Wellhead and manifolds
Ring joint gaskets: R, RX and BX
Ring joint gaskets seal high-pressure flanges metal to metal: oval and octagonal R rings, pressure-energized RX rings for 6B flanges, and BX rings for 6BX flanges made up face to face.
A ring joint gasket is a solid metal ring that seals a flange joint by being squeezed into matching grooves in the two flange faces. R rings, oval or octagonal in section, fit type 6B API flanges and ASME B16.5 ring joint flanges; RX rings fit the same grooves but are pressure energized; BX rings fit type 6BX flanges, which are made up face to face. We supply all three in soft iron, low carbon steel, F5 and stainless steels, each ring softer than its groove and marked with its number and material.
R, RX and BX
| Type | Section | Fits | How it seals |
|---|---|---|---|
| R oval | Oval | API 6B and ASME B16.5 ring joint flanges | Line contact, squeezed by bolt load |
| R octagonal | Octagonal | API 6B and ASME B16.5 ring joint flanges | Flat contact faces, squeezed by bolt load |
| RX | Octagonal outside, flat inside | The same octagonal grooves as R | Pressure energized: line pressure pushes the ring onto the groove |
| BX | Square with tapered faces, pressure passage hole | API 6BX flanges and hubs | Pressure energized, flanges made up face to face |
Ring dimensions follow API 6A and ASME B16.20. Order by ring number, such as R-24, RX-24 or BX-152.
Materials and hardness
A ring seals by deforming plastically into the groove, so it must be softer than the flange groove it seats in. These are the maximum hardness values ASME B16.20 gives for common ring materials:
| Material | Maximum hardness | Typical use |
|---|---|---|
| Soft iron | 90 HB | General service with carbon steel flanges |
| Low carbon steel | 120 HB | General service with carbon and low alloy steel flanges |
| F5 (4 to 6% chromium) | 130 HB | Higher temperatures and mild corrosion |
| 304, 316, 347 stainless | 160 HB | Corrosive service, stainless or inlaid grooves |
| 410 stainless | 170 HB | Corrosive service with hard grooves |
Maximum hardness per ASME B16.20. Nickel alloy rings are made to order for grooves inlaid with corrosion-resistant alloy.
A ring harder than its groove damages the flange instead of sealing. For sour service, choose a ring material that meets NACE MR0175 / ISO 15156 and is still softer than the groove, often 316 stainless or an inlaid groove with a nickel alloy ring.
Ordering by ring number
Each flange size and rating has one ring number. R-24 or RX-24 fits a 2-1/16 in 5,000 psi type 6B flange, and BX-152 a 2-1/16 in 10,000 or 15,000 psi type 6BX flange. Give the ring number and material, or the flange size, rating and type, and we confirm the ring. Each ring is stamped with its number and material and hardness tested.
We make these parts to the API 6A requirements your order calls up: material, dimensions, tests and marking as specified. We do not hold an API license, so the parts do not carry the API Monogram. If your specification requires monogrammed equipment, the quotation says so plainly.
Ordering
Ring joint gasket, BX-154, 316 stainless, 160 HB maximum, hardness tested, EN 10204 3.1, 20 pcs
Ring joint gasket, RX-24, soft iron, 90 HB maximum, coated, EN 10204 3.1, 50 pcs
Frequently asked questions
Can an RX ring replace an R ring?
Yes, in a type 6B flange or an ASME B16.5 ring joint flange: an RX ring of the same number fits the same octagonal groove and is pressure energized. The flange gap is slightly larger with an RX ring. An R ring cannot replace an RX ring where the design relies on the RX.
Why does a BX ring have a hole?
The small hole through a BX ring connects the space between the ring and the groove, so pressure is not trapped there as the flanges are made up face to face.
Can ring gaskets be reused?
No. A ring joint gasket seals by deforming into the groove, and once it has been made up it should be replaced. Reusing a ring is a common cause of flange leaks.
Do you coat soft iron and carbon steel rings?
Yes. They are usually supplied with a protective coating against rust in storage; the coating is stated on the quotation.