Latest FKM Material Sets a New Industry Benchmark for Aero Engine Low Temperature Sealing
In tests, this new generation fluorocarbon (FKM) offers the best low temperature sealing performance of any currently available FKM. Reliable sealing down to -55 °C/ -67 °F is combined with outstanding stability in aggressive higher thermo-oxidative stability (HTS) oils where it demonstrates significantly less swell than older-generation FKMs. This ensures sealing integrity and contributes to long seal life, helping maximize aircraft flight hours.
International standards AMS7287 and AMS7379 set the low temperature requirement for elastomer aerospace materials at -30°C/ -22°F and -40°C/ -40°F respectively. However, engine manufacturers are demanding reliable sealing at even lower temperatures as well as at high operating temperatures and with the ability to provide long service life in the now universally-used HTS oils.
The performance of AeroXLT™ V8T11 in a wide range of aerospace fluids has been proven in tests against a bisphenol cured FKM that meets AMS 7276 standard and a nitrile conforming to AMS-P-83461. The materials were immersed in HTS Reference Oil 300 at 200 °C (NBR at 100°C), in Mil PRF-83282 at 135 °C and Fuel B at 23 °C, in each case for 70 hours. The NBR exhibited excessive swell in the Reference Oil and Fuel B and more than 10% in Mil PRF-83282. The older-generation FKM performed better overall but still swelled by over 20% in HTS Reference Oil 300. AeroXLT™ V8T11 demonstrated exceptional stability across the range of fluids, with a maximum of just over 5% volume swell in the Reference Oil 300 and only 2% in MIL PRF-83282.
AeroXLT™ V8T11 offers reliable static sealing down to -55 °C/ -67 °F in the most demanding seal applications, beyond the low temperature rating of FKMs designed to meet AMS7287 and AMS7379 international standards. Demonstrating outstanding chemical resistance and stability in a wide range of aircraft engine lubricants, fuels and hydraulic fluids, the material exhibits excellent resistance to compression set at high temperatures. With its better fluid resistance and operating temperatures, it has the potential to replace conventional elastomers such as nitrile and fluorosilicone.
Especially suited to use in engine applications where seal integrity is paramount to their efficient operation, such as gearboxes, lubrication, scavenge and fuel systems, AeroXLT™ is available in all standard international O-Ring sizes and cross-sections along with custom-engineered solutions and specially designed seal profiles.
Development and testing
Chris Busby, Product Manager for the AeroXLT™ V8T11 material, says: “Aircraft and aero engine manufacturers need their equipment to operate at ever lower temperatures. To provide efficient transport services, they want planes that can take off even after standing for relatively long periods in extreme temperatures.
“Trelleborg has devoted a considerable amount of development and testing resources to formulating a material to go beyond the current minus 40 degree benchmark for low temperature sealing; AeroXLT™ V8T11 sets a new benchmark.
“It’s important that aerospace engineers recognise that there are big differences in performance between older-generation FKMs and the newer generation ones, such as AeroXLT™ V8T11. Undoubtedly, better life can be achieved with the new-generation compounds, extending intervals between planned maintenance, which can have a significant impact on extending flight hours. It is particularly important to differentiate between materials in aerospace engine applications requiring high temperature performance combined with low temperature capabilities, something older generation FKM materials cannot achieve.”