Last updated: April 2026
Spiral wound gaskets are a semi-metallic sealing element formed by alternately winding a thin V-shaped metal strip with a soft non-metallic filler. They are the default choice for Australian refinery, chemical processing, and steam flange duties where soft-faced gaskets lack the recovery or pressure rating — covering ASME B16.5 Class 150 through 2500, and temperatures from cryogenic service to ~900°C depending on filler.
GritGasket manufactures spiral wound gaskets to ASME B16.20 / API 601 with carbon-steel, 304 or 316 stainless-steel centring rings and your choice of flexible graphite, PTFE, or mica filler. Stocked in standard NPS sizes from ½" to 24"; non-standard sizes and materials cut to order in our Sydney workshop.
What Is a Spiral Wound Gasket?
A spiral wound gasket (SWG) is a semi-metallic gasket whose sealing element is a continuous spiral of V-section metal strip (typically stainless steel) alternately layered with a non-metallic filler such as flexible graphite or PTFE. An outer centring ring (usually carbon steel) locates the gasket in the flange and acts as a compression stop; an optional inner ring prevents filler blow-out on Class 600+ duties.
The wound construction gives the gasket exceptional recovery — the ability to maintain a seal as the bolt load fluctuates through thermal cycling, pressure spikes, or creep relaxation. This is what sets SWGs apart from soft-faced gaskets, and why they dominate refinery and petrochemical service.
Construction and Variants
| Component | Typical Materials | Role |
|---|---|---|
| Centring (outer) ring | Carbon steel (zinc-plated), 304SS, 316SS | Locates gasket in flange, limits compression |
| Winding metal | 304SS, 316L, 321, Monel, Inconel 625, Hastelloy | Provides elastic recovery and corrosion resistance |
| Filler | Flexible graphite, PTFE, mica, ceramic | Fills micro-surface irregularities; carries the seal |
| Inner ring (optional) | 304SS, 316SS (matches winding) | Prevents filler erosion on high-pressure duties |
How Do You Choose the Right Filler?
- Flexible graphite — workhorse filler for steam, hydrocarbons, and most refinery service. Handles -200°C to +450°C (oxidising) or +650°C (non-oxidising). Best recovery and thermal cycling tolerance.
- PTFE — for aggressive acids, alkalis, solvents, and high-purity media where graphite contamination is unacceptable. Lower upper temperature limit (~260°C) but broad chemical compatibility.
- Mica / ceramic — specialised fillers for very high temperatures (800–1000°C) or fire-safe service where graphite oxidation is a concern.
What Pressure and Temperature Can a Spiral Wound Gasket Handle?
The flange rating (ASME Class 150, 300, 600, 900, 1500, 2500) sets the cold working pressure. The winding and filler then determine the temperature envelope. A typical selection matrix for a 304SS-wound gasket:
| Filler | Continuous max temp (°C) | Peak temp (°C) | Flange class range |
|---|---|---|---|
| Flexible graphite | 450 (oxidising) / 650 (inert) | 800 | 150–2500 |
| PTFE | 260 | 280 | 150–900 |
| Mica | 800 | 1000 | 150–2500 |
| Ceramic | 1000 | 1200 | 150–2500 |
Where Are Spiral Wound Gaskets Used?
- Oil & gas refining — fractionation columns, crude preheat, hydrotreaters.
- Chemical processing — reactor manways, corrosive-service lines.
- Power generation — HP steam lines, turbine bypass, boiler feedwater.
- LNG & cryogenic — graphite-filled SWGs tolerate -200°C duties.
- Water treatment — large-bore pipelines on potable and wastewater plants.
Installation and Bolt-Up
Spiral wound gaskets must be compressed uniformly to achieve a seal without over-crushing the winding. ASME PCC-1 gives the reference bolt-tightening procedure: four-pass crosswise sequence, with target assembly stress set by the gasket's seating stress (typically 175 MPa for flexible graphite-filled SWGs). See our bolt torque calculator to convert target stress into torque values for your bolt size and lubricant.
Stocked Spiral Wound Gaskets
SW150-CS/304/GR
SW300-316/316/PTFE
Frequently Asked Questions
A spiral wound gasket is a semi-metallic sealing element made by alternately winding a thin V-section metal strip with a soft filler (typically flexible graphite or PTFE), bounded by a carbon-steel or stainless-steel centring ring. The combination gives a gasket with excellent elastic recovery, making it the default sealing choice for Class 150 through 2500 flanges in refinery, petrochemical, and steam service.
Spiral wound gaskets seal by compressing a soft filler in the flange face and are used on ASME B16.5 raised-face flanges. Ring-joint (RTJ) gaskets are solid metal rings (octagonal or oval) that sit in a machined groove on API 6A or Class 600+ ring-joint flanges. RTJs seal by metal-to-metal contact and are preferred at very high pressures (typically above Class 900) and for hydrocarbon service at wellheads.
For general refinery, steam, and hydrocarbon service up to 450°C, flexible graphite is the default. For aggressive chemicals, acids, or where graphite contamination is unacceptable, choose PTFE (limit 260°C). For very high temperatures above 800°C or fire-safe duties, mica or ceramic fillers are used. We can advise on chemical-compatibility for specific media — ask for a materials data sheet.
For Class 150 and Class 300 duties, most applications do not require an inner ring. For Class 600 and above, or where the process media can erode the filler (high-velocity fluids, vacuum service, or thermal-cycling duties), an inner ring in the same material as the winding is recommended and often specified in piping standards such as API 601.
Target assembly stress for a flexible graphite-filled spiral wound gasket is typically 175 MPa (25,400 psi). Convert this to bolt preload by multiplying by the gasket contact area, then to torque using the nut factor K for your lubricant (≈0.20 for dry, 0.16 for general-purpose anti-seize). Follow ASME PCC-1 four-pass cross-pattern bolt-up. Our bolt torque calculator handles this conversion for you.
Related Products
- PTFE gaskets — soft-faced alternative for chemical service
- Graphite gaskets — for HP steam and thermal cycling
- RTJ / ring-joint gaskets — for Class 600+ API-spec flanges
Learn More
Sources
- ASME B16.20 — Metallic Gaskets for Pipe Flanges: Ring-Joint, Spiral-Wound, and Jacketed
- ASME PCC-1 — Guidelines for Pressure Boundary Bolted Flange Joint Assembly
- API 601 — Metallic Gaskets for Raised-Face Pipe Flanges and Flanged Connections