Introduction

Threaded flanges are mechanical components used to create secure, leak-resistant connections in piping systems. They feature internal threads that allow them to screw onto the external threads of a pipe or fitting, eliminating the need for welding. This makes threaded flanges especially useful in applications where welding could be hazardous or impractical, such as in explosive or flammable environments. Typically used in low-pressure, low-temperature systems, threaded flanges provide flexibility, ease of installation, and easy disassembly for maintenance.

Types of Threaded Flanges

Threaded flanges come in various designs to suit different applications and industry standards. The primary types include:

  • Raised Face (RF) Threaded Flange: The most common type, featuring a slightly raised surface around the bore where the gasket is placed. This design improves sealing capabilities in medium-pressure applications.

  • Flat Face (FF) Threaded Flange: These flanges have a flat contact surface, making them ideal for low-pressure, low-temperature applications where the risk of warping is minimal. The flat surface evenly distributes the gasket compression.

  • Ring Type Joint (RTJ) Threaded Flange: This design includes a precision-machined groove into which a metal ring gasket is inserted. RTJ flanges are used in high-pressure, high-temperature environments where a metal-to-metal seal is required for reliability.

Design Features

Threaded flanges incorporate several design elements that contribute to their performance and versatility:

  • Threaded Connection: Threaded flanges feature internal threads, typically matching NPT (National Pipe Thread) or BSP (British Standard Pipe) standards, depending on regional usage. These threads are precisely cut to ensure secure attachment to the pipe or fitting.

  • Flange Face: The face of the flange can vary depending on the type (RF, FF, or RTJ), with the raised or flat surfaces providing different sealing efficiencies. The flange face must align with the pipe or fitting to ensure a tight seal.

  • Bolt Holes: The flange includes bolt holes arranged in a standard pattern to secure it to another flange or piece of equipment. The number and size of these holes vary according to the flange's pressure rating and pipe size.

  • Material Selection: Threaded flanges are manufactured using a wide range of materials, including stainless steel, carbon steel, and plastic, to meet the specific requirements of the application, such as resistance to corrosion, temperature, or pressure.

Advantages of Threaded Flanges

Threaded flanges offer several key advantages:

  • Ease of Installation and Removal: Since threaded flanges do not require welding, they can be easily installed and removed, making them highly convenient for systems that require frequent disassembly for inspection or maintenance.

  • No Welding Required: Threaded flanges are ideal for hazardous environments where welding is not feasible due to safety concerns, such as the presence of flammable gases or liquids.

  • Reusability: Threaded flanges are highly reusable, as they can be quickly detached and reattached without damaging the pipe or fittings. This feature makes them cost-effective for temporary piping systems or applications where frequent modifications are needed.

  • Suitability for Low-Pressure Systems: These flanges are particularly useful in low-pressure, low-temperature systems, such as in water, air, and certain chemical processing applications, where welding or high-pressure flanges might be excessive.

Conclusion

Threaded flanges are a versatile and convenient solution for creating strong, reliable connections in piping systems without the need for welding. Available in different types such as Raised Face (RF), Flat Face (FF), and Ring Type Joint (RTJ), threaded flanges can meet the specific needs of various industries, including oil and gas, chemical processing, and water treatment. Their ease of installation, reusability, and suitability for hazardous environments make them a valuable component in low-pressure, low-temperature applications. Proper material selection and installation practices ensure these flanges perform optimally and maintain long-term system integrity.