Safety approach for composite pressure vessels for road transport of hydrogen. Part 2: Safety factors and test requirements

Composite pressure vessels for transporting hydrogen on roads are a promising and efficient solution for supplying refueling stations. The safety factors of current ISO design standards are perceived as being restrictive for design. In this paper, new safety factors are calculated based on a probabilistic approach and by extending the methods used in the DNV Offshore standard DNV-OS-C501 "Composite Components". Short-term and long-term conditions are addressed. The safety factors are dependent on the acceptable probability of failure and are very dependent on the coefficient of variation (Coy) of the burst strength of the pressure vessel. It is shown that according to the calculated special cases (COV = 6%, standard deviation of the SN curve log N of 0.5 and a lifetime 20 years), the safety factors can be reduced considerably compared to ISO 11119-3. Obtaining the required statistical information of the properties of the pressure vessels requires extensive testing. Testing many large pressure vessels is practically not feasible and sub scale testing would be preferred. Acceptance criteria are suggested for testing on sub scale specimens instead of full-scale pressure vessels. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.