Fuelled by the need to save weight and reduce evaporative emissions, a great deal of innovative design and materials work is going into vehicle fuel tank systems, writes Matthew Beecham.
In the early 1970s, all fuel tanks were of steel. Since then plastic fuel tanks have superseded steel to the point where more than 90% of all light vehicles built for the European market are made of plastic. Plastic fuel tank manufacturers are quick to point out the benefits of plastic over steel, including lighter weight, non-corrosive and geometric flexibility. They believe that the trend in favour of plastic fuel tanks will continue to grow until the market is saturated.
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So given the legislation in Europe and California, can steel tanks really make a comeback? Magna Steyr believes that the advantage of steel tanks with respect to the legislation in California is more and more challenged by the improving technologies for plastic tanks. “Sooner or later the technology needed will be available for plastic as well. Pieces can also be covered by plastic,” said Gerhard Stiegler, vice president operations, Magna Steyr. “Another advantage of steel tanks in terms of higher pressure resistance can be provided to hybrid vehicles. During the electric driving mode of hybrid vehicles, the fuel-powered internal combustion engine has been shut off. This leads to a pressure increase in the fuel system, which requires the good performance of steel tanks. Furthermore, the large-volume tanks like those for trucks are made of steel or aluminium – and this will not change in the future. In summary, we believe these new requirements and technologies create new opportunities for steel tanks, which will keep their market niche in addition to the existing mass market for plastic tanks.”
In line with these market trends, Magna has strategically decided to develop and supply fuel systems for all applications — in plastic, steel and aluminium technology — to offer the best solution for the specific customer needs.
Biodiesel is already popular in Europe and spreading to the North American market. And yet there appears to be some issues concerning vehicle manufacturers using plastic fuel tanks to store biodiesel. Can steel do a better job? Stiegler added: “A steel tank is inherently adequate for the use of biodiesel but, with some material improvements, plastic tanks can also be made to fit for these applications. To some extent, aluminium tanks prove to be disadvantageous when using urea as biofuels for the “AdBlue systems” where we have to cover the inner layer of the tank with plastic.”
On the other hand, biodiesels bring different challenges and may also generate more NOx. Indeed, the challenges presented by biodiesels are significantly different. Handling and storage is another issue. “The handling and storage of biodiesel is definitely an issue compared to classical diesel fuel, especially because of the different chemical behaviour, degradation of biodiesel and different types of biodiesel that are available around the world. As a consequence, there might be a negative impact on the long-term durability of the fuel tank and its plastic components.
“Therefore it is necessary to chemically improve the resistance of the types of plastics used and to take some measures at the fuel pumps.
“The latest generations of fuel systems have addressed these effects and so we are in the position to provide a complete system which meets the increasing requirements that have been generated due to the use of biodiesels.”
