Category
Piping & Fittings
Subcategory
Components
Applicable standards
3
Issuing bodies
1
Description
Flange gasket — spiral wound (B16.20), ring joint (B16.20), or non-metallic (B16.21).
Applicable Standards (3)
ASME — 3 standards
ASME B16.20
Metallic Gaskets for Pipe Flanges — Ring-Joint, Spiral-Wound, and Jacketed
Materials, dimensions, marking for spiral-wound, RTJ, kammprofile and jacketed gaskets.
Key requirements (6)
- Metallic gaskets for pipe flanges — ring-joint, spiral-wound, jacketed.
- Spiral-wound: alternating metal strip + filler (graphite, PTFE, ceramic).
- Ring-joint (RTJ): octagonal (most common) or oval; soft iron, low-CS, SS, monel.
- Spiral-wound dimensions: per ASME B16.5/B16.47 flange face dimensions.
- Inner ring (CG/CGI): prevents inward buckling at high pressure.
- Color coding: outer ring color = winding metal; stripe color = filler material.
ASME B16.21
Nonmetallic Flat Gaskets for Pipe Flanges
Dimensions and tolerances for non-metallic full-face and ring gaskets.
Key requirements (6)
- Nonmetallic flat gaskets for pipe flanges.
- Materials: rubber, PTFE, compressed non-asbestos fiber (CNAF), graphite.
- Standard thickness: 1.6 mm (1/16"), 3.2 mm (1/8").
- For Class 150 / 300 services typically; not for higher pressures.
- Inside dimension matches pipe ID; outside dimension fits flange bolt circle.
- Full face or ring (raised face) configurations.
ASME B16.5
Pipe Flanges and Flanged Fittings: NPS 1/2 through NPS 24
Flange dimensions, ratings, materials and tolerances for NPS 1/2–24, Class 150–2500.
Key requirements (8)
- Pipe flanges & flanged fittings for NPS 1/2 to 24.
- Pressure classes: 150, 300, 400, 600, 900, 1500, 2500.
- Class 150 CS: 285 psig at 100 °F, 200 psig at 400 °F.
- Class 300 CS: 740 psig at 100 °F, 555 psig at 700 °F.
- Flange types: weld neck, slip-on, socket weld, threaded, lap joint, blind.
- Facing types: raised face (RF), ring-type joint (RTJ), flat face (FF).
- Bore matching: weld neck bore selected to match pipe schedule.
- Hydrotest: per pressure class temperature/pressure rating chart.