What Is an ASME B16.20 RTJ Gasket?
A ring-joint (RTJ) gasket is a solid metal ring that seals by plastic deformation into the machined groove of an RTJ flange. ASME B16.20 (Part RJ) covers Type R rings (oval and octagonal cross-section), together with RX and BX styles for API 6A / ISO 10423 wellhead equipment. RTJ gaskets are the standard choice for high-pressure, high-temperature piping in oil & gas and refinery service.
Pressure Classes
RTJ gaskets are specified for Class 600 through Class 2500 flanges per ASME B16.5 and B16.47. Ring-to-flange matching is defined in B16.20 Table RJ-5-2 (pipe size by pressure class for each ring number).
Representative Type R Ring Dimensions — B16.20 Table RJ-5-1 (mm / in.)
Common smaller rings R-11 through R-49 are listed below. The full standard contains 94 rings (R-11 through R-105) including large B16.47 rings; complete dimensions per ASME B16.20 Tables RJ-5-1 and RJ-5-2.
| Ring No. | Pitch dia. P (mm/in.) | Width A (mm/in.) | Oval height B (mm/in.) | Octagonal height H (mm/in.) | Flat width C (mm/in.) | Radius R1 (mm/in.) |
|---|---|---|---|---|---|---|
| R-11 | 34.14 (1.344) | 6.35 (0.250) | 11.2 (0.44) | 9.7 (0.38) | 4.32 (0.170) | 1.5 (0.06) |
| R-12 | 39.70 (1.563) | 7.95 (0.313) | 14.2 (0.56) | 12.7 (0.50) | 5.23 (0.206) | 1.5 (0.06) |
| R-13 | 42.88 (1.688) | 7.95 (0.313) | 14.2 (0.56) | 12.7 (0.50) | 5.23 (0.206) | 1.5 (0.06) |
| R-14 | 44.45 (1.750) | 7.95 (0.313) | 14.2 (0.56) | 12.7 (0.50) | 5.23 (0.206) | 1.5 (0.06) |
| R-15 | 47.63 (1.875) | 7.95 (0.313) | 14.2 (0.56) | 12.7 (0.50) | 5.23 (0.206) | 1.5 (0.06) |
| R-16 | 50.80 (2.000) | 7.95 (0.313) | 14.2 (0.56) | 12.7 (0.50) | 5.23 (0.206) | 1.5 (0.06) |
| R-17 | 57.15 (2.250) | 7.95 (0.313) | 14.2 (0.56) | 12.7 (0.50) | 5.23 (0.206) | 1.5 (0.06) |
| R-18 | 60.33 (2.375) | 7.95 (0.313) | 14.2 (0.56) | 12.7 (0.50) | 5.23 (0.206) | 1.5 (0.06) |
| R-19 | 65.10 (2.563) | 7.95 (0.313) | 14.2 (0.56) | 12.7 (0.50) | 5.23 (0.206) | 1.5 (0.06) |
| R-20 | 68.28 (2.688) | 7.95 (0.313) | 14.2 (0.56) | 12.7 (0.50) | 5.23 (0.206) | 1.5 (0.06) |
| R-21 | 72.24 (2.844) | 11.13 (0.438) | 17.5 (0.69) | 16.0 (0.63) | 7.75 (0.305) | 1.5 (0.06) |
| R-22 | 82.55 (3.250) | 7.95 (0.313) | 14.2 (0.56) | 12.7 (0.50) | 5.23 (0.206) | 1.5 (0.06) |
| R-23 | 82.55 (3.250) | 11.13 (0.438) | 17.5 (0.69) | 16.0 (0.63) | 7.75 (0.305) | 1.5 (0.06) |
| R-24 | 95.25 (3.750) | 11.13 (0.438) | 17.5 (0.69) | 16.0 (0.63) | 7.75 (0.305) | 1.5 (0.06) |
| R-25 | 101.60 (4.000) | 7.95 (0.313) | 14.2 (0.56) | 12.7 (0.50) | 5.23 (0.206) | 1.5 (0.06) |
| R-26 | 101.60 (4.000) | 11.13 (0.438) | 17.5 (0.69) | 16.0 (0.63) | 7.75 (0.305) | 1.5 (0.06) |
| R-27 | 107.95 (4.250) | 11.13 (0.438) | 17.5 (0.69) | 16.0 (0.63) | 7.75 (0.305) | 1.5 (0.06) |
| R-28 | 111.13 (4.375) | 12.70 (0.500) | 19.1 (0.75) | 17.5 (0.69) | 8.66 (0.341) | 1.5 (0.06) |
| R-29 | 114.30 (4.500) | 7.95 (0.313) | 14.2 (0.56) | 12.7 (0.50) | 5.23 (0.206) | 1.5 (0.06) |
| R-30 | 117.48 (4.625) | 11.13 (0.438) | 17.5 (0.69) | 16.0 (0.63) | 7.75 (0.305) | 1.5 (0.06) |
| R-31 | 123.83 (4.875) | 11.13 (0.438) | 17.5 (0.69) | 16.0 (0.63) | 7.75 (0.305) | 1.5 (0.06) |
| R-32 | 127.00 (5.000) | 12.70 (0.500) | 19.1 (0.75) | 17.5 (0.69) | 8.66 (0.341) | 1.5 (0.06) |
| R-33 | 131.78 (5.188) | 7.95 (0.313) | 14.2 (0.56) | 12.7 (0.50) | 5.23 (0.206) | 1.5 (0.06) |
| R-34 | 131.78 (5.188) | 11.13 (0.438) | 17.5 (0.69) | 16.0 (0.63) | 7.75 (0.305) | 1.5 (0.06) |
| R-35 | 136.53 (5.375) | 11.13 (0.438) | 17.5 (0.69) | 16.0 (0.63) | 7.75 (0.305) | 1.5 (0.06) |
| R-36 | 149.23 (5.875) | 7.95 (0.313) | 14.2 (0.56) | 12.7 (0.50) | 5.23 (0.206) | 1.5 (0.06) |
| R-37 | 149.23 (5.875) | 11.13 (0.438) | 17.5 (0.69) | 16.0 (0.63) | 7.75 (0.305) | 1.5 (0.06) |
| R-38 | 157.18 (6.188) | 15.88 (0.625) | 22.4 (0.88) | 20.6 (0.81) | 10.49 (0.413) | 1.5 (0.06) |
| R-39 | 161.93 (6.375) | 11.13 (0.438) | 17.5 (0.69) | 16.0 (0.63) | 7.75 (0.305) | 1.5 (0.06) |
| R-40 | 171.45 (6.750) | 7.95 (0.313) | 14.2 (0.56) | 12.7 (0.50) | 5.23 (0.206) | 1.5 (0.06) |
| R-41 | 180.98 (7.125) | 11.13 (0.438) | 17.5 (0.69) | 16.0 (0.63) | 7.75 (0.305) | 1.5 (0.06) |
| R-42 | 190.50 (7.500) | 19.05 (0.750) | 25.4 (1.00) | 23.9 (0.94) | 12.32 (0.485) | 1.5 (0.06) |
| R-43 | 193.68 (7.625) | 7.95 (0.313) | 14.2 (0.56) | 12.7 (0.50) | 5.23 (0.206) | 1.5 (0.06) |
| R-44 | 193.68 (7.625) | 11.13 (0.438) | 17.5 (0.69) | 16.0 (0.63) | 7.75 (0.305) | 1.5 (0.06) |
| R-45 | 211.15 (8.313) | 11.13 (0.438) | 17.5 (0.69) | 16.0 (0.63) | 7.75 (0.305) | 1.5 (0.06) |
| R-46 | 211.15 (8.313) | 12.70 (0.500) | 19.1 (0.75) | 17.5 (0.69) | 8.66 (0.341) | 1.5 (0.06) |
| R-47 | 228.60 (9.000) | 19.05 (0.750) | 25.4 (1.00) | 23.9 (0.94) | 12.32 (0.485) | 1.5 (0.06) |
| R-48 | 247.65 (9.750) | 7.95 (0.313) | 14.2 (0.56) | 12.7 (0.50) | 5.23 (0.206) | 1.5 (0.06) |
| R-49 | 269.88 (10.625) | 11.13 (0.438) | 17.5 (0.69) | 16.0 (0.63) | 7.75 (0.305) | 1.5 (0.06) |
Materials
| Material | Typical Use |
|---|---|
| Soft iron | Carbon-steel flanges, easy deformation |
| Carbon steel (A105) | General hydrocarbon service |
| 304 / 316 / 321 stainless | Corrosive service |
| Inconel / Monel | High-temperature and corrosive service |
The ring is always chosen softer than the flange groove material, so the ring deforms and the groove survives re-use.
Related Standards
- ASME B16.20 — Metallic Gaskets (Parent Standard)
- ASME B16.20 Spiral Wound Gaskets
- ASME B16.20 Metal Jacketed Gaskets
- ASME B16.5 — Pipe Flanges (NPS 1/2–24)
- ASME B16.47 — Large-Diameter Flanges (NPS 26–60)
- Our Metallic Gasket Range
- ASTM A105 Carbon Steel
- ASTM A182 F304 Stainless Steel
FAQ
What is the difference between oval and octagonal RTJ rings?
Both seal in the same BX-style groove. Octagonal rings give a better line contact and are preferred for new flanges; oval rings are used when retrofitting older oval-groove flanges.
Which pressure classes use RTJ gaskets?
Class 600 through Class 2500. Lower classes normally use spiral-wound or nonmetallic gaskets.
How do I pick the right ring number?
Match your flange NPS and pressure class to B16.20 Table RJ-5-2, which lists the ring number for each flange size/class combination, or simply send us your flange drawing.
Can an RTJ ring be reused?
Because the ring seals by plastic deformation, it is normally replaced each joint; the flange groove is re-used. Never re-use a deformed ring.
What hardness should the ring have?
Rings are supplied softer than the flange material — hardness limits per ASME B16.20 Table RJ-3.2-1 (e.g. 90 HB soft iron, 120 HB carbon steel).
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