ASME B16.5 and B16.47
The two ASME standards that cover the bulk of industrial pipe flange supply. B16.5 governs catalog sizes through 24 inch. B16.47 covers large diameter through 60 inch in two series. Together they cover most refinery, petrochemical, power, and chemical process flange work.
ASME B16.5
B16.5 covers pipe flanges and flanged fittings in nominal pipe sizes 1/2 inch through 24 inch. Pressure classes are 150, 300, 400, 600, 900, 1500, and 2500. Each class is a numeric designator, not a pressure rating. Actual pressure-temperature ratings depend on the material grade and the operating temperature, tabulated in the standard as P-T tables.
Standard facings include raised face (RF), flat face (FF), ring-type joint (RTJ), tongue and groove (T&G), and large male and female (LMF). Standard flange types include weld neck, slip-on, blind, threaded, socket weld, lap joint, reducing, and orifice.
ASME B16.47
B16.47 covers large diameter pipe flanges from 26 inch through 60 inch nominal. The standard has two series with different historical origins. Series A is derived from MSS SP-44 and is the heavier pattern with larger bolt circle and bolt count, designed for cyclic and severe service (150# and up). Series B is derived from API 605 and is the lighter pattern, dimensionally compatible with API 605 legacy installations (75# and up, not generally available above Class 600). Series A and Series B are not interchangeable. The project spec calls one or the other.
B16.47 pressure classes span 75 through 900. Series A (derived from MSS SP-44) covers 150# and up; Series B (derived from API 605) covers 75# and up but is not generally available above Class 600. Material grades, facings, and P-T tables match B16.5 where applicable.
Common Materials
A105 forged carbon is the default for room-temperature pressure service. A350 LF2 carries impact testing for low-temperature service down to minus 50 degrees F. A694 high-yield grades (F42 through F70) mate to API 5L X-grade pipe on pipeline lines. F304L and F316L stainless cover corrosion service. F11, F22, F91, and F92 chrome-moly cover elevated temperature service from 800 degrees F up.