Below is a general butterfly valve seat selection guide. When selecting seats, always consult the pressure / temperature charts and corrosion resistant guide or contact the factory for engineering help.
EPDM (E)
Rated for temperatures -30°F to 250°F. EPDM is an abbreviation of a compound called Ethylene Propylene Diene Monomer. It is also commonly called EPT, Nordel, and EPR. EPDM is used extensively in the HVAC industry due to its resistance to polar compounds such as water, phosphate, esters, ketones, alcohols, and glycols. The EPDM material is also applicable for handling concentrated sulfuric acid, 20% sodium hypochlorite (bleach), chlorinated water for swimming pools, and other alkaline solutions. EPDM is not resistant to hydrocarbon solvents and oils, chlorinated hydrocarbons, turpentine, or any other petroleum based oils.
BUNA-N (B)
Rated for temperatures 0°F to 180°F. Buna-N is also commonly identified as NBR, NITRILE, or HYCAR. It is an excellent general-purpose elastomer suitable for use with air, water as well as most petroleum oils and greases, automotive gasolines (except those which have additives), alcohols and glycols, L-P gases, propane and butane, fuel oils and many other fluids. It also exhibits good abrasion resistance, and excellent resistance to compression set.
PTFE (P)
Rated for temperatures -20°F to 300°F. The Teflon liner overlays EPDM which is bonded to a rigid phenolic ring on the outside seat perimeter. The PTFE extends over the seat faces and outsides flange seal diameter, completely covering the EPDM elastomer layer of the seat, which provides the resilience for sealing valve stems and the closed disc.
VITON (V)
Rated for temperatures 0°F to 300°F. Viton is an E.I. DuPont trademark. Flourel is 3M’s trademark for the equivalent fluorocarbon elastomer. This material offers higher temperature resistance and outstanding chemical resistance. It is resistant to hydrocarbon products and mineral acids, both dilute and concentrated solutions. However, it is never to be used in steam applications and is relatively poor in water service.
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