Packaging of the composite storage units (yellow/black tanks) of a hydrogen vehicle (Toyota Mirai)

Packaging of the composite storage units (yellow/black tanks) of a hydrogen vehicle (Toyota Mirai)

Source: Toyota Motor Corporation

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/ ECE R134) criteria.

This paper analyses the behaviour 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 cylinder designs, potentially unsafe due to a very high scat-ter of burst strength results. It is also shown that existing design types are already designed up to the property margins specified by regulations. A further weight and cost reduction of composite cylinders is closely related to the approval criteria. An example based on UN GTR No. 13 (global technical regulation on hydrogen and fuel cell vehicles) 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 poten-tially unsafe design types.

Statistical analysis of burst requirements from regulations for composite cylinders in hydrogen transport
Ben Becker, Georg W. Mair
Materials Testing: Vol. 59, No. 3, pp. 226-232.
BAM Department Containment Systems For Dangerous Goods