by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

Seals for Cryogenic Space Applications: Why PTFE Spring-Energized Seals Are the Solution

Seals for cryogenic space applications must survive conditions that push materials and engineering itself to the edge. Temperatures can drop below -250°C. There’s no atmospheric pressure. No lubrication. No margin for error. And when these seals are used in systems like cryogenic fuel transfer, attitude control thrusters, or deep-space instruments, failure isn’t just inconvenient: it’s catastrophic.

That is where PTFE spring-energized seals come in. These seals combine low-temperature flexibility, chemical inertness, and a constant, adaptive sealing force, making them one of the most reliable options for cryogenic sealing in space.

In this article, we break down how they work, what materials and energizers are involved, and why they outperform traditional sealing technologies in the vacuum and cold of space. We also tackle the biggest challenges in cryogenic aerospace sealing—and show how these advanced seals meet them head-on.

What Are Spring-Energized Seals?

A spring-energized seal utilizes a precision metal spring embedded within a polymer jacket (e.g., filled PTFE, PEEK, FEP)  to apply a continuous force against the sealing surface, ensuring reliable, low-friction sealing even under extreme temperatures, pressure variations, and material contraction. These seals have proven ideal for some of the harshest environments, including static and dynamic cryogenic systems.

Spring energizers are available in various configurations, including cantilever for light loads and dynamic applications, helical for low temperatures and vacuum conditions, and canted coil for high-pressure, high-temperature environments.

For cryogenic PTFE spring-energized seals, the most common grades used are

  • Virgin PTFE (low friction, extreme temperature tolerance)
  • Glass-filled PTFE (better wear resistance)
  • Carbon-filled PTFE (enhanced dimensional stability)
  • MoS₂ or graphite-filled PTFE (lower wear, improved dry run)
Cryogenic Seals for Low Temperature Situations
Cryogenic Seals for Low Temperature Situations

Seals for Cryogenic Space Applications: Challenges

Engineers face several challenges when specifying cryogenic sealing solutions for space applications. These include thermal contraction, outgassing, material stability, lubrication, rapid pressure transitions, and seal life.

Challenge #1: Thermal Contraction

The extreme cold in space causes both hardware and seals to contract, with traditional elastomeric seals often shrinking and losing sealing force at cryogenic temperatures. PTFE spring-energized seals maintain contact via the spring energizer as it compensates for seal shrinkage. In fact, spring energizers adapt to radial or axial changes, maintaining sealing pressure even at temperatures as low as -250°C.

Challenge #2: Outgassing and Material Stability

Materials with a high volatile content can outgas in a vacuum, leading to the contamination of optics and electronics. However, Virgin PTFE and high-purity filled PTFE variants exhibit minimal outgassing, meeting NASA/ESA standards. They are chemically inert and stable under ultra-high vacuum (UHV) conditions.

Challenge #3: Friction and Lubrication in Vacuum

In space, the lack of atmosphere can make lubrication extremely difficult (especially if vacuum pressures are involved). PTFE is self-lubricating and has one of the lowest coefficients of friction among polymers. In addition, filled PTFE (e.g., graphite or MoS₂) enhances dry-run performance and the spring-energized design ensures low breakout friction and a consistent force profile.

Challenge #4: Rapid Pressure Transitions

Systems transitioning from launch (atmospheric) to space (vacuum) face rapid pressure differential, and traditional elastomeric seals can blow out, crack, or fail to reseat. On the other hand, spring-energized PTFE seals accommodate pressure variations with a controlled energizer preload, while the elastically deforming PTFE jacket absorbs shock without sustaining permanent damage. Additionally, options are available for high-vacuum to moderate-pressure regimes.

Challenge #5: Seal Longevity and Wear

Another serious complication when designing seals for space is that maintenance is likely not possible once a system is deployed in space. Seal wear over long mission durations can lead to leakage or mechanical failure, but PTFE’s wear resistance is enhanced through fillers (carbon, glass, bronze). And the spring maintains sealing force over millions of cycles without fatigue. Advanced EMC also provides fully characterized wear data for mission planning.

Why Choose Seals for Cryogenic Space Applications from Advanced EMC?

Advanced EMC Technologies brings deep materials science expertise and aerospace-focused engineering to the design and production of PTFE spring-energized seals, especially for extreme environments like cryogenic sealing in space.

Every mission has unique sealing requirements, and Advanced EMC offers an extensive portfolio of PTFE formulations, energizer types, and precision manufacturing options to meet them. Whether the application calls for ultra-low friction, minimal outgassing, or long-term performance under high-cycle dynamic loads, Advanced EMC engineers work closely with aerospace clients to specify the right PTFE grade—virgin, carbon-filled, glass-filled, or dry-lubricant-enhanced—and pair it with the optimal spring geometry (canted coil, helical, or cantilever) for consistent seal loading across a wide thermal range.

Advanced EMC’s cleanroom-compatible production standards, vacuum-bakeout-capable materials, and helium leak testing ensure that components meet the strict demands of satellite, propulsion, and orbital systems. These seals are not only designed to function below -250°C, but also engineered for endurance under pressure transitions, vibration, and long-duration service without re-torque or adjustment.

With an emphasis on low outgassing, dimensional precision, and thermal resilience, Advanced EMC’s spring-energized seals deliver proven reliability in systems where seal failure is not an option.

Conclusion

In the unforgiving environment of space, cryogenic sealing is not just a design challenge—it’s a mission-critical priority. Seals must withstand extreme cold, rapid pressure transitions, and the absence of lubrication, all while maintaining dimensional integrity and sealing force over long durations.

PTFE spring-energized seals provide a robust and reliable solution. With their combination of chemically inert PTFE jackets and precisely engineered metallic energizers, they provide consistent performance where traditional sealing technologies fail. Whether mitigating thermal contraction, eliminating outgassing concerns, or ensuring low-friction sealing in high-vacuum conditions, these seals deliver the reliability aerospace engineers demand.

When you need seals that perform flawlessly in cryogenic space applications, turn to the experts. Advanced EMC Technologies offers custom-engineered PTFE seals tailored to meet the highest standards of thermal, mechanical, and environmental performance. Backed by material expertise and decades of field-proven results, our sealing solutions are ready to meet the demands of your next mission.

by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

How Labyrinth Seals Work: The Science Behind Non-Contact Sealing Solutions

How labyrinth seals work is a subject that blends fluid dynamics, thermodynamics, and smart mechanical design. These non-contact sealing devices are engineered to control the flow of fluids or gases by utilizing a carefully designed path, thereby eliminating friction, direct contact, and the need for lubrication. Especially when made from advanced polymers like PEEK or PTFE, labyrinth seals offer a high-performance solution in applications ranging from cryogenic compressors to high-speed turbines.

In this article, we will examine how labyrinth seals operate, the scientific basis behind their unique effectiveness, the benefits they provide, and the optimal applications for these remarkably efficient sealing solutions.

What Is a Labyrinth Seal?

A labyrinth seal is a non-contact, tortuous-path sealing solution used to control leakage in rotating and reciprocating equipment. Unlike traditional contact seals that rely on mechanical interference to create a barrier, labyrinth seals use a series of grooves, teeth, or ridges that form a tight path for gases or fluids to follow. As the medium moves through this narrow, winding passage, its pressure and velocity drop sharply, reducing the likelihood of leakage.

There are multiple configurations, including radial, axial, and combined-flow labyrinth seals. These can be tailored to suit the specific application, whether the seal is integrated into a rotating shaft, compressor housing, or piston rod assembly.

Polymer labyrinth seals, such as those made from PEEK or PTFE blends, are gaining traction due to their low friction, high chemical resistance, and excellent performance in cryogenic and high-speed environments. They are ideal in applications where thermal expansion, corrosion, or dry running are concerns, such as in aerospace compressors, liquefied gas pumps, and medical devices.

The Science Behind Non-Contact Sealing

At the heart of how labyrinth seals work is a deceptively simple but highly effective principle: use geometry—not contact pressure—to control leakage. The seal’s internal structure forces fluids or gases to navigate a winding, narrow path filled with chambers, grooves, and ridges. As the medium traverses this tortuous route, it undergoes multiple sharp changes in direction and velocity, which induce turbulent flow and result in significant pressure drops across each cavity.

These pressure drops are key to reducing the driving force behind leakage. Instead of stopping flow outright—as contact seals attempt to do—a labyrinth seal gradually dissipates energy from the escaping medium until there’s not enough left to continue moving forward.

Spring Energized Teflon Seals

In rotating applications, the seal can also utilize centrifugal force to push fluids away from the shaft or axis of rotation, creating an additional barrier to leakage. In some designs, particularly those used in compressors and turbines, the grooves or teeth are machined to create swirl-inducing features that further resist forward flow.

When constructed from high-performance polymers, the effectiveness of a labyrinth seal is influenced by the material’s thermal expansion, dimensional stability, and surface finish. For instance, seals made from PEEK or PTFE must maintain tight tolerances to preserve the critical gap that ensures both minimal leakage and non-contact operation. Material selection also affects how well the seal performs under extreme temperature differentials, especially in cryogenic or high-vacuum environments where even minor thermal distortion can impact seal behavior.

Ultimately, labyrinth seals represent a shift from brute-force sealing to fluid dynamic control, making them a superior option where traditional contact seals fall short due to concerns about wear, friction, or contamination.

Advantages of Labyrinth Seals

One of the key advantages of labyrinth seals lies in their non-contact design. Because the seal does not rely on friction between moving parts to function, it eliminates wear from rubbing surfaces, which dramatically extends its service life, especially in high-speed or high-temperature environments. This also eliminates the need for lubrication, reducing system complexity and long-term maintenance costs.

Another significant benefit is the ability to operate under extreme conditions. Labyrinth seals made from polymers such as PEEK or PTFE can withstand wide thermal gradients, resist chemical attack, and maintain sealing performance even when exposed to cryogenic temperatures or dry-running conditions. These materials also offer excellent dimensional stability and low thermal expansion, which is critical in precision applications.

Additional advantages include:

  • Low leakage with minimal energy loss: While not completely leak-proof, labyrinth seals offer an excellent balance of leakage control and energy efficiency, ideal for gas handling and rotating machinery.
  • Contamination resistance: With no metal-on-metal contact or lubricants required, the risk of particulate generation or contamination is minimized. This makes them ideal for cleanroom, medical, and semiconductor environments.
  • Versatility in design: Labyrinth seals can be tailored to a wide range of geometries, clearances, and performance targets. This allows engineers to optimize them for specific pressure differentials, rotational speeds, and media types.

Taken together, these benefits make labyrinth seals a compelling option for engineers who need reliable, maintenance-free sealing in demanding environments.

Limitations and Design Considerations

Despite their many advantages, labyrinth seals are not a one-size-fits-all solution. The very features that make them excellent for non-contact, low-maintenance sealing can also limit their suitability in specific applications.

A key limitation to consider is that labyrinth seals are not completely leak-tight, which is how they are designed to work. They are designed to significantly reduce flow—especially gases—but not eliminate it. This makes them unsuitable for sealing low-viscosity liquids under high pressure, where even minimal leakage can be problematic or dangerous.

Additionally, their performance is highly dependent on precise manufacturing tolerances. Maintaining the optimal clearance between rotor and stator elements is critical: too wide, and leakage increases; too tight, and there is a risk of contact during thermal expansion or shaft deflection. This makes proper design and installation crucial to long-term effectiveness.

Other key considerations include:

  • Material selection: Polymer labyrinth seals must account for thermal expansion, chemical compatibility, and creep. PEEK and PTFE are popular due to their dimensional stability; however, the design must accommodate potential cold flow or softening at high temperatures.
  • Environmental compatibility: While these seals excel in dry, clean environments, they may not be suitable for use where solids, particulates, or slurries are present. The small clearances can become clogged or abraded over time.
  • Installation precision: Slight misalignments during assembly can compromise performance, especially in high-speed rotating systems. Advanced EMC emphasizes the importance of partnering with experienced sealing engineers to ensure proper design integration.

Conclusion

Understanding how labyrinth seals work reveals the remarkable power of precision engineering and fluid dynamics when combined with the right materials. These non-contact sealing solutions offer a unique combination of performance, longevity, and reliability, particularly in high-speed, high-temperature, or cryogenic applications where traditional seals often fail to meet expectations. While they aren’t ideal for every situation, their advantages make them a trusted solution across aerospace, industrial, and motorsports industries.

Suppose you’re looking for a sealing solution that can withstand your most demanding applications. In that case, Advanced EMC Technologies offers industry-leading expertise in polymer labyrinth seals, including custom designs in PEEK, PTFE, and other high-performance materials. Contact us today to find the proper labyrinth seal for your system. Let our engineering team help you seal in performance without compromise.