The Importance of Selecting the Right Gasket Material for Low Temperature Applications02 July 2019
Gasket installers run the risk of creating untenable situations when they install the wrong products on low-temperature fittings. At the very least, the wrong gasket material will harden and lose elasticity. It’ll experience creep and glass-transition brittleness. Upon stiffening, gaskets can’t compress, not without experiencing damage. As a worst case scenario, cracks propagate throughout seals because they can no longer deform when compressed. So, just to recap, low-temperature applications absolutely require low-temperature gaskets.
All About Subzero Gasket Hardening
Most pliable rubbers can handle light chills. However, few synthetic polymers have the wherewithal to hang loose when attacked by subzero conditions. Whether the cold is outside, perhaps on a pipeline that’s crossing the arctic tundra, or it is part of the flow conditions, as set up on a cryogenics facility, those lesser gasket materials experience compression set issues. Essentially, their tractable long-polymer chains come to a full stop because they can’t endure the ultra-low temperatures. When that happens, the potential energy stored inside a once pliable gasket turns against itself. The energy can no longer be contained by the stiffening sealing substance, so the material starts to crack and break down.
Worst Case Incidents: Cryogenics Leaks
If an inert liquid, a substance that’s normally a gas, leaks out of a freeze-damaged gasket, it’s not going to combust. That doesn’t mean it is safe, not at all. Taken down as low as -150°C, the escaping liquid is dangerous. A few seconds of exposure to that heavier-than-air substance would be enough to cause a nasty case of thermal burn. Skin and soft tissues literally freeze solid when such leaks occur. Then there’s the fact that the leak is probably evaporating. The frozen mist takes to the air and causes respiratory damage. And this is just an inert medium. What about cryogenically frozen hydrogen compounds and methane-based chemicals? As the cracks spread on an incorrectly specced gasket, these escaping fluids combust and explode. Heavier than air, these frozen mist clouds must be avoided at all costs.
Damaged gaskets, those that leak cold fluids, can cause serious harm to life and property. Even strong alloys can become brittle when suddenly exposed to low-temperature fluids. Also, on evaporating, a semi-chilled gaseous cloud represents an asphyxiation risk. Then there’s the possibility of a combustion hazard. Liquid hydrogen will obviously combust explosively. Although not exactly combustible, liquid oxygen will burn energetically when fueled by a spark. Finally, some liquefied gasses (including frozen ammonia) become toxic when released. At the end of the day, having assessed all of these destructive scenarios, gasket designers use freeze-resistant graphite, PTFE and Teflon materials to assure seal deformability.
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