Case Study

Case Study: Eclipse Develops Polymer Superfinishing Technique for Optimal Cryogenic Gas Sealing

From mud and road dust to processed cheese to chemicals with names no one can pronounce, Eclipse has designed and manufactured sealing solutions for many different medias.

But one of the most challenging medias to seal is the first element on the periodic table: Hydrogen.

Hydrogen’s extremely small molecule size and the fact it needs to be sealed at cryogenic temperatures, make it a difficult element for all seal designs and materials to handle.

“ Eclipse's efforts 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.”

The Client’s Issue

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

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

With ever increasing payload requirements and intensive cost sensitivity, rocket booster design and technology has been advanced to meet the demands and requirements.

Current Sealing Technology and Requirements

Sealing technology, being a critical part of performance and efficiency, has been pushed to new limits as well.

Sealing Requirements:

  • Media: GH2
  • Pressure, Operating/Proof/Burst: 4,750/6,500/12,500 PSIG
  • Life Cycles: 10,000
  • 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 our team 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 wide, extreme temperature range and friction requirements of the valve meant the use of soft, high sealabilty materials would not be possible.

We knew the application parameters meant using a PTFE based seal material would be required. We also knew that a typical, standard PTFE spring energized seal would not meet the customer’s leakage requirement.

We turned our attention to surface interaction between the seal lip and hardware surface.

The Eclipse Solution

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.

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

In this case, to further improve sealability performance, we used its EZ030 [link to spec sheet] modified PTFE.

How it Performed

EZ030’s higher molecular structure density (when compared to standard PTFE) both improved gas permeability resistance and allowed for an exceptional surface finish.

Our team’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.

Find out how you can benefit from Eclipse’s superfinishing technique.

Find out how you can improve the seal performance and longevity of your reciprocating machinery

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