An Overview of Flange standards

A flange standard lays down the dimensions, surface finish, facing type, marking, material and technical specifications for flanges. 

Industry Standard Flange

Flange - Industry Standard Flange (also called Large Diameter Flange) (26"-larger)

Industry Standard Flanges have no national standard code or are they covered by any governing body.

• Slip-on Flange: Class 300, Class 400, Class 600, Class 900, Class 1500

• Threaded Flange: Class 300, Class 400, Class 600, Class 900, Class 1500

• Weld Neck Flange: Class 300, Class 400, Class 600, Class 900, Class 1500, Class 2500

• Blind Flange: Class 75, Class 125, Class 175, Class 250, Class 350

• Welding Neck Flanges: Class 75, Class 125LW, Class 125, Class 175, Class 250, Class 350

• Slip-on Flanges: Class 75, Class 125LW, Class 125, Class 175, Class 250, Class 350

ASME STANDARDS

• ASME B16.1 - Gray Iron Pipe Flanges and Flanged Fittings: Classes 25, 125, and 250

• ASME B16.5 - Pipe Flanges and Flanged Fittings: NPS 1/2 through NPS 24 Metric/Inch Standard

• ASME B16.24 - Cast Copper Alloy Pipe Flanges and Flanged Fittings: Classes 150, 300, 600, 900, 1500, and 2500

• ASME B16.36 - Orifice Flanges

• ASME B16.42 - Ductile Iron Pipe Flanges and Flanged Fittings: Classes 150 and 300

• ASME B16.47 - Large Diameter Steel Flanges, NPS 26 Through NPS 60

AWWA STANDARDS

AWWA C207

• Steel Ring Flange: Class B, Class D, Class E, Class F

• Steel Hub Flange: Class D, Class E

• Blind Flange: Class B, Class D, Class E, Class F

• Steel Ring Flange: Class B, Class D, Class E, Class F

• Steel Hub Flange: Class D, Class E

• Blind Flange: Class B, Class D, Class E, Class F

ASTM STANDARDS

• ASTM A105 / A105M - Specification for Carbon Steel Forgings for Piping Applications

AWWA STANDARDS

• AWWA C115 - Standard for Flanged Ductile Iron Pipe with Ductile-Iron or Gray-Iron Threaded Flanges

MSS STANDARDS

• MSS SP-9 - Spot Facing for Bronze, Iron and Steel Flanges

• MSS SP-25 - Standard Marking Systems for Valves, Fittings, Flanges, and Unions

• MSS SP-44 - Steel Pipeline Flanges

• MSS SP-106 - Cast Copper Alloy Flanges and Flanged Fittings Class 125,150, and 300

ASME/EN SPECIFICATIONS

The ASME B16.5 specification covers flanges for piping applications up to 24 inches in diameter, whereas the ASME B16.47 specification covers pipe flanges above 24 inches (series A and B are available).

More in detail, the following ASME standards apply to main and companion flanges in pipe works:

• ASME B16.1: this standard applies to integral cast iron flanges and blind flanges

• ASME B16.36, Orifice Flange (1/2"-24")
  

• ASME B16.5, Classes 150, 300, 600, 900, 1500 up to NPS 24 and class 2500 up to NPS 12. Class 400 carbon steel flanges shall not be used

• Flanges larger than NPS 24 to be specified in accordance with ASME B16.47. ASME B16.47 series A for NPS 26 to NPS 60 in class 150 to 900 replaces these flange sizes in MSS SP-44

• Series B replaces API 605 in sizes NPS 26 to 60 (ASME B16.47 Series B is used for pipelines and is restricted to flanges used for joints)

• MSS SP-44 shall be used for steel pipeline flanges for sizes smaller than ASME B16.47 where the material grade is not listed in ASME B16.5

• Flanges of unlisted materials and flanges not covered by the above standards shall be designed in accordance with ASME Section VIII Div 1, Appendix 2, and for blind flanges, in accordance with ASME Section VIII Div 1, Section UG-34

  
  

Tolerances for flanges shall be in accordance with ASME B16.5, section 7 for flanges up to NPS 24, and ASME B16.47 for flanges over NPS.

Pipe flanges for European piping systems are covered by the EN 1092-1 specification  (weld neck flange type 11, plate flange type 01, blind flange type 05, threaded flange type 13).

MATERIAL GRADES

The key material grades for pipe flanges, examined in a separate article, are:

• ASTM A105 (carbon steel flanges for high-temperature service)

• ASTM A350 (CS flange for low temperature)

• ASTM A694 (high yield carbon steel flange for line pipes)

• ASTM A182 F1 to F91 (alloy steel flange)

• ASTM A182 F304, F316, F321 (stainless steel flange)

• ASTM A182 F51, ASTM A182 F53/55 (duplex and super duplex flange), and higher grades (Inconel, Hastelloy, Monel flange).