Wafer Butterfly Valve — WCB Body, SS304 Disc and PTFE Coated EPDM Seat

This wafer butterfly valve combines three materials selected to offer moderate chemical resistance at the lowest possible cost: WCB carbon steel body internally protected by the seat, CF8 disc (cast equivalent of 304 stainless steel), and a PTFE coated EPDM seat — a hybrid seat featuring a PTFE fluoropolymer layer as the only surface in contact with the fluid, over an EPDM core that provides the elasticity necessary for a durable, tight seal.

It is the right choice when greater chemical resistance is required than the standard cast iron butterfly valve with EPDM seat, but the budget does not justify the higher-cost SS316L body. The PTFE-coated EPDM seat protects the EPDM from direct contact with the fluid — significantly extending the seat's lifespan in fluids that would degrade pure EPDM.

Construction Materials

• Body: WCB Carbon Steel — high mechanical strength support structure and lower cost than SS316
• Disc: CF8 (ASTM A351 Gr. CF8) — cast equivalent of 304 stainless steel. Higher corrosion resistance than the cast iron body; more economical than the SS316 disc in other variants
• Seat: PTFE coated EPDM — elastomeric core for resilience and elastic recovery + outer PTFE layer in contact with the fluid for chemical resistance
• Shaft / Stem: SS316 Stainless Steel with PTFE retainers

SS304 vs. SS316 in the Disc — Justified Cost Difference

The CF8 disc (cast equivalent to SS304) has a lower molybdenum content than SS316 — which means lower resistance to chloride pitting compared to SS316. However, in this valve, the disc is in contact with the fluid only in the open position, and the PTFE-coated EPDM seat is the primary chemical barrier in the closed position. For most moderately corrosive aqueous fluids where this valve applies, the CF8 disc offers sufficient resistance at a significantly lower cost than SS316.

For fluids with high chlorides (seawater, brines) or higher concentration acids where the CF8 disc might suffer pitting in continuous service, specify the variant with SS316L body and SS316L disc.

Technical Specifications

• Mounting Type: Wafer — between DIN PN10/16 or ANSI 150 flanges
• Nominal Pressure: PN16
• Operating Temperature: -20 °C to +130 °C (limited by the EPDM core of the seat)
• Available Diameters: DN50 (2") to DN600 (24")
• Design Standard: EN 593
• Actuator Interface: ISO 5211

Compatible Fluids

• ✅ Industrial process water with pH 4–10
• ✅ Water with moderate chlorides up to 500 ppm (verify with CF8 disc)
• ✅ Sulfuric acid H₂SO₄ up to 20%
• ✅ Hydrochloric acid HCl up to 15%
• ✅ NaOH up to 20%
• ✅ Sodium hypochlorite NaClO up to 10%
• ✅ Acetic acid up to 50%
• ✅ Chlorinated water up to 5 ppm
• ✅ Wastewater with moderate chemical content
• ⚠️ Seawater and chlorides >500 ppm: CF8 disc may pit — prefer variant with SS316 disc
• ⚠️ Oils and fuels: outer PTFE is compatible but the EPDM core may be affected — use NBR or Viton seat
• ⚠️ Maximum temperature 130 °C — EPDM core limits temperature

Positioning within the range of EPDM/PTFE Seated Butterfly Valves

Available Actuation Versions

• Manual with lever: DN50 to DN200
• Manual with gear reducer: DN200 to DN600
• With pneumatic actuator: Single acting NC or NO, double acting. ISO 5211 + NAMUR.
• With electric actuator: 24 VDC, 110 VAC, 220 VAC. ON/OFF or modulating 4–20 mA.

For the complete range of SS316 butterfly valves, see stainless steel butterfly valve category →

Technical Data Sheet

Data Sheet