Pipes & Fittings
Flange gaskets: spiral wound, RTJ and sheet gaskets
CRS PLUS sources gaskets for flanged joints in oil & gas, refinery and utility service — spiral wound gaskets with inner and outer rings, ring-type joint gaskets for high-pressure flanges, compressed non-asbestos fibre and PTFE sheet gaskets, and insulating kits for cathodically protected lines. Gaskets are quoted to the flange size, class and facing, with winding, filler and ring materials stated per line.
Gasket types we quote
Sourced through the qualified supplier base. Sizes, ratings and grades are shown as ranges; send your bill of materials and every line is quoted against its exact specification.
| Product | Standard | Sizes | Rating / class | Materials |
|---|---|---|---|---|
| Spiral wound gasket (with inner and outer ring) | ASME B16.20 | NPS ½ to 60 | Class 150 to 2500 | SS304 / SS316L windings, graphite or PTFE filler, CS or SS rings |
| Ring-type joint gasket (R, RX, BX) | ASME B16.20 / API 6A | R-11 to R-105; BX-150 to BX-169 | Class 600 to 2500; API 2000 to 15000 psi | Soft iron, low-carbon steel, F5, SS304, SS316 |
| Compressed non-asbestos fibre (CNAF) | ASME B16.21 | NPS ½ to 48 | Class 150 to 300 | Aramid or glass fibre with NBR binder, 1.5 to 3 mm |
| PTFE and expanded graphite sheet gasket | ASME B16.21 | NPS ½ to 48 | Class 150 to 300 | Virgin / filled PTFE, flexible graphite with SS insert |
| Kammprofile (grooved metal) gasket | ASME B16.20 | NPS ½ to 48 | Class 150 to 2500 | SS316L core with graphite or PTFE facing |
| Flange insulating gasket kit | Manufacturer standard | NPS ½ to 48 | Class 150 to 2500 | GRE / phenolic gasket, sleeves and washers |
How a spiral wound gasket is specified
A spiral wound gasket line states the flange size and class, then the winding metal, the filler, and the inner and outer ring materials — for example "4 in class 150 RF, SS316L / graphite, SS316L inner ring, CS outer ring, 4.5 mm". The outer (centring) ring locates the gasket inside the bolt circle and acts as a compression stop; the inner ring protects the windings from the process and is required by ASME B16.20 for certain sizes, classes and fillers, and widely specified on all.
Spiral wound gaskets are often ordered by a manufacturer's brand name. CRS PLUS quotes the make specified, or an equivalent manufactured to ASME B16.20 where the specification allows, and states which on the quotation.
Which gasket for which flange
Raised-face flanges in class 150 and 300 take spiral wound gaskets for hydrocarbon, steam and elevated-temperature service, and CNAF or PTFE sheet gaskets for water, utilities and low-pressure duties. Ring-type joint flanges take a metal ring gasket matched to the groove number; the ring material should be softer than the flange so it deforms into the groove. Flat-face flanges take a full-face sheet gasket.
Documentation and supply terms
- Mill test certificate
- EN 10204 3.1 certificate for every line, traceable to the heat number marked on the item. EN 10204 3.2 with third-party witness on request.
- Marking
- Material grade, size, rating and heat number marked on each item to the governing standard (MSS SP-25 for valves, flanges and fittings).
- Inspection
- Positive material identification, dimensional checks and third-party inspection arranged where the project specifies them.
- Sour and low-temperature service
- NACE MR0175 / ISO 15156 hardness limits and impact testing applied where the piping class calls for them, and stated on the certificate.
- Quotation
- Each line states the standard, grade, origin, lead time and certification before you commit. Listing does not indicate stock held by CRS PLUS.
Frequently asked questions
What is a spiral wound gasket?
A spiral wound gasket is made by winding a preformed metal strip and a soft filler — usually graphite or PTFE — into a spiral, held between an outer centring ring and, usually, an inner ring. It seals reliably under temperature and pressure cycling and is the standard gasket for raised-face process flanges.
Why does a spiral wound gasket need an inner ring?
The inner ring stops the windings buckling inward into the bore, protects them from erosion and reduces turbulence at the joint. ASME B16.20 makes it mandatory for some sizes, classes and PTFE-filled gaskets, and many operators specify it for all spiral wound gaskets.
What does "R-24" or "BX-153" mean on an RTJ gasket?
It is the ring number, which fixes the ring size and cross-section to match the groove machined in the flange. R rings are oval or octagonal; RX and BX are pressure-energised rings used in higher-pressure and API 6A wellhead flanges.
What is CNAF?
CNAF stands for compressed non-asbestos fibre: a sheet gasket material made from aramid, glass or mineral fibres bound with rubber. It replaced asbestos sheet and is used for utilities, water and low-pressure services in class 150 and 300 flanges.
Can gaskets be supplied with the flanges and bolting?
Yes. Gaskets, stud bolts and flanges are normally quoted together per joint so that size, class and facing match across the package.
Request a gasket quotation
A structured offer follows within 72 hours.
Manufacturer and brand names, where mentioned, are used for identification only. CRS PLUS sources these products through its qualified supplier base and holds no distributor, reseller or agency appointment from any manufacturer.