Flange Face Types Explained: Raised Face vs Flat Face vs Ring Type Joint (RTJ)
When it comes to building strong, leak-proof piping systems, flanges are the backbone. But not all flanges are created equal. One key detail that often goes unnoticed — yet plays a critical role — is the flange face type. The right flange face ensures leak-proof connections, maintains system integrity under varying pressures and temperatures, and extends the lifecycle of the entire assembly.
In this blog, we’ll break down the most common flange face types — Raised Face (RF), Flat Face (FF) and Ring Type Joint (RTJ) — helping you choose the right one for your next project with complete confidence.
Whether you’re working in oil & gas, chemical processing, water treatment, food industry, or EPC projects, understanding flange face types is essential to ensuring performance, safety, and compliance with international standards like ASTM, ANSI, and DIN
What Are Flange Face Types?
The face of a flange is the surface where two flanges are bolted together with a gasket in between. The type of flange face affects the sealing performance, gasket choice, and even the pressure rating of the piping system.
Choosing the right flange face ensures reliable, long-lasting connections, minimizes downtime, and prevents costly leaks — especially in critical industries like oil and gas or chemical plants.
1. Raised Face (RF) Flanges
What is a Raised Face Flange?
Raised Face (RF) is the most widely used flange face type globally. It features a small raised surface around the bore where the gasket sits, concentrating the sealing force over a smaller area for a tighter, more efficient seal.
Key Features:
• Pressure Classes: ANSI Class 150 to 2500 / DIN PN 10 to PN 400
• Standards: ASME B16.5, DIN EN 1092-1
• Materials: ASTM A105 (carbon steel), ASTM A182 (stainless steel), EN 10222-5
• Gasket Types: Spiral wound, metallic, non-metallic
• Applications: Oil & gas pipelines, chemical plants, power generation
Real-World Example:
In offshore oil rigs, Raised Face flanges are preferred for high-pressure high-temperature piping systems fluid transfer lines because they can withstand extreme pressure while maintaining a strong seal.
Best Practices:
• Use spiral wound gaskets for better sealing in RF flanges.
• Ensure the raised face is free from scratches and corrosion to maintain sealing integrity.
Where is a Raised Face (RF) flange used?
Raised Face flanges are most commonly used in oil & gas, petrochemical, and high-pressure piping systems where a strong, tight seal is required using gaskets.
Flange type with Raised Face
Appearance:
• Gasket seating area is slightly raised above the bolt circle.
2. Flat Face (FF) Flanges
What is a Flat Face Flange?
Flat Face (FF) flanges have a completely flat sealing surface. They are typically used where the mating flange or piping component is made of a brittle material like cast iron or fiberglass, which cannot handle the concentrated loads created by a Raised Face flange.
Key Features:
• Pressure Classes: ANSI Class 125 to 300 / DIN PN 10 to PN 40
• Standards: ASME B16.1 (for cast iron), ASME B16.5, DIN EN 1092-1
• Materials: ASTM A105, A182, EN 1092-1 compliant steels
• Gasket Types: Full-face gaskets
• Applications: Water treatment plants, HVAC systems, fire protection piping
Real-World Example:
In municipal water treatment plants, where systems often involve cast iron piping, Flat Face flanges are ideal to prevent overstressing the brittle piping material. Suitable for low-pressure piping systems.
Best Practices:
• Always use a full-face gasket with FF flanges.
• Do not mix FF and RF flanges to avoid leaks and mechanical failures.
Where is a Flat Face (FF) flange used?
Flat Face flanges are typically used in low-pressure applications, such as water treatment plants, pump connections, and cast iron equipment where bending stresses must be minimized.
Flange type with Flat Face
• Cast Iron Flanges
• PVC Flanges
• Ductile Iron Flanges
Appearance:
• Entire flange face is flat and even with the bolt circle.
.
Ring Type Joint (RTJ) Flanges
What is a Ring Type Joint Flange?
Ring Type Joint (RTJ) flanges are precision-machined with a groove cut into the face where a metallic gasket (typically oval or octagonal) sits. When bolted, the gasket gets deformed into the groove, creating a metal-to-metal seal — perfect for extreme pressures and temperatures.
Key Features:
• Pressure Classes: ANSI Class 600 and above / DIN PN 64 to PN 400
• Standards: ASME B16.5, API 6A, DIN EN 1092-1 (Type B, C flanges)
• Materials: ASTM A105, ASTM A182, EN 10222-5
• Gasket Types: RTJ metal gaskets (R-style, BX, RX)
• Applications: Oil & gas drilling rigs, refineries, petrochemical plants
Real-World Example:
In high-pressure refinery applications where temperatures exceed 400°F (204°C), RTJ flanges are a must to ensure zero leakage and compliance with international standards.
Best Practices:
• Always match the RTJ gasket to the flange groove dimensions precisely.
• Regularly inspect gaskets for wear and deformation in critical services.
Where is a Ring Type Joint (RTJ) flange used?
Ring Type Joint flanges are used in high-pressure (above 600#) and high-temperature service such as oil drilling, refineries, and chemical process plants, where absolute leak-proof connections are critical.
Flange type with Ring Type Joint Face
Appearance:
• Flange face has a machined groove to hold a metal ring gasket.
Flange Face Type Selection Guide
| Application | Preferred Flange Face | Reason |
|---|---|---|
| Water pipelines | Flat Face (FF) | Suitable for cast iron piping |
| Oil & Gas pipelines | Raised Face (RF) | High pressure, tight sealing |
| Refineries | Ring Type Joint (RTJ) | Extreme pressure and temperature |
| Food processing | Flat Face (FF) | Clean surfaces, non-metallic piping |
International Flange Standards to Know
| Standard | Region | Scope |
|---|---|---|
| ASME B16.5 | USA/Global | Pipe flanges and flanged fittings, NPS ½” to 24″ |
| DIN EN 1092-1 | Europe/Global | Circular flanges for pipes, valves, and fittings |
| ASTM A105 | USA/Global | Carbon steel forgings for piping components |
| ASTM A182 | USA/Global | Forged or rolled alloy and stainless steel pipe flanges |
C-Way Engineering Exports ensures all our flanges comply with these stringent international standards, delivering products you can trust.
| Flange Type | Common Face Type |
|---|---|
| Weld Neck Flange | Raised Face (RF) / RTJ |
| Slip-On Flange | Raised Face (RF) / Flat Face (FF) |
| Socket Weld Flange | Raised Face (RF) |
| Blind Flange | Raised Face (RF) / RTJ / Flat Face (FF) |
| Cast Iron Flange | Flat Face (FF) |
| High-Pressure Alloy Steel Flange | Ring Type Joint (RTJ) |
Conclusion: Choose the Right Flange Face with Confidence
The choice between Raised Face, Flat Face, and Ring Type Joint flanges depends on your application’s pressure, temperature and material requirements. Making the right choice ensures system safety, longevity, and performance.
At C-Way Engineering Exports, we manufacture a wide range of industrial flanges tailored to meet global standards, with full ISO 9001:2015 and CE certifications. Our expertise helps industries across the world create reliable, leak-proof piping systems.
Need help choosing the right flange for your project?
Contact our experts today for technical support or request a quick quote for high-quality industrial flanges!
