Valve Standard Reference
ASME B16.47
AmericanLarge Diameter Steel Flanges NPS 26 Through NPS 60 Metric/Inch Standard
ASME B16.
Overview — ASME B16.47
ASME B16.47 covers large-diameter steel flanges for pipe sizes NPS 26" through NPS 60" in pressure classes 75 through 900, filling the size gap above ASME B16.5 (which only covers up to NPS 24"). The standard provides two distinct flange dimension series: Series A (based on the former MSS SP-44 large pipe flange standard) and Series B (based on the former API 605 standard). The two series have different bolt hole patterns, flange dimensions, and weights, so Series A and Series B flanges are NOT interchangeable — this is critically important for procurement and field installation of large-bore pipeline and industrial valves.
Scope
Covers carbon steel and alloy steel welding-neck, slip-on, blind, threaded, socket-welding, lap-joint, and orifice flanges in NPS 26" through NPS 60", pressure classes 75, 150, 300, 400, 600, and 900. Series A dimensions follow MSS SP-44; Series B dimensions follow the superseded API 605. Applicable to large-bore pipeline mainline flanges, large compressor station piping, terminal storage piping, and large chemical plant piping.
Applicable Valve Types
Gate Valves — large bore (NPS 26" and above) with flanged ends
Ball Valves — large bore trunnion-mounted with flanged ends
Butterfly Valves — large bore double-flanged
Check Valves — large bore flanged
Applicable Pressure Classes
Key Requirements — ASME B16.47
Two non-interchangeable series: Series A (MSS SP-44 heritage) and Series B (API 605 heritage)
Pressure classes covered: Class 75 (Series A only), 150, 300, 400, 600, 900
Material groups aligned with ASME B16.5: Groups 1.1 through 2.3 for P-T ratings
Flange type: welding neck (most common for large bore), blind, slip-on, ring-type joint
Bolt holes: different count and diameter between Series A and B for same class/size — never mix series
Maximum size: NPS 60" Class 300 in Series A; NPS 60" Class 150 in Series B
All dimensions in both inch and metric (dual dimensioning)
Material marking: class, size, material designation, heat number, and standard (B16.47) on flange face
Testing Requirements — ASME B16.47
Dimensional inspection per ASME B16.47 Series A or B tables
Hydrostatic shell test at 1.5× rated pressure for flanged valves
PMI verification for alloy steel and stainless steel flanges
Documentation Required for ASME B16.47 Compliance
ASME B16.47 Series designation (A or B) on documentation and marking
Pressure class marking on flange
Material Test Reports (MTR) per EN 10204 3.1
Dimensional inspection report confirming series and class compliance
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