Filtern
Dokumenttyp
- Vortrag (6)
- Zeitschriftenartikel (1)
- Monografie (1)
Sprache
- Englisch (8)
Schlagworte
- Acceptance rate (8) (entfernen)
Organisationseinheit der BAM
Eingeladener Vortrag
- nein (6)
First the acceptance rates resulting from the analysis of different minimum burst ratios and standards are displayed and explained. Especially the problems resulting from a further reduction if the minimum burst ratio are shown.
For a better understanding of these results the process of analysing the acceptance rate is explained in detail. This contains the alleged contradiction between safety of samples due to its scatter while the rejected sample provides a higher mean strength.
Then the importance of batch testing is explained and leads to the recommendation to have a strong interaction between provided mean strength and requested maximum of production scatter.
The simulation of strength experiments by the Monte-Carlo method enables the numerical generation of data representing a complete populations of composite pressure vessels. In the case of composite pressure vessels used for hydrogen storage, properties like burst strength or fatigue cycle strength are of interest. This paper provides comprehensive information on how populations are generated and how samples can be taken and evaluated; it also explains how to determine the acceptance rate of random samples from simulated populations for passing the approval test "minimum burst pressure". A word of caution is also expressed regarding the evaluation of acceptance rates from a small sample.
The presentation is divided in two parts, each evaluates a different aspect of safety.
It starts with the analysis of consequences resulting from worst case ruptures of gas cylinders. The number of harmed persons and fatalities dependent from the pressure-volume product and the kind of stored gas. In parallel, there is a national accepted rule for accepted failure rates depending from this pV-product created by BAM. When combining both aspects it become clear that the pressure-volume product can be used as a good indicator for consequences. At a level of about 120 MPa m3 the maximum consequence starts to become catastrophic character. This shows the reason why the representatives of DIN insisted in limiting relevant pV-limits for tubes and cylinders to 1 Mio. bar litres.
The second part gives a raff overview on the parameters influencing the acceptance rates of borderline basic populations. This is added by some slides giving an idea for the improvement of the minimum burst requirement and finally completed by a proposal for improved acceptance criteria for the burst test.
The basic idea is: an increased pV-product of tubes has the be reflected by an increased safety level.
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 presentation explains the term “safety” in a broader sense and 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 the ECE R 134 are and in which direction the GTR 13 could be optimized during the currently running phase 2. For this purpose, it is helpful to improve the currently operated tool for Monte Carlo simulation, for which BAM introduced the research idea “MoCaSiB”.
This presentation explains how the evaluation of technical requirements in regulations effects safety level. This shown by using the Monte-Carlo experiment consequently.
The first step is to explain how deterministic requirements and how probabilistic requirements work. Then the statistical behaviour of the generally unknown basic population can be described and that his behaviour is independent from the regulatory approach. Subsequently, the concept of evaluating sample test results with respect to deterministic requirements is explained. The item “acceptance rate” of the basic population that is behind each sample and behind each individuum in a sample is defined. On this collective understanding, the differences in evaluation between the probabilistic approach PA and the most important RC&S are discussed. Some areas are validated in contradictorily. Then the parameters for acceptance of burst strength in the UN-GTR#13 are varied and opens the door for an accurate improvement of acceptance criteria. Finally, the special aspects of degradation in load cycle testing are shown. There, two aspects must be differentiated, the current reliability and its degradation by ongoing load cycles. This is a convincing argument against the very common opinion, which means that the number of hydraulically tested load cycles pro-vides a figure for the number of acceptable filling cycles.
Featuring a detailed analysis of current approval requirements and the relevant safety assessment methods for gas cylinders in general and with main focus on composite cylinders for storing ompressed natural gas and hydrogen, this book demonstrates how current regulations and standards limit the ability to reduce cost and weight. Based on this data, it then highlights the potential offered by the proposed approval procedure based on probabilistic safety assessment.
After addressing the economic potential of probabilistic safety assessments, the book details working procedures and improving cycles and (slow) bursts as methods for assessing residual strength. It then discusses methods for statistically evaluating test data, as well as sample- size and distribution character considerations. A definition of sample strength is elaborated in terms of the performance sheets developed by the author. On this basis, it discusses safety as a property of service life and interpreted as an issue of degradation, and explores aspects of artificial aging for simulating the end-of-life reliability level. Lastly, the book considers control and inspection aspects: quality of production, degradation prediction using destructive sample tests parallel to operation, retesting periods and correcting for underand overestimates of safe lifetime.
Presented in schematic diagrams, illustrations and tables, this information enables manufacturers and operators to use this new approach in practice and supports the improvement of current regulations and standards.
The set of slides summarises the expectations of participants discussed during the opening session. Then the most important aspects of the presentations during the first two days are compiled. At the end the conclusions coming out of a joint discussion are presented. This show what participants expect BAM to do for implementation of the PA in near future.