Spiral wound gaskets are the workhorse sealing element for raised-face flange joints across Australian industry — water utilities, petrochem, mining process plant, refineries, food and pharma processing, pulp and paper, and power generation. They handle higher pressures and temperatures than fibre or rubber gaskets, recover well after thermal cycling, and are far more forgiving of small flange surface imperfections than solid metal gaskets.
They also have specific rules around what flange faces they can be used on, which winding and filler materials suit which service, how to read the markings on the outer ring, and how to torque the bolts to seat them correctly. Get any of these wrong and you get a leak — usually at the worst possible time.
This guide covers the construction, materials, ASME B16.20 colour code system, the AS 4087 / AS 2129 / ASME B16.5 flange standards used in Australia, flange face compatibility (with the safety warnings most spec sheets bury), installation torque, alternatives, and how to identify or specify a replacement.
What is a spiral wound gasket?
A spiral wound gasket — often abbreviated SWG in trade — is a flange gasket made by alternately winding a V-shaped or chevron-shaped metal strip with a softer filler material into a tight spiral. The metal strip provides mechanical strength and resilience; the filler provides the sealing surface that conforms to the flange face.
The result is a semi-metallic gasket that combines the best properties of pure metal gaskets (strength, temperature resistance, recovery) and soft gaskets (conformability, low seating stress requirement). Spiral wound gaskets seal by being compressed between two flange faces — as the bolts are torqued, the metal winding compresses elastically and the soft filler is pushed into the surface roughness of the flange face, creating a continuous seal.
SWGs are the default choice for medium-to-high pressure raised-face flange joints in industrial process piping. They handle pressures from vacuum to Class 2500 (~430 bar), temperatures from cryogenic to over 1,000°C with the right filler, and they recover better than solid graphite or fibre gaskets after the joint experiences thermal cycling, vibration or temporary loss of bolt load. AIMS stocks the AAP brand spiral wound gasket range — see our gaskets collection for the full lineup.
How spiral wound gaskets are constructed
A finished SWG looks like a flat metal washer with a coloured band around the outside and another band on the inside. Cross-section, it has up to four distinct elements:
- Winding strip — a V-shaped or chevron-profile metal strip, typically 304, 316, 316L stainless or higher alloys. The V-shape gives the spring action that lets the gasket recover after being compressed.
- Filler material — a soft, conformable strip wound alternately with the metal. Graphite, PTFE, mica, or ceramic depending on service. The filler is what actually seals against the flange face.
- Outer ring (centring ring) — a flat metal ring on the outside of the wound section. Centres the gasket on the flange, acts as a compression stop to prevent over-compression of the spiral, and carries the colour-code identification marks.
- Inner ring (compression-limiting ring) — an inner flat metal ring that fills the space between the spiral and the bore. Prevents inward buckling of the spiral under pressure, protects the filler from process fluid erosion, and reduces dead space in the joint.
Standard SWGs are designated by their construction style:
- Style R — wound element only (no inner or outer ring). Used in male-female and tongue-and-groove flanges where the flange itself constrains the gasket.
- Style RIR — wound element plus outer ring. Common, but rarely specified now.
- Style CG (CGI) — wound element plus outer (centring) ring. The most common style for raised-face flanges. Sometimes written CGI for "with centring ring".
- Style CGI — wound element plus outer centring ring AND inner ring. The most robust style. Mandatory for high-pressure (Class 900+) and recommended for cyclic services. Modern ASME B16.20 specifies inner rings for Class 900 and above, and for all PTFE-filled gaskets.
Inner ring vs outer ring — what each does
This is one of the most common engineering questions about SWGs (it comes up repeatedly on Eng-Tips and similar forums): people see two metal rings and assume they're redundant. They are not — they do completely different jobs.
The outer (centring) ring does three things:
- Centres the gasket between the bolt circle, so the wound element sits squarely on the raised face.
- Acts as a compression stop — when the bolts are torqued, the outer ring contacts the flange face once the spiral has compressed to the design thickness, preventing over-compression that would crush the spiral and destroy the recovery characteristic.
- Carries the identification colour code (winding strip colour on the outer edge, filler stripe colour on the face) — see the colour code section below.
The inner ring does two things:
- Provides a barrier between the process fluid and the soft filler — particularly important for graphite filler in steam, hydrocarbon, or aggressive service where filler erosion would otherwise degrade the seal.
- Prevents inward buckling of the spiral under pressure differential. Without an inner ring, the wound element can collapse inward into the pipe bore at high pressure, deforming the gasket and causing leakage.
Modern ASME B16.20 mandates inner rings for Class 900 flanges and above, for all flexible graphite filler in steel pipework, and for all PTFE-filled gaskets regardless of class. The trend in good engineering practice is to specify inner rings on most high-value or critical-service joints — they cost a little more and remove a major failure mode.
Filler materials
The filler material is what actually seals against the flange face. Selection is driven by service temperature, chemical compatibility, and pressure class.
| Filler | Temperature range | Service | Notes |
|---|---|---|---|
| Flexible graphite | −240°C to +500°C (steam); +650°C in inert atmosphere | Steam, hydrocarbons, hot oil, most general process service | The most common filler. Excellent temperature range and recovery. Not suitable for strong oxidisers (nitric acid, concentrated sulphuric, hot air above 450°C). |
| PTFE | −240°C to +260°C | Strong acids, caustics, food and pharma, oxidising chemicals | Chemically inert against almost everything. Lower temperature ceiling than graphite. Cold flow under sustained load means inner ring is mandatory. Suitable for food and FDA-compliant grades available. |
| Mica | Up to +1,000°C | High-temperature steam, exhaust, fired equipment | Used where graphite oxidises — elevated temperature in oxidising atmosphere. More expensive than graphite. Less forgiving of vibration. |
| Ceramic | Up to +1,200°C | Furnace, kiln, exhaust manifolds | Specialty high-temperature service. Brittle compared to graphite — handle with care. |
| Asbestos (legacy) | — | — | Banned in Australia. If replacing an asbestos gasket on legacy plant, specify a non-asbestos equivalent — graphite for most service, mica or ceramic for above 500°C. |
Filler selection in seawater service is a frequent forum question. The standard answer: PTFE filler with 316L or higher winding (Inconel 625 for severe service). Graphite can suffer galvanic corrosion in chloride environments and is not recommended for sustained seawater contact. For desalination and offshore process work, PTFE-graphite blends or pure PTFE with metal-jacketed alternatives are the typical specification.
Winding strip materials
The winding strip carries the mechanical load and provides the elastic recovery. Material is selected for service temperature, corrosion resistance, and cost.
| Winding material | Max temp | Common use |
|---|---|---|
| Carbon steel | +500°C | Low-cost general service. Limited corrosion resistance — only for non-corrosive dry process. |
| 304 / 304L stainless | +550°C | General-purpose stainless. Common for water, steam, and mild process service. |
| 316 / 316L stainless | +550°C | Better chloride resistance than 304. Standard for marine, chemical, and food service. The default upgrade from 304. |
| 317L stainless | +550°C | Higher molybdenum than 316 — better resistance to pitting in chloride and acid service. |
| Alloy 20 | +550°C | Sulphuric acid service. |
| Monel 400 | +540°C | Hydrofluoric acid, salt water, and some caustics. |
| Inconel 600 / 625 / X-750 | +1,090°C | High temperature, chloride stress corrosion resistance, high-pressure service. |
| Hastelloy C-276 | +1,090°C | Severe chemical service — wet chlorine, oxidising acids, mixed-acid streams. |
| Titanium | +540°C | Specialty corrosion service, particularly chlorinated environments. |
Should I upgrade 304 to 316? A common spec question. The answer is almost always yes if the service involves any chloride exposure (seawater, brackish water, chlorinated chemicals, hot tap water in some regions), or if the joint is in a marine atmosphere even when the process fluid itself is benign. The cost difference is small relative to a flange leak. 316L (low-carbon variant) is preferred for welded or stress-relieved applications to avoid sensitisation.
ASME B16.20 colour code system
SWGs to ASME B16.20 are colour-coded so that the winding material and filler can be identified visually without needing the original packaging. The code uses two colours:
- Outer ring solid colour band (around the edge) — identifies the winding strip material.
- Outer ring stripe colour (on the flat face) — identifies the filler material.
Reference colours (per ASME B16.20):
| Element | Colour | Material |
|---|---|---|
| Winding strip (outer ring band) |
Silver | 304 stainless |
| Yellow | 316L stainless | |
| Maroon | 317L stainless | |
| Olive Green | Monel 400 | |
| Gold | Inconel 600 | |
| Beige | Hastelloy C-276 | |
| Filler (stripe colour on face) |
Grey | Flexible graphite |
| White | PTFE | |
| Light Green | Mica (Therma-Mica or similar) | |
| Pink | Ceramic |
So a yellow band with a grey stripe = 316L winding with graphite filler. A silver band with a white stripe = 304 winding with PTFE filler. The combination, plus the size and pressure class stamped on the outer ring, fully identifies the gasket.
This colour code is universal across ASME B16.20-compliant manufacturers. AS 4087 gaskets sold in Australia by major suppliers typically follow the same convention even though the standard does not formally require it.
Flange standards: ASME B16.5 vs AS 4087 vs AS 2129 vs DIN vs JIS
The single most important point about flange gaskets: a Class 150 ASME flange is not the same as a PN 16 AS 4087 flange, even at the same nominal size. The bolt circle, gasket OD/ID, and bolt count are different. You cannot interchange gaskets between standards. Order to the standard your flange is built to, not to the nominal size alone.
| Standard | Origin | Typical use in AU | Pressure designations |
|---|---|---|---|
|
ASME B16.5 (flanges) ASME B16.20 (metallic gaskets) |
USA | Petrochem, oil and gas, refineries, large-scale process plant. Default for new petrochem builds. | Class 150, 300, 600, 900, 1500, 2500 |
| AS 4087 | Australia | Water industry — water utilities, water treatment, pump stations. WSAA-aligned. | PN 14, PN 16, PN 21, PN 35 |
| AS 2129 | Australia (older) | Legacy AU plant. Tables D, E, F, H, J — different pressure ratings. Still seen on older mining, pulp and paper, food plant. | Tables D, E, F, H, J, K |
| DIN EN 1092 | Europe | European-built equipment, some imports. | PN 6, 10, 16, 25, 40, 63, 100 |
| JIS B 2220 | Japan | Japanese-built equipment, mining and industrial imports. | 5K, 10K, 16K, 20K, 30K, 40K |
In practice on Australian sites you'll commonly see AS 4087 on water service, ASME B16.5 on petrochem and gas, and AS 2129 hanging on from older installations. JIS and DIN appear on imported pumps, valves, and machinery. The OD, ID, bolt circle and number of bolts all change between standards — measure the existing gasket carefully and confirm the flange standard before ordering replacements.
Pressure-temperature classes
Pressure class defines the gasket's design pressure-temperature envelope, the bolt loading required to seat the gasket, and (for ASME) the construction style required.
| Standard | Class | Approx max pressure (cold) | SWG style required |
|---|---|---|---|
| ASME B16.20 | Class 150 | ~20 bar | Style CG (no inner ring required, but recommended) |
| Class 300 | ~52 bar | Style CG | |
| Class 600 | ~104 bar | Style CG (inner ring recommended) | |
| Class 900 | ~155 bar | Style CGI (inner ring mandatory) | |
| Class 1500 | ~260 bar | Style CGI | |
| Class 2500 | ~430 bar | Style CGI | |
| AS 4087 | PN 14 | ~14 bar | Style CG typical |
| PN 16 | ~16 bar | Style CG | |
| PN 21 | ~21 bar | Style CG | |
| PN 35 | ~35 bar | Style CGI recommended |
Pressure ratings reduce as temperature increases — a Class 150 carbon steel flange rated 20 bar at ambient is rated only ~14 bar at 200°C and ~10 bar at 400°C. Always check the flange rating curve in the relevant standard against your service conditions, not just the nominal class.
Flange face compatibility
This is where SWGs go wrong most often, and where forum threads (Eng-Tips, r/pipefitter) consistently warn against the wrong combinations.
| Flange face | Correct gasket | SWG suitable? |
|---|---|---|
| Raised face (RF) | Spiral wound (Style CG / CGI), or Kammprofile, or sheet ring gasket | YES — this is what SWGs are designed for |
| Flat face (FF) | Full-face fibre, rubber, or PTFE gasket | NO — see warning below |
| Ring-type joint (RTJ) | RTJ ring gasket only (oval or octagonal section, soft iron or stainless) | NO — RTJ requires its own ring gasket type |
| Tongue-and-groove (T&G) | Style R SWG (no rings) or solid filler | YES (Style R) |
| Male-and-female (M&F) | Style R SWG (no rings) | YES (Style R) |
Warning: Never use a spiral wound gasket on a flat-face flange.
SWGs are designed to seat on a raised-face flange where the gasket sits inside the bolt circle and is constrained by the centring ring. On a flat face, the spiral can extend past the flange edge under bolt load, fail to develop the correct seating stress, and leak — sometimes catastrophically. Pipefitter forum consensus: raised face gets a ring gasket; flat face gets a full face gasket. If you have a flat face flange, specify a full-face fibre, rubber, or PTFE gasket — not an SWG.
Cast iron vs steel flange torque warning
Warning: SWGs may crack cast iron flanges.
Spiral wound gaskets require higher seating stress than soft fibre or rubber gaskets — typically 30–70 MPa across the gasket face. Cast iron pump bodies and valve flanges are not designed for that level of bolting load. The classic failure (well documented in pipefitter and r/pipefitter threads): a steel raised-face flange is bolted to a cast iron pump flange with an SWG between them. The steel side torques up fine; the cast iron flange cracks under the asymmetric load. Use a soft full-face gasket on cast iron pump flanges, not an SWG. If you must use an SWG (high-pressure or high-temperature service), confirm the cast iron flange rating allows the required bolt load — and torque to the lower of the two flange ratings.
Installation and torque
Correct installation is more important than gasket selection — a perfect gasket installed badly will leak. The procedure for spiral wound gaskets is:
- Clean both flange faces. Remove all old gasket residue, paint, scale, and corrosion. The sealing surface should be clean bare metal with no pits, scratches across the seal track, or radial scoring. A wire brush, scraper, and emery cloth are the standard kit. Do not use angle grinders — they leave radial scoring that creates leak paths.
- Inspect the flange face. Confirm the surface finish is suitable for SWG seating — typically 3.2 to 6.3 µm Ra (concentric or phonographic finish per ASME B16.5). Damaged or scored faces must be re-machined before fitting an SWG.
- Centre the gasket. The outer centring ring should sit within the bolt circle, not over the bolts. Confirm the inner ring (if fitted) does not protrude into the pipe bore — it should match the flange ID.
- Lubricate the bolt threads and the underside of the nuts with a copper anti-seize compound or molybdenum disulphide grease. Do not apply anti-seize to the flange face or the gasket itself — it reduces friction at the seal and can cause the gasket to spin under load.
- Hand-tighten all bolts to ensure the gasket is snug and centred, then begin torque sequence.
- Apply torque in a cross (star) pattern in 3 to 5 progressive passes. Typical sequence: 30%, 60%, 100% of target torque, then a final pass at 100% in clockwise rotation to even out load. For Class 600 and above, more passes (4-5) are recommended.
- Re-torque after 24 hours of service for graphite-filled gaskets, and after the first thermal cycle for high-temperature service. Both filler and bolt experience some relaxation that needs to be made up.
Bolt torque values must come from the flange / bolt / gasket combination — there is no single torque table that fits all SWGs. Use the gasket manufacturer's torque table for the specific gasket / bolt grade / flange combination, or calculate from the gasket seating stress (typically y = 30 N/mm² and m = 3.0 for spiral wound graphite, per ASME PCC-1). Use a calibrated torque wrench — see our Torque Wrench Guide for selection and our Torque Wrench Calibration Guide for accuracy intervals.
Anti-seize tip from the trade: Apply Never-Seize or copper anti-seize to bolt threads and under nuts only — NOT to the gasket face or flange face. Anti-seize on the seal surface reduces friction, allows the gasket to spin under load, and creates a leak path. The anti-seize on threads and nuts makes future disassembly straightforward without damaging studs.
Spiral wound vs alternatives
Not every flange joint needs an SWG. Selection depends on pressure, temperature, service, and flange face type.
| Gasket type | Best for | Limits |
|---|---|---|
| Spiral wound (SWG) | Medium-to-high pressure raised-face flanges, thermal cycling, vibration | Cannot use on flat face. Higher seating stress than soft gaskets. |
| Kammprofile (grooved metal core with soft facing) | Higher integrity than SWG. Heat exchangers, critical services. Reusable in some cases. | More expensive than SWG. Specific surface finish requirements. |
| Metal-jacketed | Heat exchanger tube sheets, narrow gasket spaces | Single-use. Lower recovery than SWG. |
| Sheet (compressed fibre, PTFE, rubber) | Low pressure, flat-face flanges, water and air service | Lower temperature and pressure ceiling. AAP compressed fibre and rubber sheet gaskets cover this in the AIMS range. |
| RTJ (ring-type joint) | High pressure (Class 900+), API 6A wellheads, RTJ-grooved flanges only | Solid metal — needs perfect groove condition. Cannot use on RF or FF flanges. |
| Liquid gasket / form-in-place | Low-pressure flat-face flanges where access is awkward, gearbox covers, oil pans | Limited temperature and pressure. See our RTV Silicone Gasket Maker Guide for the field of use. |
Common applications and industries
Spiral wound gaskets appear in nearly every industrial sector that uses flanged piping. Typical Australian applications include:
- Water utilities and water treatment — AS 4087 PN 16 / PN 21 SWGs on water mains, valve stations, and pump houses. 304 winding with graphite filler is the default; 316 winding for chlorinated or coastal service.
- Petrochem, oil and gas — ASME B16.20 Class 150 to Class 2500 SWGs on process piping, refinery columns, separators, gas plant. 316L winding with graphite filler dominates; specialty alloys (Inconel, Hastelloy) for severe service.
- Mining process plant — slurry, leach, flotation circuits. SWGs on tank flanges, pump connections, valve flanges. Often AS 2129 Tables E or F on legacy plant.
- Heat exchangers — SWGs on shell flanges, channel covers, manholes. Increasingly Kammprofile in newer designs for higher integrity.
- Power generation — steam piping, condensers, feedwater heaters. Graphite filler standard for steam service.
- Pulp and paper — black liquor, white liquor, condensate. 316L or higher alloys due to corrosive process.
- Food, beverage and pharma — PTFE filler with 316L winding. FDA-compliant grades available. Hygienic clamp connections often use EPDM or silicone gaskets instead.
How to identify, specify or order a replacement
If you have a leaking flange and need a replacement SWG, here is what to measure and confirm before ordering.
- Flange standard — ASME B16.5? AS 4087? AS 2129 (which Table)? DIN? JIS? This is the single most important piece of information. Check the flange stamping if visible, the original equipment data sheet, or the P&ID.
- Nominal pipe size (NPS / DN) — the pipe size, e.g. 100 NB, DN 150, 4-inch.
- Pressure class — Class 150 / 300 / 600 etc. for ASME, or PN 14 / 16 / 21 / 35 for AS 4087, or Table D / E / F / H / J for AS 2129.
- Flange face type — raised face, flat face, RTJ, tongue-and-groove, or male-and-female.
- Gasket OD and ID — measure the existing gasket if you have it. Check it against the flange standard table.
- Service conditions — fluid (water, steam, hydrocarbon, acid, etc.), temperature, pressure. Drives filler and winding selection.
- Existing markings — the colour code on the outer ring (winding band colour + filler stripe colour), any size and pressure class stamped on the outer ring, and any manufacturer markings.
For a complete spec, send AIMS the above plus a photo of the existing gasket (front and edge — the colour code and stamping should be visible) and a photo of the flange face if you can. We can confirm the right replacement and stock or source it.
Spiral wound gaskets at AIMS Industrial
AIMS stocks the AAP brand spiral wound gasket range plus a complete line of insertion gaskets, fibre gaskets, rubber gaskets, and clamp gaskets. Highlights:
- AAP Insertion Gasket — Spiral Wound — multiple sizes for AS 4087 and AS 2129 flanges, 316 winding with graphite filler.
- AAP Insertion Gasket — Compressed Fibre Table-E and Table-D — soft gaskets for low-pressure flat-face flanges and water service.
- AAP Insertion Gasket — Natural Rubber Table-E — for water service on legacy AS 2129 flanges.
- Dixon EPDM and FKM clamp gaskets — for tri-clover and hygienic clamp connections.
For sizes, materials, or pressure classes we don't show online — including ASME B16.20 Class 600+, specialty alloys (Inconel, Hastelloy), or large-bore sizes — call us on (02) 9773 0122 or use our contact page. Bring the photos and we will work out what you need.
Frequently Asked Questions
What is a spiral wound gasket used for?
Spiral wound gaskets are used to seal raised-face flange joints in process piping, particularly where pressure is medium to high (above Class 150), temperature is elevated, or the joint experiences thermal cycling or vibration. They are the default gasket choice for petrochem, oil and gas, refining, water utilities at PN 16 and above, mining process plant, heat exchangers, and power generation. They handle vacuum to Class 2500 (~430 bar) and cryogenic to over 1,000°C with the right filler material.
How do you read the colour code on a spiral wound gasket?
ASME B16.20 colour code uses two colours on the outer (centring) ring. The solid band of colour around the edge identifies the winding strip material — silver for 304 stainless, yellow for 316L, gold for Inconel 600, beige for Hastelloy C-276. The stripe colour painted on the face identifies the filler — grey for flexible graphite, white for PTFE, light green for mica, pink for ceramic. So a yellow band with a grey stripe means 316L winding with graphite filler. The size and pressure class are stamped on the outer ring face.
Can I use a spiral wound gasket on a flat face flange?
No. Spiral wound gaskets are designed for raised-face flanges where the gasket sits inside the bolt circle and is constrained by the centring ring. On a flat face flange the spiral can extend past the flange edge under bolting load, fail to develop the correct seating stress, and leak. Use a full-face fibre, rubber, or PTFE gasket on flat face flanges. The pipefitter trade rule: raised face gets a ring gasket, flat face gets a full face gasket.
What is the difference between the inner and outer rings of a spiral wound gasket?
The outer (centring) ring centres the gasket on the flange, acts as a compression stop preventing over-compression of the spiral, and carries the colour-code identification marks. The inner ring sits between the spiral and the pipe bore — it stops the spiral buckling inward under pressure, protects the soft filler from process fluid erosion, and reduces dead space at the joint. Both rings do different jobs and are not interchangeable. Modern ASME B16.20 mandates inner rings for Class 900 and above, all PTFE-filled gaskets, and graphite-filled gaskets in steel pipework.
What's the difference between a spiral wound gasket and a Kammprofile gasket?
A spiral wound gasket has a wound metal-and-filler spiral with rings. A Kammprofile (or grooved metal) gasket has a solid metal core with concentric grooves on each face, and a soft facing (graphite or PTFE) bonded to each side. Kammprofile gaskets are more robust, recover better, and tolerate higher loads than SWGs — but they cost more and need a specific flange surface finish. They are commonly used on heat exchangers and critical service flanges where reliability is paramount. SWGs are the cheaper general-purpose choice for most flange joints.
Should I use 304 or 316 stainless winding for my application?
Use 316 (or 316L) if there is any chloride exposure — seawater, brackish water, chlorinated process fluids, marine atmosphere, or coastal location. Use 304 only for non-chloride service (steam, hot oil, freshwater, dry gas). The cost difference between 304 and 316 is small relative to the cost of a flange leak. 316L (low-carbon variant) is preferred for welded or stress-relieved fabrication to avoid sensitisation. For severe chloride or acid service, upgrade further to 317L, Inconel, Monel, or Hastelloy depending on the chemistry.
What filler material should I use for high-temperature service?
Flexible graphite is the default up to about 500°C in steam or 650°C in inert atmospheres. Above that, or in oxidising atmospheres above 450°C where graphite oxidises, use mica filler — good to 1,000°C. For furnace, kiln, and exhaust manifold service above 1,000°C, ceramic filler is the option. Match the winding strip to the temperature too — Inconel 600 or 625 winding for service above 550°C.
What is ASME B16.20?
ASME B16.20 is the American standard "Metallic Gaskets for Pipe Flanges". It defines the construction, materials, dimensions, marking, and colour-coding of metallic and semi-metallic gaskets — including spiral wound, ring joint, and Kammprofile gaskets — for use with ASME B16.5 raised-face flanges. It is the dominant standard for petrochem, oil and gas, and refining service worldwide. AS 4087 and AS 2129 gaskets sold in Australia typically follow the same colour code convention even though it is not formally part of those standards.
What is the difference between AS 4087 and ASME B16.5 flange standards?
They are completely different standards with different bolt circles, gasket dimensions, and pressure designations. AS 4087 uses PN 14 / 16 / 21 / 35 pressure ratings and is used in Australian water utilities and water treatment. ASME B16.5 uses Class 150 / 300 / 600 / 900 / 1500 / 2500 and is the international standard for petrochem, oil and gas, and most large-scale process plant. Gaskets are NOT interchangeable between the standards even at the same nominal pipe size — order to the standard your flange is built to, never assume they match.
Can I use a spiral wound gasket on a cast iron flange?
With caution. Spiral wound gaskets require higher seating stress than soft gaskets — typically 30 to 70 MPa. Cast iron pump bodies and valve flanges may not tolerate that bolt load and can crack under the asymmetric stress when the steel side of the joint torques up against them. The standard pipefitter advice is to use a soft full-face fibre or rubber gasket on cast iron pump flanges. If pressure or temperature requires an SWG, confirm the cast iron flange rating supports the required bolt load and torque to the lower-rated side of the joint.
How do I torque the bolts when installing a spiral wound gasket?
Use a calibrated torque wrench. Apply lubricant to the bolt threads and under the nuts, but not to the flange face or gasket itself. Hand-tighten all bolts first, then apply torque in a cross (star) pattern in three to five progressive passes — typically 30 percent, 60 percent, 100 percent of target torque, with a final clockwise rotational pass at 100 percent to even out load. Re-torque after 24 hours of service, and after the first thermal cycle for high-temperature applications. Bolt torque values come from the gasket manufacturer's table for your specific gasket, bolt grade, and flange combination — there is no single torque value for "all SWGs".
Are spiral wound gaskets reusable?
No. Spiral wound gaskets are single-use. Once compressed, the soft filler has flowed into the surface roughness of the flange face and the spiral has lost some of its elastic recovery. Reusing a compressed SWG is a near-certain leak path. Always replace the gasket whenever the flange is broken, even if the gasket looks intact. Kammprofile and metal-jacketed gaskets have similar one-use rules with rare exceptions.
What does "CG" or "CGI" mean on a spiral wound gasket?
CG indicates a spiral wound gasket with an outer (centring) ring only. CGI indicates the same gasket but with both outer centring ring and inner ring. CGI is mandatory for ASME B16.20 Class 900 and above, for all PTFE-filled gaskets regardless of class, and for flexible graphite filler in steel pipework. Style R is the wound element only with no rings, used in tongue-and-groove and male-female flanges where the flange itself constrains the gasket.
What's the maximum temperature a spiral wound gasket can handle?
It depends on both the winding strip and the filler. With Inconel 600 winding and ceramic filler the gasket can handle over 1,000°C — furnace and kiln duty. With 316L winding and graphite filler the practical ceiling is around 500°C in steam or 650°C in inert atmospheres. Standard 304 stainless winding with graphite filler is good for around 500°C. Above 450°C in an oxidising atmosphere graphite filler oxidises away, so mica filler is needed.
How do I order a replacement spiral wound gasket from AIMS?
Send us the flange standard (ASME B16.5, AS 4087, AS 2129, etc.), nominal pipe size, pressure class (Class 150, PN 16, Table E, etc.), flange face type (raised face, flat face, RTJ), and the service conditions (fluid, temperature, pressure). Photos of the existing gasket front and edge — showing colour code and any stampings — and of the flange face are extremely helpful. We will confirm the right replacement and stock or source it. Contact AIMS via our contact page or call (02) 9773 0122.