Flanges and its types, classification of flange face

Flanges And Its Types, Functions & Classification Of Face Of Flange _________________________________________________________________________

After welding the pipe flanges are the second most frequently used joining method. They are used when dismantling of joints is needed. It allows flexible maintenance. Flange attaches the pipe to various valves and equipment there are three elements of a flanged joint; flanges, gaskets, and bolting; which are assembled by a pipe fitter.

Flange Face Classification

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Flat Face (FF): The flat-face flange has a gasket surface in the same plane as the face of the bolt circle. Applications using flat face flanges are often those in which a casting is made of the mating flange or flange fitting.

Raised Face (RF): The Raised Face flange can be easily identified as the most common type used in process plant applications. It is called an uplifted face because the surfaces of the gasket are raised above the face of the bolting circle. Each type of face enables a large range of gasket styles to be used, including types of flat ring sheets and metallic composites such as spiral wound and double jacket types.

Ring-Type Joint (RTJ): Ring joint flanges (RTJ) create a metalto-metal seal between the mating flanges and are therefore used in high-pressure and high-temperature (800 ° F / 427 ° C ) services. Flanges facing RTJ have circular grooves hosting metallic ring joint gaskets (RTJ type).

Tongue-and-Groove (T&G): These flanges have to match the Tongue and Groove faces. One face of a flange has a raised ring (Tongue) machined onto the face of the flange while the mating flange has a matching depression (Groove) machined in its face.

Male-and-Female (M&F): The flanges must be matched with this type too. One flange face has an area that stretches beyond the normal face of the flange (Male). The other flange or mating flange has a corresponding depression (Female) machined into the face of it.

Standards For Different Types Of Flanges The key grades of materials for pipe flanges, examined in a separate article, are:

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Standard ASTM A105 - carbon steel flanges for hightemperature service Standard ASTM A350 - CS flange for low temperature Standard ASTM A694 - high yield carbon steel flange for line pipes Standard ASTM A182 F1 to F91- alloy steel flange Standard ASTM A182 F304, F316, F321 - stainless steel flange Standard ASTM A182 F51, ASTM A182 F53/55 - duplex and super duplex flange, and higher grades (Inconel, Hastelloy, Monel flange).

Types Of Flanges  Welded Neck - As its name suggests, this is a flange that is connected to a pipe by welding neck of flange Due to its long neck it is expensive but more suitable for highpressure applications because the neck provides the flange with important reinforcement. The flange bore matches the pipe bore thereby reducing turbulence and erosion.

ďƒ˜ Slip-On - The flange is slipped over the pipe and placed on the top and bottom side of the flange by welding. They are used to provide a connection with sufficient strength to avoid leakage. This flange is preferred over welded neck flanges as less precision is required when cutting pipe to length, the cost of producing is lower but the result is almost the same. ďƒ˜ Socket Weld - in outline this is similar to a slip-on flange, but the bore is counter-bored to accept pipe The diameter of the remaining bore is identical to the pipe's inner diameter. The flange is fitted by a filet weld around the flange hub to the pipe In highstress applications an optional interval weld may be applied. It's most commonly used in highpressure systems like hydraulic and steam lines.

 Lap Joint - It has a radius and a flange face at the intersection of the bore to accommodate a lap-stub end.

The face on the stub end forms the face on the flange of the gasket. This type of flange is used in applications that require a quick and easy dismantling of sections of piping systems for inspection or replacement.  Threaded - The bore is threaded, allowing for assembly without welding. It clearly limits its application to systems of relatively low-pressure piping.

After assembly, the flange can be welded around the joint but this is not considered a suitable method of increasing its applications.  Blind flange - This flange is not having a bore. Also known as a blanking flange, it is used to fix or seal an end of a piping frame or shut off a piping system or opening

of a vessel. Vessel inspection or piping system is simpler, and access to it is easier. Depending on the requirements a blind flange can be supplied with or without the hub. ďƒ˜ Groove Flanges / Tongue Flanges - These flanges have to match the Groove and Tongue faces.

One face of a flange has a raised ring (Tongue) machined onto the face of the flange while the mating flange has a matching depression (Groove) machined into its face Facings of the tongue and groove are standardized in both the large and small types They differ from male-and-female because the tongue-and-groove's inner diameters do not extend into the flange base, thus retaining the gasket on its inner and outer diameter. ďƒ˜ Long Neck Flanges - These flanges are unique due to their simple connectivity to other pipes. Besides, these flanges are widely used in refining industries for linking purposes.

ďƒ˜ orifice flanges - The function of an orifice flange is to provide access to a gas or liquid meter line. When installed in a line, an orifice plate is clamped between a pair of flanges and the whole assembly is referred to as an orifice flange joint. The orifice plate, the measuring device, consists of a thin plate with a concentric, square edge and a circular hole in the centre. Two pressure tap holes are drilled in each flange to measure pressure difference through the orifice. ďƒ˜ Spectacle Flanges - This is a pressure retention plate with one solid end and one open end attached to a web or ties bar the open end forms a seal between two flanges and permits a normal flow of fluid through the operation of the pipe. If the solid end is swung to the position it effectively blanks the pipe and stops the flow.

Uses and applications of flanges  Manufacturing and food processing industry  Industrial pumps, valves and vessels  Municipal pipe systems & Waterworks  Heat exchangers and Heating systems  Mechanical system and plumbing  Service for fire protection  Nuclear power plants and the power industry  Oil, gas, and chemical assembly

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