by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

Polymer Labyrinth Seals for Wind Turbine Gearboxes: Reducing Contamination and Extending Service Life

Wind turbine gearboxes operate in some of the harshest environments, from salty offshore platforms to dust-laden plains, and must run continuously for years with limited access to maintenance. At the heart of these systems lie high-speed rotating components, including the gearbox output shaft, the generator interface, and, in some direct-drive designs, high-speed rotor hubs.

This blog post examines polymer labyrinth seals as a solution for sealing the gearbox in powerful wind turbines.

Wind Turbine Gearboxes 

The gearbox is one of the most critical components in a wind turbine. It converts the relatively slow rotation of the blades into the high-speed rotational motion required by the generator. If the gearbox fails, the entire turbine is offline, leading invariably to lost power production and costly repairs. The fact that turbines are often installed in remote or offshore locations means that repair logistics can be difficult, expensive, and dangerous. 

The Challenge of Gearbox Contamination in Wind Turbines

Wind turbine gearboxes are highly susceptible to contamination and loss of lubricant through seal leaks. Sources of contamination are many, including dust, moisture, salt spray, and environmental particulate matter, all of which depend on the location of the turbine. Such contamination leads to several problematic issues, including accelerated bearing and gear wear, significant efficiency losses, and lubrication degradation. 

Spring Energized Teflon Seals

Traditional sealing solutions, such as lip seals and metal labyrinth seals, often fail short in long-term wind turbine use. 

Polymer Labyrinth Seals for Wind Turbine Gearboxes

Labyrinth seals address sealing challenges with a non-contact design that forms a tortuous path to block ingress and retain lubrication without generating friction, heat, or wear. Most contaminants and lubrication will lose their kinetic energy before they are able to traverse the entire labyrinth. This design makes it extremely difficult for dust, moisture, or lubricant to move in or out. The fact that it is non-contact means that it does not add any friction and eliminates the heat generated and energy loss associated with it.

When PTFE, PEEK, and Torlon labyrinth seals are used in place of metal, the final result is a lightweight, corrosion-resistant seal that can stand up to harsh conditions while keeping friction and wear to a minimum. In addition, these polymers support more design freedom when it comes to geometries as well as excellent tribological performance even under the harsh environments associated with wind turbine gearboxes. 

These non-contact seals prevent contamination and lubrication by making it almost impossible to pass through the labyrinth without losing energy, extend the service of the wind turbines, and support less frequent (and often dangerous) maintenance. 

Performance Benefits in Wind Turbine Gearboxes

Polymer labyrinth seals are ideal solutions for wind turbine gearboxes. They are non-contact solutions, which eliminate the friction and wear experienced by traditional lip seals. This also means that the gearboxes will not suffer a loss of efficiency related to seal wear, as well as the accelerated wear associated with the ingress of problematic contamination and the problematic loss of lubrication. Because they are polymers and have excellent chemical compatibility, corrosion issues are eliminated. Polymer labyrinth seals are also resistant to ozone aging, depending on the type of material selected.

The effectiveness and long life of these polymeric seals extend the service life of wind turbine gearboxes. This also reduces the costly downtime and logistics associated with repair and regular maintenance.

Conclusion

Polymer labyrinth seals are a critical reliability upgrade for wind turbine gearboxes, with benefits that include extended service life, reduced downtime, and lower maintenance costs. The combination of a non-contact seal with engineering polymers leads to an excellent solution for the numerous sources of contamination that could otherwise destroy a wind turbine gearbox.

If you are working on a new wind turbine or seeking to upgrade existing wind turbines, it is hard to go wrong with high-quality polymer labyrinth seals. And that happens to be one of our specialities at Advanced EMC.

PTFE Spring Energized Seals for Cryogenic Applications
by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

Designing Spring-Energized Seals for Cryogenic Hydrogen Systems

Cryogenic hydrogen systems are among the most challenging to specify reliable sealing solutions for, with issues ranging from the extremely low temperatures to hydrogen permeability and embrittlement. 

This blog post explores the challenges and proposes a proven solution: PTFE spring-energized seals. And discusses how Advanced EMC can help.

Challenges of Sealing in Cryogenic Hydrogen Systems

There are several key problems that arise when specifying a sealing solution for a cryogenic hydrogen application. Four of these are discussed below.

Extremely Low Temperatures

The first issue with sealing cryogenic hydrogen is the temperature. On average, hydrogen is stored and transported at about  253 °C. At such low temperatures, conventional elastomers will lose elasticity, shrink, and possibly crack. In addition, thermal contraction will cause the seal contact pressure to drop. And just because a seal is predicted to work at room temperature, it will fail disastrously when the temperatures drop to H2 storage temperature. 

Hydrogen Permeability and Leakage Risks

Hydrogen is extremely small, with diatomic hydrogen being the smallest molecule in the known universe. This small molecular size means that  H2 can diffuse through many different materials. The resulting permeability leads to serious risks of leakage or even explosive decompression during warm-up cycles. Resolution of these issues includes sealing solutions with exceptionally high tolerance, with a seal lip material that maintains integrity even at the molecular level.

Hydrogen Embrittlement

Hydrogen embrittlement is a problem for many materials. In short, hydrogen can diffuse into metal components and make them increasingly brittle over time. This embrittlement leads to cracked metal seal housings. 

Material Compatibility

Many conventional seal materials will become unsuitable when cryogenic temperatures are reached. Examples include thermal expansion mismatches between components and a loss of flexibility, which are among the top problems. Material selection quickly becomes limited to options such as PTFE and certain fluoroelastomers because only a handful of materials can retain their flexibility, dimensional stability, and roughness at the temperatures required for handling H2.

Spring Energized PTFE Seal

Spring-Energized Seals for Cryogenic Hydrogen Systems

Spring-energized seals are advanced solutions composed of a polymer seal jacket with an internal metallic spring energizer. Because of the spring energizer, a consistent sealing force can be achieved even in the presence of issues such as dimensional shifts and contraction. 

A properly designed spring-energized seal can effectively maintain a seal in liquid H2 environments. Such a seal can handle pressure cycling and dimensional changes, and reduces friction and wear compared to conventional seals.

Here’s a summary of how a spring-energized seal with a PTFE / filled PTFE jacket addresses the challenges described thus far:

ChallengeProblemPTFE Cryogenic Seal Advantage
Low TemperaturesElastomers shrink, crack, and lose sealing force at –253 °C.PTFE stays flexible and dimensionally stable with low thermal contraction.
Hydrogen PermeabilityH₂ diffuses through many materials, causing leakage or decompression.PTFE has low gas permeability; spring-energized lips maintain tight contact.
Hydrogen EmbrittlementMetals become brittle and crack under hydrogen exposure.PTFE is immune to embrittlement and protects surrounding components.
Material CompatibilityMost materials fail due to brittleness or expansion mismatch.PTFE retains flexibility, stability, and chemical resistance at cryogenic temperatures.

Advanced EMC Spring-Energized Seals

At Advanced EMC, we specialize in PTFE spring-energized seals. We offer cryogenic-rated PTFE jackets that use corrosion-resistant metal allows, such as Hastelloy or Inconel, for the enclosed energizers. Precision engineering and manufacturing mean optimized hacket profiles for containing H2 and machining as needed to achieve an extended service life. We have developed sealing solutions for various industries, and offer tailored spring force, geometry, and material properties for spring-energized solutions.

Conclusion

Sealing cryogenic liquid H2 involves major challenges. The extremely low temperatures, hydrogen permeability, hydrogen embrittlement, and material compatibility all lead to problems that conventional sealing solutions do not address well.  Spring-energized PTFE seals, however, address these issues and more for a robust, rugged, and reliable solution.

Advanced EMC’s expertise ensures seals that meet the unique demands of cryogenic hydrogen systems, enabling safe, efficient use of hydrogen in advanced energy applications. Contact us today to learn more!