Flange according to Standard ASME B16.5

Pipe Flanges and Flanged Fittings: NPS 1/2 through NPS 24, Metric/Inch Standard B16.5 – 2020

ASME B16.5 Pipe Flanges and Flanged Fittings: NPS 1/2 through NPS 24 Metric/Inch Standard covers pressure-temperature ratings, materials, dimensions, tolerances, marking, testing, and methods of designating openings for pipe flanges and flanged fittings. Included are:
(1) flanges with rating class designations 150, 300, 400, 600, 900, and 1500 in sizes NPS 1/2 through NPS 24 and flanges with rating class designation 2500 in sizes NPS 1/2 through NPS 12, with requirements given in both metric and U.S. Customary units with diameter of bolts and flange bolt holes expressed in inch units;

The flange types include weld neck(WN), slip on(SO), threaded(THD), socket welding(SW), lap joint(LPJ), blind(BL), long weld neck(LWN), and reducing flange. The end flange facings can be furnished as raised face(RF), ring joint face(RTJ), flat face(FF), large or small male/female face, small male/female face, large or small tongue face, and large or small groove face. Among all of the facings, raised face(RF) and ring joint face(RTJ) are most commonly used. You can click below table to see the dimension and weight details for each class rating of ASME B16.5 pipe flanges.

(2) flanged fittings with rating class designation 150 and 300 in sizes NPS 1/2 through NPS 24, with requirements given in both metric and U.S. Customary units with diameter of bolts and flange bolt holes expressed in inch units;
(3) flanged fittings with rating class designation 400, 600, 900, and 1500 in sizes NPS 1/2 through NPS 24 and flanged fittings with rating class designation 2500 in sizes NPS 1/2 through NPS 12 that are acknowledged in Non-Mandatory Appendix E in which only U.S. Customary units are provided.

ASME B16.5 is limited to flanges and flanged fittings made from cast or forged materials, and blind flanges and certain reducing flanges made from cast, forged, or plate materials. Also included in this Standard are requirements and recommendations regarding flange bolting, flange gaskets, and flange joints.
This Standard is to be used in conjunction with equipment described in other volumes of the ASME B16 Series of Standards as well as with other ASME standards, such as the Boiler and Pressure Vessel Code and the B31 Piping Codes.

Dimension tolerance according to Standard ASME B16.5

• Bore (or Inside Diameter, ID): The bore refers to the internal diameter of the flange, which matches the pipe size.
• Bolt Holes: The standard specifies the number of bolt holes and their dimensions, including the bolt circle diameter (BCD).
• Face Types: The most common face types specified are flat face (FF), raised face (RF), and ring-type joint (RTJ).
• Thickness (or Thickness at the Flange Face): The thickness is dependent on the size and pressure class of the flange.
• Pressure Rating Classes: These are determined based on material and flange size, often ranging from 150 to 2500.

Here are some common flange materials as specified by ASME B16.5:

1. Carbon Steel

• ASTM A105:
• ASTM A350 LF2: This is a low-temperature carbon steel used for flanges intended for service in low-temperature applications (down to -50°F / -45°C).

2. Alloy Steel

• ASTM A182 F11: This is a chromium-molybdenum alloy steel used for high-temperature applications. It’s commonly used in power plants and chemical processing industries due to its strength at elevated temperatures (up to 1100°F / 593°C).
• ASTM A182 F22: This is another chromium-molybdenum alloy steel, designed for higher-pressure applications and can be used in service temperatures up to 1100°F (593°C).
• ASTM A182 F5: A low-alloy steel used in high-temperature service, it’s resistant to oxidation and corrosion.

3. Stainless Steel

• ASTM A182 F304/304L
• ASTM A182 F316/316L: Contains molybdenum for improved corrosion resistance in marine and chloride environments. It is used in applications where pitting and crevice corrosion are concerns, such as in seawater or chemical processing.
• ASTM A182 F310: High-temperature stainless steel, designed for higher service temperatures, up to around 2000°F (1093°C), often used in furnaces or high-temperature reactors.

4. Duplex Stainless Steel

• ASTM A182 F51/F53: These are duplex stainless steels, which combine the properties of austenitic and ferritic steels, offering higher strength and better resistance to pitting and stress corrosion cracking. They are ideal for use in marine or chemical processing applications.

5. Nickel Alloys

• ASTM B164 (Alloy 400): This nickel-copper alloy is used in corrosive environments and can withstand high temperatures and corrosion, particularly in marine environments.
• ASTM B564 (Alloy 625): This nickel-based alloy is known for its excellent resistance to corrosion, oxidation, and high-temperature oxidation. It is often used in applications such as chemical processing and aerospace.

6. Titanium

• Grade 2 Titanium: Titanium flanges offer excellent resistance to corrosion, especially in seawater or acidic environments. Titanium is highly resistant to stress corrosion cracking and is used in industries like aerospace, chemical, and marine.

7. Copper Alloys

• ASTM B62 (Bronze): Copper-based alloys like bronze or brass can be used for low-pressure applications where corrosion resistance is important. These alloys are commonly used in marine or water treatment applications.

8. Other Materials

• Gray Cast Iron and Ductile Iron: These materials can be used for flanges in low-pressure applications or for use in waterworks systems. However, their use is generally limited to lower-pressure and lower-temperature applications.
• Aluminum: In specialized industries like aerospace or lightweight piping systems, aluminum flanges can be used for lower-pressure applications.