Latest FKM Material Sets a New Industry Benchmark for Aero Engine Low Temperature Sealing

Trelleborg Sealing Solutions introduces AeroXLT™ V8T11 to meet aerospace market demands for sealing materials that perform well at extremely low temperatures.

AeroXLT V8T11 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.

Increased performance
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.”

Rubore® Design Guideline in Development

In addition to the information surrounding existing Rubore® products, a new guideline aims to simplify commissioning a new project that uses this advanced technology.

Trelleborg is developing a design guideline to ensure all the technical details are covered when it comes to initiating a new project that makes use of Rubore® products. Alongside specific information on the products and their manufacture, the guideline covers such aspects as the choice of materials, construction, mechanical properties and materials testing.Rubore Products

With regard to the latter, the guideline adopts a different approach depending on the type of product planned and its possible application. In the case of the Rubore® Frame Seal and Rubore® Cap Seal, for example, the testing is based on a single case study, with aging simulated by way of constant strain rate (CSR) and finite element analysis (FEA). FEA modeling is also used for testing the Rubore® Flat Seal and Rubore® Cover Seal, along with creep testing at various temperatures and pressures.

Depending on the intended use, further application tests are carried out on current live projects, and include thermal cycles, torque loss, and thermal shock. As a result, information is obtained on potential areas of application, structural design constraints and feasibility of the Rubore® products, compared to conventional sealing systems.
The guideline is a collaborative project involving several Trelleborg Sealing Solutions groups. R&D is coordinated by the product development in Fort Wayne, USA while the manufacturing details and expertise are the responsibility of Kalmar, Sweden. Trelleborg Sealing Solutions Stuttgart (R&D) is also supporting the project, and the AutoHub is in charge of contacting customers to realize application-based projects.

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Trelleborg@Brembo – World Class Supplier For Brake Systems

As part of Trelleborg’s current roadshow offer, five specialists from AutoHub Sales Engineering recently visited their customer Brembo, in Stezzano, Italy, where carbon ceramic brake discs are designed, developed, and produced in collaboration with another company. The aim of this meeting was to offer the customer a comprehensive overview of Trelleborg’s activities and provide their engineers with a deeper technical knowledge of the products and solutions.

Supplier For Brake SystemsThere was obviously much interest on Brembo’s part, with no fewer than 30 engineers attending the presentation. Brembo had made its largest training room available for the roadshow, and among those participating were such key decision-makers as the R&D manager and the head of the motor racing department.

Following an introduction to the Trelleborg Group and the AutoHub in particular, the roadshow presented specialized knowledge on the materials used by the company. Alongside an explanation of the major stages involved in elastomer production, the Brembo engineers were also given an insight into the criteria governing the design of piston seals and O-rings. Finally, the team offered a critical analysis of the standards established by Brembo, a topic that was enthusiastically received.
Nor was the presentation simply a one-way lecture. The Brembo engineers were equally motivated, and used this opportunity to begin considering which applications could utilize Trelleborg seals. The resulting lively discussions continued on into the early evening. As a result, the Trelleborg specialists returned to Stuttgart with a large folder filled with requests that will need to be investigated over the forthcoming weeks.

The feedback gathered from the evaluation forms confirmed the positive impression the Trelleborg Sealing Solutions experts took away from the meeting. Brembo has even expressed a desire for further visits, specifically requesting deeper technical details and special training for their employees in the sales department and QA.

Needless to say, Trelleborg is only too happy to meet these customer requests and is looking forward to returning to Stezzano before too long.

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Trelleborg Qualifies A350 Main Landing Gear on World’s Most Powerful Test Bench for Hydraulic Seals

To support its customers in proving seals for critical applications, Trelleborg Sealing Solutions invested in the world’s most powerful test bench for hydraulic rod seals. This unique facility allows testing to be carried out that has previously never been possible and has been utilized to qualify the seals for the landing gear of the Airbus A350.

The sealing system has successfully passed 20,000 full landing cycles plus additional tests for ice scraping and water spray. To support its customers in proving seals for critical applications, Trelleborg Sealing Solutions invested in the world’s most powerful test bench for hydraulic rod seals. This unique facility allows testing to be carried out that has previously never been possible and has been utilized to qualify the seals for the landing gear of the Airbus A350. The sealing system has successfully passed 20,000 full landing cycles plus additional tests for ice scraping and water spray.
Test Bench for Hydraulic Seals
Installed in a specially constructed well, the 18 ton, 260 kW floating-mount rod seal test bench is located at Trelleborg’s research and development center in Stuttgart, Germany. It is capable of simulating, as realistically as possible, the patterns of movements and stresses faced by hydraulic rod seals in some of the most demanding rod seal applications.

Simulating real world conditions

“The test bench is about simulating the real world as closely as possible in the laboratory,” says Eric Seeling, the engineer responsible for the design of the test bench. “The rig can perform long-term endurance and development tests, reproducing the effect on hydraulic rod seals. In particular, it excels in aerospace applications where it can check parameters such as braking or lateral forces on landing gear and even simulate life-like knocking caused by uneven runways; what might be called a bumpy landing.”

A resource for the Trelleborg Sealing Solutions international R&D network, over 35 years of testing experience went into the design of the test bench. The entire bench was installed in a concrete well so that vibrations can be isolated from the surrounding building. The drive unit was set up in a separate room so that energy otherwise lost through emissions can be used in an environmentally-friendly manner to reheat the building.

Testing for high performance

The test bench is suitable for seals from 100 to 400 millimeters/ 4 to 16 inches in diameter and can test a complete sealing configuration in a single test construction, replicating the pressure between the primary and secondary seals realistically. Travelling at speeds of up to 1 meter/ 3.3 feet per second or frequencies up to 10 Hz, it can generate movements and pressure patterns in sine waves, trapezoidal forms and even freely modeled patterns.

One of the test bench’s more novel features is a lateral force cylinder mounted at the bottom of the bench. Capable of exerting forces of up to 225 kN, it can place permanent radial loads on the seals, or, depending on the stroke, exert dynamic loads. Another special feature is the ability to simulate different atmospheric temperatures between -60 °C and +90 °C/ -76 °F and +194 °F. Results can be fully documented, allowing customers to provide their clients with proof of performance related to prescribed parameters.