What are the options for sealing materials for single flange butterfly valves?

1. Soft sealing materials
Rubber:
EPDM (ethylene propylene diene monomer rubber): resistant to weak acid, alkali and water media, applicable temperature -40℃~120℃, commonly used in municipal water supply and drainage systems.
Fluororubber (FKM/VITON): resistant to highly corrosive media (such as acid and oil), temperature range -30℃~204℃, suitable for the chemical industry.
Silicone: resistant to low temperature (-50℃~150℃), suitable for clean media such as food or medicine.
Polytetrafluoroethylene (PTFE):
Resistant to highly corrosive media (such as concentrated acid and organic solvents), temperature resistance -200℃~200℃, but poor creep resistance, requires elastic support structure.
2. Metal hard sealing materials
Stainless steel seal:
304/316L stainless steel: good corrosion resistance, applicable temperature ≤450℃, commonly used in high temperature steam or particle-containing media.
‌Carbide (such as Stellite coating): resistant to high temperature (≤650℃) and high pressure (≤10MPa), suitable for the oil and power industries.
‌Nitrided steel/boronized steel:
Surface nitriding or boronizing treatment improves wear resistance, suitable for high pressure (PN≤32MPa) and frequent opening and closing conditions.
3. Composite sealing materials
‌Graphite composite seal:
‌Flexible graphite + stainless steel wire braiding: temperature resistance -250℃~650℃, stable sealing performance, commonly used in high-temperature gas or steam pipelines.
‌PTFE impregnated graphite: has both PTFE corrosion resistance and graphite temperature resistance, suitable for temperatures -200℃~280℃.
‌Multilayer composite structure:
‌Such as rubber + PTFE combination, elastic compensation improves sealing reliability, suitable for medium and high pressure (PN≤6.4MPa) conditions.
4. Materials for special working conditions
‌Parallel polyphenylene:
Temperature resistance up to 400°C, strong corrosion resistance, suitable for extreme chemical environments.
‌PEEK (polyetheretherketone):
High strength, wear resistance, applicable temperature -100°C~260°C, suitable for high cleanliness pharmaceutical or food grade media.