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Flanges face surface is of utmost importance for sealing efficiency, durability, and safety. This guide explores different types of flange face surfaces, their unique characteristics, and how they differ in industrial applications.
Flat face flanges are completely smooth and flat on the raised surface with a flush bolting circle. Full-face gaskets extend across the entire face from inner to outer diameter, exerting even pressure over a large sealing area.
Flat face flanges find application in systems that require low pressure and temperature, like water treatment and plumbing. FF flanges are generally used together with brittle materials, such as cast iron, in order not to crack.
Advantages of FF flanges include ease of alignment, economy, and minimal warping under bolt pressure. However, they are not recommended for high-pressure applications because of limited sealing integrity, and they cannot be mated with raised face flanges without modifications.
RF flanges have a raised circular ridge around the bore, elevating the sealing surface above the bolting plane. The height of this ridge varies by pressure class
Dominant in oil and gas, chemical processing, and high-temperature systems, these RF flanges allow for spiral-wound, composite, or non-metallic gaskets.
RTJ flanges have a machined groove that accommodates a metal ring gasket-oval or octagonal. Under compression, the gasket elastically deforms into the groove to create a metal-to-metal seal.
Application: These flanges are used in high-pressure applications (Class 600+) and high-temperature (>800°F/427°C) systems, hence finding crucial applications in offshore drilling, petrochemicals, and subsea pipelines.
RTJ flanges offer excellent resistance to leaks under extreme conditions, with very tough gaskets that experience minimal movement. However, they require precise alignment, and the metal gaskets are very expensive, and groove surfaces must be provided with a mirror-like finish (≤63 µin Ra).
T&G flanges have interlocking tongue and groove surfaces. The gasket is placed inside the groove, out of the way of external forces.
Application: They find applications in high-pressure steam systems and pipelines that move toxic or flammable fluids. They are also found in pump covers and valve bonnets.
The male flange has a raised ring while its female counterpart has a groove. It is just the opposite design for correct positioning and tightening of soft or metallic gaskets.
Application: M&F flanges are very common in heat exchanger applications as well as in other high pressure industrial applications.
These flanges minimize gasket blowout and provide optimal compression in specific applications. These, however have to be installed in matched pairs.
Lap joint flanges are clamped with a stub end, which allows rotation to align. The sealing surface is provided by the stub end and not by the flange itself.
Application: Lap joint flanges are used in systems under low or moderate pressures and temperatures where frequent dismantling is required such as food processing and in pharmaceuticals.
Lap joint flanges’ main advantages are the ease of maintenance and the alignment and cost-effectiveness of services that don't require high standards.
Pressure & Temperature: RF & RTJ Flanges are the best options when dealing with a high-pressure system. FF Flanges are normally used in applications that require a low level of pressure.
Compatibility of Gasket: FF and RF flanges use soft gaskets like those made of rubber. RTJ flanges shall be fitted with metal gaskets.
Industry Requirements: The selection of the flange type shall be according to ASME, API, or DIN.
Difficulty of Installation: RF flanges are easier to install compared to RTJ or T&G designs.
The flange face surface selection is fundamental to operational safety, efficiency, and regulatory issues.RF flanges are widely used for general purposes, while RTJ and T&G designs excel in extreme conditions. Fluido specializes in diverse flange face surfaces, including Flat Face (FF), Raised Face (RF), and Male and Female (M&F) flanges, catering to varied application needs.
With more than 20 years of experience, Qingdao Fluido Industrial Co. Ltd. focuses on the production and exportation of steel valves, fittings, and flanges to serve over 35 countries across the world. Besides manufacturing its own flanges, FLUIDO also cooperates with several factories in Shandong and Hebei to offer a full product range and one-stop sourcing.
