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Organisationseinheit der BAM
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.
In Europe, tanks designed on different safety philosophies are used for transporting one and the same liquid dangerous goods (Krautwurst, 2011). Owing to this circumstance, the BAM was commissioned by the BMVBS to conduct a research project designed to analyse and assess the equipment of tanks. Furthermore in these project were researched some failure mechanism of pressure relief devices (PRD).
Based on the knowledge gained, possible solutions were worked out under safety-relevant aspects that would benefit tank transport by providing a lower hazard potential. Besides looking at the mode of operation and the construction of PRV, their blow-off characteristics and total flow rate are considered from a safety engineering point of view.
Based on in-depth studies, a concept for and the further approach to examinations of the failure limits of PRD, especially of spring loaded relief valves, was developed and comprehensively described in the report “The use of safety devices, particularly safety valves, on transport containers” (Pötzsch, Reich, & Jochems, 2011).
The purpose of this study was to investigate failure causes of safety valves by normal modes and accidental fire heat loads. A series of investigations for different influences using safety valves for tanks were obtained. Testing vibration modes and corrosion presents some design limits. Experimental study of a pressure vessel engulfing in fire identify significant design limits. The complete set of results provides direct information of fail-safe modes and discusses the usage.
The outputs from a simplified mathematical designed to simulate the liquid cargo-vehicle interaction during an emergency braking maneuver, have been compared with full scale data regarding the sloshing pressure on one of the vehicle chambers. While the specific dimensions and fill level of the fluid within the chamber in the full scale testing, have been considered for the simulation model, the vehicle has been simplified to a straight truck instead of an articulated truck. Nevertheless, the pressure within the chamber is realistically modelled, concerning the maximum and minimum pressures attained, with differences lower than 10% between the simulation and the experimental data. Consequently, these results suggest that the articulation pertaining to the articulated vehicle, does not affect in a significant manner the maximum and minimum values of the pressure within the chamber. A nonlinear model for the suspension, however, could improve the model performance. On the other hand, simulation results suggest that the effect of sloshing could cause a loss of braking efficiency on the order of 7%, when such performance is measured in terms of the stopping time.
Limit load analysis is a well known method to calculate the allowable design pressure of container components. A limit load of a pressurized container is achieved, when the stress of a wall and the flow stress are equal. In the following paper the transferability of limit load analysis from small scale tank containers up to large scale containers (railway tank) are investigated. Finite element calculations are carried out and compared with experimental results. It can be concluded that the limit load analysis works very well. Furthermore, the yield strength of the material should be used as flow stress.
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.
A testing rig for the measurement of the dynamic loads on the rails due to cargo sloshing,has been proposedin this paper. The system represents a scale-down approach that simulates astraightening maneuver of the railway car after negotiating a turn. As part of the experimental effort, a mathematical model was developed that, oncevalidated, will provide more insights about the potential effect of many other cardesign factors, on the level of stress developed in the raildue to the sloshing cargo.A fundamental output from the testing, will be the objective comparison between the railloads due toa sloshing and a non-sloshing cargo, together with a validated model that wouldallow parametric studies in relation withthe potential effect,of several track and carproperties,on the magnitude of the sloshing forces on the rail.
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.
Greenhouse gas emissions caused by human activities remain one of the most important subjects of international discussions. The routine gas flaring has been estimated to be responsible for as much as 1% of global carbon dioxide emission per year. Gas flaring analysis is one of the key-interest subjects in remote sensing community. Some of the existing publications use remote sensing techniques with satellite imagery to derive information about flame temperature and further about to estimate the volume of the flared gas. The often missing element is an in-situ measurement analysis of gas flames, combining signals recorded by a camera on-ground and data on flared gas volume, temperature and gas type. In order to address this problem, an experiment was conducted, in which the gas flame was recorded by thermal cameras on-ground, simultaneously to an aerial survey and the gas flow was measured at the same time on-ground. The measurement setup was designed in cooperation between Institute of Optical Sensor Systems of German Aerospace Center (DLR) and German Federal Institute for Materials Research and Testing (BAM). Cameras recording in thermal and mid-wave IR wavelengths were used to record the burning gas on-ground and from the aerial survey. All the measurements have been compared and statistically analysed with respect to the recorded temperature. The purpose of the examination was to describe the signal changes in thermal imagery with respect to changes in energy, emitted by the burning process. This approach will allow for later calculation of the amount of energy in form of thermal radiation sent from the flame to the satellite.
A simplified model, based upon physical principles, is proposed the simulate the effect of sloshing on the pressure developed in the tanker chambers. The model has been validated in good extent, with experimental data from full scale testing. The characteristic that mostly affects the pressure developed with the chambers of the tanker is the length of the chamber. While a reduction in this property could decrease the pressure developed within a given chamber, the analysis should take into account an overall approach, as a shortening of the individual chambers would influence the number of chambers necessary to carry a certain amount of product. Consequently, the resulting model could be used to study different effects of the sloshing cargo on the carrying vehicles, including the length and position of the chambers along the tanker body.
A dynamic simulation model for a tanker ship along the Rhine River has been proposed, based on a simplified computational scheme, involving a two-degree-of-freedom roll plane multibody system, subjected to lateral accelerations estimated on the basis of measured data. The resulting equations of motion are solved through the transition matrix approach. The results suggest that many contributing factors were involved in the capsizing of the ship, including the relatively high speed of the river water and the meandering path of the infrastructure, further affected by dynamic effects derived from the behavior of the payload and from the steering maneuvers performed.
Rear-end crashes involving heavy trucks as the leading vehicle, and cars as the impact vehicle, cause many deaths and permanent injuries to car´s occupants. Measures have been thus taken in the trucks to prevent underride crashes, including the mounting of stiffer underride guards, set at car´s bumper height. In this respect, an active acceleration system(AAS), installed in the truck, could also contribute to mitigate the effects of These crashes, through the decrease of the relative Speed of the vehicles at the instant of the crash. In this paper, an AAS system is proposed, under the principles of ultrasonic sensors and an actuator for the truck´s accelerator mechanism. Simulation results of the operation of this AAS system, suggest that such a system could decrease the relative impact speed around 8% for an initial relative speed of 10 m/s.
The application of lightweight materials for tanks for transportation appears promising. Besides saving weight and therefore transportation costs, new complex geometries that depart from common cylindrical shapes of steel tanks can be manufactured. For transportation of dangerous goods, fire and explosion safety must be maintained to prevent accidents with serious consequences. In this work the fire behavior of lightweight tanks made from glass fiber reinforced plastics (GFRP) with complex geometries is investigated. Pretests on intermediate scale GFRP plates are conducted to identify suitable fire protection systems and surface treatments for composite tanks. The fire resistance is shown to be improved by addition of fire protective coatings and integrated layers. Finally, a complex rectangular GFRP tank with a holding capacity of 1100 liters is fire protected with an intumescent fire coating. The tank is filled up to 80 % with water and burned under an engulfing fully developed fire. It was shown that the intumescent layer could expand before the decomposition of the resin occurred. Furthermore, the adhesion between tank surface and coating was maintained. The structure could withstand a fire for more than 20 min.
Commidities and rail damage
(2018)
A roll-plane simplified model, representing the suspended body-cargo of a railway car, was developed to simulate thedynamic response of a railway car while subjectedto lateral acceleration derived from its traveling along curved tracks. The model provides the means to calculate the suspension forces, which are supposed to be transmitted to the bogie´s wheelset. For the analysis of the potential effect of such forces on the railway fatigue life, different performance measures were considered, under different concepts. A family of curves were produced to analyze the effect of the height of the center of gravity of the body-cargo system, on the different performance measures. The resultingdiagramswereused to assess the rail damage potentials offour different railway cars. Results suggest that the height of the center of gravity, associated to the different types of railway cars, nonlinearly and strongly affects the fatigue lifeof the rail, with the double stack car being the moreinfrastructure-aggressive. In this respect, experimental evidence should be provided about such remarkable effects, so as to supportsome operational recommendationsthat shouldbe taken to mitigate these effects, including, for example, the regulation of the traveling speed of some vehicles.
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.
An experimental testing rig has been proposed to study the dynamic interaction between a liquid cargo and the carrying vehicle during turning maneuvers. The basic operational principle of the testing rig consists in simulating the lateral accelerations associated to turning maneuvers through the use of a tilt table.
While the experimental capabilities of the testing rig include the analysis of the effects of the cars on the whole transport infrastructure, including sleepers and ballast, a first use of the rig considered the effect of sloshing cargo on the level of dynamic forces transmitted to the rails. Such test was used to validate a simplified theoretical approach consisting of a two degree-of-freedom double pendulum mechanical system, where a simple pendulum, representing the sloshing cargo, is articulated to the spring-supported vehicle chassis, which is modelled as an inverted torsional pendulum. While the theoretical results exhibit a high correlation with the experimental data, the main discrepancy between both outputs, relates with the frequency of the residual vibration, once the lateral acceleration input is ceased. Such difference in frequency, would imply an underestimation of the number of loading cycles to which the infrastructure is subjected. On the other hand, the peak values are within acceptable difference levels.