A flange, often called a pipe flange or flange gasket, is a type of mechanical element used to join two pipes together, or serves as a provisional seal for the end of a single pipe. These round disks contain holes for bolts around the rim and come in a variety of shapes, sizes, diameters, and materials. As such, some are utilized for blocking high-pressure pipes while others are used to attach two pipes of differing materials. In this blog, we will be covering the different types of flanges and their uses, as well as the materials and shapes they come in so that you can better understand what kind of flange your application requires.
Flanges present themselves as a protruding lip or ridge that serves to increase the strength between two objects like valves, adapters, pipes, etc. Flanges provide ease of attachment for dissimilar materials being joined together and work to stabilize and guide the movements of a machine or its parts. Moreover, flanges are often the fittings of choice because they make cleaning, inspection, modification, and repairs easy.
A flanged joint connection is the common method used to join the flanges together when being fastened onto a pipe, valve, or other specialized item. This method requires two mating flanges, one set of flange bolts, and two gaskets made of a metallic or non-metallic material. The process and materials used rely on the type of flange being utilized. For this reason, we will be going over the seven main types of flanges: welding neck, long welding neck, slip-on, socket weld, lap joint, threaded, and blind flanges.
One of the most common types of flanges, welding neck flanges have a long tapered hub that extends from the center and can be welded with a pipe. The hub, or neck, is thin and malleable, a feature that enables the flange to melt quickly onto a pipe. Moreover, the neck relieves mechanical stress between the pipe and flange, which allows welders to detect possible leakages or welding defects. This flange type is ideal for high-pressure and high/low temperature applications that require the free flow of a fluid through a pipeline.
Long Welding Neck
Long welding neck flanges are similar to welding necks except the neck is extended and acts as a boring extension. This type of flange is typically used on vessels, columns, or barrels. Moreover, they come in the heavy barrel (HB) and equal barrel (E) types. Heavy barrel flanges are defined as a type of nozzle that provides additional reinforcement. In contrast, an equal barrel flange’s defining feature is the barrel and flange sharing the same outside diameter.
Socket weld flanges feature an extended lip or rim at the end of the stub-end. Typically, the installation involves inserting the pipe into the socket of the flange and then welding it into place. The sockets help stabilize the pipe during the welding process. Socket weld flanges are used for small-size and high-pressure pipes that hold non-corrosive fluids. A corrosive fluid could reach the gaps between the pipe and socket, which could cause damage to the system.
Similar to a slip-on flange, lap joint flanges come with two components: a disk with a hollow center and a neck piece that fits perfectly through the bore hole. The neck piece, typically called a stub-end, is secured to a pipe using a fillet weld or fastened by the pressure of bolts. The combination of stub-ends and flanges is a cost-effective solution for stainless steel or nickel alloy pipelines because these components can be made from a lower grade material.
Slip-on flanges are a one-piece version of the lap joint flange featuring a short pipe coming out of one end which creates a pocket for a pipe to slide into. The pipe is welded along the disk and the innermost rim of the flange, which provides extra support. This kind of flange has a shorter service life because of the absence of a tapered hub, which in the case of long welding neck flanges, distributes the mechanical stress between the pipe and flange evenly. Additionally, slip-on flanges can only be fitted to pipes.
A threaded flange is disk-shaped and has extra material coming out of one end as well as thread to feed the pipe onto the flange. Moreover, they can be attached to the piping with or without welding. This is especially important for flanges being used in explosive areas, such as gas stations and power plants where welding can be dangerous.
A blind flange is a solid disk used as a seal for the end of a pipeline, a valve or pressure vessel, or to prevent the flow of a fluid. Their simplistic design allows for easy access to the pipeline; however, they are one of the more expensive types of flanges.
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