Threaded Pipe Flanges

Threaded Flange

Threaded pipe flanges, also known as companion or screw flanges, connect to pipes without welding. They feature a tapered internal thread that fits onto the pipe’s external thread, similar to slip-on or socket weld flanges. Sometimes, a seal weld is also used. Midas manufactures these flanges with facing options like RF, FF, and RTJ, and sizes ranging from ½ inch to 78 inches, adhering to standards such as ASTM A105 and ASTM A182.

Threaded pipe flanges mostly is used in small diameters pipeline. The most popular threaded flanges range in ½ inch to 6” nominal pipe size, but we are able to offer NPT threaded flanges up to 78” if necessary. 

Threaded Flange Types

Threaded flanges come with various facing types to suit different sealing and connection requirements:

1. RF (Raised Face): This type has a raised surface around the flange's bore, which provides a tight seal when mated with a gasket. It's commonly used in general applications.

2. FF (Flat Face): The flange face is flat, which ensures a full contact seal with the gasket. It’s typically used in applications where both flanges have flat surfaces.

3. RTJ (Ring Type Joint): This type features a groove for a metal ring gasket, which provides a high-pressure seal. It’s used in high-pressure and high-temperature applications where a reliable seal is critical.

Referred Standard and Grades

ASTM A105: Standard forged carbon steel pipe components for environmental and high temperature / high pressure systems.
ASTM A182: The standard for alloy and stainless threaded flanges. Common alloy grades: F5, F9, F11, F22, F91; Stainless steel grades: F304, 304/, F316, F316L.

Application in Special Circumstance

Threaded flanges are ideal for applications where welding is impractical or impossible, such as when preserving a pipe's galvanized coating. However, they are unsuitable for pipes subjected to frequent temperature changes or operating outside the range of -45°C to 260°C. According to ASME B31.3, for steel pipes used in steam services above 250 psi or water services above 100 psi with temperatures over 220°F, the pipe must be seamless and at least as thick as schedule 80 of ASME B36.10.

Installation and Maintenance

Threaded flanges are attached to pipes via internal threads, eliminating the need for welding. This design simplifies both installation and maintenance compared to other flange types like slip-on or socket weld flanges.

FAQ

1. **What is a threaded pipe flange?**  

   A threaded pipe flange connects to a pipe using internal threads, avoiding the need for welding.

2. **What are the common facing types for threaded flanges?**  

   Common facing types include Raised Face (RF), Flat Face (FF), and Ring Type Joint (RTJ).

3. **Where are threaded flanges typically used?**  

   They are used in situations where welding is impractical, such as preserving pipe coatings or in locations where frequent disassembly is needed.

4. **Are threaded flanges suitable for high-temperature applications?**  

   No, they are generally not recommended for temperatures above 260°C or below -45°C due to potential sealing issues.

5. **What standards govern the use of threaded flanges?**  

   Standards such as ASTM A105, ASTM A182, and ASME B31.3 provide guidelines for their use, particularly concerning pressure ratings and material specifications.

6. **How do I install a threaded flange?**  

   Simply screw the flange onto the threaded pipe, ensuring it is tightened properly to create a secure connection.

7. **Can threaded flanges be used for high-pressure applications?**  

   They can be used in high-pressure situations, but ensure that the pipe and flange meet the required specifications, such as those outlined in ASME B31.3 for steam and water services.