced thermal boundary conditions.
Initial tests undertaken during commissioning may indicate that fire exposure of the vessel wall just above the liquid level can have a notable influence on the pressurization rate, by increasing the degree of superheat. Further experimental and modelling work is required to confirm and quantify this effect, or to rebut this conclusion.
Exposure of pressure vessels to fire can result in catastrophic explosion and escalation of accidents. The safe transportation of cargo in pressure vessels therefore requires knowledge of what will happen to the cargo in the event of a vehicle derailment or rollover resulting in fire exposure. The chapter presents an overview of selected testing and modelling work undertaken to understand the thermohydraulic processes within a vessel that drive pressurization during fire. A series of experiments highlighting the importance of adequate design and selection of protection systems are summarized. It is concluded that pressure relief alone is typically insufficient to prevent vessel rupture, but the combination of relief and thermal coatings can be effective.
An overview of test standards and regulations relevant to the fire testing of pressure vessels
(2021)
Fire exposure of storage and transportation vessels of hazardous materials (including pressure liquefied gases) can result in BLEVEs and other high-consequence incidents with large societal and economic impacts. To reduce risk most countries have numerous regulations, codes of practice and guidance notes covering the design, operation and maintenance of vessels and thermal protection systems. Yet despite such regulations there remains no internationally accepted fire test procedure for pressure vessel and accompanying thermal protection systems that is capable of meeting a range of regulatory requirements. This paper considers some of the regulations in place in the western world and considers the origin of these based on large and medium-scale testing conducted to date. It examines conditions found in these tests to propose a set of recommendations on which to base a standard method of test. These recommendations are proposed as being representative of a credible large pool fire scenario that may occur.
The interest in hydrogen-based green energy is increasing worldwide, and the same is true for hydrogen-powered vehicles. Among the possible solutions to store hydrogen in such vehicles, cryogenic tanks equipped with multi-layer insulation (MLI) are the most promising to increase the amount of energy stored per unit volume. However, MLI is affected by severe deterioration when exposed to an external source of heat such as a fire following a car accident, leaving the tank unprotected and leading to failure in a relatively short time. In this work, a one-dimensional model to evaluate MLI thermal degradation when a liquid hydrogen tank is exposed to fire is presented. The relevance of taking MLI degradation into account when simulating the pressure increase due to external fire exposure is here demonstrated through the analysis of several case studies. The results show that MLI systems performance depletes within a few minutes of exposure to hydrocarbon poolfire.
The importance of tanks for storing cryogenic fluids in the energy industry is increasing because of ongoing political conflicts and the implementation of more environmentally friendly energy sources. Key representatives for the application of cryogenic tanks are natural gas in the form of Liquefied Natural Gas (LNG) and hydrogen, e. g. in the form of Liquefied Hydrogen (LH2), for which significantly higher transport capacities can be achieved with the same transport volume using cryogenic storages than with storages based solely on overpressure.
What applies to all cryogenic transported fluids in common is their condition that must be maintained. Hence heat flows into the preserved fluid must be minimized. Thermal super Insulations (TSI) based on e. g. multilayer insulations (MLI), perlites, and vacuum are utilized for this purpose and have already proven themselves in similar applications. However, for the use of tanks for cryogenic fluids in the transport sector, there is insufficient knowledge regarding the course and consequences of incidents, which is due to the still short period of use and the few documented incidents, hence few investigations carried out in this field. Typical scenarios in the transport sector represent car accidents with collisions, fires, and their combination, which are associated with extraordinary loads on the tank.
The focus of this study is to investigate the behavior of TSI as a result of their thermal exposure to a heat source representing a fire. It is worth mentioning that this could lead to an increase of the heat flux into a tank by several orders of magnitude, and to permanent damage of the TSI, ultimately rapid release of flammable gas as well as a Boiling Liquide Expanding Vapour Explosion (BLEVE). For this purpose, a high temperature thermal vacuum chamber (HTTVC) has been developed that allows thermal loading of MLI or perlites in a vacuum and simultaneous measurement of heat flow through this TSI. The HTTVC is designed to represent realistic insulation conditions and to withstand thermal loads from typical design fires.
The HTTVC was applied to investigate TSI based on MLI and vacuum. It is shown that the thermal stress caused permanent damage to the TSI, with shrinkage, phase change, pyrolysis, and condensation being significant damage mechanisms. The results are relevant for the evaluation of accident scenarios and can thus contribute to the improvement of TSI and the development of emergency measures for the protection of persons and infrastructures.
The importance of tanks for storing cryogenic fluids in the energy industry is increasing because of ongoing political conflicts and the implementation of more environmentally friendly energy sources. Key representatives for the application of cryogenic tanks are natural gas in the form of Liquefied Natural Gas (LNG) and hydrogen, e. g. in the form of Liquefied Hydrogen (LH2), for which significantly higher transport capacities can be achieved with the same transport volume using cryogenic storages than with storages based solely on overpressure.
What applies to all cryogenic transported fluids in common is their condition that must be maintained. Hence heat flows into the preserved fluid must be minimized. Thermal super Insulations (TSI) based on e. g. multilayer insulations (MLI), perlites, and vacuum are utilized for this purpose and have already proven themselves in similar applications. However, for the use of tanks for cryogenic fluids in the transport sector, there is insufficient knowledge regarding the course and consequences of incidents, which is due to the still short period of use and the few documented incidents, hence few investigations carried out in this field. Typical scenarios in the transport sector represent car accidents with collisions, fires, and their combination, which are associated with extraordinary loads on the tank.
The focus of this study is to investigate the behavior of TSI as a result of their thermal exposure to a heat source representing a fire. It is worth mentioning that this could lead to an increase of the heat flux into a tank by several orders of magnitude, and to permanent damage of the TSI, ultimately rapid release of flammable gas as well as a Boiling Liquide Expanding Vapour Explosion (BLEVE). For this purpose, a high temperature thermal vacuum chamber (HTTVC) has been developed that allows thermal loading of MLI or perlites in a vacuum and simultaneous measurement of heat flow through this TSI. The HTTVC is designed to represent realistic insulation conditions and to withstand thermal loads from typical design fires.
The HTTVC was applied to investigate TSI based on MLI and vacuum. It is shown that the thermal stress caused permanent damage to the TSI, with shrinkage, phase change, pyrolysis, and condensation being significant damage mechanisms. The results are relevant for the evaluation of accident scenarios and can thus contribute to the improvement of TSI and the development of emergency measures for the protection of persons and infrastructures.
Liquefied Hydrogen (LH2) or Liquefied Natural Gas (LNG) establish themselves as important energy carriers in the transport sector. Its storage requires tanks with Thermal Super Insulations (TSI) to keep the transported fluid cold. TSI has proven itself in various applications over a long time, but not in the land transport sector, where accidents involving collisions, fires, and their combination are to be expected. The focus of this study is to investigate the behavior of different types of TSI when exposed to a heat source that represents a fire. Therefore, a High-Temperature Thermal Vacuum Chamber (HTTVC) was used that allows the thermal loading of thermal insulation material in a vacuum and measuring the heat flow through the TSI in parallel. Within this study, 5 samples were tested regarding 3 different types of MLI, rock wool, and perlites. The thermal exposure caused different effects on the samples. In practice, this can be connected to the rapid release of flammable gases as well as a Boiling Liquid Expanding Vapour Explosion (BLEVE). These results are relevant for the evaluation of accident scenarios, the improvement of TSI, and the development of emergency measures.
Degradation of material properties significant for lifetime extension of nuclear power plants
(2010)
The discussion about the right energy sources or alternative energy generation goes around the world, mostly in connection with green-house gas reduction. Therefore, some countries have started to consider extending operation of nuclear power plants. This demands an extensive plant life management as well as the knowledge of the degradation in material properties. The Basis Safety Concept (BSC) in Germany observed this circumstance. Still, lifetime extension is not an issue in Germany due to phase out of nuclear energy. Part of the BSC is the application of non-destructive examination (NDE) methods from the beginning, i.e. from component manufacture, to the end of life. The application of a NDE method to detect and size defects in components in nuclear power plants is presented. Some material properties and their degradation during increase of operation time are also in the focus of this paper.
Nondestructive Testing (NDT) and fracture mechanics are two different disciplines in applied engineering science. Both areas are very important for the evaluation of the component integrity. Unfortunately the technical understanding in both disciplines is not identically, what lead to misunderstandings. In the present paper, the basic ideas about fracture mechanics and the input parameters coming from the NDT side are explained, concerning the integrity evaluation of the components. The widely used NDT methods are magnetic particle, dye penetrant, electrical eddy currents, radiography and ultrasonics. But not all of these common NDT methods can deliver parameters satisfy the fracture mechanics requirements. The first two can detect only surface-breaking or immediately sub-surface defects. Eddy current can also find defects in deeper sub-surface layers, while radiography and ultrasonics can also find embedded, remote defects. These three methods have furthermore a high potential for defect sizing and are therefore predestined to provide fracture mechanics input parameters. At the example of steam generator tube inspection the interplay of eddy current and fracture mechanics as related to tube integrity will be explained.
Steam generator (SG) tubes are part of the primary circuit of pressurised water reactors and therefore also part of the pressure retaining boundary components. Furthermore, steam generator tubes are the components which guarantee the separation between the primary and secondary circuits. Therefore the knowledge of the loss of tube integrity as soon as possible is an essential. Optimised nondestructive testing methods based on the eddy current array technique are used to find material degradation, especially intergranular stress corrosion cracks during the periodical in-service inspection. These methods are supported by the measurement of the leakage rate during operation based on radioactivity and Tritium measurement regarding a high crack grows. Shutdown criteria depending on leakage rates which are described in the operation procedures but there are no specifications about the conditions for the measured leakage. Is the leakage coming from a single crack or are there multiple cracks or is this the leakage of a critical crack. With the help of FE calculations answer about the uncertainties of leakage rate versus critical crack grows were found. Shutdown criteria must guarantee to avoid critical crack sizes, i.e. between the measured tritium activity and the critical crack size must be a safety gap.
Parameter study for CFD in the bottle – grid resolution plays an important role on the temperature at the specific positions, 2D axi-symetrical calculation is a sufficient solution strategy in regards to the examined particular Problem. The intensity of filling process can be controlled by pressure “User defined function” provided by experiments. Numerical simulation demonstrated feasibility to predict temperature progress during the filling process successfully validated by experiments. The turbulent model k-w SST is the best strategy for the turbulent property calculations. The most intensive turbulent kinetic energy appeared in the middle region of the pressure bottle, the impact of the eddy viscosity on the wall was mostly in the wall region.
A filling process of the pressure bottle used for the air storage was investigated by numerical simulations. During the filling process, the temperature was rising up to maximal value and after that started to decline. The good match was found between experimental and numerical results. In order to reproduce the experimental conditions, the process of the filling bottle was controlled by the pressure which varied in time. This filling strategy influenced furthermore the mass flow rate and the air flow velocity. Because of the geometrical symmetry, the simulation was calculated as an axisymmetric problem.
Ermittlung explosionsfähiger Gemische beim Gefahrguttransport unter normalen Beförderungsbedingungen
(2009)
Given the frequent incidences of Non-Accident Releases (NARs) of hazardous materials from tank cars, there in an increasing interest in transporting hazardous materials in total containment conditions (i.e., no pressure relief devices). However, the ability of tank cars to meet thermal protection requirements provided in the Code of Federal Regulations under conditions of total containment has not been established. Also, the modeling tool commonly used by industry to evaluate thermal protection, AFFTAC, has not been validated under these conditions. The intent of this effort was to evaluate through a series of third-scale fire tests, the ability of tank cars to meet the thermal protection requirements under total containment conditions, and also, to validate AFFTAC for such conditions.
This paper describes the test design and planning effort associated with this research, including the design and evaluation of a fire test setup to simulate a credible, fully engulfing, pool fire that is consistent and repeatable, and the design and hydro-static testing of a third-scale tank specimen. The fire design includes controls on the spatial distribution and temperature variation of the flame temperature, the heat flux, and the radiative balance, to best reflect large liquid hydrocarbon pool fire conditions that may be experienced during derailment scenarios.
The dynamic response of a vehicle during braking is influenced by the tangential forces developed at the wheel-rail’s contact surface. The friction coefficient affects the load transfer from the wheel’s tread to the vehicle. In this work, the vibrations of a scale-down railway vehicle are monitored during braking and their relationship with the friction coefficient between wheel and rail is found out. The vehicle is instrumented with encoders, accelerometers, and is controlled via Bluetooth.
The tests are carried out with clean and friction-modified rails. The tangential forces transmitted from the wheel to the railcar’s body are visualized in time and frequency using a proposed correlation algorithm based on the outputs of the ContinuousWavelet Transform (CWT). The results demonstrate
that tangential forces have a significant impact on railway vehicles under conditions of high friction coefficients and large creep values.
Hunting is a potentially dangerous phenomenon related to the lateral oscillation of the wheels that impacts the rails and causes the wear of the infrastructure’s components. Therefore, the analysis and timely detection of hunting can lead to the application of corrective maintenance tasks, reducing damages, and costs and even derailments as a result. In this work, the vibration response of a finite element model of a rail with hunting-induced loads by a single wheel is analyzed in three directions: longitudinal, lateral, and vertical. The contact patch forces are calculated by means of Simpack® using the Kalker linear theory and the contact Hertz theory. The system is solved by using the Newmark-_ approach. The results of the deflection and vibration analysis, following the proposed methodology, show how the different characteristics of the loads impact the rail.
Die Vorhersage der Beanspruchung bei plastischem Versagen von zylindrischen Druckbehältern wird häufig mittels Finite Elemente Berechnungen durchgeführt. Die Berechnung der zulässigen Beanspruchung erfordert ein elastisch-plastisches Werkstoffmodell und die Berücksichtigung von nichtlinearen geometrischen Effekten. Das plastische Versagen verursacht eine gesamte Strukturinstabilität und kann nicht direkt aus der Finite Elemente Analyse bestimmt werden. In dem vorliegenden Beitrag wird die Beanspruchung für plastisches Versagen eines zylindrischen Druckbehälters mittels eines analytischen Verfahrens basierend auf einem linear elastischen ideal-plastischen Materialmodell bestimmt. Wenn Plastizität auftritt, wird zum einen der Werkstoff als inkompressibel und zum anderen der Tensor der plastischen Dehnungen als parallel zum Spannungsabweichungstensor angenommen. In diesem Fall kann die Spannungs-Dehnungs-Beziehung von Henkel angewendet werden, um den Druck zu berechnen, bei dem plastisches Fließen und Versagen eintritt. Die analytischen Ergebnisse werden von den Finite Elemente Berechnungen vollkommen bestätigt.
The prediction of the plastic collapse load of cylindrical pressure vessels is very often made by using expensive Finite Element Computations. The calculation of the collapse load requires an elastic-plastic material model and the consideration of non-linear geometry effects. The plastic collapse load causes overalls structural instability and cannot be determined directly from a finite element analysis. The ASME (2007) code recommends that the collapse load should be the load for which the numerical solution does not converge. This load can be only determined approximately if a expensive nonlinear analysis consisting of a very large number of sub steps is done. The last load sub step leading to a convergent solution will be taken as the critical load for the structure. In the instability regime no standard finite element solution can be found because of the lack of convergence of the numerical procedure. Other methods for the calculation of the allowable pressure proposed by the ASME code are the elastic stress analysis and the limit load analysis. In the present paper the plastic collapse load for a cylindrical pressure vessel is determined by an analytical method based on a linear elastic perfectly plastic material model. When plasticity occurs the material is considered as incompressible and the tensor of plastic strains is parallel to the stress deviator tensor. In that case the finite stress-strain relationships of Henkel can be used for calculating the pressure for which plastic flow occurs at the inside of the vessel wall or in the case of full plasticity in the wall. The analytical results are fully confirmed by finite element predictions both for axisymmetric and high costs three dimensional models. The analytical model can be used for fast predictions of the allowable load for the design of a large variety of pressure vessels under safety considerations. The accuracy of the predicted collapse load largely depends on the quality of the temperature dependent wall material data used both in the analytical and numerical calculations.
This paper presents a method for processing acceleration data registered on a train and determining the health condition of a subway’s substructure. The acceleration data was converted into a dynamic deformation by applying a transfer function defined using the Empirical Mode Decomposition Method.
The transfer function was constructed using data produced on an experimental rig, and it was scaled to an existing subway system. The equivalent deformation improved the analysis of the dynamic loads that affect the substructure of the subway tracks because it is considered the primary load that acts on the track and substructure. The acceleration data and the estimated deformations were analyzed with the Continues Wavelet Transform. The equivalent deformation data facilitated the application of a health monitoring system and simplified the development of predictive maintenance programs for the subway or railroad operators. This method better identified cracks in the substructure than using the acceleration data.
Scaled-down experimental facility: Can reproduce actual failures; can produce simulated data for identifying cracks in the substructure or other defects. The acceleration data can be converted into an equivalent deformation. The experimental facility can analyse dynamic loads. Equivalent force data: Facilitates the application to a health monitoring system; simplifies the development of predictive maintenance. These data is helpful in validating analytical or simulation models.
Liquid cargo has a significant impact on the interface wheel-track interaction. The sloshing affects the track-railcar's dynamic behavior. The effect is detectable at the track level and at the vehicle. Its characterization requires the combination of different techniques:
Empirical Mode Decomposition (EMD)
Time-Frequency Maps
Sloshing occurred when significant perturbations happened in the railcar:
The railcar entered a curve
Reduction in its travel speed
A railcar with a tank is a clear example of a multibody dynamic system with a nonlinear behavior.
This paper presents the study of the impact caused by a liquid Cargo on a railway infrastructure. The dynamic behavior of a tank car corresponds to a multibody dynamic system with several degrees of freedom. This study’s data were obtained from a scale experimental fixture consisting of a track and a railcar with a tank. The track was instrumented with strain gauges and the railcar with accelerometers. The data showed non-periodic and periodic terms; therefore, the results were analyzed with the Empirical Mode Decomposition method (EMD).
It was found that the EMD identified the signal components that were related to the sloshing. These components represent the mode shapes of the original signal.
The location of the sloshing in the track was found applying spectrograms to the accelerometer data. This paper’s experimental outputs suggest that the sloshing effect is detectable at the track and in the vehicle dynamics.
Vergleich von Risiken
(2013)
Vielen Entscheidungsprozessen geht ein Vergleich voraus. Bei einem Produktvergleich werden dazu Kriterien festgelegt, etwa der Kaufpreis, die Güte, Haltbarkeit, Handhabung usw. Der Testsieger ist meist derjenige, der die am höchsten bewerteten Kriterien erfüllt. Voraussetzung für derartige Vergleiche ist also die Gleichartigkeit der Vergleichsobjekte. Risiken untereinander zu vergleichen ist komplizierter. Die Notwendigkeit von Risikovergleichen ergibt sich, wenn nur unklare Vorstellungen, z. B. über die Risiken einer neuen Transporttechnologie, existieren und keine Erfahrungswerte zur Verfügung stehen. Aus bekannten und akzeptierten Risiken soll mittels eines Vergleichs die Tolerierbarkeit eines (noch) unbekannten Risikos abgeleitet werden. Der Beitrag setzt sich mit der Problematik von Risikovergleichen auseinander.
This paper describes the testing methods used to determine the thermal properties of insulation materials and mechanical properties of materials used for the load-bearing structure for pressure tanks (up to 4 bar, relative) and cryogenic liquids (LNG, −166 °C to -157 °C at atmospheric pressure). Goal is to design a transportation tank that does not exceed 4 bars (relative) within 10 h, starting at atmospheric pressure. PUR-foam is a suitable material for the insulation. A 12,5 l small scale tank prototype reached 4 bar (relative) within 87 minutes, which is, regarding the influence of the size, a satisfying result. The mechanical properties change significantly at cryogenic temperatures. The bending modulus is similar at first, but decreases at a certain point by appr. 50 %. However, the maximum stress is much higher and could not be reached within this testing setup.
The use of glass-fiber reinforced plastic (GRP) can reduce the weight of tanks significantly. By replacing steel with GRP in tanks for gases (propane, etc.) a weight reduction of up to 50 % was reached. In this project not only the material should be optimized, but also the design. Previous tanks consist of a double-walled structure with an insulation layer between the two shells (e.g. vacuum). Goal of this project is to realize a single-walled construction of GRP with an insulation layer on the outside.
To determine the temperature dependent material values, two different experiments are performed: In the first experiment, temperature dependent material properties of liquid nitrogen found in literature research are validated in a simple setup. The level of liquid nitrogen in a small jar is measured over the experiment time. Numerical simulation shows the change of nitrogen level with sufficient precision. In the second experiment, a liquid nitrogen is applied on one side of a GRP plate. Temperature is measured with thermocouples on top and bottom of the GRP plate, as well as in the middle of the plate. By use of numerical simulation, temperature dependent thermal conductivity is determined.
In the third experiment, a test stand is designed to examine different insulation materials. In this test stand, the insulation material can easily be changed. A numerical simulation, in which the determined material data is used, is performed as well for this test stand.
The experiments show, that GRP can be used in cryogenic environments. Multiphase simulations are a suitable tool to describe the energy absorption of thermal energy due to thermal phase change. Results on different insulation materials will follow.
To reduce the emission of carbondyoxide (CO2) of combustion engines, liquefied natural gas (LNG) is used as an alternative fuel. LNG is transported via truck, ship or railway for long distances. Double walled stainless steel tanks are used for transportation, which are heavy and expensive. The vacuum insulation between the two walled structure ensures that the LNG stays liquid over the transportation time (boiling point of LNG: -162 ◦C). This causes a high temperature difference between the transported good and the ambient air.
A simplified tank construction is used to reduce the weight and price of the tank. Instead of stainless steel, glass fiber reinforced plastic (GFRP) is used. The design is changed to a single walled construction with a solid insulation material outside on the GFRP structure.
Goal of this work is the characterization of a suitable insulation material and configuration as well as the analysis of the mechanical properties of GFRP under cryogenic conditions. Several experiments are carried out. Numerical models of these experiments can then be used for parameter studies.
Forschen für die Sicherheit
(2013)
In-service inspection Atucha
(2011)
Gashochdruckleitungen
(2012)