Federal-Mogul helps thin out fuel-cell stacks

  • 31-Aug-2009 09:27 EDT
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Federal-Mogul says its LEM gasket can provide a superior seal between a fuel-cell membrane and bipolar plate at half the size and weight of a conventional molded gasket.

Federal-Mogul Corp. has developed a fuel-cell gasket technology that capitalizes on the industry shift from two-dimensional stamped fiber gaskets toward more advanced elastomer molded products.

The patented Liquid Elastomer Molding (LEM) gaskets are constructed with small engineered elastomeric beads molded thinly onto thin metallic carriers that provide superior sealing performance while significantly reducing the size and weight of each fuel-cell stack, according to the company.

“Federal-Mogul's LEM gasket provides a unique sealing technology, offering one of the smallest sealing cross sections and lowest load to seal in the industry,” said Gerard Chochoy, Senior Vice President, Federal-Mogul Powertrain Sealing and Bearings. “Our sealing technology can contribute to a more optimized fuel-cell package and reduced weight, which can support fuel-cell technology to become more widely accepted.”

A typical fuel-cell stack is composed of several hundred fuel cells. Each cell contains an ion-exchange membrane and bipolar plates. An electrochemical reaction takes place on the surface of the membranes to combine hydrogen with oxygen, releasing electrical energy and water as a byproduct. Each membrane must be sealed from the other layers and from the external environment. A fuel-cell stack requires hundreds of bipolar plates and membrane elements that need to be sealed.

The low-profile triangular engineered sealing beads with variable height are adaptable to any deflection of the mating parts. Each LEM gasket can be 0.3 to 0.5 mm (0.01 to 0.02 in) thick, whereas the conventional molded gasket measures at least double that, according to the company.

The inherent advantage of LEM regarding manufacturing is the fast-curing technology coupled with a one-piece-flow operation with maximum material utilization. The gaskets are processed in a coil form. The first step is cleaning and application of the adhesive to the coil, followed by screen printing of the liquid elastomer in the desired pattern of the gasket. The elastomer pattern is then subjected to heat and pressure in a compression mold press to cure, followed by stamping of the finished gasket.

The material in LEM gaskets is silicone, although other liquid elastomers also can be used.

Federal Mogul says the technology offers significant advantages over traditional molded rubber gasket technology. LEM requires one of the smallest flange widths to seal a joint. The minimum flange width requirement for an LEM gasket is 4 mm (0.2 in) vs. 8 to 10 mm (0.3 to 0.4 in) for traditional press-in-place or edge-molded rubber gaskets. Its thin profile allows much flexibility in the design of flanges for sealing.

Also, compared to other technologies in such applications, LEM requires the lowest load to seal. In various benchmark studies, LEM is demonstrated to function at 60% less load compared to edge-molded rubber and place-in-place gaskets, and one-tenth the load compared to rubber-coated metal gaskets. The thin carrier and small sealing beads not only reduce the thickness of the gasket but also reduce the weight contributed to the gasket.

LEM technology offers the potential to directly incorporate the gasket into the bipolar plates, offering further reduction in assembly complexity.

LEM technology has been in production for engine, transmission, and gearbox sealing applications since 2001, including oilpan, cam cover, and water pump gaskets. Fluids sealed include engine and transmission oils as well as coolant.

The advantages of LEM technology in internal-combustion engines are the same for fuel-cell applications, the company says. Among the several design challenges in fuel cells are packaging, weight, and cost. The LEM gasket is one such enabling technology that would allow fuel-cell manufacturers to make compact and lightweight fuel cells while managing costs.

Federal-Mogul is collaborating with a major developer of fuel cells. The company says LEM gaskets can be used as stand-alone sealing elements in a fuel-cell stack, but also open the opportunity to incorporate the sealing element with other components of the fuel-cell stack.

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