Case Study: Polymer Superfinishing for Optimal Cryogenic Gas Sealing

Doug Montgomery • May 28, 2025

Over the years, Eclipse has designed and manufactured sealing solutions for media ranging from mud to processed cheese to chemicals with names no one can pronounce and most everything in between.


By far, one of the most challenging media to seal is the first element on the periodic table, Hydrogen. Its extremely small molecule size and the fact that sealing needs to be done at cryogenic temperature present difficulties for all seal designs and materials.

Eclipse was approached by a valve component manufacturer for a sealing solution to be used on a heavy-lift expendable launch vehicle. 


The valve is used in the Hydrogen fuel side of advanced rocket boosters designed to carry the next generation of both cargo and manned exploration vehicles to deep space. 


With ever-increasing payload requirements and intensive cost sensitivity, rocket booster design and technology have been advanced to meet the demands and requirements. Sealing technology, being a critical part of performance and efficiency, has been pushed to new limits as well.


Sealing Requirements:

  1. Media: GH2
  2. Pressure, Operating/Proof/Burst: 4,750/6,500/12,500 PSIG
  3. Life Cycles: 10,000
  4. Operating Temperature Range: -200 to +200°F

While Eclipse’s Spring Energized Seals regularly perform under these operating conditions, the extremely stringent leakage requirement needed by the customer presented Eclipse with a unique challenge. Normally, such tight leakage constraints are achieved with the use of very soft and compliant seal materials such as specialized O-Rings or Thermoplastic Elastomers.


But the extreme temperature range and friction requirements of the valve meant that the use of soft, highly sealable materials would not be possible.


Polymer Superfinishing


Eclipse knew that the application parameters meant the use of a PTFE based seal material would be required. Eclipse also knew that a typical, standard PTFE spring energized seal would not meet the customer’s leakage requirement. Eclipse turned their attention to surface interaction between the seal lip and hardware surface. If the seal lip and hardware surface finish could be optimized to exceedingly high levels then the permeability of the Hydrogen between the mating interfaces could be greatly reduced.


Superfinishing has been a technique used on metals for many years, but methods used for metals don’t typically translate or work well for polymers. Eclipse’s in-house manufacturing and design team developed both special tooling and techniques to provide a similar superfinish on PTFE based seal materials.


Eclipse’s many years’ worth of PTFE machining experience was key in developing and making this technique production ready.

Optimizing PTFE Machining with Eclipse’s EZ030 Technology


It might be easy to think that machining plastic would be less difficult than steel or metallic materials, but anyone who has tried probably quickly found out it’s not the case. Eclipse grinds much of its own tooling and utilizes cutting inserts out of high-speed steel, carbide, and diamond.


Eclipse developed special large-radius tooling to aid in the finishing. From there, “speeds and feeds” were adjusted in the CNC until the best finish was possible was achieved. While taking more time than standard machining techniques, the gains in the end were well worth it.


To further improve sealability performance, Eclipse used its EZ030 modified PTFE. EZ030 is the unfilled variant of our enhanced PTFE. It retains all the advantages of standard PTFE, including chemical compatibility, friction properties, and temperature range. The key benefit of this modified version is its improved material adhesion during processing, which leads to a denser final structure. This denser structure enables EZ030 to achieve superior machined finishes on seals and offers enhanced permeation resistance. Consequently, it provides an unparalleled seal for use in gaseous media such as oxygen, hydrogen, nitrogen, and natural gas.


Eclipse’s effort in developing the superfinish technique, combined with the excellent properties of EZ030, resulted in a seal that met both the customer’s tough leakage requirement and life cycle targets.


If you have an application that can benefit from Eclipse’s superfinishing technique, please contact us today.

The Different Types of Seal Glands and How to Choose the Right One

By Doug Montgomery • October 21, 2026
When designing a successful sealing system, factors such as leakage control, wear resistance, and seal material selection often receive the most attention. However, another critical component can have just as much influence on performance: the seal gland. A seal gland, also referred to as a groove, is the space within the hardware that houses and retains a seal. Its design affects not only how the seal functions but also how easily it can be installed, removed, or replaced. Different seal materials and configurations require different gland designs. For example, an elastic O-Ring may be relatively easy to install in a solid gland, while a PTFE spring-energized seal may require a split or stepped configuration to prevent damage during installation. Understanding the different types of seal glands is essential when selecting a sealing solution. Below, we'll explore four common gland designs, their advantages and limitations, and the seals best suited for each. What Are the Four Main Types of Seal Glands? The four common types of seal glands used in rod and piston sealing applications are solid, open, split, and stepped glands. Each offers different benefits depending on the seal material, installation requirements, and hardware configuration. Solid glands feature a simple rectangular groove and are commonly used with O-Rings and certain O-Ring energized PTFE seals. Open glands allow seals to be installed directly into a counterbore and are typically best suited for metal-cased seals, including rotary lip seals and cased spring energized seals. Split glands use a removable retaining component to simplify seal installation, removal, and maintenance. They are particularly useful for spring energized seals and applications requiring frequent seal replacement. Stepped glands incorporate a small retaining step that secures the seal without additional hardware. They are often used in spring energized sealing applications where a one-piece hardware design is preferred. Choosing between these designs involves balancing installation requirements, manufacturing complexity, and long-term seal performance. Solid Glands

Rotary Lip Seals: Crimped Case Seal vs. Componentized Design

By Doug Montgomery • September 14, 2026
Compare Crimped Case Seals and traditional componentized rotary lip seals, including their advantages, limitations, costs, and ideal applications.

The Pros and Cons of Channel Seals

By Doug Montgomery • August 26, 2026
Learn the advantages and limitations of Channel Seals, including friction, wear life, PTFE performance, machining requirements, and dynamic sealing considerations.
CIP Spring Seal Silicone

Clean-in-Place (CIP) Seals and FDA Compliance in Sealing Applications

By Doug Montgomery • July 15, 2026
Learn how Clean-in-Place (CIP) seals improve sanitation, reduce downtime, and support FDA-compliant sealing applications in food, pharmaceutical, and industrial equipment.