by Sara McCaslin, PhD Sara McCaslin, PhD 1 Comment

Spring-Energized Seals for Cryogenic Environments

Cryogenic environments deal with temperatures that range from below freezing all the way down to absolute zero, which is -460° F (or -273° C). Trying to seal fluids and gases at those types of extreme temperatures, but one of the most effective sealing solutions for cryogenic environments is the use of a spring-energized seal. 

Spring-Energized Seals

Energized seals are often used in situations where standard seal designs simply cannot provide the performance needed. And when cryogenic temperatures are involved, finding a reliable seal design is extremely challenging — and failure to do so can be fatal. 

How Spring-Energized Seals Work

A spring-energized seal includes a metallic spring (usually in the form of a coil) that applies a near constant load throughout the circumference of the seal. That load enables the lip to remain in contact with the mating surface, even during pressure and temperature variations as well as dimensional changes. In addition, the spring helps the seal compensate for eccentricity, misalignment, and wear. More importantly in cryogenic environments, energized seals can compensate for dimensional changes related to temperature variations.

The result of using a spring energizer is a highly reliable, almost leak-proof seal. This can be especially important when there are safety and environmental regulations are involved, as is often the case when cryogenic materials are in use. In addition, spring-energized seals can be used with both static and dynamic applications, with dynamic including rotary, linear, and oscillating motion (as well as any combination of these).

There are several different types of spring-energizers, from simple elastomeric o-rings and familiar coil springs to V springs, helical flat springs, and cantilevered finger springs. For cryogenic applications, V ribbon springs are typically used. They are found in the harshest of applications, including vacuum pressures and/or cryogenic temperatures.

 

For cryogenic applications, the spring lip is often made of PTFE and the energizing spring is made of metal. Typical spring metals include 17-7 precipitation hardening stainless steel or 301/304 stainless steel, Elgiloy, Hastelloy, Inconel, or 316 stainless steel.

Cryogenic Applications for Spring-Energized Seals 

Spring-energized seals are successfully being used for a wide in a variety of cryogenic applications:

  • Magnetic resonance imaging (MRI)
  • Biosystems
  • LNG fueling systems and compressors
  • Pharmaceutical and medical research
  • Rocket propulsion filling systems
  • Scientific instrumentation
  • Specialty gas manufacturing
  • Infrared telescopes
  • Radio astronomy
  • Satellite tracking systems

Typical fluids and gases involved include LOX (Liquid Oxygen), liquid Helium, liquid Hydrogen, liquid Xenon, refrigerants, coolants, liquid methane, LNG (Liquid Natural Gas), and LPG (Liquid Petroleum Gas). More specific examples include LAR (Liquid Argon) used in surgical environments, LN2 (Liquid N2) used in environmental test chambers, LCO2 (Liquid CO2) for cleaning and deburring. 

Conclusion

While finding a solution for a cryogenic sealing application can be challenging, it is certainly far from impossible. Spring-energized seals can provide durable, reliable sealing power in even the harshest conditions — including extremely low temperatures. By combining the right type of coil, seal geometry, and materials, you can engineer the right spring for applications ranging from rocket development to bioengineering.

— One Comment —

  1. We are developing a cryovalve for scientific instrument applications that require s spring energized PTFE O-ring seal, and we can accept a seal in the range of 0.07-0.08″ cross section and a 0.39-0.43″ ID. What seals do you have in this range and what are your lead times? Thank you.

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