On a raised face (RF) flange in high-pressure service, the practical shortlist is a spiral-wound gasket, a kammprofile (cam-profile) gasket, or a metal ring-joint when the flange carries an RTJ groove, with class, temperature, and media driving the final call [S1][S3].
RF flanges are the default facing in ASME B16.5 and B16.47 inventories because the raised sealing surface concentrates bolt load on a smaller gasket footprint, lifting the joint's effective seating stress above what a flat face (FF) of the same class delivers [S2][S4]. Typical raised face height is 1.6 mm (1/16 in) for ASME Class 150 and 300, stepping to 6.4 mm (1/4 in) for Class 600 and higher [S1].
Why the RF Geometry Changes the Gasket Decision
RF flanges focus compressive force onto the gasket's inner edge, which is exactly the behaviour high-pressure and high-temperature joints need, but it also means soft, low-density sheet gaskets get crushed beyond their useful range once the class climbs past 300 [S2][S4].
RF is not itself a pressure rating: a 2-inch ASME B16.5 Class 150 RF in carbon steel is rated to roughly 285 psi at 100 °F, while the same nominal size in Class 600 reaches about 1480 psi, so the gasket has to be re-selected for the actual pressure-temperature envelope, not the face type [S3]. Engineers should treat the RF as a load-concentrating geometry, then pick a gasket construction that can carry that load without losing recovery across thermal cycles [S3][S6].
The Three Gasket Constructions That Actually Work on RF
Spiral-wound gaskets (alternating metal V-strip windings with filler such as graphite or PTFE) are the workhorse for Class 300 and above on RF flanges, because they combine metallic strength with a resilient filler that handles thermal cycling and vibration [S1][S3].
Kammprofile gaskets use a solid metal core with concentric raised cam profiles and a soft sealing layer (typically graphite) bonded to both faces, giving higher blowout resistance than spiral-wound at the cost of tighter flatness and surface-finish control on the flange [S1][S3].
Ring-type joint (RTJ) gaskets are solid metal rings, oval or octagonal, that sit in a precision-machined groove on the flange face; once the class crosses into the high-pressure regime, the RTJ variant of the RF flange (with that groove milled in) takes over and only metallic rings are acceptable, with hardness differential between ring and groove required for a leak-tight seal [S1][S5][S8]. Soft cut gaskets, compressed fibre, and elastomer sheet can still be used on RF in low-pressure utility service, but they are out of their depth once the line approaches Class 600 steam or hydrocarbon service [S3][S4].
Decision Criteria Across the Three Options
The two engineering variables that move the answer between spiral-wound, kammprofile, and RTJ are the pressure-temperature rating required and how much thermal cycling the joint will see, with media compatibility sitting underneath both [S3].
Spiral-wound gaskets cover the widest pressure-temperature band on standard RF flanges and tolerate differential thermal expansion between flange and bolt better than solid metal gaskets, which is why they dominate refinery, chemical, and power-plant RF joints in Class 300 to Class 1500 [S1][S3]. Kammprofile is preferred where seating stress and blowout resistance are pushed to the limit, for example high-temperature steam headers and cyclic hydrocarbon service, because the solid metal core resists extrusion better than a wound construction [S3]. RTJ is the only choice once the service climbs into API 6D / ASME B16.5 Class 600 and above with hydrocarbons or high-pressure steam and the flange has been grooved accordingly, because the metal-to-metal seal inside the groove survives pressures that would blow a soft or semi-metallic gasket out of an ungrooved RF face [S1][S5][S8].
Material pairing is the next filter: spiral-wlow 316L stainless windings with graphite filler suit most refinery and chemical duties, while kammprofile graphite-faced 316L cores handle steam and hydrocarbon cycling; RTJ rings are typically soft iron (low carbon), 304/316 stainless, or alloy grades matched to the groove hardness on a 30 to 40 HB differential, per ASME B16.20 [S1][S8].
Where Each Choice Breaks Down
Spiral-wound gaskets fail by relaxation and filler extrusion if the bolt load is not re-tightened after the first thermal cycle, and they are intolerant of flange-face damage and Ra finish outside the typical 125 to 250 µin Ra band [S3].
Kammprofile gaskets are unforgiving of flange flatness and require controlled torquing; the soft facing layer can also degrade in strongly oxidising media unless a mica or PTFE barrier is added, which then caps the temperature ceiling [S3]. RTJ is unforgiving of groove geometry: any score, corrosion, or wrong hardness pairing in the groove turns the metal-to-metal seal into a leak path, and the joint cannot be re-seated without re-machining the groove or replacing the flange [S5][S8].
None of the three should be used on a flat face (FF) flange, where brittle cast iron or FRP mating components need load spread across the whole face; forcing a spiral-wound or kammprofile onto an FF joint is a common cause of cracked flanges in pump suction and water service [S2][S4].
Standards, Spec Sheets, and What to Verify on Paper
RF dimensions, raised face height, and bore sizes are governed by ASME B16.5 (NPS 1/2 to 24) and ASME B16.47 (Series A and B, larger sizes), while RTJ groove geometry and ring hardness are fixed by ASME B16.20 [S1][S2]. Pressure-temperature ratings for the selected material (carbon steel, stainless, alloy) must be taken from the relevant ASME B16.5 / B16.47 table at the design temperature, not the cold class number alone [S2][S3].
When the line carries flammable or process fluids, sour-service clauses under NACE MR0175 / ISO 15156 limit ring and winding materials, and the gasket supplier's data sheet must show compliance as a separate line item, not buried in a generic "suitable for refinery service" note. For steam and boiler-feed service above the graphite oxidation ceiling (around 425 °C in air, lower in superheated steam), mica-faced or vermiculite-filled spiral-wound and kammprofile gaskets are the documented workaround, and the data sheet should call out the temperature grade explicitly [S3]. A complete RF joint specification always lists, at minimum, flange standard and class, facing (RF or RTJ), gasket type and standard, winding/ring material, filler, facing thickness, design temperature, design pressure, and the bolt-tightening procedure that will be used on site [S1][S3].
For adjacent specifications on valves, strainers, and fittings that share the same pressure-class envelope, a ball valve data sheet follows the same ASME B16.34 class logic, and a complete pipe fitting datasheet uses an identical class-to-pressure mapping, so a procurement team can keep the RF gasket class and the valve or fitting class consistent across the same line. Where the RF joint sees PTFE or FKM wetted components upstream, the cost and compliance picture for the elastomer side is covered separately in PTFE, PVDF, FKM price 2026, which is relevant because spiral-wound fillers and elastomer O-rings are often the first items flagged under PFAS-related supply rules.
Spec-level background on the components involved: flange, gasket, and face shield.