ANSI - ASME B 16.5

ANSI/ASME B 16.5

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The ANSI accredited ASME Standard B 16.5 requires that the flange face have a specified roughness to ensure the compatibility of the surface with the gasket and a high quality seal. This Sealing Sense is intended to be consistent with this standard.

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Piping flanges are typically made from forged materials and machined according to standard dimensions. These parts are widely used to connect process equipment and piping lines to each other.

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ASME flanges are made to standards called out by ASME B16.5 or ASME B16.47 and have machined surfaces.

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B16.5 refers to nominal pipe sizes (NPS) from 1/2 to 24.

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B16.47 covers NPSs from 26 to 60.

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Each specification further delineates flanges into classes 150, 300, 400, 600, 900, 1500 and 2500 for B16.5.

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B16.47 delineates its flanges into classes 75, 150, 300, 400, 600, 900.

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The ANSI Standards unify the production of flanges up to 24" size for nominal pressures up to 1500 p.s.i and for nominal pressures of 2500 p.s.i up to 12" size.

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ANSI flanges are of various types according to the required functions, they are divided into seven groups of nominal pressures called « series » in which the nominal pressures is indicated in « pounds per square inch»(p.s.i).

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These groups are the series 150, 300, 400, 600, 900, 1500, 2500 p.s.i.; they correspond to PN 10, 16, 25, 40, 64, 100, 175, kh/cm2 provided by UNI and DIN standards in the limits foreseen by the connection between pressure and temperature.

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ANSI designations such as ANSI 150, ANSI 300 and so on are often followed by a # (hash symbol).

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The ANSI number does not directly relate to a pressure rating, but to a class of  flange.

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For example, the hash (#) or 'pound' reference; e.g. 300 pound, can be misleading in that an ANSI 300 flange is actually rated for a test pressure of 740 psi (~5100 kPa), and only within a certain working temperature range (-20 to 100 deg F.) In most cases these are not interchangeable (e.g. an ANSI flange will not mate against a JIS flange).

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Further many of the flanges in each standard are divided into "pressure classes", allowing flanges to be capable of taking different pressure ratings. Again these are not generally interchangeable (e.g. an ANSI 150 will not mate with an ANSI 300).

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The flange faces are made to standardized dimensions and are typically "flat face", "raised face", "tongue and groove", or "ring joint" styles, although other obscure styles are possible.

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Flange designs are available as "welding neck", "slip-on", "boss", "lap joint", "socket weld", "threaded", and also "blind".