Selecting the right butterfly valve seat material is crucial for ensuring sealing performance, service life, and operational reliability. EPDM, NBR, and PTFE are among the most common seat materials for butterfly valves; however, it is not a simple case of one being inherently "better" than the others—each is suited to different operating conditions.
So, should you choose an EPDM, NBR, or PTFE seat for your butterfly valve?
The answer depends on several factors, including the conveyed medium, medium concentration, operating temperature, pressure, cycling frequency, and valve construction.
Quick Comparison of EPDM, NBR, and PTFE Butterfly Valve Seats
Before diving into the details, you can make a preliminary assessment using the table below:
|
Property / Application |
EPDM |
NBR |
PTFE |
| Water | Excellent | Good | Excellent |
| Potable water | Excellent* | Limited* | Excellent* |
| Mineral oil | Poor | Excellent | Excellent |
| Fuel | Poor | Excellent | Excellent |
| Chemicals | Good** | Moderate** | Excellent** |
| Acids | Limited/Good** | Limited** | Excellent** |
| Alkalis | Good** | Moderate | Excellent** |
| Temperature resistance | Good | Good | Excellent |
| Ozone/weather resistance | Excellent | Moderate | Excellent |
| Typical cost | Low–Medium | Low–Medium | Higher |
| Typical applications | Water, HVAC, wastewater | Oil, fuel, hydraulic systems | Chemicals, corrosive media |
NOTE: * Confirmation required based on specific rubber compound and target market certification requirements.
** Chemical compatibility depends on the specific medium, concentration, temperature, and duration of exposure.
This table serves only as a preliminary reference. The final choice of butterfly valve seat material should be confirmed based on actual operating conditions.
1. How to Choose Butterfly Valve Seat Material?
When selecting a seat, the first question many people ask is, "Which seat material is the best?" Consider buying shoes: if you ask, "What is the best shoe?", the salesperson will surely ask, "Where do you plan to go?" You wear running shoes for running, hiking boots for mountain climbing, and dress shoes for formal occasions.
It is not that hiking boots are "better" than running shoes; rather, they are designed for different usage scenarios. By the same token, regarding valve seat materials, a more pertinent question to ask is:
"Which valve seat material is best suited for my specific operating conditions?"
A comprehensive selection process for butterfly valve seats should consider at least the following factors:
Conveyed medium
Medium concentration
Operating temperature
Operating pressure
Cycling frequency (opening/closing frequency)
Valve structure and maintenance requirements
The same seat material can yield vastly different performance results depending on the combination of operating conditions.
For instance, while EPDM is highly suitable for cooling water, NBR is generally the more logical choice if the pipeline medium is mineral oil.
Similarly, although PTFE offers excellent chemical resistance, EPDM is the most economical choice for standard water systems.
2. EPDM Butterfly Valve Seats: A Common Choice for Water Systems
2.1 EPDM butterfly valve seats are widely used in systems handling water and water-based media.
EPDM demonstrates excellent compatibility with water, ozone, weather conditions, and many diluted chemical media, making it a common choice for:
Water supply and drainage systems
Drinking water systems
Water treatment
HVAC
Cooling water
Irrigation systems
Sewage treatment
Fire protection systems
General industrial water systems
For standard water pipelines—provided there is no contamination by oil-based media—EPDM typically strikes an optimal balance between sealing performance and cost.
When used in drinking water systems, it is also necessary to verify that the specific EPDM compound complies with the drinking water certification requirements of the target country or region.
2.2 When is EPDM not recommended?
2.2.1 Situations where EPDM is unsuitable.
A major limitation of EPDM is its poor compatibility with petroleum-based oils and fuels; if the butterfly valve handles mineral oil, fuel, or similar hydrocarbon media, NBR or another more suitable seat material should generally be considered.
It is worth noting the underlying mechanism here for clarity: hydrocarbon molecules in mineral oil easily penetrate the EPDM rubber matrix → the rubber absorbs the oil and swells → changes occur in the molecular structure and mechanical properties.
2.2.2 What happens during use?
Several issues typically arise:
- Seat swelling
The rubber increases in volume after absorbing oil, causing the dimensions of the seat to change. -Changes in sealing force
Deformation of the valve seat can alter the contact interface between the valve disc and the seat, leading to increased operating torque or reduced sealing performance.
-Gradual loss of original rubber properties
Prolonged exposure can result in softening, reduced strength, and permanent deformation.
-Potential for valve leakage or operational issues
In severe cases, the valve may fail to close tightly, experience increased opening/closing torque, or even suffer seat damage.
3. NBR butterfly valve seats: The preferred choice for oil-based applications
NBR (Nitrile Butadiene Rubber) butterfly valve seats are frequently used with petroleum-based media.
Common applications include:
Mineral oil
Hydraulic fluid
Lubricating oil
Fuel
Oil-water mixtures
Industrial equipment
Compared to EPDM, a key advantage of NBR is its superior resistance to oil and fuel. However, this does not mean NBR is unsuitable for water treatment; rather, its primary strength lies in oil resistance rather than long-term water resistance. For general water, hot water, and many water treatment applications, EPDM is usually the better choice for the seat material due to its superior aging resistance in long-term aqueous environments.
However, NBR should not simply be viewed as an "oil-resistant version of EPDM."
The two materials differ in terms of chemical resistance, ozone resistance, weatherability, and temperature adaptability.
For instance, if a butterfly valve is installed outdoors, one must consider not only the internal pipeline medium but also the impact of ozone, sunlight, ambient temperature, and long-term outdoor exposure on the seat material.
Therefore, the specific operating environment should be taken into account when selecting NBR.
4. PTFE butterfly valve seats: Suitable for highly corrosive chemical applications
PTFE butterfly valve seats are typically used in applications requiring high chemical corrosion resistance.
PTFE offers excellent resistance to many corrosive chemical media, making it common in:
Chemical manufacturing
Corrosive fluid transport
Acid and alkali systems
Solvent systems
Pharmaceutical industry
High-purity media
Certain semiconductor-related processes
PTFE also features low-friction properties and generally offers a wider operating temperature range than standard rubber seats. For instance, in water treatment systems, the operating temperature range for NBR is -10°C to 80°C. Therefore, EPDM is the best choice for the 80°C–110°C range, while PTFE is mandatory for the 110°C–180°C range.
However, please note:
PTFE is not superior to EPDM or NBR in every operating scenario.
For example, if EPDM already meets the requirements for standard cooling water piping, using PTFE might increase costs without necessarily providing tangible benefits—a situation described by the Chinese proverb: "Why use a butcher's cleaver to kill a chicken?"
5. Does the pressure rating determine the seat material?
Not entirely.
A common misconception is that because PTFE seats offer higher performance, butterfly valves equipped with them must have higher pressure ratings.
In reality, a butterfly valve's pressure capability depends not only on the pressure rating but also on the body material, disc material, stem structure, valve size, operating temperature, design standards, and more.
Generally speaking, assuming other conditions remain constant, small-bore butterfly valves with EPDM seats can achieve PN25, whereas those with PTFE seats are limited to PN16. For large-bore butterfly valves, EPDM seats can reach PN16, while PTFE seats are limited to PN10.
Therefore, seat material and pressure rating should be evaluated independently before determining the final, comprehensive valve configuration.
6. Do not select the seat based solely on temperature
While operating temperature is certainly crucial, it should not be the only criterion for selection.
A more rational approach involves a comprehensive assessment of:
Medium + Concentration + Temperature + Pressure + Cycling frequency
For example, a specific chemical medium might be highly compatible with a certain material at ambient temperature, yet the actual operating conditions could shift as the temperature rises. EPDM generally shows good compatibility with dilute sodium hypochlorite (NaOCl) solutions at lower temperatures; however, as the temperature increases, the oxidizing medium accelerates the aging of the rubber, potentially compromising the seat's service life and sealing performance.
Similarly, the actual temperature limits for EPDM and NBR depend on the specific rubber compound formulation and the valve design. For critical or complex operating conditions, it is recommended to request specific material compatibility data from the valve manufacturer rather than relying solely on a generic temperature chart found online.
7. The frequency of daily operation also influences the choice of valve seat.
7.1 The number of daily opening and closing cycles is a factor easily overlooked in actual engineering practice.
The requirements for the valve seat differ significantly between a butterfly valve that cycles only a few times a month and an automated butterfly valve that cycles dozens or even hundreds of times a day.
High-frequency cycling can increase:
Seat wear
Friction between the disc and the seat
Operating torque
Actuator load
Mechanical stress
Therefore, for butterfly valves subject to high-frequency operation, one should not limit the material selection to just EPDM, NBR, or PTFE.
Consideration should also be given to:
Seat design
Disc surface quality
Stem design
Valve operating torque
Actuator selection
Cycle life testing
If the valve requires long-term, high-frequency operation, it is advisable to ask the manufacturer for actual cycle test data.
Actual test data is often more valuable than a mere statement regarding a "theoretical service life of many years."
7.2 What if the butterfly valve remains idle for extended periods?
Not all butterfly valves operate frequently.
Butterfly valves in fire protection systems, standby pipelines, seasonal equipment, and certain emergency systems may need to remain in a fixed position for months or even longer.
In such cases, the valve seat remains under compression for an extended period and may also be affected by temperature fluctuations, material aging, and environmental factors.
Therefore, for butterfly valves kept in long-term standby, one cannot focus solely on sealing performance at the time of installation.
Greater attention should be paid to:
Can the valve seat maintain a reliable seal and proper opening/closing functionality after prolonged periods of inactivity?
For applications such as fire protection and standby water pipelines, this aspect is particularly important to consider during the selection phase.
8. What about media containing particles?
Another factor that is easily overlooked is the presence of particulate matter in the medium.
Sewage, water treatment fluids, slurries, and certain industrial pipeline media may contain varying amounts of suspended particles. At this point, the question is no longer simply:
"Which material offers the best chemical corrosion resistance?"
One must also consider:
Particle size
Particle concentration
Valve disc design
Valve seat design
Wear characteristics
Cleaning and maintenance requirements
In other words, even if a material possesses excellent chemical corrosion resistance, it may still suffer mechanical wear if exposed to high concentrations of abrasive particles over the long term.
For instance, if the medium contains only a small amount of particulates, selecting a seat material compatible with the medium's chemical properties is sufficient. However, if there is a high concentration of particulates, it may be necessary to forgo soft-seated designs in favor of an eccentric hard-seated configuration.
Therefore, when dealing with complex media, both chemical compatibility and mechanical operating conditions must be considered simultaneously.
9. EPDM, NBR, or PTFE? How do you make a quick choice?
You can make a preliminary assessment based on the following guidelines:
9.1 Choose EPDM if:
The medium is primarily water-based
Used for water supply, drainage, or water treatment
Used for HVAC or cooling water systems
Good ozone and weather resistance is required
You wish to control valve costs
9.2 Choose NBR if:
Transporting mineral oil
Transporting fuel
Used in hydraulic oil systems
Good oil resistance is required
9.3 Choose PTFE if:
Transporting highly corrosive chemical media
High acid and alkali resistance is required
Solvents are involved
Operating temperatures are high
Strict media isolation is required
These serve only as preliminary selection guidelines; specific material compatibility verification is still necessary for complex operating conditions.
10. What parameters should be provided when requesting a quote from a butterfly valve manufacturer?
Instead of simply telling the supplier:
"DN200 PN16 butterfly valve, EPDM seat."
It is better to provide as complete a picture of the operating conditions as possible.
It is recommended to provide at least the following:
-Medium:
-Medium concentration:
-Normal operating temperature:
-Maximum operating temperature:
-Operating pressure:
-Valve size:
-Connection standard:
-Cycling frequency:
-Required certifications:
-Actual operating environment:
With this information, the manufacturer can evaluate the valve configuration holistically, rather than recommending a seat based solely on basic parameters like DN and PN.
11. Conclusion: No single seat suits every butterfly valve
When comparing EPDM, NBR, and PTFE butterfly valve seats, there is no single "best material" that fits every application.
EPDM is generally suitable for water-based applications such as water, cooling water, HVAC, and water treatment.
NBR is better suited for petroleum-based media, including mineral oils, fuels, and hydraulic fluids.
PTFE is ideal for operating conditions that demand high chemical resistance, temperature tolerance, or media isolation capabilities.
A truly reliable selection process involves a comprehensive assessment of the following factors:
Media → Concentration → Temperature → Pressure → Cycling frequency → Valve structure
Decisions should not be based on a single material property alone.
If you are unsure whether to choose EPDM, NBR, or PTFE, you can provide the complete operating parameters to the butterfly valve manufacturer. They can then evaluate components such as the valve body, disc, stem, seat, liner, pressure rating, and actuation method to determine the most suitable valve configuration.
Post time: Sep-17-2026