Last updated: April 2026
Spiral wound and ring-joint (RTJ) gaskets sit at the high end of the gasket selection chart, but they're not interchangeable. The two gasket types use entirely different sealing mechanisms and require entirely different flange faces — so the choice is usually made by the flange standard, not by the engineer specifying the gasket. This piece covers when each is the right answer, and what to do when you're free to pick.
The Short Answer
- Use spiral wound on ASME B16.5 raised-face flanges from Class 150 through Class 2500 — the vast majority of process-plant flanges. Default for refinery, petrochemical, power, and chemical service.
- Use RTJ on ring-joint-grooved flanges (ASME B16.5 RJ face or API 6A flanges) — wellheads, HP / HT hydrocarbon trees, and Class 900+ pipework where the flange was specified ring-joint at design.
- You can't swap one for the other on an existing flange — the flange face is different. RTJ flanges have a machined groove; raised-face flanges don't.
Side-by-Side
| Spiral Wound | Ring-Joint (RTJ) | |
|---|---|---|
| Sealing mechanism | Soft filler compresses into flange face; metal winding provides recovery | Solid metal ring deforms plastically into a machined flange groove (metal-to-metal) |
| Flange face required | Raised face (RF) or flat face (FF) — ASME B16.5 standard | Ring-joint groove (RJ) — machined to ASME B16.20 / API 6A profile |
| Flange standard | ASME B16.5, AS 2129, BS EN 1092-1 | ASME B16.5 RJ, API 6A (wellhead), API 17D (subsea) |
| Class range (typical) | 150 – 2500 | 600 – 2500 (ASME); up to 20,000 psi (API 6A) |
| Temperature limit | Set by filler — 260°C (PTFE) to 1000°C (ceramic) | Set by ring material — soft iron, 304SS, 316SS, Inconel; up to 650°C+ |
| Material standard | ASME B16.20 / API 601 | ASME B16.20 / API 6A |
| Reusable? | No — single-use | Sometimes (Type R after light-duty disassembly); usually replaced |
| Bolt load required | Moderate (175 MPa seating stress for graphite) | High — must plastically deform the ring |
| Cost | Lower | Higher (machined solid ring) |
| Sensitivity to flange surface | Tolerant — concentric serrations 125–250 µin Ra | Very sensitive — groove must be machined precisely; damage means re-machining the flange |
When Spiral Wound Is the Right Answer
- The flange is raised-face (RF) or flat-face (FF) per ASME B16.5 — the default for almost all process pipework.
- Service is Class 150 through Class 2500 on standard process media (steam, hydrocarbons, water, light chemicals).
- You need filler flexibility — different chemistries on different flanges, all sealable with the same gasket type and flange spec.
- You want lower cost per joint at otherwise-equivalent rating.
- The plant is established Class 600 or below — almost no reason to introduce RTJ flanges.
When RTJ Is the Right Answer
- The flange standard mandates it: API 6A wellheads, API 17D subsea, ASME B16.5 RJ-face Class 900+.
- Service is at extreme pressure — Class 1500, Class 2500, or up to 20,000 psi on wellhead trees.
- HP hydrocarbon service where the metal-to-metal seal is preferred for fire-safe credentials and longer integrity in the event of a fire.
- Service involves severe vibration or thermal shock that would relax a soft filler.
- You're working on an existing ring-joint-grooved flange — you can't put a spiral wound in it.
What If I'm Designing the Flange and Have a Choice?
Below Class 900 — pick spiral wound. The cost difference, the lower bolt-load requirement, and the ease of repair if something goes wrong all favour the spiral wound choice. The pressure and temperature envelopes overlap completely in this range.
At Class 900 and above — pick RTJ if the service is HP hydrocarbon or sour gas, the plant already runs RTJ piping standards, or fire-safe certification is a project requirement. Otherwise, modern spiral wound construction (316SS or Inconel winding with inner ring) seals Class 1500 and Class 2500 reliably and at lower cost than RTJ.
Common Failure Modes — Both Types
Spiral wound
- Filler erosion or buckling on Class 600+ duties without an inner ring → specify inner ring.
- Wrong filler for the chemistry (graphite in oxidisers, PTFE above 260°C) → see filler selection.
- Under-bolted joint — bolt-up to ASME PCC-1, hot re-torque on Class 600+.
RTJ
- Damaged flange groove from previous gasket removal — re-machining required, costly downtime.
- Wrong ring hardness (harder than the flange) → groove damage.
- Cross-contamination (Type R vs Type RX vs Type BX) — all look similar, all incompatible.
Frequently Asked Questions
No. RTJ flanges have a machined groove (the ring-joint face); raised-face flanges do not. A spiral wound gasket cannot seat in a ring-joint groove, and an RTJ ring will not seal on a raised face. Replacing the gasket type means re-machining or replacing the flange — major work.
Both types cover Class 600 through Class 2500 on ASME flanges. RTJ extends higher on API 6A wellhead service — up to 20,000 psi at the API end of the range. For ASME B16.5 process flanges below Class 1500, modern spiral wound construction (316SS or Inconel winding with inner ring) seals as reliably as RTJ at lower cost.
Yes — the metal-to-metal seal of an RTJ gasket survives the loss of any soft filler in a fire. Spiral wound gaskets with mica filler also achieve fire-safe certification (API 6FB / ISO 10497) and are commonly specified for fire-safe valve and flange duties on raised-face flanges where RTJ is not an option.
Standardising the flange face across a plant simplifies inventory (one gasket type), reduces the chance of a mis-installation, and lets a single bolting procedure apply across the whole site. Refineries usually run raised-face (spiral wound) for the bulk of process piping and reserve RTJ for hot HP hydrocarbon service and wellheads.
Yes — but the target preload is higher because the ring must plastically deform into the flange groove to seal. ASME PCC-1 covers RTJ assembly procedures with similar four-pass cross-pattern logic to spiral wound, but at higher target torques. Always check the bolt yield stress is not exceeded on Class 1500+ assemblies.
Related
- Spiral wound gaskets — full range
- What is a spiral wound gasket?
- Filler selection guide
- Bolt-up to ASME PCC-1
Sources
- ASME B16.20 — Metallic Gaskets for Pipe Flanges: Ring-Joint, Spiral-Wound, and Jacketed
- API 6A — Wellhead and Tree Equipment
- API 601 — Metallic Gaskets for Raised-Face Pipe Flanges