Industrial gasket selection resolves to a triangular trade-off between operating temperature, internal pressure, and chemical compatibility with the process fluid, with material cost and creep-relaxation as secondary filters. Most process plants stock three families and choose among them: non-metallic sheet (compressed fibre, graphite, PTFE, rubber), semi-metallic (spiral wound, kammprofile, double jacketed), and metallic (ring joint RTJ, corrugated, solid metal).
Typical operating envelopes are well documented: standard rubber gaskets lose integrity above 150°C [S4], compressed fibre sheets with rubber binder are rated from 5°F to 390°F (≈ −15°C to 200°C) with poor steam resistance [S3], while metal gaskets routinely hold wellhead pressures above 15,000 psi (≈ 103 MPa) and survive exhaust-turbine temperatures that would vaporise polymers [S2]. Spiral wound and kammprofile dominate the 300–800°C, Class 300–1500 service window that kills both soft sheet and solid metal.
Non-Metallic Sheet Gaskets: Cheap, Conformable, Thermally Limited
Compressed fibre, graphite, PTFE and rubber sheets fill 80–90% of low-pressure chemical, water, and HVAC flange duty, because they conform to surface finish Ra 3.2–6.3 µm without a machined groove and cost a fraction of a metal joint [S3]. A 1.5 mm (1/16″) thin sheet gives higher blowout resistance because less bore area is exposed to internal pressure, and lowers through-gasket permeation versus a 3 mm (1/8″) thick part [S5][S6].
The trade-off is brutal at the high end. Standard rubbers soften and leak above 150°C; only fluoroelastomer (FKM) and perfluoroelastomer (FFKM) push that ceiling, at significantly higher unit cost and limited chemical breadth [S4]. Compressed fibre with a nitrile binder scores well on hot compression (typical load 14 MPa / 2000 psi or higher in industrial bolted joints) but degrades in hot water and steam service [S3]. PTFE and ePTFE give the widest chemical compatibility of any polymer family, tolerating strong acids, bases, and solvents, yet they cold-flow under sustained load and require a filler or stainless inserter for pressures above Class 150 [S7].
Semi-Metallic Gaskets: The 300–800°C Middle Ground
Spiral wound, kammprofile, and double-jacketed styles are built as a metal core (typically stainless steel 316L, Monel, Inconel, or graphite-faced) wound or stamped into a geometry that combines metal strength with a soft filler. They handle thermal cycling from cryogenic LNG up to roughly 800°C in oxidising service and pressures from vacuum to Class 1500, with the metal windings acting as the pressure-energising element and the filler providing the seal [S2][S5].
On the selection side, spiral wound is the default for refinery and steam-service ASME B16.5 flanges because the winding geometry maintains seating stress after creep relaxation, while kammprofile is preferred where flange faces are warped or where the operator wants a reusable, low-leakage joint (typically ≤ 1×10⁻³ mbarl/s of helium on a class 100 ppm target). Double-jacketed gaskets carry the heat of exhaust and boiler manways but have a known failure mode: the soft filler can fail at the inner jacket edge under thermal shock, which is why most EPCs now specify solid spiral wound for new boiler penetrations above 50 bar.
Metallic Gaskets: Highest Pressure, Highest Prep Cost
Ring-joint (RTJ) oval and octagonal profiles, soft-iron, low-carbon steel, stainless 304/316, Monel 400, and Inconel 600–625 are machined or die-formed, then wedged into a precision groove cut into the flange face. The seal gets tighter as internal pressure rises because the media itself energises the joint, a behaviour that makes RTJ the only legal choice in many ASME B16.5 Class 600–2500 hydrocarbon and wellhead services [S2][S3].
The chief disadvantage is preparation: a groove must be machined into both flange faces, with typical groove depth 5.5–7.0 mm and surface finish Ra 0.8–1.6 µm, which is on top of the harder flange material specification (often AISI D2 tool steel or 17-4PH for high-pressure blocks) required to resist brinelling from repeated make-ups [S1]. For copper gaskets specifically, the same source notes the extra machine work and prep as the leading practical drawback, while nickel-alloy RTJs trade higher unit cost for corrosion resistance in sour service where NACE MR0175 applies. Procurement of exotic alloys, and the fact that RTJ gaskets are essentially non-reusable after two or three make-ups, keeps them out of any application that does not need their pressure ceiling.
Thickness: The 1.5 mm vs 3 mm Decision
Gasket thickness is the single most under-discussed selection variable. FSA / ESA Gasket Handbook guidance, echoed in independent selection guides, splits the decision cleanly: thin gaskets (≤ 1.5 mm / 1/16″) win on blowout resistance, through-gasket permeation, fastener torque retention, and creep-relaxation resistance, because for a given material creep relaxation resistance improves as thickness decreases [S5][S6].
Thick gaskets (≥ 3.0 mm / 1/8″) win on flange-surface compensation: they can absorb warpage, minor misalignment, and pitted faces, and they tolerate larger differential thermal expansion between flange and gasket. For non-metallic sheet on cast-iron or glass-lined flanges, that added forgiveness is often worth the higher leak rate. For metallic and semi-metallic joints the rule inverts: most manufacturers cap RTJ, spiral wound, and kammprofile at the thinnest profile the flange finish supports, because thicker profiles in these geometries lose their pressure-energising behaviour and increase the radial bore area exposed to the fluid.
Flange Pairing and Installation Constraints
Every gasket advantage evaporates if the flange is wrong. A full-face sheet gasket on a tongue-and-groove face will not seat, a spiral wound on a flat face needs a compression ring, and an RTJ only seats on a ring-joint groove with the correct hardness differential (typically 30–40 HB below the flange). Acceptance checks, torque patterns, and re-torque intervals after the first hot cycle are covered in Flange Gasket Installation: Procedure, Failure Modes, and Acceptance Checks. [S2]
Storing gaskets in direct sunlight, near ozone-generating equipment, or at temperatures outside the material's published shelf range degrades rubber and graphite binders well before installation, and the FSA handbook treats storage and handling as a first-class selection criterion rather than a procurement detail [S5]. For hydrocarbon, chemical, and steam services the operator should also confirm the material's compliance with the governing standard for the service: ASME B16.5 for pipe flanges, ASME B16.20 for ring-joint gaskets, EN 1514 for European gaskets, and NACE MR0175 for sour H₂S environments.
Material Comparison at a Glance
Four decision criteria line the families up cleanly. (1) Temperature: rubber 5–150°C, compressed fibre −15–200°C, ePTFE / graphite −200–260°C, spiral wound −200–800°C, RTJ metallic up to 1100°C with Inconel. (2) Pressure: rubber and fibre cap around Class 150–300, ePTFE/graphite reach Class 600 with inserts, spiral wound covers Class 150–1500, RTJ covers Class 600–2500 and wellhead above 15,000 psi. (3) Chemical compatibility: rubber is strong on acids/alkalis but weak on hydrocarbons (NBR excepted), fibre is broad but fails in hot water, ePTFE is the widest polymer envelope, metallic depends on alloy with Inconel 625 covering sour H₂S. (4) Reusability: rubber and compressed fibre are single-use, spiral wound is single-use but inspectable, kammprofile is reusable after re-facing, RTJ is essentially single-use after two or three make-ups [S2][S3][S4][S5][S7].
Specifying engineers should treat those four columns as a checklist rather than a recommendation list, because the right answer is always defined by the worst-case combination of temperature, pressure, and chemistry rather than by any single metric. The next decision node is the flange-facing finish and fastener torque plan, both of which feed into the leak-tightness acceptance target that the flange gasket installation procedure will verify on first hot cycle.
Spec-level background on the components involved: checking and testing apparatus, and construction machinery and equipment.