Gasket Material Recommendations for Strong Chemicals08 June 2018
Caustic chemicals cause strong materials to smoke and sizzle. Even vulnerable metals experience fatigue and corrosion when a particularly concentrated alkali or acid attacks. If corrosive chemicals can eat durable metals, what chance does a gasket stand of enduring such an attack? To answer that question, read on and learn about the specialized sealing materials that are capable of enduring these aggressive chemical attacks. Let’s begin with sulphuric acid.
Polytetrafluoroethylene is known as Teflon by most. It’s a synthetic polymer that’s equipped with a good-to-moderate acid and alkali resistance feature. Modified PTFE adds exotic fillers to the fluoropolymer backbone so that the soft gasketing material gains mechanical strength.
Ethylene Propylene Diene Monomer
Although EPDM is vulnerable to oil-based fluids, it’s a good candidate for a chemical processing system that’s loaded with salts, acids, and alkalis. For that reason, an engineer clearly wouldn’t select this material as a petrochemical sealer, but the selection process would quickly skip to EPDM if the chemical base was an aggressive chemical. Incidentally, PTFE envelopes are known to further reinforce the capabilities of this gasket material.
This neutral element doesn’t react to the presence of strong chemicals. Instead, the exfoliated flakes withstand high pressures, temperature extremes, and caustic chemical loads. However, graphite is a soft material, which means it won’t perform well when large compressive forces are applied. To solve this issue, steel inserts or wires are added to the carbon base.
Adopting Metal Gaskets
When polymers and fibres don’t work, metal gaskets take up the slack. However, there are countless options here, and some metals will react unfavourably when they’re attacked by a specific chemical. For example, copper and brass are both superior choices, but they will fail if the liquid stream contains an oxidizing agent. Steel is another option, but some ferrous-heavy gaskets are known to corrode when super-heated oxidizing fluids are at hand. Select an alloy that won’t corrode or harden when a selected chemical base receives a heat-induced kick.
Then there are the composites, the gaskets that mix-and-match these different materials. EPDM is a logical choice as a harsh chemical seal, but the ring of material works better when it’s covered in a PTFE envelope. Certain rubbers are moderate chemical resistors, but they gain strength when they’re bound with aramid fibre. Likewise, carbon flakes are mechanically soft but chemically inert. Just add metal to the flexible graphite to equip the gasket with strength. Glass-reinforced Teflon or metal, alloy or metal-reinforced polymer, the materials all defy the oxidizing effects of strong chemicals. But remember, this feature can only be demonstrated if the chemical stream is known.
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