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In this paper a technique for integrating copper coated silica optical fibers into AS-4/PEEK composite for Structural Health Monitoring (SHM) is presented. The integration steps are described in detail. X-ray and microscopic images indicate a successfully integrated optical fiber which does not seem to affect the fiber/matrix distribution around it. Optical backscatter reflectometry shows losses of approximately 2dBm-1 along the integrated parts of the optical fiber due to temperature induced shrinkage of the composite.
The present contribution reports on specific aspects of safety engineering in heterogeneously catalysed oxidation reactions. Results for ethene-oxygen-mixtures in a continuous-flow micro reactor are reported related to the safety issues of the ethylene oxide process. Initial pressure is ranging from below 1 bar up to 10 bar at initial temperatures ranging from room temperature up to 673 K. Micro structured reactors offer an extended range of operating conditions. The key issue to be discussed in the present contribution is how to safely operate a micro reactor at conditions in conventional devices to be characterised as inside the explosion region. Within certain limits suppression of explosion inside a micro reactor can be achieved.
This holds true for chain reactions as well as runaway reactions. Nevertheless it is not possible to safely operate micro structured reactors at any condition. Therefore, explosion propagation through a Micro structured reactor and initiation of gas phase explosions by hot spots inside the reactor were investigated.
The investigation methods applied are subject to actual standardization.
Many industrial processes include a gas explosion hazard. If safety measures are not adequate to prevent a potentially explosive atmosphere or to avoid effective ignition sources in enclosures, at least the effects of an explosion can be limited e.g. by gas explosion venting systems.
For the design of gas explosion venting systems for confinements only little guidance is given when considering the constructional boundary conditions or process conditions. For this reason conservative assumptions are prevalent in practice and in many cases the protective systems become significantly oversized. From safety perspective such safety margins in venting areas can lead to a critical acceleration of the pressure rise. Moreover, a gas explosion venting at turbulent conditions caused by over sizing or by obstacles rather leads to an under-sized system. The present investigation was focused especially on the influence of certain obstacles as well as the influence of elevated initial pressures on explosion venting
behaviour of quiescent hydrogen, methane or ethylene in air.
Since its invention in the early 1990’s, self-consolidating concrete has never become well established in the ready-mix sectors worldwide. The reason for this can be mainly found in the fact that the sophisticated compositions are sensitive against changing environments. This lack of robustness can be attributed to the interaction between cement hydration reaction and high range water reducing agent (HRWRA). Understanding the relevant mechanisms that control the initial flow performance as well as the flow retention helps optimizing SCC mixtures that perform either steadily in one specific environment or that perform largely similarly at steadily changing environments.
This paper depicts how HRWRAs interact with clinker and hydration phases and discusses the important role of the charge density of a polycarboxylic HRWRA in the way the rheology is affected. Based on rheometric results and observations of the Vicat setting times, it is shown that increasing charge densities of the HRWRA and decreasing water to powder ratios (w/p) reduce the flow retention and have lesser retarding effect on the setting. Based on the discussion, optimization procedures for the mixture composition and the HRWRA modification are suggested to achieve optimized performance for varying environmental situations or highest robustness for specific conditions.
Fibre optic sensors for monitoring in safety-relevant structures have to be validated in order to proof their reliability under typical structural load conditions. The reliable use of optical fibre sensors depends strongly on an appropriate and qualitative application. Diagnostics of the physical condition of embedded and surface-applied fibre optic strain sensors are demonstrated on field examples. Distributed strain measurement based on Rayleigh backscattering is used to determine breakage of the fibre, interface adhesion problems and to identify application related strain transfer mechanisms.
More than 400 Mt of dangerous materials are transported in Germany every year, of which 150 Mt are by road. Tank containers, tank vehicles and rail tank cars are used for the carriage of dangerous goods in large quantities. Data on the operating life of tanks are only available, in practice, to a minor degree. They are only partly published, mainly after accidents.
The BAM-List - Requirements for Tanks for the Carriage of Dangerous Goods, which has compatibility evaluations of metallic and polymeric materials, has been the basis for substance-related prototype approvals for tank containers and portable tanks designed for the carriage of dangerous goods by the BAM since publication of the first edition in 1989. These data are also used for the approval of rail tank cars and road tank cars and are used as a source of knowledge not only in Germany but also worldwide.
Tank leakages caused by tanks or rail tank cars being made of tank and sealing materials which are not resistant to the fill goods are avoided by using the material resistance data of the BAM.
Corrosion damage is among the main causes of damage. Uniform and non-uniform area corrosion without mechanical stress in aqueous substances is one of the most frequent types of corrosion during the transport of chemicals in tanks. Much damage by pitting corrosion occurs during the transport of substances containing chlorides or substances which separate chloride ions in the presence of moisture.
Operational stresses are caused by the effects of both the road and the dangerous goods being transported. Mechanical damage often results from long-term overstressing and occurs after longer operating times.
Operational failures cause damage which may appear during the service of tank containers, road tank cars or rail tank cars. The damage results from the inattention of employees when opening and closing the valves. Traffic accidents also cause damage to tanks and frames.
Many cases of damage are due to weld area cracks resulting from four basic errors in construction, material, manufacturing and operation. Manufacturing errors can be undetected and the starting point of cracks which only grow under service conditions.
Manufacturing errors result from variations in measurement and design, fittings, state of surface (hardness, abrasiveness) and mechanical surface damage (scratches, cracks). Incorrectly welded joints and errors during mechanical deformation are typical mistakes when installing the component parts. Variations in the wall thickness or combinations of different materials lead to manufacturing errors too. A lot of tanks are not used for the transport of dangerous goods before the end of their service life as they do not fulfil the revised technical safety requirements in the Dangerous Goods Regulations.
Predictions in the BAM-List based on literature data and corrosion test results are reflected in the service (operating) life. Rail tank cars made of carbon steel, for example, which are mainly used for the transport of petroleum products, can achieve a service life of 40 – 50 y.
Rail tank cars produced of austenitic CrNi- or CrNiMo-steel can reach an operating life of at least 30 y, whereby the corrosiveness of the transport substances plays an important role.
Recent progress in the development of ultrasonic fibre-optic sensors for detecting acoustic emission from partial discharge in elastomeric insulations is presented. These sensors are an important part of a proposed comprehensive scheme for the fibre-optic monitoring of cable accessories. After specifying the underlying design goals the improved fibre-optic sensor design is outlined. It is experimentally shown that it offers about ten-fold improvement over a previously investigated resonant cantilever-type design in terms of detection limit, making it competitive with conventional piezoelectric transducers, however with the added compatibility with strong electrical fields and electromagnetically noisy environments.
Modified setup of 20-L-sphere for the determination of safety characteristics of nano powders
(2013)
This paper describes a modified experimental setup for the test apparatus 20-L-Sphere (also known as 20-L Siwek Chamber), that enables the test samples to be kept under inert atmospheric conditions nearly until ignition. This setup was designed to allow the determination of safety characteristics of nanopowders under most critical circumstances (e.g. minimisation of the influence of oxidation before the test itself). The aim of this modification was to determine, whether or not the current setup and procedures underestimate the explosion violence and ignitability of nanopowders. The work includes experimental results of micrometer dusts to validate the modified setup. Moreover first results of nanometer iron and Aluminium dusts are presented, which were kept at inert conditions until shortly before the ignition. The tested nano iron was found to react pyrophoric, as soon as it gets in contact with air, while the tested nano Aluminium did not generally show such behaviour.
According to international standards several safety characteristics of dusts are determined in the 20-Lsphere (also known as SIWEK Chamber). Dust cloud ignition is carried out using pyrotechnical igniters.
Due to various disadvantages of such igniters the need for alternative ignition sources arises again and again. An alternative ignition source could be the so called 'exploding wire' or 'fuse wire'. The paper presents test results of a comparative study between both ignition sources for the determination of the safety characteristics Maximum Explosion Pressure and Maximum Explosion Pressure Rise of five selected dusts in the 20-L-sphere. In addition to that the ignition mechanisms of both ignition sources were analysed by high speed camera recordings and the ignition energy was determined with electric and calorimetric recordings.
According to international Standards several safety characteristics of dusts are determined in the 20-L-sphere (also known as SIWEK-Chamber). Dust cloud ignition is carried out using pyrotechnical igniters. Due to various disadvantages of pyrotechnical igniters the need for alternative ignition sources arises again and again. An alternative ignition source could be the socalled “exploding wire” or “fuse wire". The paper presents test results of a comparative study between both ignition sources for the determination of the safety characteristics Maximum Explosion Pressure and Maximum Rate of Explosion Pressure Rise of selected dusts in the 20-Lsphere.
In addition to that the flame/arc propagation of both ignition sources was analysed by high speed and IR camera recordings. Tests in a windowed autoclave were performed to get information on the influence of turbulence generated due to dispersion of the dust on the shape of the generated flame and its propagation. Turbulence measurements in the windowed autoclave as well as in the 20-L-sphere with a LDA System allowed investigation if the igniter led to turbulence increase at the moment of ignition in comparison to tests without ignition.