Filtern
Dokumenttyp
- Vortrag (5)
- Beitrag zu einem Tagungsband (3)
Sprache
- Englisch (8) (entfernen)
Referierte Publikation
- nein (8)
Schlagworte
- Composite (8) (entfernen)
Organisationseinheit der BAM
Eingeladener Vortrag
- nein (5)
Conventional approval requirements exclusively ask for minimum strength values, which have to be met. The probabilistic approach estimates how likely none of the comparatively manufactured units fails during operation.
Both questions are juxtaposed and compared here with respect to the load cycle tests. The influence of the sample sizes is discussed additionally.
Hydrogen is an attractive energy carrier that requires high effort for safe storage. For ensuring safety they have to undergo a challenging approval process. Relevant standards and regulations for composite cylinders used for the transport of for on-board storage of hydrogen are currently based on deterministic (e.g. ISO 11119-3) or semi-probabilistic (UN GTR No. 13) criteria. This paper analysis the properties of such methods in regards to the evaluation of load cycle strength. Their characteristics are compared with the probabilistic approach of the BAM. Based on Monte-Carlo simulations, the available design range (mean value and scatter of strength criteria) of current concepts were exemplarily estimated. The aspect of small sample sizes is analysed and discussed with respect to the evaluation procedures.
Existing regulations and standards for the approval of composite cylinders in hydrogen service are currently based on deterministic criteria (ISO 11119-3, UN GTR No. 13). This paper provides a systematic analysis of the load cycle properties resulting from these regulations and standards. Their characteristics are compared with the probabilistic approach of the BAM. Based on Monte-Carlo simulations the available design range of all concepts is compared. In addition, the probability of acceptance for potentially unsafe design types is determined.
The publication is an extended abstract on the modelling of the manufacturing process related residual stresses in type 4 pressure vessels for hydrogen storage. A 2D analytical model based on the classical laminate theory and a 3D finite element model are introduced. The calculated residual stress state after the filament winding process as well as the stress state in service are presented and discussed.
Emergency response units increasingly use pressure cylinders made from fibre composites for breathing air as elements of personal protective equipment (PPE). Such applications expose the composite cylinders to harsh temperature and handling conditions. At least in Europe, standards have been used for certifying PPE, which are designed and mandatory for the approval of pressure receptacles for the transport of dangerous goods. Therefore, service conditions specific to PPEs are not accounted for in these standards. In this paper, BAM (Federal Institute for Materials Research and Testing) investigates the residual safety of a composite cylinder design at the end of their designated service life of 15 years. The cylinders (test pressure PH 450 bars; 6.8 Litres) are of one design type with aluminium liner and fully wrapped with carbon fibres, which is commonly considered a “Type III” cylinder. All cylinders were used as PPE by the Berlin fire department and randomly picked in three samples of 25 cylinders each before tested.
At BAM, the cylinder samples underwent hydraulic load cycle tests (LCT), conventional burst tests (BT) and so called slow burst tests (SBT). A concept for quantification of strength degradation already introduced by BAM was applied. This concept is based on a probabilistic assessment of the average strength and scatter of each sample of cylinders. The strength distributions of the used PPEcylinders is shown and analysed. Some unexpected effects are shown and a refinement of the statistical assessment is introduced.
The presentation explains the intended way of BAM in tackling the safety issues in the project TAHYA.
The way how the term “safety” is used in TAHYA leads to the need for a more risk-based understanding of safety. Based on this, the Monte Carlo simulation is used to show where the weak points of current regulations are. Thus, a concept for optimization of relevant regulations, codes and standards will be elaborated during the project. For this purpose, it is helpful to improve the currently operated tool for Monte Carlo simulation, which will need additional data for monitoring the outcome. Strength data, that will be determined by BAM and the other partners during the already agreed test program can be used for this purpose without additional effort.
The application range of CPV (composite pressure vessels)
is multifaceted. But also the failure forms and the spectrum of measurement methods is manifold. On various, at BAM observed effects, it is shown why the micromechanical analysis of the composites is of such great interest for the prediction of aging effects of CPVs.
This presentation provides general data about BAM, the structure of department 3 and a short impression of the application of pressure vessels for hydrogen in stationary use, supply chain and onboard storage.
It guides to the actions of BAM as competent authority on this area and shows a lot different methods for testing operated at BAM. Based on this additional research has been detected as necessary for a competent tackling of the tasks as competent authority. After having mentioned several important research projects a figure is presented that compares the development of regulations with relevant re-actions of BAM. The outcome was a concept of a risk based definition of accepted failure rates in combination with probability-oriented safety assessment over entire service life.
The second aspect raised at INERIS is the issue of advising the BMVI concerning pressure vessels for hydrogen. Since the pressure is high for saving material consumption and weight there is still high interest in changing regulatory requirements. Therefor we developed an approach for the display of minimum requirements of regulations in diagrams (sample performance charts; SPC) and the probabilistic analysis for these deterministic requirements. This is done by Monte-Carlo simulation and the analysis of acceptance rate and survival rate of basic populations all over the SPC.
This finally provide same knowledge of non-approvable but safe ranges of parameters and even approvable but non-safe constellations. In addition, this analysis allows to optimise deterministic requirements in regulations to the intended level of safety for approved populations of pressure vessels, which is shown on the example of the GTR#13.