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Five type 4 all-composite compressed natural gas (CNG) fuel tanks produced in 1994 were acquired to study the effects of time and environmental exposure. Tank durability was demonstrated by the ability of the tanks to meet or exceed the ANSI/CSA NGV2-20001 standards after 9 years of field service. All tanks passed the NGV2-2000 standard production test requirements, including hydrostatic pressurization testing and standard leak testing. NGV2-2000 design qualification tests were performed on three of the tanks. Design qualification testing included liner and composite mechanical properties, cyclic pressurization, burst testing, and permeation testing as defined by NGV2-2000. All tanks exceeded the NGV2-2000 test requirements and exhibited no adverse effects from time, environment, and cyclic pressurization.

Lincoln Composites has conducted research to reduce cost and weight of all-composite NGV fuel containers. This research was conducted in cooperation with Battelle and others under GRI funding. Heavy tow carbon fiber was investigated as a means of reducing material cost. Advantex® glass fiber was evaluated as a replacement for conventional E-glass. Changes to the dome contour reduced fiber stresses due to bending. Other design and manufacturing issues were addressed. The design was finalized and passed all required NGV2 qualification tests, which were conducted by Powertech Labs. The overall program goals for cost and weight were achieved.

Studies have been published which address fast filling of Natural Gas Vehicle (NGV) fuel containers. Diggins states that NGV fuel containers cannot be fully filled during a fast fill, and that all-composite fuel containers cannot be filled as full as other types of fuel containers. There are issues in this prior work which may have a significant effect on the author’s conclusions. Fast fill testing conducted by Powertech Labs shows the Lincoln Composites’ fuel container has significantly better fill performance than projected by Diggins. Testing of a dispenser control system by Kountz and Blazek demonstrates all types of fuel containers can be properly filled with proper dispenser control algorithms and performance.