Overview
A spiral wound gasket is a semi-metallic seal made from a preformed V-shaped metal strip wound alternately with a soft filler tape. The metal supplies resilience and recovery; the filler does the sealing. Inner and outer rings add compression control. ASME B16.20 governs the dimensions used in pipe flanges.
How a Spiral Wound Gasket Is Built
A thin metal strip is preformed into a V-shaped or W-shaped profile, then wound on a mandrel in alternating turns with a softer filler tape, so every layer of metal sits against a layer of filler. The coil is spot welded at the start and finish.
The construction is a division of labour. Metal is elastic and recovers when the load comes off, while filler flows into the microscopic valleys of a machined flange face. A flat soft sheet does both jobs with one material and recovers poorly.
That difference decides thermal cycling. As a steam line heats up, the flanges grow, the bolts stretch, and the joint relaxes. A spiral gasket built on a preformed metal V acts like a stack of small springs, storing energy at bolt-up and returning it as the joint moves. Residual load stays above the stress a gasket seal needs.
The Four Components of a spiral wound gasket
The winding
The alternating metal and filler wind is the sealing element. Under axial load, the V profile flattens, the filler is pressed into the flange finish, and the metal holds load in reserve. Strip thickness and winding density are set to give a defined compressed thickness at a defined seating stress.
The filler
The filler is what actually stops the fluid. Its chemistry sets the temperature ceiling and chemical range of the joint, the largest single gasket material decision on the part.
The inner ring
A solid metal ring fitted inside the wind. It acts as a compression stop, prevents the innermost turns from buckling inward under pressure, and shields the wind from turbulence and erosion. It also fills the annular gap at the bore, removing dead space and reducing flange erosion.
The outer centring ring
Usually carbon steel, the outer ring sits around the wind. It centres the sealing element in the bolt circle, and limits compression once the flanges close on it. That prevents crushing, adds blowout resistance, and carries the identification markings.
Choosing the Winding Metal
The winding should resist the process fluid as well as the piping does. Austenitic 304 covers general service. 316L suits refinery and chemical duty where chlorides matter. Stabilised 321 and 347 resist sensitisation after long exposure to heat, suiting superheated steam and hot gas. Monel suits hydrofluoric acid, caustic and seawater; Inconel high temperature oxidising service, and titanium suits oxidising chloride media. The wider metallic gasket family is covered separately.
Choosing the Filler
Filler chemistry sets what a spiral wound gasket can actually hold.
| Filler | Approximate ceiling | Suits | Watch for |
|---|---|---|---|
| Flexible graphite | around 450 degC in air, higher in steam | steam, hydrocarbons, refinery duty | oxidation in air |
| PTFE | roughly -200 to +260 degC | acids, alkalis, chlorine, food and pharma | cold flow, needs an inner ring |
| Ceramic or mica | in the region of 1000 degC | furnace, flue gas, superheater duty | brittle, careful handling |
| Non-asbestos fibre | typically about 350 degC | water and low-pressure utilities | narrow chemical range |
Limits shift with the compound and the duty cycle, so confirm any gasket material claim against real line conditions.
Standards, Pressure Classes and Styles
ASME B16.20 is the governing dimensional standard for a spiral wound gasket in pipe flanges. Flange dimensions come from ASME B16.5 for smaller sizes and ASME B16.47 for large diameters, in classes 150, 300, 600, 900, 1500 and 2500. An industry colour coding convention identifies winding metal and filler on the outer ring, useful at site as a cross-check.
Four styles are in common commercial use: winding only, winding with an inner ring, winding with an outer centring ring, and winding with both. Among process piping gasket types, the both-rings style is the usual default.
Fitting It Correctly
Clean the flange faces and check for radial scoring, pitting and warp. Centre the part accurately, since an off-centre part loads unevenly and leaks on the light side. Tighten in a staged cross pattern at 30, 60 and 100 per cent of target torque, then a final pass, using a calibrated wrench and controlled stud lubrication.
Over-compression is the most common site error, because once the wind is crushed, its spring is gone. A used spiral wound gasket must never go back into a flange, even if it looks undamaged.
Where It Belongs
A spiral wound gasket earns its place in refineries, petrochemical plants, power generation, heat exchanger bonnets, boiler and superheater connections, main steam lines and oil and gas piping. Where a joint sees thermal cycling or pressure swing, a spiral gasket beats a flat soft sheet. For extreme pressure wellhead duty, a solid ring joint takes over.
What to Send With an Enquiry
Approaching spiral wound gasket manufacturers in India goes faster with a complete enquiry: flange standard and size, pressure class and facing, operating temperature, media and concentration, winding metal and filler, style, and quantity. A drawing settles any non-standard dimension. The DeePee Rubber team asks for the same list.
Why Buyers Across India Choose DeePee Rubber
Sealing failures on hot cycling flanges are rarely about price. They come from the wrong filler, an under-specified winding, or a crushed wind with no recovery left. DeePee Rubber has supplied industrial sealing components since 1965, with over five decades of experience across manufacturing, chemical, power, oil and gas and OEM applications in India. The DeePee Rubber team specifies fromreal-worlde conditions rather than a part number. Share your flange drawing, operating temperature, pressure class and media details, and request a quotation for the spiral wound gasket construction your joint calls for.
Conclusion
The construction rewards attention to detail. A winding chosen for the media, a filler chosen for the temperature, rings chosen for the pressure class and a bolt-up sequence that respects compressed thickness will hold a hot flange closed for years. Miss one of those and the joint becomes a recurring maintenance item. A spiral wound metallic gasket is an engineering decision rather than a purchase line, so bring real operating data to the specification stage. Set the duty first, and the metallic gasket you fit will do what the design intended.
Key Takeaways
- Metal supplies recovery and filler supplies sealing, which is why the construction survives cycling.
- Match the winding to the media and temperature, then the filler to the chemical range.
- Inner rings control compression and erosion; outer rings centre the part and limit crush.
- Among high-pressure gasket types, ASME B16.20 covers classes 150 through 2500.
- Torque in a staged cross pattern, and never refit a compressed wind.
Frequently Asked Question
No. Compression permanently flattens the metal winding and consumes the elastic recovery that keeps a joint tight. A reused part seats at lower residual load, so the gasket seal tends to leak on the next thermal cycle.
Fit one with PTFE filler in the higher pressure classes, and wherever erosive or turbulent media reach the flange bore. It acts as a compression stop and blocks inward buckling of the winding
Flexible graphite, paired with 316L, 321 or 347 winding depending on temperature. Above the graphite range, ceramic or mica fillers take over for furnace and flue gas duty.
Flange standard, size, pressure class, facing, media, temperatures, winding metal, filler and style, plus a drawing for any non-standard flange. Complete inputs give you a comparable spiral wound metallic gasket offer instead of guesswork.
