Statistical analysis of burst requirements from regulations for composite cylinders in hydrogen transport

Abstract

Abstract Existing standards for the approval of composite cylinders in the transport of compressed hydrogen are currently based on deterministic (ISO 11119-3) and semi-probabilistic (UN GTR No. 13) criteria. This paper analyzes the behavior of these procedures with respect to the evaluation of burst strength. Their characteristics are compared with the probabilistic approach developed at BAM. Based on Monte-Carlo simulations, the available design range (mean value and scatter of burst strength) of all concepts are assessed. In addition, the probability of acceptance for potentially unsafe design types is determined. Due to current approval criteria, the results show large areas of burst properties with a sufficient reliability which cannot be used for the design of composite cylinders. On the other hand, existing standards allow the approval of potentially unsafe designs in case of a very high scatter regarding their burst strength. It is also shown that existing design types are already designed to the limits of the available design area. A further weight and cost reduction of composite cylinders is closely related to the approval criteria. An example based on UN GTR No. 13 shows how an approval criterion can be optimized by using statistical methods. The example shows that a reduced minimum burst pressure can be combined with a lower probability of acceptance for potentially unsafe design types.