API 6B and 6BX flanges are the two flange families of API 6A wellhead and christmas tree equipment. Type 6B flanges cover the lower pressure ratings and seal with R or RX ring gaskets with a gap left between the flange faces; Type 6BX flanges cover the high pressures and seal with BX pressure-energised rings, with the raised faces in contact after make-up.
Raaj Fittings manufactures flanges to API 6B and 6BX dimensions at our two plants in India for wellhead, manifold and high-pressure production piping.
| Type 6B | Type 6BX | |
|---|---|---|
| Pressure ratings | 2,000, 3,000 and 5,000 psi | 2,000 to 5,000 psi in larger sizes; 10,000, 15,000 and 20,000 psi |
| Ring gasket | R or RX | BX |
| Make-up | Standoff: faces do not touch | Face-to-face contact on the raised face |
| Sealing | Ring compressed in the groove; RX is pressure-energised | BX ring pressure-energised; faces carry external loads |
With 6B flanges, the bolt load is carried through the ring gasket, and a standoff gap remains. 6BX flanges are designed so that, once the BX ring has seated, the raised faces meet: the flange faces then carry bending and external loads, which matters at 10,000 psi and above. A BX ring must never be fitted in a 6B groove, and vice versa.
Ring gaskets are made to API 6A / ASME B16.20 in soft iron, low-carbon steel or stainless steel, and must be softer than the flange groove. In corrosive and sour service, ring grooves are often inlaid with a corrosion-resistant alloy. Read more on our RTJ flanges page.
Every API 6B / 6BX flange is made from PMI-verified material, dimensionally inspected against the ordered standard and marked with material, size, rating and heat number. Orders are supplied with EN 10204 3.1 certificates; EN 10204 3.2 certification and inspection by the buyer's nominated third-party agency are available on request.
6B flanges use R or RX ring gaskets and are made up with a gap between the faces; 6BX flanges use BX rings and are designed for face-to-face contact at higher pressures.
Yes. RX rings fit the same grooves as the matching R rings in 6B flanges and give a pressure-energised seal. BX rings are only for 6BX flanges.
6BX flanges are used for 10,000, 15,000 and 20,000 psi, and for larger sizes at 2,000 to 5,000 psi.
Not in general. Some sizes share ring numbers, but dimensions and ratings must be checked; order to the standard of the mating equipment.