Seals are critical components of butterfly valves that ensure tight shut-off and prevent leakage of fluids. Industrial butterfly valves utilize various types of seals depending on the application, operating conditions, and the characteristics of the fluids being handled. Here are some common types of seals used in butterfly valves:

1. Elastomeric Seals: These seals are made from elastomeric materials such as EPDM (ethylene propylene diene monomer), NBR (nitrile rubber), Viton (fluoroelastomer), or silicone. Elastomeric seals provide excellent flexibility and resilience, allowing them to create a tight seal even in low-pressure applications. They are suitable for a wide range of temperatures and are resistant to many chemicals.

2. PTFE (Polytetrafluoroethylene) Seals: PTFE seals, also known as Teflon seals, are used in applications where high chemical resistance and temperature resistance are required. PTFE is non-reactive and can withstand a wide range of corrosive chemicals and high temperatures. These seals provide excellent sealing performance even in harsh environments.

3. Metal Seals: Metal seals are typically used in high-pressure or high-temperature applications where elastomeric seals may degrade or fail. They are made from materials such as stainless steel or other alloys and provide a durable and long-lasting sealing solution. Metal seals are often used in critical applications where leakage is not acceptable.

4. Graphite Seals: Graphite seals offer high temperature resistance and chemical compatibility, making them suitable for extreme operating conditions. They provide excellent sealing performance in high-temperature applications such as steam service or hot gases.

5. Composite Seals: Composite seals combine different materials to achieve specific performance characteristics. For example, a composite seal may consist of a PTFE layer for chemical resistance combined with an elastomeric layer for flexibility. These seals offer a balance of properties tailored to the requirements of the application.

6. Retrofit Seals: Retrofit seals are designed to replace worn or damaged seals in existing butterfly valves without requiring the replacement of the entire valve assembly. They are available in various materials and configurations to match the original seal design.

7. Fire-safe Seals: Fire-safe seals are designed to prevent the leakage of fluids in the event of a fire. They are typically constructed from materials that can withstand high temperatures and maintain sealing integrity even in extreme conditions.

8. FDA-approved Seals: FDA-approved seals are used in applications where compliance with food and pharmaceutical regulations is required. These seals are made from materials that are safe for contact with food and pharmaceutical products and comply with relevant regulatory standards.

Selecting the appropriate seal for a butterfly valve depends on factors such as the type of fluid, temperature, pressure, chemical compatibility, and environmental conditions. Proper seal selection is crucial to ensure the reliable and efficient operation of industrial butterfly valves.