In several recent issues of Circle Track, we took an in-depth look at firesuits and protective apparel. All of those items are designed to protect you, the driver, if a fire gets too close. Here, we take a step back and look at protecting the driver from a fire before it gets too close.
For many years, teams have placed improperly plumbed systems or household fire extinguishers somewhere in the cockpit without giving it a second thought. These things were done for many reasons. "It won't happen to me" or "it covered the rules" are the most popular reasons for using the wrong fire extinguisher or, worse yet, no extinguisher at all.
Modern fire systems for race cars have made many advances from the simple action bottle. Today's bottles are actuated in three main ways. First, there is the push/pull cable actuation. Most of these extinguishers have a safety pin to prevent accidental set-offs. Once the pin is removed, based on the option selected, the knob is either pulled or pushed to set off the extinguisher. The advantage of the cable mount is it can be mounted anywhere that makes sense for the driver and the cockpit.
Another method of actuation is the automatic discharge nozzle. This nozzle eliminates the need for the driver to pull a cable. The automatic nozzle is set to discharge when its surroundings rise to a predetermined temperature. These temperatures can be specified and range from 135 to 500 degrees F. An automatic nozzle for a fuel cell is typically set at 286 degrees F while one for an engine compartment is set at 360 degrees F. These temperature settings are far above normal operating temperatures for the cockpit, engine compartment, and fuel cell area, but they are far below the temperature that the fire will generate.
The last method of actuation is a combination of the first two and also the newest of the three. The head of the extinguisher bottle incorporates a pull cable along with automatic lines that discharge at a specific temperature. As the systems grow and cover more of the race car, this dual-actuation system seems to make the most sense. We'll discuss this more in the plumbing section.
Now that we know what options we have for actuation, we should look at what chemicals to use. The popular chemical agents used in motorsports have commonly known names, but there are many misconceptions about them. They are Halon 1211 and 1301. These Halon agents are colorless, odorless, and electrically non-conductive. They are very effective, pound for pound, compared to other agents. In fact, it only takes a 5 percent concentration of Halon, in air, to extinguish most fires. And most importantly, Halons have been proven to be remarkably safe for human exposure.
Two of the largest misconceptions about Halons are that they are banned and displace the air in order to extinguish a fire. Both of these rumors are untrue, but let's investigate them one at a time. Halon is not a banned product. In some states, it is not allowed in certain non-commercial handheld fire extinguishers. But according to the EPA, Halon releases that result from an owner failing to maintain equipment to industry standards are prohibited. But this does not apply to Halon releases for fire extinguishing when used in systems designed for that purpose.
Also, it is incorrect to think that Halon displaces the air in order to extinguish a fire. Tests preformed with Halon have shown that between 5 and 8 percent by volume will extinguish most fires. Halon puts out a fire by chemically interrupting combustion. There are more technical explanations for what happens at the chemical reaction level, but the simplified version is Halon's effect on fire centers around its ability to chemically react with the components of the fire.
Another popular chemical is DuPont's FE-36. This alternative to Halon is more environmentally friendly. FE-36 leaves no residue and is non-corrosive and electrically non-conductive. While FE-36 has its benefits, it also has a disadvantage. As compared to Halon, it takes between 1.5 and 1.8 times as much FE-36 to be as effective. So a 7.5- to 9-pound FE-36 system would be needed to put out a fire that could be extinguished by a 5-pound Halon system. This is certainly puzzling when considering a sanctioning body that mandates a 5-pound Halon or 5-pound FE-36 system as a minimum requirement. FE-36 is certainly a consideration, but having all the information before making a decision is also important. Some companies have begun using FE-36 exclusively in their motorsports products. Check with the manufacturers to see what chemicals they recommend for your application.
Plumbing Knowing where the fire is going to start and how it is going to spread makes it easy to protect the driver and car most efficiently when plumbing a fire suppression system. Since we don't know these facts ahead of time, we'll consult two theories on how to do it.
The original theory for plumbing a race car was the "save the driver" theory. This method concentrates the discharge of the extinguisher on the driver in the cockpit. It's simpler and less costly since the bottle is most often in the cockpit anyway. This is called the original theory because it was how fire systems were plumbed when they were first introduced into race cars. Experience has shown that if the fire is only fought at the driver, it will be bigger and more difficult to extinguish than if it were attacked where it started.
The "at the source" theory on plumbing a car involves concentrating discharge on where the fire starts. Concentrating the spray in the engine compartment and around the fuel cell using automatic discharge nozzles will minimize if not eliminate the fire, directing it as far away from the driver as possible. We've seen a system with two automatic nozzles, one on the fuel cell and one in the engine compartment, and a separate bottle with a pull cable to flood the driver's compartment if necessary.
No matter how the system is plumbed, a major precaution is in how the lines are run around sharp objects and through bulkheads (firewalls). If the lines have to be turned around a corner, use a generous radius to avoid kinking the line. Also, using insulating clamps to mount the lines will help prevent excess vibration of the lines, which could weaken the bottle fittings. When passing through firewalls, be sure to use grommets or bulkhead fittings (if possible) to avoid possible damage to the lines.
In addition to choice of discharge locations, bottle placement is very important to the system working properly. It is recommended that the extinguisher be mounted horizontally in the vehicle. In most stock car applications, behind the seat or under the front of the seat are the most popular locations. Also, most bottles have temperature limits on a label, so make sure the bottle is located strategically or has the proper shielding to not exceed these limits. Finally, mount the bottle so that the gauge and label are visible. Tech inspectors like to verify the gauge readings and service info from the label.
Cost Fire extinguisher systems vary in cost based on their complexity and size. A smaller unit with one nozzle can cost as little as $275, while a larger system with 10 pounds of chemical and three or more nozzles can be over $485. However, the cost of a system is just a small percentage of the damage a fire can do to the race car, even if the driver is unharmed. The manufacturers we spoke with said that their systems can be found even cheaper through their larger distributors.
Maintenance Maintaining a fire extinguisher system is very important, but also very simple. First, check the bottle pressure. Any downward movement in the pressure indicates that other areas should be examined. Secondly, check the valve assemblies and/or remote cables to be sure they are clean and lubricated to prevent corrosion that would impede their proper function. Inspect the lines; they should be clear and not obstructed with dirt or other foreign material. Look for fraying or chafing on the lines. Finally, check to see that the pull cable is firmly tightened into the valve body.
When we looked at firesuits and fire protection in past issues, we found that the suits provide great protection, but only for a limited time. The use of a quality, well-designed fire extinguisher system in addition to a quality firesuit further protects any driver, allowing them to exit a burning vehicle while providing extra time for the safety crew to arrive. Racing is a dangerous sport. It should be everyone's goal, from the safety companies to the drivers themselves, to take the precautions that will allow all of us to race and walk away the safest way possible.