Metallic ring type gaskets are used in ring type joints which excel in high-pressure, high-temperature applications such as oil field drilling equipment. These joints are also used on valves and pipework assemblies.
Metallic gasket is fabricated from one or a combination of metal to the desired shape and size. Common metallic gasket is ring-joint gasket and lens rings. It is suitable for high-pressure and temperature applications and require high bolt load to seal.
They are precision-engineered components designed to be used in conjunction with precision-machined flanges. All Ring Joints are manufactured according to ASME B16.20 and API 6A.
Material of Construction
The gasket material is selected on a number of grounds primarily; chemical compatibility with the media and the hardness of the flange. The gasket material ideally needs to be roughly 30 Brinell less than the flange material to ensure sufficient deformation of the gasket without damaging the flange facing.
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Shapes
Ring joint gaskets are either oval or octagonal in cross section. Exact shape depends on style of gaskets.
Style BX Ring Joint Gasket
The Style BX ring type joint is manufactured in accordance with API 6A and ASME B16.20. All BX ring type joints incorporate a pressure passage hole to allow for pressure equalization each side of the sealing faces. On assembly, metal to metal contact of the flange faces is achieved. The Style BX is not interchangeable with any other style, and is only suited for API 6BX flanges. Style BX ring type joints are designed to seal pressure up to 20,000 psi in accordance with API 6A pressure ratings.
Style R Ring Joint Gasket
The Style R ring type joint is manufactured in accordance with API 6A and ASME B16.20, to suit API 6B and ASME B16.5 flanges.
Style R ring type joints are manufactured in both oval and octagonal configurations. Both styles are interchangeable on the modern flat bottom groove, however only the oval style can be used in the old type round bottom groove.
Style R ring type joints are designed to seal pressure up to 6,250 psi in accordance with ASME B16.5 pressure ratings and up to 5,000 psi in accordance with API 6A pressure ratings.
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Style RX Ring Joint Gasket
Size/Pressure Class:
1 ½” to 20” : 720 to 5000 API 6A
Applications:
- Used for high pressure applications.
- The Style RX is designed to fit the same groove design as a standard style R making joints interchangeable.
- The Style RX has an increased height and utilizes the internal system pressure to energize and improve the seal as internal pressure increase.
- Suitable for flat bottom groove flanges.
Hardness
Ring joint gaskets are made from soft metal so that they can be compressed after bolt tightening, thus making perfect sealing to avoid any kind of fluid leakage. ASME B16.20 specifies maximum hardness for these gaskets.
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Marking
ASME B16.20 specifies that the outer surface of each gasket shall carry the manufacturer’s name or identification trademark and gasket number prefixed by the letters R, RX, or BX, followed by the gasket material identification. Materials shall be identified as shown in Table 2. The gasket shall also be marked with an ASME B16.20 designation. The marking shall be applied so as not to harmfully distort the gasket or affect the integrity of the seal.
Surface Finish
ASME B16.20 specifies that Types R and RX gaskets shall have a surface finish not rougher than 1.6 micro-meters (63 micro-inch.) roughness. Type BX gaskets shall have a surface finish not rougher than 0.8 micro-meters (32 micro-inches.) roughness. Surface finish shall pertain to the gasket-sealing surface. The sealing surfaces on the ring joint grooves must be smoothly finished to 63 Micro-inches and be free of objectionable ridges, tool or chatter marks.
Damaged Gaskets
Worn, pitted or corroded flange sealing surfaces can impede the sealing ability of RTJ gaskets. In such instances, a serrated octagonal RTJ gasket, covered with flexible graphite or a Maxiflex CR-RJ, can provide a temporary or emergency solution until the flange can be repaired or replaced.
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Sample Piping Material Specification
- Name : Octagonal Ring Type Joint Gasket
- Material : Soft Iron
- Rating : 600#
- Std : ASME B16.20
- Flanges : B16.5
- Size/Pressure Class:
- ½” to 24” “ 150 to 2500 ASME B16.20
- 26” to 36” : 300 to 900 ASME B16.47 Series A
- 1 ½” to 20” : API 6A
Typical Properties:
- High integrity seal at high pressures
- The octagonal cross section has a higher sealing efficiency than the oval and would be the preferred gasket
- Suitable for flat bottom groove flanges
- Available in Ring numbers R11 to R105