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Safety aspects of the storage containments of hydrogen are independent from the kind of usage: The main criteria is the resistance against the pressure load. On the 2nd level there are aspects specific to the usage as e.g. crash loads etc.
Safety is achieved when the probability (frequency) of a failure during the service life is acceptable!
But an aspect common for all usages is the scatter of properties resulting from the material and the production. Therefore, it is worth to have a look on the current approach of minimum burst ratios from an unknown point of view: the basic populations of a product – based on exemplarily assessments.
According to this approach, several diagrams with Monte-Carlo generated basic populations in new and aged conditions have been shown. Thus, it has been demonstrated that not the conditions at the begin of life are the critical ones. No, the end of life properties are the critical ones.
This has been combined with the acceptance rate of borderline basic populations. The approach of minimum burst ratios leads to the acceptance rate of 40 % and higher for the approval of critical basic populations – critical due to their production scatter.
This problem becomes much more critical when taking into account the unknown effects of degradation and in-service ageing.
Therefore, we cannot support the proposed reduction of minimum burst ratio without having a stronger assessment of production scatter.
Safety criteria for the transport of hydrogen in permanently mounted composite pressure vessels
(2019)
The recent growing of the net of hydrogen fuelling stations increases the demands to transport compressed hydrogen on road by tube-trailers in composite pressure vessels. As transport regulation the ADR is applicable in Europe and adjoined regions and used for national transport in EU. This regulation provides requirements based on the burst pressure of each individual pressure vessel, regardless the capabilities of the transported hydrogen and relevant consequences resulting from worst case scenarios. In 2012, BAM (German Federal Institute for Materials Research and Testing) introduced consequence-dependent requirements and established them in national requirements concerning the “UN service life checks” etc.) to consider the transported volume and pressure of gases. However, this results in a stringent requirement in case of using large pressure vessels (tubes) on tube-trailers. In the studies presented here, the key safety factors for using hydrogen trailers are identified and reviewed through some safety measures from some countries like Japan, USA and China. Subsequently, the risk, chance, failure consequences of using trailers are evaluated, in addition, the difficulties for approving huge pressure vessels (large tubes) are addressed. There, a maximum acceptable pressure-volume product is defined. Finally, a performance-based criterion for the balance of chance and risk of hydrogen trailers is suggested to add into regulations and consequently into standards for hydrogen trailers.
The presentation summarizes all the safety concerns that have led DIN to reject an ISO project about extremely large gas/hydrogen transport units.
The core point is the consequence potential, which has increased considerably with the scope of the standardization project in comparison with state of the art systems. At the same time, there is a lack of an approach to take into account the reliability requirements that depend on the consequences, at least up to the level of a catastrophe.
The presentation starts with the first agreement of making a national attempt for the introduction of a pV-limit for hydrogen transport. It explains aspects of the technical development, provides an impression of catastrophic incidents, and explains the difference between risk control and consequence limitation. Then the process of determining consequences and the result from the discussion at the UN-WG are explained. The next part summarises the approach for counting the number of impacted persons as a function of the model of pressure wave, the pressure peak, the limits of injured persons and the population density. Finally, the latest state of the discussion and the subsequent recommendations for a pV-value and the adequate phrases for explanation are introduced.
This slides explain the functionality and the procedure of the UN-service life checks as they are operated by BAM as German authority. These are based on the probabilistic approach including evaluation of current safety level and its comparison with assessments of different status of degrdation including extrapolation towards end of safe service life.
The similarity to the approach for determiantion of retest periods by BAM is explained.
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.