Publications

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This report summarizes the investigation of the release of approximately 300kg of hydrogen at the AC Transit Facility in Emeryville, CA. The hydrogen release was avoidable in both the root cause and contributing factors. The report highlights the need for communication in all phases of project planning and implementation. Apart from the failed valve, the hydrogen system functioned as designed, venting the hydrogen gas a safe distance above surrounding structures and keeping the subsequent fire away from personnel and equipment. The Emeryville Fire Department responded appropriately given the information provided to the Incident Commander. No injuries or fatalities resulted from the incident.

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Steel pressure vessels are commonly used for the transport of pressurized gases, including gaseous hydrogen. In the majority of cases, these transport cylinders experience relatively few pressure cycles over their lifetime, perhaps as many as 25 per year, and generally significantly less. For fueling applications, as in fuel tanks on hydrogen-powered industrial trucks, the hydrogen fuel systems may experience thousands of cycles over their lifetime. Similarly, it can be anticipated that the use of tube trailers for large-scale distribution of gaseous hydrogen will require lifetimes of thousands of pressure cycles. This study investigates the fatigue life of steel pressure vessels that are similar to transport cylinders by subjecting full-scale vessels to pressure cycles with gaseous hydrogen between nominal pressure of 3 and 44 MPa. In addition to pressure cycling of vessels that are similar to those in service, engineered defects were machined on the inside of several pressure vessels to simulate manufacturing defects and to initiate failure after relatively low number of cycles. Failure was not observed in as-manufactured vessels with more than 55,000 pressure cycles, nor in vessels with relatively small, engineered defects subjected to more than 40,000 cycles. Large engineered defects (with depth greater than 5% of the wall thickness) resulted in failure after 8,000 to 15,000 pressure cycles. Defects machined to depths less than 5% wall thickness did not induce failures. Four pressure vessel failures were observed during the course of this project and, in all cases, failure occurred by leak before burst. The performance of the tested vessels is compared to two design approaches: fracture mechanics design approach and traditional fatigue analysis design approach. The results from this work have been used as the basis for the design rules for Type 1 fuel tanks in the standard entitled "Compressed Hydrogen-Powered Industrial Truck, On-board Fuel Storage and Handling Components (HPIT1)" from CSA America. Copyright © 2012 by ASME.

As hydrogen fuel cell technologies achieve market penetration, there is a growing need to characterize a range of structural metals that are used in the hydrogen environments that are encountered in gaseous hydrogen fuel systems. A review of existing data show that hydrogen can significantly accelerate fatigue crack growth of many common structural metals; however, comprehensive characterization of the effects of hydrogen on fatigue properties is generally lacking from the literature, even for structural metals that have been used extensively in high-pressure gaseous hydrogen environments. This report provides new testing data on the effects of hydrogen on fatigue of structural metals that are commonly employed in high-pressure gaseous hydrogen. Copyright © 2011 by ASME.

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