If the words “Fire Seal” bring to your imagination a Sea World show gone terribly wrong, then you probably won’t be interested in this blog. But, for anyone associated with the field of aviation, you’ll recognize a crucial element of aircraft safety. Fire Seals are barriers located within an aircraft nacelle that, in the event of an engine fire, work to keep it contained within the immediate area and deny it the oxygen it needs to propagate. This provides the opportunity to safely shut down the engine or APU.
Few things worry the cautious traveler more than the idea of an aircraft engine fire. After all, it’s not like you can pull over 6 miles above the ground and call Triple-A. But, the reality is that without fire, a flight would be impossible. It is the controlled burn of fuel within the engine that generates the thrust necessary for flight. So, what those burdened with ensuring aircraft safety focus on is the prevention, detection, and suppression of unwanted engine fire. To combat this, aircraft are designed with redundant systems for fire detection which alert the flight crew to engage in appropriate countermeasures. These include cutting off fuel to the compromised engine and activating fire extinguishers. These are examples of active measures for fire control.
Fire seals fall into the category of passive systems. Passive systems are always in place and require no external engagement to function.
Fire seals typically feature a composite structure. A flame-resistant elastomer is layered with a fire-resistant fabric which helps to maintain the structural integrity of the seal for a specific period of time. Typical materials used are silicone, aramid fabrics, ceramic, or other inorganic fabrics. Seals are typically molded for finite lengths (typically < 12 feet long) and can be spliced to meet longer length requirements or irregular geometries. Intricate custom shapes are possible employing salt core molding techniques.
Typical configurations include:
The main specifications governing fire seals are ISO 2685 and AC20-135. These documents define the test methods and acceptance criteria for evaluating seal performance. Seals are evaluated by their ability to survive exposure to a 2000 degree flame for a specified period of time. Components can be classified as either fire-resistant (5 minutes) or fireproof (15 minutes).
Parker's Engineered Materials Group supplies fire seals through our Composite Sealing Systems Division (CSS), headquartered in San Diego, CA. Our seals have been tested by a third-party laboratory and have been proven to meet the requirements of the governing specifications. Testing consists of exposing a production-representative component to a set of application-specific conditions that may include pressurization, airflow, and vibration, all while exposed to a calibrated 2000°F flame. The component must not allow any burn-through during the entire test and should not self-ignite after the burner is removed.
Parker is a major supplier to many major aerospace OEMs. To learn more about how we can help support your production, reliability, and safety goals, contact us.
Learn more by watching our video on all our sealing solutions for aerospace.
Article contributed by Brian Alessio, business development engineer, Engineered Materials Group, Parker Hannifin.
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