An Introduction to Fuel Cells and Certification
Radium Engineering offers top of the line fuel delivery solutions for the motorsports market, including fuel cells. Many consider fuel cells as a simple metal container, when in fact a proper motorsports fuel cell is more complex. A basic aluminum, stainless, or mild steel container is more susceptible to fracturing in the event of a collision. This would create leak(s) and could lead to a dangerous fire situation. Even a minor fender bender or the flexing of the chassis during hard driving could create enough force to distort and crack the metal container. Fuel weighs 6.3~6.6 lbs per gallon. With a 14 gallon fuel cell that is 90 lbs of fuel sloshing, flexing the walls, and applying strain to the welds. When that much weight is subject to g-loading, the resulting forces are very large and can damage a poorly designed metal container. Furthermore, the thermal expansion created by elevated fuel, exhaust, and ambient temperatures put excessive stress on the can. Lastly, chemical compatibility, weld quality, and corrosion are concerns when using a metal container for fuel storage. In short, Radium Engineering does not recommend these types of fuel containers on performance vehicles.
Fuel cells used in motorsport racing often require FiA or SFI certification to ensure safety requirements are met. The guide below helps explain how a fuel cell works and why certification is necessary.
What is a Fuel Cell?
As shown, competition-grade fuel cells are generally comprised of three components: the outer shell (enclosure or can), the bladder (where fuel resides) and the foam baffling.
Radium Engineering fuel cell enclosures are made from lightweight aluminum, but other brands may use steel or other materials. The enclosure is the first part of the fuel cell to absorb damage and help prevent a catastrophe. This layer is similar to the construction of a helmet. The outer enclosure aids in safety but is not the most critical part. FIA and SFI specifications do not cover the outer can material alloy or thickness, only the internal bladder. Other governing bodies require a certain outer can thickness. For instance, SCCA requires a fully enveloped enclosure comprised of 0.036” steel or 0.059” aluminum.
The fuel cell bladder contains the fuel and protects from spills. The bladder must be resilient against impacts, punctures, and tears. The material also needs to be flexible enough to prevent cracking or fuel leakage in the case of impact and thermal expansion. These requirements have led to the development of different high-tech bladder materials used in the industry. Radium Engineering chose to only focus on molded polymer bladders as they have the best chemical compatibility and still meet all the structural testing requirements put forth by SFI and FiA.
The foam baffling is essentially a large open-cell sponge inside the fuel cell and serves several purposes. If catastrophic failure were to happen, this porous foam helps absorb the fuel and prevent an explosion. It also suppresses explosion potential by preventing fuel vapor buildup inside the cell. As an added benefit, it helps prevent fuel slosh which can cause fuel starvation. Fuel cell foam is a wear part and should be inspected periodically to ensure integrity. Loss of elasticity or degradation of any kind are signs the foam should be replaced.
What is FiA?The Federation Internationale de l’Automobile (FiA) has been around for over a century. It is an international organization that promotes road safety around the world and creates rules and regulation governing all forms of motorsports. FIA's most prominent role is licensing and sanctioning of Formula One, World Endurance Championship, World Rally Championship and various forms of sports car and touring car racing.
For the safety of the driver, FiA homologation (certification) is required in many forms of racing. This covers many safety related components including fuel cell bladders. FiA has a few distinct classifications regarding fuel bladders: FT3, FT3.5, and FT5. There are other standards required by other sanctioning bodies, but FiA is the gold standard.
All of the ratings clearly define the requirements for materials, construction, and testing. The only difference between the ratings is the strength of the bladder material. All tests utilize the same procedures but the levels of certification are based on test results. FT3 is the first level requiring the lowest minimums while FT5 requires the highest. For example, Formula-1 requires FT5, but SCCA requires FT3 (although FT3.5 and FT5 are also acceptable.) Check with your sanctioning body to see what requirements your vehicle must meet.
What is SFI?The SFI Foundation, Inc. (SFI) is a non-profit organization established to issue and administer standards for the quality assurance of specialty performance and racing equipment. The SFI Foundation has served the automotive aftermarket and the motorsports industry since 1978. Their service to the industry is a system of developing and administering various standards, certifications and testing criteria for use in motorsports.
Like FiA, SFI has a few different specification levels. SFI Spec 28.1 is the lowet and is for polymer foam-filled fuel cells. SFI Spec 28.2 is for crash resistant fuel cells and SFI Spec 28.3 is for competition fuel cells. Radium Engineering RA-Series fuel cells are certified SFI Spec 28.3.
Testing and Quality Control
Both SFI and FiA evaluate the bladder's structural integrity and perform rigorous mechanical testing including: tear, puncture, tensile, and compression.
Radium Engineering takes this process one step further. Before they leave our facility, every individual bladder is quality control tested as shown above.
Fuel cell certification expires 5 years after the date of manufacture. Check the label on the fuel cell bladder for the expiration date.
Heat, UV light, vibrations, and fuel are all factors that contribute to elastomers breaking down in a bladder. Water and alcohol fuels also can cause deterioration. Fortunately, all Radium Engineering bladders are made from a special polymer that are not as susceptible to chemical deterioration like coated fabric bladder variations (shown below) that are glued together.
However, all fuel cell bladders should be regularly inspected and replaced as needed.
Fuel cells generally require some level of maintenance. Regular maintenance ensures the fuel cell will last the full 5 years or longer in non-certified applications.
Maintenance tips: The fuel cell should be drained whenever the vehicle is stored for a long period of time. This will extend the life of the fuel cell. Alcohol is most damaging to the foam. Proper care of this part of the cell is crucial for maintenance. Foam breaks down over time and particles can clog the fuel system so it is imperative to use pre pump filtration. It is ideal to periodically replace the foam in the cell to increase cell longevity. Always follow the guidelines included with every Radium Engineering fuel cell.
Inspection: While replacing the foam, always inspect the bladder for any signs of wear, damage or degradation.
To conclude, metal box style "fuel cells" are prevalant on the discount market, however, they offer little to no engineering in regard to safety. The added cost of a certified bladder-style fuel cell can be easily justified in the event of a collision or other disaster.