4 Common Types of metal sealing gaskets

Metal sealing gaskets serve the joints where soft materials give up: high pressure, high temperature, and repeated thermal cycling. The four common families - spiral wound, metallic ring joint, serrated, and corrugated - seal by different mechanisms, and each one has its own pressure, temperature, and flange limits. This guide explains how each family works so the gasket matches the medium, the bolting, and the duty; for lighter services the wider range of flange gaskets still covers the job.

Spiral Wound Gaskets

A spiral wound gasket is a semi-metallic composite. Pre-formed metal strips - 304 or 316 stainless steel, Hastelloy, titanium - are wound alternately with a non-metallic filler such as graphite, PTFE, or ceramic fibre. The metal winding carries the bolt load and springs back after compression; the filler conforms to the flange face and closes the leak path. Match the pair to the duty: graphite for heat and steam, PTFE for aggressive chemicals, ceramic fibre where temperatures exceed what organic fillers survive.

• Type A (basic): no inner or outer ring. General service below 5.0 MPa between -200 C and +600 C on raised face flanges handling water, oil, or steam.
• Type B (inner ring): the ring limits compression, holds bolt load in check, and shields the windings from flow erosion. Suited to pressure swings and thermal cycling.
• Type C (outer ring): the ring centres the gasket, resists radial movement, and protects the windings. Used up to 25 MPa where flange alignment matters.
• Type D (inner and outer rings): the full configuration for critical joints up to 42 MPa, thermal cycling with temperature differences above 300 C, and corrosive media.

Metallic Ring Joint Gaskets

A metallic ring joint gasket is a solid, one-piece metal ring with a machined cross-section that seals by line or area contact against a groove. Because the ring seats in that groove, the joint needs matching pipe flanges: modern flat-bottom grooves machined to API 6A Type 6B dimensions for R rings, and API 6BX flanges for BX rings. Sealing is metal-to-metal, so groove finish and clean threads matter as much as bolt load.

Table 1. Metallic ring joint gasket profiles, contact geometry and typical service limits.

RX rings react to internal pressure: the medium reaches the back of the gasket through the outer grooves, so sealing stress rises with system pressure. BX rings balance cavity pressure through internal channels and are tightened with hydraulic torque wrenches in staged, cross-bolted sequences.

Serrated Metal Gaskets

A serrated metal gasket is machined from a metal plate with concentric grooves on both faces. The shallow serrations concentrate bolt load into narrow contact bands, while the soft facing does the sealing and the serrations distribute the load.

• Serration geometry: 0.05-0.1 mm deep, 0.5-1.0 mm pitch, 60-90 degree tooth angle, 0.05-0.1 mm crest width.
• Materials: soft iron, low-carbon steel, stainless steel, aluminium, or copper, typically HB 90-250.
• Surface treatment: tin or silver plating, or a graphite coating, lowers friction and evens out bolt-up.
• Thickness 1.5-3.0 mm keeps the elastic deformation needed for flange rotation and thermal movement.
• Service: 4.0-20 MPa working pressure (up to 42 MPa), -200 C to +600 C, with steam, oil and gas, hydrogen, ammonia, or organic solvents, on raised face, flat face, or male-and-female flanges.

Corrugated Metal Gaskets

A corrugated metal gasket is formed from thin metal sheets (0.1-0.5 mm) rolled or stamped into a regular wave. The wave acts like a spring, so the gasket seals at low bolt load and follows flange movement caused by pressure and temperature.

• Wave geometry: sine, rectangular, or trapezoidal profiles, wavelength 2-10 mm, wave height 0.3-2.0 mm.
• Laminated construction: 2-4 corrugated layers, with non-metallic material optionally sandwiched between them.
• Material pairs: stainless steel waves with graphite filler, or special alloy waves with ceramic fibre; edges boxed by an outer ring or fitted with locating tabs.
• Low-load sealing: about 30% of the compressive force a flat gasket needs, useful where bolting is limited.
• Temperature and size: -250 C to +800 C (up to +1000 C without filler layers), diameters to 3000 mm and beyond, including carbon-to-stainless joints.

Three builds cover most duties: all-metal for high temperature and radiation service, filler-laminated for chemical lines and low-temperature storage, and outer-ring types for large heat exchangers and tower flanges where installation positioning matters.

Frequently Asked Questions

When should I choose a ring joint gasket instead of a spiral wound gasket?

When the joint has a machined groove and the pressure is high. Ring joints seal metal to metal and cover the highest pressures; spiral wound gaskets fit standard raised face flanges and are more forgiving of surface finish and alignment.

Can a serrated metal gasket be reused after the joint is opened?

No. The serrations and any soft facing take a permanent set during bolt-up, so a reused gasket gives uneven contact and early leakage. Fit a new gasket whenever the joint is broken.

What limits the service temperature of a corrugated metal gasket?

The facing and filler, not the metal. Stainless or alloy waves survive far more heat than the filler allows; without a filler layer the construction reaches about +1000 C.

Does a ring joint gasket fit any flange?

No. R rings need grooves machined to API 6A Type 6B dimensions, RX rings need their matching groove, and BX rings fit only API 6BX flanges. Check the groove drawing on the flange before fitting.