STainless steel flange/Carbon steel flange/Duplex flange

ASTM / ASME / ANSI / ASA Standards Flange
B16.47 Large Diameter Steel Flanges: NPS 26 through NPS 60 This Standard covers pressure-temperature ratings, materials, dimensions, tolerances, marking, and testing for pipe flanges in sizes NPS 26 through NPS 60 and in ratings Classes 75, 150,0300, 400, 600, and 900. Flanges may be cast, forged, or plate (for blind flanges only) materials. Requirements and recommendations regarding bolting and gaskets are also included.

The American Society of Mechanical Engineers issues standards for mechanical and piping design. ASME standard B16.47 covers large diameter pipes up to a 60-inch bore. ASME standard B16.7 series A flanges are equivalent to MSS SP44 flanges. ASME standard B16.7 series B matches API 605 flanges.

B16.5 Pipe Flanges and Flange Fittings standard covers pressure-temperature ratings, materials, dimensions, tolerances,marking, testing, and methods of designating openings for pipe flanges and flanged fittings.The standard includes flanges with rating class designations 150, 300, 400, 600, 900, 1500, and 2500 in sizes NPS 1/2 through NPS 24, with requirements given in both metric and U.S units. The Standard 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.

API Standards Flange
API flanges are designed to handle very high pressures and temperatures. API flanges have a smaller bolt circle than MSS flanges. All API flanges are ring joint flanges. API flange standards start with a number followed by a letter. API standard 17D is the specification for sub-sea well head flanges.

"The Differents Between API and ANSI Flanges"
The difference between ASME / ANSI and API flanges is the fabrication material and the higher rated API operating pressure. ASME / ANSI flanges are common in industrial process systems handling water, steam, air and gas. API flanges are manufactured for high strength operating refinery systems with products such as oil and explosive gases. The flange standards API 6A and ASME / ANSI B16.5 are similar dimensionally - but the API 6A flanges are rated for higher pressures as shown in the table below:
 

1) In the old API standard, flanges ranged from 11/2 to 10(20) inches.

MSS Standards
MSS flange standards were adopted by American National Standards Institute. MSS flange standards start with an SP followed by a number. MSS SP-9 is the standard for spot facing flanges. MSS SP-44 is the standard for steel pipeline flanges. MSS SP-60 is the standard for connecting flange joint.

MSS SP-9 is the standard for spot facing flanges.
MSS SP-44 is the standard for steel pipeline flanges.
MSS SP-60 is the standard for connecting flange joint.

AWWA Standards
AWWA C207 Steel Pipe Flanges for Waterworks Service--Sizes 4 In. Through 144 In. (100 mm Through 3600 mm).

JIS Standards
B2220 Steel Welding Pipe Flanges.

KS Standards
B1503 Steel Welding Pipe Flanges.

DIN Standards Flange
DIN 2501 Flat Flanges
DIN 2502 Flat Flanges
DIN 2503 Flat Flanges
DIN 2527 Blind Flanges
DIN 2573 Flat Flanges
DIN 2576 Flat Flanges
DIN 2631 Weld Neck Flanges
DIN 2632 Weld Neck Flanges
DIN 2633 Weld Neck Flanges
DIN 2634 Weld Neck Flanges
DIN 2635 Weld Neck Flanges
DIN 2636 Weld Neck Flanges
DIN 2637 Weld Neck Flanges
DIN 2565 Threaded Neck Flanges
DIN 2566 Threaded Neck Flanges
DIN 2641 Lap Joint Flange, Loose Flanges
DIN 2642 Lap Joint Flange, Loose Flanges
DIN 2655 Socket Joint Flanges