Gasket for FF and RF Flanges - Differences
Flanges play a key role in piping systems across many industries, from petrochemicals to construction. They ensure the integrity and efficiency of pipe systems by creating a secure, reliable, and tight connection between pipes, valves, and other components.
What is a flange facing?
The flange facing is the surface that contacts the gasket and the corresponding surface of another flange or fitting. The facing directly influences the tightness of the flanged joint. Its selection depends on factors such as pressure, temperature, and maintenance requirements.
The most popular types include Flat Face (FF) flanges and Raised Face (RF) flanges. When choosing the appropriate flange, it is crucial to understand their types and specifications. Each is used in different operating conditions – from low-pressure installations to high-pressure and high-temperature systems.
A properly selected flange facing increases the durability of the connection and minimizes the risk of leaks.
Flat Face (FF) Flanges
Features of FF Flat Face Flange
Construction and Characteristics
A Flat Face (FF) flange provides a wide contact surface with the gasket. Its contact surface is smooth, completely flat, and has no protruding elements. The entire surface of the flange contacts the surface of the connected pipe or other components, which is particularly useful for large-diameter pipe connections or those made of delicate materials. The flat surface ensures even distribution of compressive load on the gasket, providing a tight connection. The design and production of flat face flanges typically meet the requirements of ASME B16.5 and EN 1092-1 standards.
Flat face flanges should not be connected with raised face flanges, as this can cause leaks.
Sealing Method
FF flanges utilize soft (non-metallic) and full-face gaskets that cover the entire flange surface, increasing tightness by evenly distributing pressure. They are mounted between two flat flanges, directly on the front sealing surface of the flange blade, i.e., in the same plane as the bolt circle surface.
Operating Pressure Range
Due to their design, Flat Face flanges are commonly used in low-pressure applications, in ANSI pressure classes 125 and 150.
Gasket Material Compatibility
FF type flanges are typically used with cast iron, copper, and plastics to avoid bending or cracking. They are ideal for use with non-metallic gaskets, such as rubber gaskets, which effectively cooperate with the sealing surface.
Application of FF Flat Face Flanges
Flat face flanges are commonly used in low-pressure, non-critical applications and when connecting with materials such as cast iron. Examples of applications:
- water treatment systems (HVAC systems, water pipes, sewage treatment pipes)
- low-pressure equipment connections (connections between pumps, valves, or heat exchangers)
- low-pressure pipelines for steam, air, natural gas transport
Raised Face (RF) Flanges
Features of RF Raised Face Flange
Construction and Characteristics
A Raised Face (RF) flange has a slightly elevated surface around the bore, which extends beyond the bolting plane of the flange. This provides a smaller and concentrated sealing surface, allowing for greater pressure to be applied to the gasket, effectively increasing its tightness and reducing the risk of leakage. This is particularly important in high-pressure conditions and high-temperature applications. The design and production of raised face flanges typically meet the requirements of ASME B16.5, ASME B16.47 standards.
Sealing Method
RF flanges utilize non-metallic or semi-metallic gaskets that fit the raised face. The smaller gasket area means that pressure is more concentrated, which improves tightness and reduces the risk of leakage in high-pressure conditions.
Operating Pressure Range
The raised face of the RF flange allows for greater pressure to be applied to the gasket, ensuring a reliable seal in high-temperature and high-pressure conditions across all classes. The pressure level in the flange determines the height of the raised face.
Gasket Material Compatibility
RF type flanges can be made from various materials, including carbon steel, stainless steel, and alloy steel. They can be used with different gasket materials, from metallic to non-metallic, making them adaptable to various piping systems and pressure conditions.
Application of RF Raised Face Flanges
Thanks to their concentrated sealing surface, raised face flanges are ideal for applications requiring resistance to high pressure and temperature. They effectively maintain tightness under varying pressure and temperature conditions, finding application in oil and gas pipelines, refineries, power plants, and chemical processing. Examples of applications:
- high-pressure and high-temperature piping systems
- pipeline connections for crude oil and gas transport and processing
- connections in industrial systems
- pipelines in chemical plants and power generation
What are the differences between FF and RF flanges?
As mentioned earlier, Flat Face (FF) flanges and Raised Face (RF) flanges are two types of flanges commonly used in piping systems.
Differences between FF (Flat Face) and RF (Raised Face) flanges
| Type | FF Flange (Flat Face) | RF Flange (Raised Face) |
|---|---|---|
| Construction | Flat sealing surface, no protruding elements | Slightly raised sealing surface, providing concentrated pressure |
| Pressure/Temperature Range | Designed for low-pressure and low-temperature environments | Ideal for medium and high-pressure, and high-temperature environments |
| Pressure Class | Most commonly 125, 150 | All classes |
| Sealing Performance | Lower sealing parameters, suitable for use with brittle materials such as cast iron | Provides higher sealing pressure, reducing the risk of leakage |
| Gasket Type | Soft, non-metallic | Non-metallic or semi-metallic |
| Material Suitability | Cast iron, copper, and similar | Carbon steel, stainless steel, alloy steel |
| Areas of Application | Water treatment, HVAC systems, low-pressure applications | Oil and gas industry, chemical, power generation, high-pressure systems |
| Installation Method | Flat flange surface contacts the gasket directly | Raised part of the flange fitted to the gasket; even, concentrated pressure |
The choice of flange type depends on the environmental requirements of the specific application. As presented in the table above, FF flanges are suitable for low-pressure applications requiring simpler installation, while RF flanges perform well in high-pressure and high-temperature applications where concentrated pressure helps achieve a hermetic seal, reducing the risk of leakage.
Where to buy gaskets for FF and RF type flanges?
At the Power Rubber store, we offer high-quality rubber gaskets designed for pressure work, resistant to high temperatures and chemicals. Both standard and custom-made gaskets are available.
Our gaskets for FF flanges are ideal for low-pressure applications where effective sealing over the entire contact surface is required. In turn, gaskets for RF flanges are made of materials resistant to high pressure, temperature, and compression, which makes them perfectly suitable for applications where reliability and tightness are crucial.
Production of rubber gaskets
Are you looking for a proven manufacturer of rubber gaskets? At Power Rubber, we specialize in the production of precise technical gaskets from high-quality rubber compounds. We make gaskets to order based on technical documentation or a provided sample.
Feel free to contact us by phone: +48 222 924 024 or +48 505 160 303, or by email (power|powerrubber.com| rel="nofollow"|Power|PowerRubber.com) or via our contact form