Flange Face Types: RF, RTJ & FF Explained

Flange face types define how a flange seals against a gasket or mating flange. The three most common face types used in industrial piping are Raised Face (RF), Ring Type Joint (RTJ), and Flat Face (FF). Each face type has specific applications depending on pressure, temperature, and sealing requirements.
Flange Face Type Diagrams Coming Soon (RF, RTJ, FF)

What Is an ASME Flange Pressure Class?

A flange pressure class defines the maximum pressure-temperature rating of a flange according to ASME B16.5. The higher the class number, the stronger and thicker the flange. Pressure capability is affected by flange material, temperature, and gasket type.

What Are Flange Face Types?

Flange faces determine the type of gasket that is used and the sealing method of the connection. Choosing the correct face type ensures proper sealing, prevents leaks, and maintains pressure integrity in pipelines.

The most common flange face types are:

  • RF – Raised Face
  • RTJ – Ring Type Joint
  • FF – Flat Face

Raised Face (RF) Flanges

Raised Face (RF) is the most commonly used flange face type. A small raised portion around the bore increases the gasket compression, improving the seal.

RF flanges are used for:

  • Low to medium pressure
  • Most process piping systems
  • ASME Classes 150, 300, 600, 900

Ring Type Joint (RTJ) Flanges

RTJ flanges use a metal ring gasket seated in a machined groove. As the joint is tightened, the soft metal gasket deforms into the groove, creating a leak-proof metal-to-metal seal.

RTJ flanges are used in:

  • High pressure systems
  • High temperature service
  • Critical oil & gas applications
  • ASME Classes 600, 900, 1500, 2500

Flat Face (FF)

Flat Face (FF) flanges have a completely flat sealing surface. They are used to prevent stress or cracking that could occur if bolting a raised face flange to cast iron or fiberglass equipment.

FF flanges are used for:

  • Low pressure service
  • Cast iron pumps and valves
  • Water and wastewater systems

Comparison Table

Face Type Best For ASME Classes
RF (Raised Face) General service, low–medium pressure 150–900
RTJ (Ring Type Joint) High pressure & high temperature 600–2500
FF (Flat Face) Low pressure, cast iron equipment 150–300

Conclusion

RF, RTJ, and FF flanges each serve different purposes based on pressure class, temperature, and equipment compatibility. Choosing the correct face type ensures reliable sealing and safe pipeline operation. Always match the face type with appropriate gaskets and mating flanges.

Recommended Reading

FAQ Block

What is the difference between RF and RTJ flanges?

RF uses a flat gasket and is common for general service. RTJ uses a metal ring gasket and is used for high pressure and high temperature sealing.

Can RF and RTJ flanges be bolted together?

No, RF and RTJ are not compatible because the gasket styles and sealing surfaces are different.

When should flat face flanges be used?

Flat face flanges are used for low-pressure systems or when connecting to cast iron equipment to avoid cracking or flange distortion.