EnglishEPDM vs PTFE Butterfly Valve Seats: Selection Guide
In water supply, wastewater treatment, and a wide range of industrial water systems, butterfly valves are widely used for isolation, on–off control, and flow regulation. Within the butterfly valve design, the choice of seat material plays a decisive role in sealing reliability, service life, and long-term operational stability.
EPDM and PTFE are the two most commonly used seat materials. Choosing between them is not about which material is “better,” but about which one can meet the specific requirements of the application—including sealing behavior, chemical compatibility, and stability under the actual temperature and pressure conditions.
What Is an EPDM Seat?
An EPDM seat is a rubber sealing component installed on the inner surface of the butterfly valve body. As a highly elastic material, EPDM relies on elastic compression and recovery when the disc closes, forming a reliable seal against the disc edge. This elasticity allows EPDM seats to tolerate small dimensional deviations and maintain stable sealing performance under typical water service conditions.
What Is a PTFE Seat?
A PTFE seat is made from polytetrafluoroethylene (PTFE) and is classified as a semi-rigid sealing material. Unlike rubber, PTFE has very limited elasticity. When the butterfly valve closes, sealing is achieved primarily through the quality of surface contact between the disc edge and the seat.
PTFE offers excellent chemical stability and a very low coefficient of friction, making it well suited for applications involving chemical additives or where high media purity and chemical resistance are required.
What Do These Differences Mean in Practice?
1. Assembly Tolerance and Manufacturing Precision
- Able to tolerate minor dimensional deviations between the disc and the valve body
- Less demanding requirements for concentricity and roundness
- Well suited for large-diameter valves and water systems with complex or less controlled on-site installation conditions
- More sensitive to disc edge finish and roundness
- Insufficient assembly precision may lead to localized leakage
-
Better suited for projects with clearly defined service conditions and stable, well-controlled manufacturing processes
2. Operating Torque and Valve Handling
EPDM Seats
- Higher coefficient of friction
- Operating torque increases noticeably as valve size increases
- Gear operators or actuators are often required for larger diameters
PTFE Seats
- Extremely low coefficient of friction
- Smoother and lighter opening and closing operation
- More favorable for actuator selection and torque control
3. Long-Term Sealing Stability in Service
EPDM Seats
- Sensitive to temperature, water quality, and ozone exposure
- May harden over long-term service, with reduced elastic recovery
- Sealing failure is typically associated with material aging rather than sudden damage
PTFE Seats
- Practically non-aging and non-absorbent
- Excellent long-term chemical stability
- Sealing failure is more often related to wear or assembly deviation, rather than material degradation
Temperature and Pressure Limits in Water Applications
In butterfly valve water applications, EPDM seats rely primarily on their elastic properties to accommodate changes in temperature and pressure, while PTFE seats depend on material stability and precise structural contact to withstand higher or broader temperature and pressure ranges.
|
Performance Aspect |
EPDM |
PTFE |
|
Temperature Limits |
Continuous: −30 °C to +120 °C Short-term: up to +140 °C |
Continuous: −200 °C to +200 °C Short-term: up to +260 °C |
|
Key Temperature Considerations |
Above +120 °C, thermal aging accelerates, causing gradual hardening and permanent loss of elasticity. Below −30 °C, the material tends to harden and become brittle, significantly reducing sealing elasticity. |
Above +200 °C, mechanical strength begins to decline noticeably and material degradation may occur. Excellent low-temperature performance; retains toughness even under cryogenic conditions. |
|
Pressure Capability |
Typically suitable for PN10–PN25 medium- to low-pressure water systems. Pressure capability decreases significantly at elevated temperatures. |
Standard soft-seated designs are typically suitable for PN10–PN16 (approx. 1.0–1.6 MPa). Higher-pressure applications require anti-cold-flow (creep-resistant) seat designs. |
|
Pressure–Temperature Relationship |
Strongly temperature-dependent; pressure ratings must strictly follow the manufacturer’s pressure–temperature curves. |
Pressure–temperature dependence is relatively weaker; limitations are mainly governed by cold flow (creep) behavior. |
The temperature and pressure ranges above are typical engineering reference values for water-service applications. Actual allowable limits should always be determined based on the valve manufacturer’s design parameters and published pressure–temperature rating curves.
Suitable Water Quality for EPDM and PTFE Seats
EPDM Butterfly Valve Seats
EPDM seats are primarily developed for water-system applications. Under conditions where water composition is well defined and variations are controllable, EPDM offers reliable long-term sealing performance.
Typical suitable water qualities include:
- Clean water, raw water, and filtered water
- Municipal water supply and drainage systems
- Drinking water (using EPDM materials that comply with relevant hygienic approvals)
- Cooling water and circulating water systems (free from oil contamination)
- Neutral water media commonly found in standard water treatment processes
PTFE Butterfly Valve Seats
PTFE seats offer exceptional chemical stability and are largely unaffected by variations in water composition. This makes them particularly suitable for systems where water quality is complex or difficult to fully control.
Typical suitable water qualities include:
- Water containing disinfectants such as chlorine or hypochlorites
- Industrial water with chemical additives
- High-purity water and process water
- Systems where water composition may vary over different operating phases
Quick Selection Guide: EPDM or PTFE?
Choose EPDM when:
- Used in municipal water supply, firefighting, or general water treatment systems
- Large pipe diameters and complex installation conditions are involved
- Greater tolerance to installation deviation and cost control are key priorities
Choose PTFE when:
- The medium is corrosive or chemically active
- Low operating torque and long-term sealing stability are critical
- Operating conditions are clearly defined, with controlled manufacturing and installation quality
Both EPDM and PTFE seats have clearly defined application boundaries. Proper seat selection is not simply a comparison of material properties, but a comprehensive evaluation of the medium characteristics, temperature and pressure conditions, installation environment, and long-term operating requirements.
At Union Valve, EPDM and PTFE seats are selected and configured based on the actual conditions of each water system during butterfly valve design and manufacturing. This approach ensures stable and reliable sealing performance throughout long-term operation.
If you would like confirmation for a specific application, we welcome further discussion based on your actual service conditions.
