Views: 2 Author: Site Editor Publish Time: 2025-08-26 Origin: Site
In industrial pipeline systems, flanges serve as critical connecting fittings, responsible for ensuring pipeline pressure, stable operation, and preventing medium leakage. Stainless steel Weld Neck Flanges stand out among numerous flange types due to their excellent performance, becoming the preferred choice in industries such as petroleum, chemical, food, and medicine.
Stainless steel weld neck flanges, uses butt welding connection to achieve connection with pipelines. It mainly consists of a flange, a neck, and a groove welded to the pipeline. The design of the neck not only enhances the rigidity and load-bearing capacity of the flange, but also effectively reduces welding stress and improves the stability of the overall connection.
| Shape Type | Regular and Long Neck |
| Sealing Face | RF, FF, FTJ |
| Size Range | 1/2" - 48"/ DN15 - DN1200 |
| Pressure Rating | Class 150, 300, 600, 900, 1500, 2500lb |
| Standard | ASME B16.5, ASME B16.47 Series A/B EN1092-1 JIS 2220 |
| Carbon Steel | ASTM A105 / A105N |
| Low Temp Carbon Steel | ASTM A350 LF2/LF3 |
| Pipeline Steel | ASTM A694 F42 / 46 / 56 / 60 / 65 |
| Alloy Steel | ASTM A182 F11 / 12 / 5 / 9 / 91 / 92 |
| Stainless Steel | ASTM A182 F304/304L/304H, 316/316L, 310S, 317,347,904L |
| Duplex Stainless Steel | ASTM A182 F51, F53, F44 |
Weld neck flanges are usually divided into two types: regular weld neck flanges and long weld neck flanges.
Regular weld neck flanges have a shorter neck compared to long weld neck flanges. When welded to pipelines, they can meet the connection requirements under general pressure and temperature environments, and are widely used in conventional industrial pipeline systems with relatively low pressure and minimal temperature changes.
Long weld neck flange has a longer neck and thicker wall, gradually matching the thickness and diameter of the pipe wall to be docked with height. This unique design greatly increases the strength of the flange, enabling it to withstand higher pressures, temperatures, and more complex environmental changes. In scenarios where safety and stability are highly required, such as high-temperature and high-pressure steam pipelines and high-pressure reaction equipment pipelines in petrochemicals, long neck butt welded flanges play a crucial role.
When weld neck flanges to pipelines, it is necessary to weld the flange diameter end to the pipeline port. This connection method can withstand higher pressure and temperature, and has more reliable sealing performance. It is suitable for various high-pressure, high-temperature, and industrial pipeline systems with strict sealing requirements.
To ensure the quality of stainless steel weld neck flanges and meet the requirements of different standard piping systems, many countries and regions have developed production standards that meet the requirements of their respective industrial piping systems. At present, common international standards mainly include American standards, European standards, Japanese standards, etc. Different standards have certain differences in size, pressure rating, material requirements, etc., to meet the usage needs of different regions and industries.
The American National Standards Institute (ANSI) and the American Society of Mechanical Engineers (ASME) have developed the American standard for weld neck flanges, which is widely used worldwide, especially in North America and in companies that trade with North America. Its main standard numbers are ANSI/ASME B16.5 (pipe flanges and flange fittings) and ANSI/ASME B16.47 (large diameter steel flanges).
American standard flanges are represented by "Class" to indicate pressure levels. Common pressure levels include Class 150, 300, 600, 900, 1500, 2500, etc. Different pressure levels correspond to different parameters such as flange thickness, bolt quantity, and size. This standard has strict regulations on the material, manufacturing process, inspection methods, etc. of flanges to ensure their safe operation in high-pressure and high-temperature environments.
The European Standard (EN) is developed by the European Committee for Standardization (CEN), with the main standard for butt welded flanges being EN 1092-1 (Flanges and their fittings - Part 1: Steel flanges). European standard flanges are widely used in various European countries and many countries and regions that follow European standards.
The European standard flange uses "PN" (nominal pressure) to indicate pressure rating. Common PN ratings include PN 2.5, PN 6, PN 10, PN 16, PN 25, PN 40, PN 63, PN 100, etc. Compared with American standard flanges, European standard flanges have different size series and structural designs, and their sealing surface types are also more diverse, which can meet different sealing needs in various scenarios. At the same time, EN standards have strict requirements for the corrosion resistance, mechanical properties, and other indicators of flanges, emphasizing the safety and reliability of products.
The stainless steel weld neck flange standard developed by the Japanese Industrial Standards (JIS) is mainly JIS B2220 (Steel Pipe Flanges), which is widely used in Japan and some parts of Southeast Asia.
Japanese standard flanges also use PN to indicate pressure rating, and common ratings are similar to European standards, but there are differences in specific dimensions and structural details. The JIS standard has high requirements for the manufacturing accuracy and surface quality of flanges, emphasizing the practicality and economy of products, and is suitable for some industrial scenarios with moderate requirements for flange performance.
The size of stainless steel weld neck flanges is the key to ensuring accurate connection with pipelines and other components. Flanges with different standards and pressure levels have significant differences in size parameters.
The nominal diameter is one of the core parameters of flange size, used to indicate the specification size of the flange, measured in millimeters (mm). It is not the actual inner or outer diameter of the flange, but a standardized value specified to achieve interchangeability of pipeline system components. The common nominal diameter range is wide, ranging from DN 10 to DN 4000, which can meet the connection needs of pipes with different diameters. For example, DN 50 flanges are suitable for connecting to pipelines with an outer diameter of approximately 57mm, while DN 100 flanges are suitable for connecting to pipelines with an outer diameter of approximately 108mm.
As mentioned earlier, nominal pressure is an important indicator for measuring the pressure bearing capacity of flanges, and different standards use different expressions. American standards are represented by Class, while European standards, Japanese standards, and national standards (partially) are represented by PN. There are significant differences in parameters such as flange thickness, number of bolt holes, and bolt specifications corresponding to different nominal pressures. Taking American Class 150 and Class 300 as examples, under the same nominal diameter, Class 300 flanges have thicker thickness, more bolts, and can withstand higher pressure.
The sealing surface is a key part of the flange to achieve sealing function, and its size directly affects the sealing effect. Flanges with different standards and sealing surface types (such as protruding RF, concave convex MFM, tenon groove TG, etc.) have strict specifications for sealing surface parameters such as diameter, height, and roughness. For example, the sealing surface height of RF flanges is usually around 2-3mm, and the surface roughness needs to meet a certain standard to ensure a tight fit with the gasket and prevent medium leakage.
The neck is an important structural part of stainless steel butt welded flanges, and its dimensions include neck outer diameter, neck thickness, neck length, etc. The design of the neck should match the nominal diameter and nominal pressure of the flange to ensure its rigidity and welding performance. Generally speaking, flanges with larger nominal diameters and higher nominal pressures have correspondingly larger neck sizes to enhance their load-bearing capacity and deformation resistance.
In addition, the size and quantity of bolt holes on the flange are also important dimensional parameters. The diameter and quantity of bolt holes should be determined based on the nominal diameter and nominal pressure of the flange to ensure that the bolts can reliably connect the flange to other components and withstand the pressure and external forces of the pipeline system.
NPS | A | B | C | D | E | F | G | H | I | J | W |
| inch | inch | inch | inch | inch | inch | inch | No. of Holes | inch | inch | kg/pc | |
| mm | mm | mm | mm | mm | mm | mm | mm | mm | |||
| 1/2 | 3.500 | 0.620 | 0.440 | 1.880 | 0.840 | 1.190 | 1.380 | 4 | 0.620 | 2.380 | 0.48 |
| 88.90 | 15.70 | 11.20 | 47.80 | 21.30 | 30.20 | 35.00 | 15.70 | 60.45 | |||
| 3/4 | 3.880 | 0.820 | 0.500 | 2.060 | 1.050 | 1.500 | 1.690 | 4 | 0.620 | 2.750 | 0.71 |
| 98.60 | 20.80 | 12.70 | 52.30 | 26.70 | 38.10 | 42.90 | 15.70 | 69.85 | |||
| 1 | 4.250 | 1.050 | 0.560 | 2.190 | 1.320 | 1.940 | 2.000 | 4 | 0.620 | 3.120 | 1.01 |
| 108.0 | 26.70 | 14.20 | 55.60 | 33.50 | 49.30 | 50.80 | 15.70 | 79.25 | |||
| 1-1/4 | 4.620 | 1.380 | 0.620 | 2.250 | 1.660 | 2.310 | 2.550 | 4 | 0.620 | 3.500 | 1.33 |
| 117.3 | 35.10 | 15.70 | 57.15 | 42.20 | 58.70 | 63.50 | 15.70 | 88.90 | |||
| 1-1/2 | 5.000 | 1.610 | 0.690 | 2.440 | 1.900 | 2.560 | 2.880 | 4 | 0.620 | 3.880 | 1.72 |
| 127.0 | 40.90 | 17.50 | 62.00 | 48.30 | 65.00 | 73.15 | 15.70 | 98.60 | |||
| 2 | 6.000 | 2.070 | 0.750 | 2.500 | 2.380 | 3.060 | 3.620 | 4 | 0.750 | 4.750 | 2.58 |
| 152.4 | 52.60 | 19.10 | 63.50 | 60.45 | 77.70 | 91.90 | 19.10 | 120.7 | |||
| 2-1/2 | 7.000 | 2.470 | 0.880 | 2.750 | 2.880 | 3.560 | 4.120 | 4 | 0.750 | 5.500 | 4.11 |
| 177.8 | 62.70 | 22.40 | 69.85 | 73.15 | 90.40 | 104.6 | 19.10 | 139.7 | |||
| 3 | 7.500 | 3.070 | 0.940 | 2.750 | 3.500 | 4.250 | 5.000 | 4 | 0.750 | 6.000 | 4.92 |
| 190.5 | 78.00 | 23.90 | 69.85 | 88.90 | 108.0 | 127.0 | 19.10 | 152.4 | |||
| 3-1/2 | 8.500 | 3.550 | 0.940 | 2.810 | 4.000 | 4.810 | 5.500 | 8 | 0.750 | 7.000 | 6.08 |
| 215.9 | 90.20 | 23.90 | 71.40 | 101.6 | 122.2 | 139.7 | 19.10 | 177.8 | |||
| 4 | 9.000 | 4.030 | 0.940 | 3.000 | 4.500 | 5.310 | 6.190 | 8 | 0.750 | 7.500 | 6.84 |
| 228.6 | 102.4 | 23.90 | 76.20 | 114.3 | 134.9 | 157.2 | 19.10 | 190.5 | |||
| 5 | 10.00 | 5.050 | 0.940 | 3.500 | 5.560 | 6.440 | 7.310 | 8 | 0.880 | 8.500 | 8.56 |
| 254.0 | 128.3 | 23.90 | 88.90 | 141.2 | 163.6 | 185.7 | 22.40 | 215.9 | |||
| 6 | 11.00 | 6.070 | 1.000 | 3.500 | 6.630 | 7.560 | 8.500 | 8 | 0.880 | 9.500 | 10.6 |
| 279.4 | 154.2 | 25.4 | 88.90 | 168.4 | 192.0 | 215.9 | 22.40 | 241.3 | |||
| 8 | 13.50 | 7.980 | 1.120 | 4.000 | 8.630 | 9.690 | 10.62 | 8 | 0.880 | 11.75 | 17.6 |
| 342.9 | 202.7 | 28.40 | 101.6 | 219.2 | 246.1 | 269.7 | 22.40 | 298.5 | |||
| 10 | 16.00 | 10.02 | 1.190 | 4.000 | 10.75 | 12.00 | 12.75 | 12 | 1.000 | 14.25 | 24.0 |
| 406.4 | 254.5 | 30.20 | 101.6 | 273.0 | 304.8 | 323.8 | 25.40 | 362.0 | |||
| 12 | 19.00 | 12.00 | 1.250 | 4.500 | 12.75 | 14.38 | 15.00 | 12 | 1.000 | 17.00 | 36.5 |
| 482.6 | 304.8 | 31.75 | 114.3 | 323.8 | 365.3 | 381.0 | 25.40 | 431.8 | |||
| 14 | 21.00 | 1.380 | 5.000 | 14.00 | 15.75 | 16.25 | 12 | 1.120 | 18.75 | 48.4 | |
| 533.4 | 35.10 | 127.0 | 355.6 | 400.1 | 412.7 | 28.40 | 476.3 | ||||
| 16 | 23.50 | 1.440 | 5.000 | 16.00 | 18.00 | 18.50 | 16 | 1.120 | 21.25 | 60.6 | |
| 596.9 | 36.60 | 127.0 | 406.4 | 475.2 | 469.9 | 28.40 | 539.8 | ||||
| 18 | 25.00 | 1.560 | 5.500 | 18.00 | 19.88 | 21.00 | 16 | 1.250 | 22.75 | 68.3 | |
| 635.0 | 39.60 | 139.7 | 457.2 | 505.0 | 533.4 | 31.75 | 577.9 | ||||
| 20 | 27.50 | 1.690 | 5.690 | 20.00 | 22.00 | 23.00 | 20 | 1.250 | 25.00 | 84.5 | |
| 698.5 | 42.90 | 144.5 | 508.0 | 558.8 | 584.2 | 31.75 | 635 | ||||
| 24 | 32.00 | 1.880 | 6.000 | 24.00 | 26.12 | 27.25 | 20 | 1.380 | 29.50 | 115 | |
| 812.8 | 47.80 | 152.4 | 609.6 | 663.4 | 692.1 | 35.10 | 749.3 |
WN flange can be classified according to pressure levels class 150lb，class 300lb，class 400lb，class 600lb，class 900lb，class 1500lb，class2500lb, To view other product parameters, please click on the following link:
The material of stainless steel butt welded flanges directly determines key indicators such as corrosion resistance, high temperature resistance, and mechanical properties. At present, the commonly used international standards for stainless steel materials mainly include the American Society for Testing and Materials (ASTM) standards, European standards (EN), etc. Stainless steel materials under different standards have their own characteristics and are suitable for different working environments.
ASTM A182: This standard is a commonly used stainless steel forging standard in the United States, suitable for making forged pipe fittings such as stainless steel butt welded flanges. Among them, common materials include:
304 (A182 F304): This is one of the most widely used stainless steel materials, containing 18% chromium and 8% nickel. It has good corrosion resistance and can resist corrosion from various media such as atmosphere, fresh water, steam, etc. It is suitable for most neutral and weakly corrosive environments, such as general working conditions in food processing, water treatment, chemical and other industries.
316(A182 F316L): On the basis of 304 material, 2% -3% molybdenum element is added, significantly improving its ability to resist pitting corrosion, crevice corrosion, and intergranular corrosion, especially in media containing chloride ions. Suitable for highly corrosive working conditions in industries such as seawater treatment, chemical, petroleum, and pharmaceuticals.
321H(A182 F321H): By adding titanium to stabilize carbon and prevent the formation of chromium carbide at high temperatures, the intergranular corrosion resistance and high-temperature strength of the material are effectively improved. 321 stainless steel can maintain good mechanical properties in high temperature environments ranging from 800 ℃ to 900 ℃, making it suitable for high-temperature pipeline systems such as petroleum refining, chemical reaction equipment, power plant boilers, and other industries.
Chemical Composition
| CHEMICAL | LIMITS | C | Mn | P | S | Si | Ni | Cr | Mo | N | Ti |
| ASTM A182 F304 | MIN | 8.0 | 18.0 | ||||||||
| MAX | 0.08 | 2.00 | 0.045 | 0.030 | 1.00 | 11.0 | 20.0 | 0.10 | |||
| ASTM A182 F316 | MIN | 10.00 | 16.00 | 2.00 | |||||||
| MAX | 0.08 | 2.00 | 0.045 | 0.030 | 1.00 | 14.00 | 18.00 | 3.00 | 0.01 | ||
| ASTM A182 F321H | MIN | 0.04 | 9.00 | 17.00 | 4*C | ||||||
| MAX | 0.10 | 2.00 | 0.045 | 0.030 | 1.00 | 12.00 | 19.00 | 0.7 |
Mechanical Properties
| MATERIAL | T.S (MPA) | Y.S (MPA) | EL % | R/A % |
| ASTM A182 F304 | 515 min | 205 min | 30 min | 50 min |
| ASTM A182 F316 | 515 min | 205 min | 30 min | 50 min |
| ASTM A182 F321H | 515 min | 205 min | 30 min | 50 min |
The material standard for stainless steel butt welded flanges in the European Standard (EN) is mainly EN 10088 (Stainless Steel and Heat Resistant Steel - Technical Conditions for Delivery). Common materials include:
X5CrNi18-10: Similar to ASTM A182 F304 material, it has good corrosion resistance and processing performance, and is widely used in various general corrosive environments.
X2CrNiMo17-12-2: Equivalent to ASTM A182 F316L, it has excellent corrosion resistance and is particularly suitable for corrosive environments containing chloride ions. It is widely used in industries such as chemical, petroleum, and food in Europe.
Chemical Composition
| CHEMICAL | LIMITS | C | Si | Mn | P | S | Cr | Mo | Ni | N |
| X5CrNi18-10 (1.4301) | MIN | 17.5 | 8.00 | |||||||
| MAX | 0.07 | 1.00 | 2.00 | 0.045 | 0.02 | 19.5 | 10.50 | 0.10 | ||
| X2CrNiMo17-12-2 (1.4404) | MIN | 16.5 | 2.0 | 10.00 | ||||||
| MAX | 0.03 | 1.00 | 2.00 | 0.045 | 0.02 | 18.5 | 2.5 | 13.00 | 0.10 |
Mechanical Properties
| MATERIAL | T.S (MPA) | Y.S (MPA) | EL % |
| X5CrNi18-10 (1.4301) | 500 to 700 | 250min | 45min |
| X2CrNiMo17-12-2 (1.4404) | 510 to 710 | 250min | 45min |
Compared to other types of flanges and ordinary carbon steel flanges, stainless steel butt welded flanges have many significant advantages, making them widely recognized and applied in the industrial field.
Excellent Corrosion Resistance
High Strength and High Rigidity
Excellent Sealing Performance
Good Welding and Processing Performance
With its excellent performance, stainless steel butt welded flanges have been widely used in various industrial fields and have become an indispensable connecting component in pipeline systems in many industries. Its main application industries include:
Petrochemical industry
Food and pharmaceutical industry
water treatment industry
Energy and power industry
Ship and Ocean Industry
Stainless steel weld neck flanges, with their clear definition, diverse production standards, precise size specifications, high-quality material selection, excellent product advantages, and wide range of applications, have become ideal connecting components in industrial pipeline systems. Whether under harsh working conditions of high pressure and high temperature, or in environments with strict requirements for corrosion resistance and hygiene, stainless steel weld neck flanges can perform excellently, providing strong guarantees for the safe and stable operation of pipeline systems.
