The seat is the primary sealing interface between the valve disc and body. It must:
A well-chosen seat material ensures the valve performs reliably for years. A poor choice can lead to swelling, embrittlement, compression set, or chemical dissolution — all resulting in valve failure.
Best for: Water, wastewater, steam, diluted acids, and caustic solutions
| Property | Rating |
|---|---|
| Temperature Range | -40°C to +130°C (-40°F to +266°F) |
| Water Resistance | Excellent ★★★★★ |
| Oil / Fuel Resistance | Poor ★ |
| Chemical Resistance | Good (acids, alkalis) ★★★★ |
| Ozone / Weathering | Excellent ★★★★★ |
| Abrasion Resistance | Good ★★★★ |
| Relative Cost | Low |
EPDM is the most widely used seat material for butterfly valves in water and wastewater applications. It offers excellent resistance to hot water, steam, and dilute chemicals. However, it swells and degrades rapidly when exposed to oils, hydrocarbons, or petroleum-based fluids.
Best for: Oils, fuels, lubricants, and hydrocarbon-based fluids
| Property | Rating |
|---|---|
| Temperature Range | -30°C to +100°C (-22°F to +212°F) |
| Water Resistance | Good ★★★ |
| Oil / Fuel Resistance | Excellent ★★★★★ |
| Chemical Resistance | Moderate ★★★ |
| Abrasion Resistance | Excellent ★★★★★ |
| Relative Cost | Low |
NBR is the preferred choice when the process fluid contains oils, greases, or hydrocarbons. Its excellent oil resistance makes it ideal for fuel handling, lubrication systems, and industrial hydraulic applications. NBR is also available in coated disc configurations for enhanced corrosion protection.
Best for: Corrosive chemicals, high temperatures, high-purity applications
| Property | PTFE | FEP | PFA |
|---|---|---|---|
| Max Temp (Continuous) | 200°C | 150°C | 260°C |
| Chemical Resistance | Excellent | Excellent | Excellent |
| Friction Coefficient | 0.05-0.10 | 0.08-0.15 | 0.05-0.12 |
| Permeability | Low | Very Low | Lowest |
| Cost | Moderate | Higher | Highest |
PTFE lined butterfly valves are essential in chemical processing, pharmaceutical, and petrochemical applications where aggressive chemicals would destroy elastomeric seats. The inert fluoropolymer lining resists attack from nearly all industrial chemicals and provides a non-stick surface that prevents fouling.
Best for: High-temperature applications, aggressive chemicals, vacuum service
| Property | Rating |
|---|---|
| Temperature Range | -20°C to +205°C (-4°F to +400°F) |
| Oil / Fuel Resistance | Excellent ★★★★★ |
| Chemical Resistance | Excellent ★★★★★ |
| Ozone Resistance | Excellent ★★★★★ |
| Relative Cost | High |
Viton offers the broadest chemical resistance among elastomeric seat materials and the highest continuous temperature rating at 205°C. It is the material of choice when EPDM or NBR cannot meet the temperature or chemical requirements, but a fully lined PTFE valve is not justified.
Best for: Strong oxidizing chemicals, ozone exposure, outdoor applications
| Property | Rating |
|---|---|
| Temperature Range | -30°C to +120°C (-22°F to +248°F) |
| Chemical Resistance | Excellent (oxidizing) ★★★★★ |
| Weather / Ozone | Excellent ★★★★★ |
| Color Stability | Excellent (white/colored) |
| Relative Cost | Moderate |
Hypalon is valued for its outstanding resistance to oxidizing chemicals (chlorine, bleach, hydrogen peroxide) and excellent weatherability. It is commonly specified in water treatment disinfection systems and outdoor installations.
| Application / Fluid | Recommended Seat Material | Why |
| Potable water | EPDM (WRAS/NSF 61) | WRAS and NSF 61 approved, excellent water resistance |
| Wastewater / sewage | EPDM | Good abrasion resistance, cost-effective |
| Hot water / steam | EPDM | Excellent hot water resistance up to 130°C |
| Crude oil / petroleum | NBR | Superior oil and fuel resistance |
| Hydrocarbon fuels | NBR | Resists swelling in gasoline, diesel, kerosene |
| Strong acids (H₂SO₄, HCl) | PTFE Lined | Chemically inert, handles full acid concentration |
| Caustic soda (NaOH) | EPDM or PTFE | EPDM for dilute, PTFE for concentrated |
| Chlorine / bleach | Hypalon® or PTFE | Excellent oxidizing chemical resistance |
| High-temperature chemicals | PTFE / PFA Lined | Withstands up to 260°C |
| Food / beverage processing | EPDM or PTFE | FDA compliant grades available |
| Pharmaceutical | PTFE Lined | Non-contaminating, easy to clean |
| Seawater / brine | EPDM | Excellent saltwater resistance |
| Compressed air | EPDM or NBR | Both suitable, EPDM preferred if lubricant-free |
| Temperature Range | Suitable Seat Materials |
|---|---|
| -40°C to -20°C | EPDM (low-temp grade), PTFE lined |
| -20°C to +50°C | All materials suitable |
| +50°C to +100°C | EPDM, NBR, PTFE, Viton |
| +100°C to +130°C | EPDM, PTFE, Viton |
| +130°C to +205°C | Viton, PTFE lined |
| +205°C to +260°C | PFA lined (premium PTFE) |
A replaceable cartridge seat design allows the seat to be swapped out in the field without removing the valve from the pipeline. This is particularly valuable for large-diameter valves where removal is labor-intensive. Cartridge seat valves offer a lower total cost of ownership because the valve body can outlast multiple seat replacements
In some designs, the disc is coated with EPDM or NBR rubber that acts as the sealing surface against a smooth body bore. This coated disc configuration is commonly used in lug-type butterfly valves and provides excellent corrosion protection for the disc itself.
There is no single best material. EPDM is best for water/wastewater, NBR for oil/fuel, PTFE for chemicals and high temperatures. Choose based on your specific fluid, temperature, and pressure conditions.
EPDM seats handle continuous service from -40°C to +130°C (-40°F to +266°F), with peaks up to 150°C.
EPDM resists water, steam, ozone, and weathering (ideal for water/wastewater). NBR resists oils, fuels, and hydrocarbons (ideal for petroleum fluids).
Yes. PTFE handles up to 200°C, PFA up to 260°C. They are suitable for high-temperature chemical processing.
EPDM seats in water service typically last 5-10 years. PTFE seats in chemical applications may require replacement every 1-3 years depending on conditions.
A replaceable cartridge seat can be swapped in the field without removing the valve from the pipeline, significantly reducing maintenance downtime.
Need Help Selecting the Right Valve Seat Material?
Contact our engineering team for technical assistance: james@lauxvalve.com | +86 18920833829
