Types of Gasket Materials for Low Temperature and Cryogenic Freezers18 December 2017
It takes a specially designed gasket material to keep low-temperature fluids in check in cryogenic freezers. A normal seal will freeze solid when such arctic climates are encountered. At that point, jointing brittleness ensues, the issue is likely compounded by ice-saturated creep, and the high-performance substance ends up crumbling. All is not lost, for there are gasket materials that thrive in cryogenic freezers. First, however, what is cryogenics?
According to a reputable engineering resource, cryogenics is the division of science that deals with extremely cold applications. Think of an engineering system that operates below -150°C, and then add liquefied gas to that image. Specialized refrigerants, liquid nitrogen, and a host of other bitterly cold applications, they all fall under this umbrella term. Despite the frosty nature of these equipment usage domains, the ancillary components employed here look just like a middle of the road freezer system. Only, the pipes are carrying liquefied gases, not a partially chilled refrigerant. In light of the rock-bottom thermal state maintained within these pipes and fittings, we need gasket materials that can withstand this chill factor.
Cryogenic Freezers: Selecting Gasket Materials
Advances in polymer engineering have extended the operational temperature range of many advanced plastics families. Despite the kind of temperature extremes that can freeze gases in their tracks, these polymers remain ductile. Furthermore, the selected gasket material won’t contract drastically as the temperature descends perilously low. Polytetrafluoroethylene (PTFE) is often recruited when this usage domain calls for a sealing family that maintains its finest operating characteristics. Branded as Teflon, this synthetic fluoropolymer is known to be a reliable jointing solution, one that’s used in the aerospace industry and those laboratory situations that rely on extremely low temperatures. Tungsten carbide, another capable cryogenics sealing solution, proves there are several options available, including a number of cermets. Fabricated from ceramic and sintered metals, this latter group is defined as a reinforced composite group. Why, though, are these composites making headway as cryogenics gasketing products?
To answer that question, we have to look beyond gasket material ductility and those thermal contraction effects that weaken the seals within a cryogenic system. Curiously, these fluids are classed as poor lubricators. They’re ‘sticky,’ in that the icy boundaries around the gasket cause face adherence issues. Like that time someone’s finger got stuck to the surface of a freezer’s inner housing, the extreme cold creates a dry-stick effect. Fortunately, the selected glass-filled composites and their just as capable Teflon branded gaskets are designed to defeat this phenomenon.
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