What’s the Best Gasket Material for Helium Containment?15 May 2019
Helium cylinders are used in ordinary applications. For instance, florists use helium to fill their balloons. Far and above such mundane practices, the lighter-than-air gas has become an industry-essential substance. And that’s where the problems begin, for helium molecules have a talent for penetrating high-quality seals. Consequently, if a pipe or fitting seal is to thwart this gaseous escape artist, a low permeability gasket material must be sourced.
Low-Permeability Gasketing Candidates
By looking at the periodic table, a gasket designer sees that helium has an atomic number of two. Hydrogen is located at the number one spot, but that fluidic material is highly combustible. Taking that information into account, helium is hard to seal. It leaks past the smallest gaps and through materials that are porous. A good candidate as a low-porosity gasketing rubber would be nitrile. Nitrile seals are made out of dense elastomeric polymers, which won’t readily leak. EPDM (Ethylene Propylene Diene Terpolymer) can’t be penetrated easily, either. If EPDM or Nitrile gaskets don’t suit a specific application, then there are a range of capable fluoroelastomers that will. Best in this class, Viton gaskets stop helium leaks. They also perform well when fitted in applications that oppose different temperature extremes.
Application-Specific Material Impact
That latter issue forces gasket designers to alter their selected sealing materials. Case in point, a helium coolant supply cryogenically chills a bank of hot-running computer servers. The inert gas performs exceptionally well, but the installed gasket cracks because of the icy cold temperatures in use here. Nitrile is the initially chosen material. The elastomer is dense and very nearly leakproof, but it’s not cryogenically suitable. Crossing out the first choice gasket material, the designer opts instead for an equally non-permeable fluoroelastomer.
Introducing A Few Helium Gasketing Examples
Inert by nature, helium is used as a shielding gas. In arc welding applications, the gas stops weld pools from oxidizing. In electronics, the gas super cools hot circuits. Superconducting magnets also use this feature, so a helium supply will likely accompany the high voltage power lines that thread their way towards an MRI machine in a hospital. Of course, there’s the lighter than air floral balloons, too. Scaling up that usage area, large volumes of the gas allow massive blimps and weather balloons to take flight.
Of some concern, this super-light gas is running out. The two-atom molecules climb so high, so far above the Earth’s atmosphere that they escape into space. That means there’s a second reason for sourcing superior helium containment materials. The nitrile and EPDM rings are indeed expected to contain the gas, but they’re also expected to stop this increasingly rare gaseous medium from escaping the bounds of this planet’s atmosphere.
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