Introduction
The flange face type is one of the most critical design considerations in piping systems. Choosing the wrong face type can lead to leaks, premature gasket failure, and costly maintenance. This guide explains the main flange face types and their optimal applications.
Raised Face (RF)
Characteristics
Raised Face flanges have a raised ring around the bore that concentrates gasket pressure for better sealing. The raised height varies by pressure class:
- Class 150 & 300: 1.6mm (1/16″) raised face
- Class 600 and above: 6.4mm (1/4″) raised face
Applications
- Most common in oil & gas industry
- Suitable for temperatures from -20°C to 400°C
- Works with spiral wound, graphite, and non-asbestos gaskets
- Pressure ratings up to Class 2500
Flat Face (FF)
Characteristics
Flat Face flanges have a completely flat sealing surface with no raised portion. The gasket covers the entire face.
Applications
- Cast iron and brittle material flanges
- Low pressure applications (Class 125 & 250)
- Prevents bending stress on brittle materials
- Common in water treatment and HVAC systems
Ring Type Joint (RTJ)
Characteristics
RTJ flanges use a metal ring gasket that sits in a machined groove. When bolted, the ring deforms to create a metal-to-metal seal.
Applications
- High-pressure systems (Class 600 to 2500)
- High-temperature applications up to 800°C
- Offshore platforms and subsea pipelines
- Refineries and petrochemical plants
Other Face Types
Tongue and Groove (T&G)
Provides excellent gasket alignment and compression. Used in pump housings and valve bonnets.
Male and Female (M&F)
Self-aligning design with good gasket retention. Common in heat exchangers.
Selection Guide
| Application | Recommended Face Type |
|---|---|
| General oil & gas | Raised Face (RF) |
| High pressure (>600#) | RTJ or RF |
| Cast iron piping | Flat Face (FF) |
| Offshore/subsea | RTJ |
| Water systems | Flat Face (FF) |
Conclusion
Understanding flange face types ensures proper sealing and system integrity. Always consult with your flange manufacturer to confirm the best choice for your specific application.
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