Spiral wound gaskets are built by winding a V-section metal strip (typically 304 or 316L stainless, with Monel 400, Nickel 200, Inconel 600, Incoloy 825, Hastelloy B-2/C-276, or titanium as options) together with a soft filler (graphite, PTFE, non-asbestos, or mica) under controlled tension, with optional carbon-steel inner and outer guide rings [S5].
Sheet gaskets are cut from homogeneous compressed non-asbestos fibre, PTFE, EPDM, Nitrile (NBR), Silicone, or compressed non-asbestos (NAF) sheet, and rely on bolt load to compress the soft body into flange face imperfections [S1][S4]. The two families sit in different pressure and temperature envelopes, and the wrong choice between them is a common root cause of joint leakage and blowout.
Construction Differences: Wound Composite vs Cut Sheet
A spiral wound gasket is a semi-metallic composite of four parts: a preformed metal winding strip, a soft filler strip, an inner ring (centring ring), and an outer guide ring (compression stop) [S7]. The metal and filler layers alternate in a tight spiral, and when the joint is bolted up the filler flows into flange face imperfections while the metal strip supplies spring-like recovery under pressure and thermal cycling [S1][S5]. Typical designations include Type RF1 (spiral only), SG (with guide ring), RF-IR / SG-IR (with inner ring), SG-RTJ (for ring-type-joint flanges), and HX-R / HX-RIR (for large-diameter heat-exchanger pass partitions) [S5].
Sheet gaskets have no metal core: they are stamped, die-cut, or waterjet-cut from a uniform elastomer or compressed-fibre sheet, so they cannot provide the same elastic recovery or blowout resistance as a wound composite [S1][S4]. Industry practice groups spiral wound gaskets as semi-metallic, suitable for high-pressure and high-temperature service in oil and gas, petrochemical, power generation, and heat-exchanger headers [S4][S6].
Material Envelopes: Temperature, Pressure, Chemical Compatibility
Filler material sets the temperature ceiling of a spiral wound gasket: graphite is rated -200 to 550 °C at 250 bar with very good chemical compatibility (grey stripe), PTFE is rated -200 to 250 °C at 100 bar with excellent compatibility (white stripe), non-asbestos is rated -100 to 250 °C at 100 bar (pink stripe), and mica pushes the upper limit to 1000 °C at 100 bar with moderate compatibility (light green stripe) [S5].
Winding alloy sets the pressure and corrosion envelope: 304 and 316L stainless run to 550 °C and 172 bar, Monel 400 and Nickel 200 reach 600 °C at 172 bar and 138 bar respectively, Inconel 600 extends to 950 °C at 172 bar, and titanium caps at 350 °C and 103 bar [S5]. In contrast, elastomer sheet gaskets (EPDM, NBR, silicone) are typically limited to under 200 °C and below roughly 40 bar depending on flange class, with PTFE sheet reaching about 260 °C but limited by cold flow [S1][S4].
Selection Criteria: Pick by Service, Not by a Single Pressure Number
Selection is driven by four variables, not by a universal pressure cutoff: media compatibility, design pressure, design temperature, and joint geometry [S1][S3]. NBR sheet is appropriate for oils and fuels at low temperature, 316L/graphite spiral wound covers hydrocarbons and steam in refinery and high-pressure pipelines, and PTFE spiral wound or PTFE sheet suits aggressive chemicals where graphite contamination of the process stream must be avoided [S1][S5].
Joint geometry matters: tongue-and-groove, male-female, and RTJ flanges have specific spiral wound variants (SG-RTJ for ring-type-joint faces), while flat-faced flanges at low pressure accept standard cut sheet without inner rings [S5]. A practical rule of thumb from current OEM guidance: specify sheet gaskets for low-pressure water, air, and hydrocarbon service below roughly 40 bar and 200 °C, and specify spiral wound gaskets with a verified filler for refinery, steam, and high-pressure hydrocarbon service above those limits [S1][S3].
Comparison Matrix: Spiral Wound vs Sheet Gasket on Six Criteria
On cost, sheet gaskets win: elastomer and compressed-fibre sheets are cheaper per piece and run efficiently in high-volume waterjet or die-cut production, with no metallic core [S1]. On pressure and temperature, spiral wound wins by a wide margin: 250 bar / 550 °C for graphite-filled 316L versus roughly 40 bar / 200 °C for most elastomer sheet, with Inconel 600/mica pairs reaching 950-1000 °C [S5].
On chemical compatibility, PTFE (sheet or spiral wound filler) gives the broadest inert range but is limited to 250-260 °C, while graphite filler has very good chemical compatibility and is the workhorse for hydrocarbons and steam [S5]. On recovery and blowout resistance, spiral wound gaskets supply spring-back under thermal cycling, whereas sheet gaskets can extrude or blow out under pressure spikes if the sheet is too soft for the bolt load [S1][S2]. On clamping force, spiral wound designs need less seating load for a given pressure class because the metal strip carries much of the load, which reduces flange and bolt wear during install [S2]. On lead time, standard ANSI sheet gaskets ship fastest, while custom spiral wound profiles (HX-R heat-exchanger pass partitions, special alloys) carry longer lead times [S1][S5].
Use Cases and Failure Modes
Use spiral wound gaskets for high-pressure steam headers, refinery and petrochemical flanges above ASME Class 300, heat-exchanger channel and pass-partition covers (HX-R / HX-RIR), and any joint exposed to thermal cycling between ambient and 500 °C or above [S4][S5][S7]. Use sheet gaskets for low-pressure water, HVAC, lubrication oil, and chemical service on flat-faced flanges where the media, temperature, and pressure fall within the elastomer or PTFE envelope [S1][S4].
Common failure modes to design against: graphite filler oxidising above about 450 °C in oxygen-rich steam (specify mica or a GT-zone profile), PTFE cold-flowing under sustained bolt load (use a compression-stop outer ring, Type SG), elastomer sheet blistering above its temperature rating, and spiral windings crushing on misaligned flanges without an inner ring (use RF-IR or SG-IR on recessed-face flanges) [S5]. A non-asbestos sheet gasket that sees hydrocarbon above 250 °C will fail; a PTFE spiral wound that sees 300 °C steam will also fail, which is why the filler chart, not the alloy chart, is the first table to check [S5].
Standards, Sourcing, and Spec Discipline
Spiral wound gaskets are commonly specified to ASME B16.20 for dimensions and to ASME B16.5 / B16.47 for the flange class they mate with, with material combinations per ASTM filler and winding strip standards (referenced in manufacturer datasheets) [S5]. Sheet gaskets fall under ASME B16.21 for non-metallic flat gasket dimensions, with material limits published by the sheet manufacturer for each grade [S1][S4].
Spec discipline that holds up in the field: state the fluid, concentration, design pressure, design temperature, thermal cycle range, flange class and face type, required bolt load, and any cleanliness or product-contamination limit (oxygen, food, pharma); then map those to filler and winding strip from the rated tables [S3][S5]. For critical service, order with a 316L or Inconel inner ring to prevent inward buckling on recessed-face flanges, with a carbon-steel outer guide ring as a compression stop, and with colour-coded identification stripes traceable to the filler and winding alloy [S5]. For related sealing and joint hardware decisions on rotating equipment, see the single-pump vs tandem-pump HPU selection guide and the 4-point vs 6-point hard hat suspension comparison. For more on flange-side tooling, see the construction tools encyclopedia page and the gasket encyclopedia page.
Trackable signals for the next cycle: ASME B16.20 revisions for spiral wound dimensions, mica-filler adoption in 600 °C+ steam service, and the spread of GT-zone profiles for oxygen and pharma service where graphite contamination of the process stream is unacceptable [S5].
For component-level specifications, see construction machinery and equipment.