Pipe flange size specifications and classification

When selecting the size of a pipe flange, several factors need to be considered, including the size, type, and applicable standards and specifications of the flange. ‌

According to the nominal unit, the main specifications of the flange can be divided into DN10, DN15, DN20, DN25, etc., or they can also be divided into 3/8, 1/2, 3/4, 1, etc. according to the inch unit. As the specification grade increases, the corresponding hole spacing between bolts, the outer diameter of the flange ring, the diameter of the bolts, the number of bolt holes, and the thickness of the flange will also increase. For example, the selected specifications range from DN10 to DN65, the diameter of the bolt is mostly 14 or 18 mm, the number of bolt holes is 4, and the thickness is 14 mm, 16 mm, 18 mm, 20 mm, etc. The hole spacing of the bolts and the outer diameter of the flange will also increase.

Pipe flange classification:
1. According to the welding method, flanges can be divided into: flat welding flange, neck flange, butt welding flange, ring connection flange, socket flange and blind plate, etc. Other categories include thick-walled flanges, high-pressure flanges, etc.

2. According to chemical industry standards: integral flange (IF), threaded flange (Th), plate flat welding flange (PL), neck butt welding flange (WN), neck flat welding flange (SO) , socket welding flange (SW), butt welding ring loose flange (PJ/SE), flat welding ring loose flange (PJ/RJ), lined flange cover (BL(S)), flange cover (BL).

3. According to petrochemical industry standards: threaded flange (PT), butt welding flange (WN), flat welding flange (SO), socket welding flange (SW), loose flange (LJ), flange build.

4. According to the mechanical industry standards (mechanical tubing): integral flange, butt welding flange, plate flat welding flange, butt welding ring plate loose flange, flat welding ring plate loose flange, flanged ring plate loose flange, Flange cover.

Depending on the location and method of use, the types of flanges used are also different. For example, high-pressure neck flat welding flange is a common flange plate and is widely used in piping design, pipe fittings, valves and equipment parts.

In addition, there are flanges classified by material, such as stainless steel flanges, carbon steel flanges, alloy steel flanges, etc. Stainless steel flanges can be further subdivided into 304 flanges, 316 flanges, etc. 316 neck flat welding flange has high corrosion resistance and high temperature strength due to the addition of Mo element. It can be used under harsh conditions and can withstand high temperatures up to 1200-1300°C.

Standards and specifications for pipe flanges:‌

When selecting a flange size, you also need to consider applicable standards and specifications. ‌Common standards include ANSI/ASME B16.5-2017 (‌applicable to the US market and some international projects)‌ and EN/DIN 1092-1 (‌applicable to the European market and some international projects)‌. ‌In addition, ‌there are also GB/T 9119-2010 (‌China National Standard)‌ and JIS B 2220 (‌Japanese Standard)‌ etc. ‌Choose the appropriate standard according to the specific application scenario.

Pipe flange size types:

Generally speaking, the size classification of flanges is divided according to the diameter of the connection port and the thickness of the flange. The larger the size, the greater the thickness of the flange and the diameter of the connection port.

Dimensional classification of pipe flanges:
Flanges are divided into small size flanges, standard size flanges, large diameter flanges and extra large flanges according to different sizes. The size classification of flanges is mainly divided according to the diameter of the connection port and the thickness of the flange.

1. Small size flange: generally used for some low-pressure or general working conditions pipelines. The diameter of the connection port is usually less than 40mm, and the thickness of the flange is also relatively thin.
2. Standard size flange: usually used for some medium-high temperature and medium-high pressure pipes. The diameter of the connection port is usually between 40mm and 400mm. The flange thickness is moderate and thicker than small-size flanges.
3. Large-diameter flange: Mainly used for high-pressure and high-temperature pipelines. The diameter of the connection port is usually 400mm to 1000mm, and the thickness of the flange is also relatively large.
4. Extra large flange: usually used for special pipe and equipment connections. The diameter of the connection port exceeds 1000mm and the flange thickness is very large.

How to choose the appropriate pipe flange sizes & dimensions?

1. Select according to pipe diameter
The size of the flange should be the same as the diameter of the pipe to ensure that the connection between the flange and the pipe is tight and no leakage occurs. For example, a 1-inch pipe requires a 1-inch flange, not other flanges. Only in special circumstances are flanges of different specifications required.

2. Select according to fluid
Different fluids have different pressure, viscosity, density and other characteristics, so flanges of different specifications need to be selected to adapt to different fluids. The size of the flange should be selected according to an empirical formula, which includes multiple factors such as pipe size, fluid flow rate, working pressure and medium density. If the medium temperature and pressure are high, standard size flange or large diameter flange should be selected.

3. Choose according to work pressure
The size of the flange must match the maximum rated working pressure of the equipment or pipe to which it is connected. If you choose a flange that is too small, it will not be able to withstand the rated working pressure, leading to serious consequences such as pipeline leakage or damage.

4. Select according to device type
Select the appropriate size and type of flange according to the special requirements of the equipment, such as mechanical connection, hydraulic pressure, etc.

5. Select according to the installation environment
When selecting flanges, you also need to consider the installation environment. Some environments may limit the size of flanges or valves, so these environments should be taken into consideration when selecting.

Flange connection method:
Flange connection is to fix two pipes, pipe fittings or equipment on a flange plate first, add flange pads between the two flange plates, and fasten them together with bolts to complete the connection. Some pipe fittings and equipment already come with flanges, which are also flange connections. Flange connection is an important connection method in pipeline construction. Flange connections are easy to use and can withstand greater pressure. In industrial piping, as well as in homes, the pipe diameter is small and the pressure is low, with no visible flange connections. If you are in a boiler room or production site, there are flange-connected pipes and equipment everywhere.

Flange gasket:
Flange gasket is a ring made of material that can produce plastic deformation and has a certain strength.

Most gaskets are cut from non-metallic plates or made by professional factories to specified sizes. The materials are asbestos rubber plates, asbestos plates, PTFE plates, polyethylene plates, etc.; thin metal plates (tinplate, tinplate, etc.) are also used. Stainless steel) A metal-clad gasket made by wrapping non-metallic materials such as asbestos; there is also a wound gasket made of thin steel strips and asbestos strips. The most commonly used ones are stainless steel strips and graphite. Metal wound gaskets, depending on the use environment, the wrapping tape can also be made of asbestos.

Ordinary rubber gaskets are suitable for occasions where the temperature is lower than 120°C; asbestos rubber gaskets are suitable for situations where the water vapor temperature is lower than 450°C, the oil temperature is lower than 350°C, and the pressure is lower than 5MPa. For general corrosiveness Medium, the most commonly used is acid-resistant asbestos board.

In high-pressure equipment and pipelines, lens-shaped or other-shaped metal gaskets made of copper, aluminum, No. 10 steel, and stainless steel are used. The contact width between the high-pressure gasket and the sealing surface is very narrow (line contact), and the processing smoothness of the sealing surface and gasket is high.

Low-pressure small-diameter wired flanges, high-pressure and low-pressure large-diameter welded flanges are used. The thickness of the flange plate and the diameter and number of connecting bolts are different for different pressures.

Flange purpose:
Different types of flanges have different uses. For example, some flanges are mainly used for water heating pipelines, and some are mainly used for oil transportation pipelines. When purchasing flanges, you need to choose carefully, especially for oil pipelines and natural gas pipelines, it is very important to choose the right flange to ensure safe and reliable transportation.

Conclusion:

The size specifications and classification of flanges are very important to all walks of life. When selecting a flange size, consideration should be given to the size, type, and applicable standards and specifications to ensure that the selected flange can meet specific engineering needs and safety standards. At the same time, understanding the parameters of different specifications and models and the uses of different types of flanges can help us be more accurate and reasonable when selecting and using flanges.

Read more: Pipe flange production process or Stainless steel pipe fittings vs Carbon steel pipe fittings