Class 600 flanges to ASME B16.5 and B16.47 are the first of the high-pressure classes, used on gas transmission and gathering lines, high-pressure hydrocarbon and hydrogen service, compressor discharge, boiler feedwater and high-pressure steam. They are noticeably heavier than Class 300, with a taller raised face, bigger bolts and, in many oil and gas specifications, ring type joint facings.
Raaj Fittings manufactures Class 600 flanges in every type, from ½" to 60", at our two plants in India, in carbon, low-temperature and chrome-moly steel, stainless, duplex and super duplex and nickel alloys, for oil and gas, refinery and power 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) | 102.1 | 87.6 | 69.4 |
| 2.2 (ASTM A182 F316) | 99.3 | — | — |
| 2.3 (ASTM A182 F316L) | 82.7 | — | — |
At ambient temperature, Class 600 carbon steel flanges are rated 102.1 bar (1,480 psig), exactly double Class 300. Above Class 600 come Class 900, 1500 and 2500 for wellhead, injection and very high-pressure service.
| NPS | Flange OD, mm | Bolts | Bolt size |
|---|---|---|---|
| 2" | 165.1 | 8 | ⅝" |
| 4" | 273.0 | 8 | ⅞" |
| 6" | 355.6 | 12 | 1" |
| 8" | 419.1 | 12 | 1⅛" |
| 12" | 558.8 | 20 | 1¼" |
In the smallest sizes, Class 600 shares outside diameter and drilling with Class 300 and 400, but the flange is thicker and longer through the hub; from about 4" upwards the drilling differs. Always match class and size on both flanges.
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 600 is rated 102.1 bar (1,480 psig) at up to 38 °C, about 87.6 bar at 200 °C and about 69.4 bar at 400 °C. Other materials have different ratings in the ASME B16.5 tables.
Class 600 and higher-class ASME B16.5 flanges have a 6.4 mm (0.25") raised face, compared with 1.6 mm (0.06") for Class 150 and 300.
Both are used. Raised face with spiral wound gaskets is common in refinery and steam service; RTJ is common in oil and gas production, gas transmission and where the specification calls for metal-to-metal seals.
Only in a few small sizes where the drilling happens to match, and even then the joint is limited by the lower class. In general, mating flanges must be the same class and size.