Butterfly valves are widely used in industries such as water treatment, chemical processing, oil and gas, HVAC, and shipbuilding due to their compact design, easy operation, and cost-effectiveness. In these systems, the sealing performance of the valve directly impacts fluid control efficiency and the overall safety of the equipment.
Why Butterfly Valve Seals Matter
While the valve body and disc are usually made of metal, the true factor that determines whether a butterfly valve achieves a tight shut-off is the sealing ring. Different sealing materials offer varying advantages in temperature resistance, pressure capacity, and chemical compatibility.
Choosing the wrong material can result in leakage, reduced service life, or even system failure. For this reason, understanding common butterfly valve seal materials and their proper applications is essential for engineering design, procurement, and maintenance.
This article introduces several commonly used butterfly valve seal materials, examines their properties, application scenarios, and limitations, and provides selection guidance based on real-world operating conditions—helping you quickly identify the right solution for your needs.
Common Butterfly Valve Seal Materials
EPDM
EPDM provides excellent resistance to water, steam, and mild acids and alkalis. For this reason, it is widely used in water supply and treatment systems. Many butterfly valves designed for drinking water applications employ EPDM seals and carry certifications such as WRAS and NSF.
Its limitation lies in poor compatibility with oils and strong acids or alkalis, making it unsuitable for petrochemical or highly corrosive environments.
Typical applications: potable water, HVAC systems, fire protection networks.
NBR
NBR is valued for its outstanding resistance to oils and fuels, making it a common choice in petrochemical processes and fuel transfer systems. It offers stable performance at a moderate cost, making it a cost-effective sealing material.
On the other hand, NBR performs poorly when exposed to ozone and sunlight, which restricts its use in long-term outdoor applications.
Typical applications: petroleum products, hydraulic oil, fuel transfer systems.
FKM / Viton
FKM (commonly known by the trade name Viton) is a high-performance sealing material capable of withstanding high temperatures, strong acids and alkalis, and a wide range of aggressive chemicals. Highly durable, it is frequently used in critical and demanding service conditions.
Because of its higher cost, FKM is generally reserved for key applications. It is less suitable in steam service and shows weaknesses in certain esters and ketone-based media.
Typical applications: chemical processing, pharmaceutical equipment, oil and gas industry.
PTFE
PTFE is renowned for its exceptional corrosion resistance, able to withstand strong acids, strong alkalis, and nearly all corrosive chemicals. It also has an extremely low coefficient of friction and maintains stability at elevated temperatures.
However, PTFE is not a rubber material; it lacks elasticity and is prone to creep (permanent deformation) under prolonged pressure. As a result, it is often paired with elastic materials to improve recovery and sealing reliability.
Typical applications: highly corrosive chemical media, linings in food processing equipment.
Metal Seals
Metal sealing is commonly used in triple-offset butterfly valves, particularly in extreme service conditions such as high temperature, high pressure, or severe abrasive environments. Compared with elastomeric seals, metal seals can withstand much harsher conditions.
However, as a “metal-to-metal” sealing approach, their tightness is generally not as reliable as that of soft seals. They also require higher machining precision and come with higher manufacturing costs.
Typical applications: power plant steam systems, high-temperature gas pipelines, abrasive slurry transport.
How to Select the Right Seal Material
When choosing a butterfly valve seal material, the most important factors to consider are the type of medium, operating temperature, and service environment. Different materials are suited for different conditions, and selecting the right one ensures both performance and service life.
The following table provides a reference to help you quickly identify suitable sealing materials for your application.
MATERIAL | GENERAL APPLICATION | SERVICE TEMPERATURE | NOT RECOMMENDED FOR |
EPDM | Fresh Water, Sea Water, Brine, Esters, Alkalis, Ozone, Alcohols, Brake Fluid, Treated Water with Caustic Soda | -15℃ ~ +120℃ (intermittent), 0℃ ~ +100℃ (continuous) | Hydrocarbons, Oils, Fats, Greases |
NBR | Fresh Water, Sea Water, Treated Water with Caustic Soda, Hydrocarbons, Natural Gas, Oil and Fat, Air, Gasoline | -10℃ ~ +100℃ (continuous), 0℃ ~ +70℃ (L-NBR: -50℃ ~ +70℃) | Solvents, Benzene, Xylol |
VITON | Acids, Oils, Hydrocarbons | -15℃ ~ +230℃ | Steam, Ester, Freon22, Alkalis, Solvents, Ketones |
TEFLON (PTFE) | Solvents, Corrosive Products, Ketones | -60℃ ~ +230℃ (PTFE -196℃ ~ +230℃) | Fluid Containing Powders, Alkaline, Gaseous Fluorine |
Common Failures and Troubleshooting
Different butterfly valve seal materials may exhibit various failure modes during operation. Understanding these typical issues helps in quickly identifying the root cause and taking corrective measures:
- EPDM Seals: If swelling or stickiness occurs, it is usually due to contact with oils or hydrocarbons, which exceed its compatibility range. EPDM should be avoided in oil-based media.
- NBR Seals: Hardening or cracking is often the result of ozone exposure or UV aging. This can be mitigated by improving storage conditions or choosing a more weather-resistant material.
- FKM / Viton Seals: When used in high-temperature steam environments, they may lose elasticity and age rapidly. In such media, PTFE or metal seals are recommended instead.
- PTFE Seals: A common issue is creep (cold flow), where permanent deformation occurs under long-term pressure. This can be reduced by combining PTFE with elastic materials to improve recovery.
- Metal Seals: Failures typically appear as surface wear or galling, particularly under high pressure or when handling abrasive media. Surface hardening treatments or regular maintenance can help minimize these risks.
By observing these failure patterns, users can make an initial assessment of whether the problem is caused by media incompatibility, operating conditions beyond design limits, or material aging. This enables targeted improvements or timely replacement.
Although butterfly valve seals may appear to be a small and insignificant component, they directly determine the reliability and service life of the valve under different operating conditions.
By selecting the right sealing material, not only can system sealing performance be improved, but operating costs and maintenance risks can also be reduced. Of course, every material has its limitations, and the key lies in matching the seal correctly with the medium, temperature, and service environment.
With years of experience in the valve industry, TFW Valve offers butterfly valves with a wide range of sealing materials and provides expert selection guidance tailored to each customer’s application. If you are looking for high-quality and durable butterfly valves, we welcome you to contact TFW Valve. Our team is ready to deliver the most suitable valve solutions for your projects.
