by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

Space Environments: FEP-Encapsulated Helical Spring O-Rings for Cryogenic Sealing

FEP-encapsulated helical spring O-rings, a testament to engineering resilience, are redefining what engineers can expect from cryogenic sealing in space environments.

In aerospace and launch systems, where seals must endure everything from deep vacuum to cryogenic propellants, failure is not an option. Traditional elastomeric seals become brittle and unreliable at the extremely low temperatures encountered in space missions. As a result, engineers require sealing solutions that combine resilience, chemical resistance, and consistent performance under punishing conditions.

This article explores why FEP-encapsulated helical spring O-rings have become a trusted sealing solution in cryogenic aerospace systems. We’ll examine the challenges of sealing in space, the features that make these O-rings ideal for such environments, and where they are being successfully deployed in today’s launch vehicles and propulsion systems.

The Challenge of Cryogenic Sealing in Space

The unique conditions of spaceflight, including exposure to cryogenic fluids such as liquid oxygen (LOX), liquid methane, and liquid hydrogen, present a set of stresses that would compromise or destroy traditional seals. These fuels are stored and transported at temperatures approaching -420°F (-250°C), far beyond the performance limits of most elastomer-based seals.

In addition to cryogenic exposure, seals in launch vehicles must contend with extreme pressure variations, from storage tanks at 100 psi to turbopump outlets exceeding 15,000 psi; thermal shock, when materials are rapidly heated and cooled during startup and shutdown; vacuum conditions, which amplify outgassing and increase the risk of material degradation; and supercritical fluid handling, where fluids behave as both gas and liquid while demanding perfect sealing to avoid leakage or combustion risks

In such conditions, even minor leakage can result in fuel loss, combustion instability, or total system failure. Elastomeric seals, regardless of their chemical resistance, will become brittle and prone to cracking under such extreme cold. Additionally, traditional O-rings can suffer from compression set, losing their sealing force after only a few cycles of use.

Why FEP-Encapsulated Helical Spring O-Rings Work

FEP-encapsulated helical spring O-rings are designed for use in the hostile environments of space. Each seal consists of a stainless steel flat-wound helical spring core, typically made from 302 stainless steel, completely encapsulated in a seamless FEP (fluorinated ethylene propylene) jacket. This design marries the best of both worlds: a chemically inert outer surface and a mechanically resilient inner spring.

Benefits of the FEP Jacket

The FEP jacket brings several benefits:

  • Cryogenic durability: FEP maintains flexibility and integrity at ultra-low temperatures
  • Chemical resistance: Inert to LOX, liquid methane, hydrogen, and most aerospace-grade fluids
  • Non-stick surface: Minimizes friction and reduces the risk of contamination or particulate generation
  • Low permeability: Offers excellent barrier properties in vacuum and supercritical conditions

Benefits of the Helical Spring Core

The helical core adds to that with its own special (and critical) features:

  • Consistent sealing force: The spring applies uniform pressure, compensating for material deformation or wear
  • Resistance to compression set: Unlike elastomers, the spring does not relax or lose force over time
  • Temperature resilience: Maintains performance across broad thermal swings—from cryogenic fill to engine ignition

The result is a sealing solution that withstands cryogenic storage tanks, turbopump manifolds, and LOX feed systems, delivering predictable and repeatable performance, even after multiple thermal cycles.

FEP-Encapsulated Helical Spring O-Rings for Aerospace and Rocket Systems

The value of FEP-encapsulated helical spring O-rings becomes clear when examining their deployment in real-world space systems. These seals are frequently found in:

  • Cryogenic valve assemblies, where they prevent leakage at pipe junctions, manifolds, and fill ports
  • Turbopump flanges and housings, which handle rapid pressure increases and thermal fluctuations
  • Fuel and oxidizer feed lines, including stage separation and preburner systems
  • Supercritical fluid interfaces, where precise sealing is critical for performance and safety

Their use is particularly valuable in systems that transport or isolate LOX, LH2, or RP-1 (refined kerosene) in Kero-Lox and Metha-Lox configurations. In these systems, preventing cross-contamination between oxidizers and fuels is crucial, as premature mixing can lead to instantaneous ignition or explosion.

Additionally, FEP-encapsulated designs align with the industry’s push toward lightweight and low-maintenance components. Because they do not require lubrication and offer long service life, they reduce mass and complexity in the vehicle’s overall sealing strategy.

Conclusion

Sealing in space is not a job for off-the-shelf elastomers. It demands materials and designs that can withstand vacuum, cryogenics, pressure spikes, and chemically aggressive media without losing integrity. These O-rings meet these requirements and then some.

The combination of a chemically resistant FEP jacket and a load-maintaining helical spring core in these O-rings makes them ideal for aerospace systems where performance and reliability are non-negotiable. Whether you’re designing for LOX manifolds, liquid hydrogen feed lines, or cryogenic stage separation, these seals deliver the peace of mind that only proven engineering can provide.

For custom-engineered helical spring O-rings designed to thrive in spaceflight conditions, contact Advanced EMC Technologies. Our team has the experience, materials, and manufacturing capabilities to deliver high-performance sealing solutions for the most extreme environments in the universe.

by Denise Sullivan Denise Sullivan 18 Comments

Understanding FEP-Viton® (FPM/FKM) and FEP-Silicone: Advanced Seal Face Combinations

In the world of mechanical seals, choosing suitable materials for seal face combinations is crucial for ensuring optimal performance and longevity of your sealing solutions. Among the most reliable and effective materials used in the industry are FEP-Viton® (FPM/FKM) and FEP-Silicone. These materials offer exceptional properties that make them suitable for various applications. Let’s delve into what makes these combinations stand out and how they can benefit your sealing needs.

FEP-Viton®

What is FEP?

FEP, or Fluorinated Ethylene Propylene, is a type of fluoropolymer known for its excellent chemical resistance, low friction, and high-temperature stability. It provides a tough, protective outer layer that enhances the durability and performance of the underlying elastomer.

FEP-Viton® (FPM/FKM) Seal Face Combinations

Viton® (FPM/FKM): Viton®, also known as FPM or FKM, is a high-performance fluoroelastomer that offers exceptional resistance to heat, chemicals, and oils. It is widely used in applications that demand high durability and reliability under harsh conditions.

Benefits of FEP-Viton® Seals:

  1. Enhanced Chemical Resistance: The combination of FEP with Viton® ensures superior resistance to aggressive chemicals, making it ideal for chemical processing.
  2. High-Temperature Stability: Viton® can withstand temperatures up to 200°C (392°F) and, when paired with FEP, offers even more excellent thermal stability.
  3. Improved Durability: The FEP outer layer protects the Viton® core from wear and tear, extending the seal’s life.
  4. Low Friction: FEP’s low friction properties reduce wear and improve the efficiency of the sealing system.

Applications:

  • Chemical processing
  • Oil and gas industry
  • Automotive industry
  • Aerospace applications

FEP-Silicone Seal Face Combinations

Silicone: Silicone elastomers are known for their excellent flexibility, thermal stability, and biocompatibility. They are widely used in applications requiring a soft, pliable material to maintain its properties over a broad temperature range.

Benefits of FEP-Silicone Seals:

  1. Biocompatibility: The combination of FEP and silicone is ideal for medical and pharmaceutical applications due to its non-reactive and biocompatible nature.
  2. Temperature Range: Silicone can operate efficiently across a wide temperature range (-60°C to 200°C or -76°F to 392°F), making it versatile for various environments.
  3. Flexibility: Silicone’s inherent flexibility ensures excellent sealing performance, even in applications with dynamic or irregular surfaces.
  4. Enhanced Durability: The FEP layer provides additional protection, ensuring the silicone core remains intact and functional over extended periods.

Applications:

  • Medical devices
  • Food and beverage industry
  • Pharmaceutical industry
  • Electronics

Why Choose FEP-Viton® and FEP-Silicone Seals?

Combining FEP with either Viton® or silicone creates a sealing solution that leverages the best properties of both materials. These seals are designed to withstand extreme conditions, resist aggressive chemicals, and operate efficiently across a broad temperature range. Their enhanced durability and low maintenance requirements make them cost-effective for demanding applications.

Conclusion

FEP-Viton® (FPM/FKM) and FEP-Silicone seal face combinations significantly advance sealing technology. These seals meet the rigorous demands of various industries by offering superior chemical resistance, high-temperature stability, and exceptional durability. Whether you are in the chemical processing, medical, or automotive sector, these advanced seal combinations can provide reliable performance and extend the life of your equipment.

Contact us today to learn more about these innovative sealing solutions and find the perfect fit for your application needs!