Class 300 flanges to ASME B16.5 and B16.47 are the workhorse of refinery, petrochemical, chemical and power piping. With about two and a half times the rating of Class 150 at ambient temperature, and much better retention of that rating at elevated temperature, Class 300 covers most hydrocarbon process lines, medium-pressure steam headers and pump discharge piping.
Raaj Fittings manufactures Class 300 flanges in every type, from ½" to 60", at our two plants in India, in stainless steel, duplex and super duplex, nickel alloys, carbon, low-temperature and chrome-moly steel, for projects across the Middle East, Europe and the Americas.
| Material group (example grade) | −29 to 38 °C | 200 °C | 400 °C |
|---|---|---|---|
| 1.1 (ASTM A105) | 51.1 | 43.8 | 34.7 |
| 2.2 (ASTM A182 F316) | 49.6 | — | — |
| 2.3 (ASTM A182 F316L) | 41.4 | — | — |
Compare Class 150 at 200 °C (13.8 bar for carbon steel) with Class 300 at the same temperature (43.8 bar): for hot service, Class 300 is often needed even when the pressure is modest. ASME B16.5 also includes Class 400, between 300 and 600, but it is rarely specified.
| NPS | Flange OD, mm | Bolts | Bolt size |
|---|---|---|---|
| 2" | 165.1 | 8 | ⅝" |
| 4" | 254.0 | 8 | ¾" |
| 6" | 317.5 | 12 | ¾" |
| 8" | 381.0 | 12 | ⅞" |
| 12" | 520.7 | 16 | 1⅛" |
Class 300 flanges have a larger outside diameter, a larger bolt circle and usually more or larger bolts than Class 150 of the same size, so the two classes cannot be bolted together.
Every heat is PMI-verified and its chemistry and mechanical properties are confirmed against the material specification before the flanges are released. Each piece is marked with grade, size, rating and heat number for traceability to its EN 10204 3.1 mill test certificate. EN 10204 3.2 certification and inspection by the buyer's nominated third-party agency are available on request, as are PED 2014/68/EU compliance for European projects and IBR certification for Indian boiler applications.
For carbon steel (A105), Class 300 is rated 51.1 bar (740 psig) at up to 38 °C, about 43.8 bar at 200 °C and about 34.7 bar at 400 °C. Stainless steel ratings differ; use the ASME B16.5 tables for your material.
Class 300 has about two and a half times the rating at ambient temperature and keeps a much higher rating at elevated temperature. For hot hydrocarbon or steam service, Class 300 is often required even at moderate pressure.
No. Class 400 is a separate ASME B16.5 class between 300 and 600, with its own dimensions and ratings. It is rarely specified; most designs go from Class 300 to Class 600.
Spiral wound gaskets to ASME B16.20, with a centring outer ring and usually an inner ring, are the most common choice for Class 300 hydrocarbon and steam service.