Complete ASME B16.5 flange standard specification guide: NPS 1/2 to 24, Class 150-2500, pressure-temp ratings, facings (RF, RTJ, FF), materials. Quote in 30 min.
ASME B16.5 is the globally dominant standard for steel pipe flanges and flanged fittings from NPS 1/2 through NPS 24. It defines strict dimensional interchangeability, pressure-temperature rating tables across Material Groups 1.1 through 3.17, and face finish standards.
ASME B16.5 covers pressure-temperature ratings, materials, dimensions, tolerances, marking, testing, and methods of designating openings for pipe flanges and flanged fittings in sizes NPS 1/2 through NPS 24 metric/inch standard.
| Specification Parameter | ASME Standard Specification | European / Metric Equivalent |
|---|---|---|
| Size Scope | NPS 1/2" to 24" | DN 15 to DN 600 |
| Pressure System | Class 150 to 2500 | PN 2.5 to PN 400 |
| Facing Standard | RF (1.6mm / 6.3mm), RTJ | Type A, B, C, D, E, F |
| Gasket Standard | ASME B16.20 (Spiral Wound / RTJ) | EN 1514 / DIN 2690 |
Under ASME B16.5 Flange Standard, 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 B16.5 Flange Standard 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: ASME B16.5 covers pipe sizes up to NPS 24. For flanges NPS 26 and larger, ASME B16.47 Series A (MSS SP-44) or Series B (API 605) applies.
A: For Class 150 and 300, ASME B16.5 specifies a 1.6 mm (0.06 in.) Raised Face. For Class 400, 600, 900, 1500, and 2500, a 6.4 mm (0.25 in.) Raised Face is standard.
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