WHY IS SEALING HYDROGEN FLUORIDE A CHALLENGE?
Because of its harsh nature, hydrogen fluoride is a difficult chemical to seal. If leaked, in any volume, manufacturers must immediately alert an emergency response team. Gaskets for hydrogen fluoride systems must be constructed from materials capable of providing a reliable, leak-free seal and withstanding the chemical’s highly corrosive nature. The Hydrogen Fluoride Industry Practices Institute (HFIPI) offers a Materials of Construction Guideline for both Anhydrous and Aqueous Hydrogen Fluoride, which includes gasket materials.
WHAT MAKES A GASKET HYDROGEN FLUORIDE-RESISTANT?
Due to limited allowable maintenance periods, the flange inner diameter (ID) is subject to corrosion from residual moisture pockets that become trapped during routine cleaning. Use of inadequate materials can also cause flange corrosion.
HFIPI’s recommended standard lists carbon-filled PTFE as a safe and reliable gasket solution for harsh applications involving Hydrogen Fluoride.
While virgin PTFE is also listed in the HFIPI guidelines, its tendency to creep makes it a less effective sealing material.
Although carbon-filled PTFE serves as an efficient sealing material for aggressive chemical processing applications such as hydrogen fluoride, a limited number of manufacturers produce this material — and those who do typically make it very infrequently.