Butterfly Valve Seat Materials and Temperature Limits

The seat (resilient liner) is a critical component in butterfly valves, providing the primary sealing element between disc and body. Seat material selection determines the valve's temperature range, chemical compatibility, and leakage performance throughout its service life.

Elastomeric Seat Materials

• EPDM (ethylene propylene diene monomer): water, steam to 150°C, ozone resistant

• NBR (nitrile): oil and fuel service, -40°C to 100°C

• Neoprene (CR): general purpose, mild acids and alkalis

• BUNA-N: similar to NBR, good hydrocarbon resistance

• Viton (FKM): broad chemical resistance, up to 200°C continuous

PTFE Seat Characteristics

PTFE (polytetrafluoroethylene) seats provide excellent chemical resistance to nearly all process fluids except molten alkali metals and fluorinating agents. PTFE is self-lubricating, which reduces operating torque and extends seat life. Temperature range is typically -50°C to 180°C. Filled PTFE grades (glass-filled, carbon-filled) improve wear resistance and dimensional stability at elevated temperatures.

Metal Seat Materials

• 316 stainless steel: general corrosive service, temperatures to 450°C

• Stellite overlay: high-temperature abrasive or erosive service

• Inconel: high-temperature oxidizing environments

• Hastelloy C-276: highly corrosive chemical service

• Metal seats required for fire-safe certification and high-temperature service

Temperature De-Rating

Elastomeric seats lose strength and resilience at elevated temperatures, reducing sealing effectiveness and accelerating wear. Published temperature limits represent the maximum continuous service temperature; cyclically varying temperatures, steam condensate, or intermittent high temperatures may require de-rating. For steam service, EPDM is commonly selected but must be de-rated to 130°C for continuous service to ensure adequate service life.

Seat Selection for Chemical Compatibility

• Chemical compatibility charts cross-reference seat material vs. fluid exposure

• Concentration and temperature affect compatibility (dilute acid vs. concentrated)

• Hydrocarbons swell many elastomers, causing seat distortion and leakage

• Steam at high pressure and temperature limits most elastomers

• Consult manufacturer for specific fluid, concentration, and temperature combinations