When Off-the-Shelf Aerospace Sealing Solutions Fail: A Custom Engineering Approach for Critical Applications

Key Takeaways

• Standard seals often fail in aerospace environments due to extreme temperatures, pressure, vibration, and chemical exposure.
• Warning signs include premature wear, leakage, inconsistent performance, excessive friction, and material incompatibility. 
• Custom-engineered seals address application-specific requirements through optimized geometry, advanced materials, and validation testing.
• High-performance materials such as PTFE, PEEK, and proprietary elastomer compounds provide improved resistance to thermal, mechanical, and chemical stresses.
• Vertically integrated design, testing, and manufacturing processes help ensure consistent performance in mission-critical aerospace applications. 
  

Why Off-the-Shelf Aerospace Seals Fall Short

Aerospace systems operate in some of the most demanding environments in engineering. Seals must withstand extreme temperature swings, high pressures, aggressive fluids, vibration, and long service intervals while maintaining reliable performance. In these conditions, standard catalog components may meet dimensional requirements but often struggle to meet the full range of operational demands.

A commercial aircraft contains thousands of sealing elements used in fuel systems, hydraulic systems, engines, actuators, and environmental control systems. Failure of even a small seal can compromise equipment performance, increase maintenance requirements, or create safety concerns. The aerospace industry has long recognized the importance of sealing reliability, particularly in applications where failure is not an option.

Extreme Temperature Cycling

Aerospace equipment routinely experiences temperatures ranging from cryogenic conditions to extreme high-temperature operating environments. Repeated thermal cycling can cause conventional elastomers to lose elasticity, develop compression set, and experience dimensional changes that reduce sealing effectiveness. As materials expand and contract, maintaining a consistent seal becomes increasingly difficult.

High-Pressure Operating Environments

Hydraulic systems, landing gear components, and engine-related assemblies operate under significant pressure loads. These conditions can accelerate seal extrusion, material fatigue, and wear, especially when pressure cycles occur repeatedly throughout the life of the system. Standard seals may not provide the durability required for long-term performance in these environments.

Exposure to Aggressive Aerospace Fluids

Seals are continuously exposed to fuels, lubricants, hydraulic fluids, and cleaning agents. Material incompatibility can result in swelling, hardening, cracking, or loss of mechanical properties. Elevated temperatures often intensify these effects, making material selection one of the most critical factors in sealing performance.

Signs That Standard Seals Are Reaching Their Limits

Seal failures rarely occur without warning. Engineers can often identify performance limitations before major failures develop.

Premature Degradation

Fuel systems and fluid-handling equipment frequently show early signs of sealing problems through cracking, brittleness, swelling, or material deterioration. These issues often indicate that the seal material is not fully compatible with the operating environment.

Inconsistent Performance Across Flight Cycles

Changes in temperature, pressure, and vibration levels between operating cycles can cause sealing performance to vary over time. Seals that perform adequately in one condition may struggle to maintain effectiveness as operating conditions change.

Leakage of Critical Interfaces

Leakage remains one of the clearest indicators of seal inadequacy. This challenge becomes even more significant in cryogenic and high-pressure applications, where fluid properties make containment more difficult. Small leaks can quickly develop into larger reliability concerns if the underlying design issues are not addressed.

Lubricant and Fluid Compatibility Issues

Incompatible sealing materials may absorb fluids, swell excessively, or degrade chemically. These reactions can increase friction, accelerate wear, and reduce overall service life.

The Custom Engineering Advantage

When standard components cannot satisfy demanding application requirements, custom-engineered sealing solutions provide a path to improved reliability and performance.

Application-Specific Geometry

Seal geometry plays a significant role in performance. Factors such as cross-sectional design, sealing lip profiles, interference fit, surface finish, and installation conditions directly influence leakage control and wear resistance. Custom-engineered designs can be optimized to match the exact operating requirements of an aerospace system.

Advanced Material Selection

Material selection is equally important. High-performance thermoplastics and engineered elastomers are often required to withstand aerospace operating conditions.

PTFE offers low friction, broad chemical resistance, and excellent temperature capability, making it well suited for dynamic sealing applications. Filled PTFE grades can further enhance wear resistance and dimensional stability. PEEK provides exceptional mechanical strength, high-temperature performance, and resistance to aviation fuels and hydraulic fluids. These properties make it valuable in applications requiring both durability and precision.

Thermoplastic composites can also deliver significant benefits, including weight reduction, structural integrity, and chemical resistance, helping support both performance and sustainability objectives.

Validation Through Testing

Custom sealing solutions must be verified through rigorous testing. Thermal cycling, pressure testing, leakage evaluation, vibration simulation, and dimensional inspections help confirm that designs will perform as intended under real-world operating conditions. Early validation reduces program risk and supports long-term reliability.

CDI-Hallite Aerospace: Engineering Reliability into Critical Systems

CDI-Hallite Aerospace combines the engineered polymer expertise of CDI Products with Hallite's sealing technology to develop custom aerospace sealing solutions for applications where standard components may not provide sufficient performance margins.

A key example is Arylast®, CDI Products' proprietary elastomer platform. Built on decades of materials expertise and aerospace qualification experience, Arylast materials are designed to deliver low compression set, resistance to aggressive fluids, improved mechanical strength, and performance across demanding thermal cycles. These materials conform to applicable AMS and MIL specifications and can be tailored to specific application requirements.

Supporting these materials is a vertically integrated development and manufacturing process. Testing is performed in ISO/IEC 17025-accredited laboratories, while production follows Nadcap-certified processes to help ensure repeatability, traceability, and quality throughout the product lifecycle.

Conclusion

In aerospace applications, sealing performance is a critical engineering consideration rather than a simple component selection. While off-the-shelf seals may satisfy basic dimensional requirements, they often fall short when exposed to extreme temperatures, high pressures, aggressive media, dynamic motion, and stringent reliability expectations.

Custom-engineered sealing solutions address these challenges through optimized geometry, advanced materials, rigorous testing, and controlled manufacturing processes. By evaluating the complete operating environment—including temperature, pressure, media compatibility, motion, and service life requirements—engineers can improve reliability and reduce risk in mission-critical aerospace systems.

CDI-Hallite Aerospace works with OEMs and aerospace suppliers to develop sealing solutions engineered for demanding applications where performance, safety, and reliability are essential.