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Read moreFlange Gasket Types Compared: Cut Sheet, PTFE, Spiral Wound and RTJ
09 October, 2026 | Admin
Short answer: flange gaskets fall into three broad groups. Non-metallic cut gaskets (rubber, non-asbestos, PTFE, graphite and cork) suit low to moderate pressures and most utility and chemical lines. Semi-metallic gaskets such as spiral wound and kammprofile suit higher pressures and temperatures. Metallic ring joint (RTJ) gaskets suit the highest pressure classes. This guide compares the main flange gasket types and explains which to use.
Non-Metallic (Soft Cut) Gaskets
| Type | Strengths | Typical services |
|---|---|---|
| Rubber (NBR, EPDM, neoprene) | Seals at low bolt load, economical | Water, air, low-pressure oil and utility lines |
| Non-asbestos (CNAF) | Versatile, good general sealing | Water, oils, low-pressure steam, general process |
| PTFE (virgin, filled, expanded, envelope) | Near-universal chemical resistance, purity | Acids, solvents, food, pharma, water treatment |
| Graphite (plain or reinforced) | High temperature, fire-safe | Steam, thermal oil, hydrocarbons |
| Cork and rubberised cork | Very compressible, low bolt load | Transformer and gearbox covers, light flanges |
These are usually ring (inside bolt circle) or full-face gaskets cut from sheet, made to standards such as ASME B16.21 for ASME B16.5 flanges, or EN 1514-1 for EN 1092-1 flanges.
Semi-Metallic Gaskets (Context)
- Spiral wound: alternating metal strip and filler (often graphite or PTFE) wound in a spiral, with inner and outer rings. Used widely in refinery and process piping at higher pressure and temperature.
- Kammprofile: a grooved metal core with soft facing layers, used in heat exchangers and demanding flanges.
- Metal jacketed: soft filler inside a metal jacket, used on heat exchangers.
Metallic Ring Joint (RTJ) Gaskets (Context)
RTJ gaskets are solid metal rings (oval or octagonal) that seat in grooves machined in RTJ flanges. They are used at high pressure classes in oil and gas, wellheads and high-pressure process lines.
Note: Diode Trading EST supplies the non-metallic cut gasket types in the first table. Spiral wound, kammprofile and RTJ gaskets are described here for context.
How to Choose a Flange Gasket Type
- Pressure class and temperature: higher classes move you from soft cut gaskets toward semi-metallic and RTJ types.
- Fluid: check compatibility; see our gasket chemical compatibility chart.
- Flange type and condition: raised face, flat face, RTJ groove, glass-lined or plastic flanges.
- Bolt load available: light flanges need soft, compressible materials.
- Fire safety and emissions: some services require fire-safe or low-emission sealing.
Common Mistakes
- Using a full-face gasket on a raised-face flange, or the reverse.
- Using thick soft gaskets at high pressure.
- Re-using compressed gaskets.
- Choosing on price without checking the fluid.
Related reading: PTFE gasket types, gasket selection and rubber gaskets for piping. For the full selection process, see our guide on how to choose engineering plastic.
Products: Gaskets & Seal Materials, Ready-Cut Gaskets, PTFE gaskets, non-asbestos gasket sheet, graphite gaskets and cork sheet. Every order from Diode Trading EST is supplied with a Material Test Certificate.
Information to Send With a Gasket Enquiry
A flange gasket can only be selected correctly when the full service is known. Include these details in your enquiry so we can propose the right cut gasket material or refer you to the right type.
- Flange standard and size: for example ASME B16.5 or EN 1092-1, with nominal size and pressure class or PN rating.
- Facing type: raised face, flat face, tongue and groove or ring-type joint.
- Medium: the fluid or gas, its concentration and whether it is a hydrocarbon, steam, acid or alkali.
- Temperature and pressure: normal operating values and the design maximum.
- Thickness: usually 1.5 mm or 3 mm for cut gaskets, unless the drawing specifies otherwise.
- Quantity and drawing: for non-standard shapes, send a drawing or the flange dimensions.
With these details we can recommend PTFE, CNAF, graphite or rubber gaskets cut to size.
Frequently Asked Questions
What are the main types of flange gaskets?
Non-metallic cut gaskets (rubber, non-asbestos, PTFE, graphite, cork), semi-metallic gaskets (spiral wound, kammprofile) and metallic ring joint (RTJ) gaskets.
When is a spiral wound gasket used instead of a cut gasket?
At higher pressures and temperatures, typically in refinery and process piping.
What standard covers non-metallic flange gasket dimensions?
ASME B16.21 for ASME B16.5 flanges, and EN 1514-1 for EN 1092-1 flanges.
Which gasket is best for chemicals?
PTFE gaskets offer the widest chemical resistance; check our gasket chemical compatibility chart.
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