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2022.3.29
Flanges are a type of commonly used parts in piping, that come in various designs and forms to suit different applications. In this guide, we’ll get into some basics of flanges, featuring the definition, uses, types, important sizes, and more.
A flange is a type of component connected by bolts around two planes, that is, the parts connected between shafts, and it is also an important connection mode of pipeline construction. Because it needs to be closely connected with the device, the flange has holes, which can be threaded with bolts to connect the two flanges tightly, this makes the installation and disassembly are convenient.
A flange is a kind of disk-shaped part, which is the most common in pipeline engineering. Flanges are used in pairs. In pipeline engineering, the flange is mainly used for the connection of pipes. A flange plate should be installed for various pipelines to be connected. Threaded flanges can be used for low-pressure pipelines, and welded flanges can be used for pressure above 4kg. A sealing point should be added between the two flanges, and then fastened with bolts. Flange connection is to fix two pipes, pipe fittings, or equipment on a flange respectively. Between the two flanges, add a flange gasket and fasten them together with bolts to complete the connection. The flange is an essential part of construction, light and heavy industry, plumbing, electric power, and other industries.
Flanges with different pressures have different thicknesses and the matching bolts are also different. There are two important flange sizes we need to understand.
1. Pressure Nominal (PN): refers to the standardized pressure grade of a pressure vessel or pipeline, which generally refers to the maximum working pressure at the specified temperature and the pressure grade after standardization. The nominal pressure of the flange is usually close to the design pressure and slightly higher than the nominal pressure. There are two international nominal pressure classes, namely, the European system (represented by DIN standard) and the American system (represented by ASME standard). In the same system, the pipe flange standards of various countries can basically be used with each other (referring to the connection size and sealing surface size), but the flanges between the two systems cannot be used with each other.
2. Diameter Nominal (DN): it is the size series after pipe standardization to facilitate the mutual matching of fittings, which is specified by national standards. The nominal diameter of the pipe flange refers to the nominal diameter, which is a value close to the inner diameter of the pipe. The outer diameter of steel pipes with the same nominal diameter is the same, but the thickness is changed, so the inner diameter is also changed.
– Socket weld flange: a type of flange that which the end of the pipe is inserted into the flange ring ladder and welded at the end and outside of the pipe. There are two kinds with and without necks. The pipe flange with the neck has good rigidity, small welding deformation, and good sealing performance. It can be used on occasions with a pressure of 1.0~10.0MPa.
– Threaded flange: a kind of flange connected with a pipeline by a thread. In design, it can be treated as a loose flange. The utility model has the advantage that welding is not required, and the additional torque to the cylinder or pipeline caused by flange deformation is very small. The disadvantage is that the flange thickness is large and the cost is high. It is applicable to the connection of a high-pressure pipeline.
– Slip-on flange: attached to a pipe or fitting by two fillet welds, one on the inside of the flange cavity and one on the outside of the flange cavity. The bore diameter of the slip-on flange is larger than the outside diameter of the connected pipe because the pipe must slide inside the flange in order to be connected through the fillet weld.
– Blind flange: used to terminate or isolate piping systems and are essentially bolted-on blind flanges. When properly installed and combined with the correct gasket, they provide an excellent seal and are easily removable when needed.
– Weld neck flange: this type of flange has long conical hubs that can be welded to the pipe. This flange type is typically used in high pressure and high/low temperature applications where the unrestricted flow of fluids conveyed by the piping system is required.
– Plate flange: a flat disc welded to the end of a steel pipe that can be bolted to another pipe. Typically used for fuel and water piping, the two flanges will be bolted together with a gasket in between.
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