An introduction to flanged connections – FF vs RF vs RTJ explained
Flanged connections are essential in piping systems that require secure, detachable joints. They allow for easier maintenance, inspection, and replacement of components. However, not all flanges are the same. In this article, we’ll explain the most common flange face types: Flat Face (FF), Raised Face (RF), and Ring Type Joint (RTJ).
1.What Are Flanged Connections?
A flanged connection consists of:
Two flanges
A gasket between the flanges
Bolts and nuts to hold them together
Proper selection of flange face type ensures adequate sealing performance under different pressures and service conditions.
EN 1092 Q235 FF flat flanges
2.Flat Face (FF) Flange
Description: The gasket surface is entirely flat and even with the flange face.
Common Use: Cast iron, fiberglass, or brittle materials
Advantages:
Simple and economical
Good for low-pressure, non-critical applications
Limitations:
Lower sealing performance compared to RF and RTJ
Not suitable for high-temperature or high-pressure systems
Nickel Alloy ASTM B564 UNS N06625 ASME B16.5 NACE MR-01-75 RF Weld Neck Flanges
3.Raised Face (RF) Flange
Description: Has a small raised portion around the bore where the gasket sits.
Advantages:
Most common type in process piping
Allows better gasket compression
Works well with flat gaskets or spiral wound gaskets
Applications:
Oil and gas
Petrochemical
Steam and water systems
SS316 RTJ Blind Flanges
4.Ring Type Joint (RTJ) Flange
Description: Includes a precisely machined groove that holds a metal ring gasket.
Seal Mechanism: The ring is compressed into the groove to create a high-integrity seal
Advantages:
Excellent for high-pressure and high-temperature applications
Superior sealing in critical systems
Limitations:
More expensive
Requires accurate alignment and machining
Gaskets are non-reusable
5.How to Choose the Right Flange Face
Use FF flanges for:
Low-pressure, low-temperature services
Where both flange faces are cast materials
Choose RF flanges for:
General industrial applications
Systems with moderate pressure and temperature
Opt for RTJ flanges for:
High-pressure/high-temperature pipelines
Critical systems like oil refineries, offshore platforms
Haihao Group, a global leader in piping solutions, offers an extensive portfolio of sealing-surface flange products designed to meet your specific application requirements. For detailed specifications, technical support, or customized flange solutions, our expert team stands ready to assist. Contact us today to explore how we can deliver precision-engineered flange products tailored to your project needs. Email:sales@haihaogroup.com