ASME B16.47 large diameter flange guide (NPS 26 to 60): Series A (MSS SP-44) vs Series B (API 605), pressure classes 75-900, weights & bolt patterns. Quote in 30 min.
ASME B16.47 governs large-diameter steel flanges from NPS 26 through NPS 60. It incorporates two distinct series: Series A (derived from MSS SP-44) for heavy-duty industrial piping, and Series B (derived from API 605) for compact pipeline applications.
ASME B16.47 covers pressure-temperature ratings, materials, dimensions, tolerances, marking, and testing for steel pipe flanges in sizes NPS 26 through NPS 60.
| Design Feature | Series A (MSS SP-44) | Series B (API 605) |
|---|---|---|
| Origin Spec | MSS SP-44 | API 605 |
| Flange Thickness | Thicker & heavier | Thinner & lighter |
| Bolt Circle & Bolt Size | Fewer, larger diameter bolts | More, smaller diameter bolts |
| Pipeline Weight Impact | Higher weight, high bending rigidity | Compact design, lower weight |
Under ASME B16.47 Large Diameter Flanges, flange sealing face finishes are critical to leak-free joint integrity. Raised Face (RF) and Flat Face (FF) flanges are machined with a serrated concentric or serrated spiral finish having an average surface roughness between 125 µin and 250 µin (3.2 µm to 6.3 µm Ra), creating an ideal gripping surface for spiral wound or non-asbestos sheet gaskets.
For severe cyclic service or high-pressure hydrocarbons, Ring Type Joint (RTJ) grooves are precision CNC-machined to ASME B16.20 standards. Groove surfaces are finished to a mirror-smooth 63 µin (1.6 µm Ra) max roughness to ensure tight metallic sealing against octagonal or oval ring gaskets.
Compliance with ASME B16.47 Large Diameter Flanges requires permanent identification legibly stamped on the outer rim of every flange: manufacturer trademark ("REMAX"), governing standard, nominal pipe size (NPS or DN), pressure rating class (e.g. 150#, 300#, 600#), ASTM/ASME material specification and grade (e.g. A105, F316L), schedule/wall thickness, and unique heat batch number.
All markings correlate 1:1 with the accompanying EN 10204 Type 3.1 Mill Test Certificate (MTC), providing verified traceability back to the initial steel melting ladle and forging ingot.
A: No. Series A and Series B flanges have completely different bolt circle diameters, bolt hole quantities, flange thicknesses, and outer diameters. They cannot mate with each other.
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