Last updated: April 2026
A graphite gasket is a flange gasket cut from flexible expanded graphite sheet — usually reinforced with a tanged or smooth stainless-steel core. Graphite gaskets are the default sealing choice for high-temperature steam, hydrocarbon, and thermal-cycling duties because graphite has near-zero creep, excellent recovery, and a continuous service range from −200 °C to +450 °C in air (or +650 °C in inert gas).
GritGasket cuts flexible graphite gaskets from premium 98%+ purity sheet with tanged stainless-steel, perforated, or smooth-foil reinforcement — plus nuclear-grade (≥99% C) on request. Supplied in any pattern from ½" NPS to 60" diameter, delivered across Australia and New Zealand.
What Is a Graphite Gasket?
Flexible graphite is made by intercalating natural graphite flake with acid, shock-heating to exfoliate the layers, then calendering the "worm" back into a flexible sheet. The result is a pure graphite sheet — no binders, no fillers — that is soft enough to fill micro-surface irregularities and elastic enough to maintain a seal under thermal cycling and bolt relaxation.
For flange service, graphite is almost always combined with a metal reinforcement:
- Tanged stainless steel — perforated SS sheet with upward-facing tangs that mechanically grip the graphite. The workhorse construction.
- Smooth foil — plain SS foil laminated with graphite. Used where lower pull-through risk matters.
- Perforated sheet — holes punched rather than tanged; handles higher compression without tang collapse.
- Plain graphite foil — no reinforcement, for low-pressure or glass-lined service where metal contamination is unwanted.
Why Choose Graphite Over PTFE or Rubber?
Graphite dominates where temperature, steam, or thermal cycling rule out softer materials:
| Property | Flexible Graphite | PTFE | Rubber (EPDM) |
|---|---|---|---|
| Max continuous temp (air) | 450 °C | 260 °C | 120 °C |
| HP steam service | ✓ | — | — |
| Thermal cycling | ✓ excellent | — creeps | — hardens |
| Chemical range | Non-oxidising | Universal | Water, mild chem. |
| Fire-safe | ✓ | — degrades | — degrades |
Pressure and Temperature Envelope
| Construction | Max temp (air) | Max temp (inert) | Max pressure |
|---|---|---|---|
| Plain graphite foil | 450 °C | 650 °C | Class 150 |
| Tanged 316SS reinforced | 450 °C | 650 °C | Class 600 (100 bar) |
| Graphite-filled spiral wound | 450 °C | 650 °C | Class 2500 (400 bar) |
| Graphite-faced kammprofile | 450 °C | 650 °C | Class 2500 (400 bar) |
At higher flange classes, graphite is not used as a cut sheet — it is carried as the filler in a spiral wound gasket or as the facing on a kammprofile gasket.
Graphite Oxidation — the One Caveat
In air above ~450 °C graphite slowly oxidises (burns) at a rate that depends on temperature, humidity, and purity. Pure, high-density sheet (ρ ≈ 1.0 g/cm³) and oxidation inhibitors extend the life considerably, but if your service is continuously above 500 °C in air you should specify either a low-ox graphite grade or switch to mica-filled spiral wound gaskets. In inert or reducing atmospheres (N₂, H₂, refinery service), graphite handles 650 °C with no oxidation concern.
Where Are Graphite Gaskets Used?
- Power generation — HP/LP steam flanges, boiler feedwater, turbine bypass.
- Refinery & petrochemical — hydrotreaters, fractionation columns, heat exchangers.
- Mining & smelting — calciners, rotary kilns, high-temperature process lines.
- Heat exchangers — shell & tube channel covers, plate-HX service where thermal cycling is severe.
- Fire-safe service — graphite does not combust in the presence of hydrocarbons; preferred for fire-safe valve body gaskets.
Installation Notes
Graphite gaskets tolerate high assembly stress — typical seating stress is 40 MPa for plain foil, 60 MPa for tanged, and up to 175 MPa inside a spiral wound winding. Follow ASME PCC-1 four-pass cross-pattern bolt-up. Use our bolt torque calculator to convert target stress into bolt torque. Graphite sheets are brittle until clamped — handle gently, do not fold.
Stocked Graphite Gaskets
GRAPH-TSS316
GRAPH-FOIL
Frequently Asked Questions
A graphite gasket is a flange gasket cut from flexible expanded graphite sheet — pure graphite, no binders. It is usually reinforced with a tanged, perforated, or smooth stainless-steel core for pull-through resistance. Graphite gaskets handle continuous service from −200 °C to +450 °C in air (or +650 °C in inert gas) and are the go-to choice for HP steam, refinery, and thermal-cycling flange duties.
Plain graphite foil is pure graphite with no reinforcement — cheap, easy to cut, but prone to pull-through on higher-pressure flanges. Tanged graphite has a perforated stainless-steel core with upward-facing tangs that mechanically anchor the graphite. Tanged is the workhorse construction for Class 150–600 flange service; plain foil is reserved for low-pressure or glass-lined duties.
Graphite slowly oxidises in air above around 450 °C — it does not "burn" in the combustion sense, but surface graphite is consumed over time. Oxidation-inhibited grades extend this, and in inert or reducing atmospheres graphite handles 650 °C with no concern. For continuous service above 500 °C in air, switch to a mica-filled spiral wound gasket.
Yes, but specify high-purity (≥98% C, low-chloride) graphite. Natural graphite can contain trace chlorides that accelerate stress-corrosion cracking on austenitic stainless at elevated temperature. Reputable suppliers (including GritGasket) stock certified low-chloride grades for stainless-steel flange service — ask for the material certificate.
A cut graphite sheet gasket with tanged stainless reinforcement is usually rated to Class 600 (100 bar cold working pressure). Above that, graphite is used as the filler in a spiral wound gasket or as the facing on a kammprofile gasket, which together cover Class 900 through 2500 (up to ~400 bar).
Related Products
- Spiral wound gaskets — graphite-filled for Class 600+ service
- Kammprofile gaskets — graphite-faced, blow-out resistant
- PTFE gaskets — soft-faced alternative for aggressive chemicals
- Gasket sheet — graphite and CNAF sheet for custom cutting
Learn More
Sources
- ASME B16.21 — Nonmetallic Flat Gaskets for Pipe Flanges
- ASME PCC-1 — Guidelines for Pressure Boundary Bolted Flange Joint Assembly
- ASTM F104 — Standard Classification System for Nonmetallic Gasket Materials