What Is ASME B16.20?
ASME B16.20 is the American National Standard for metallic gaskets for pipe flanges, covering spiral-wound gaskets, ring-joint gaskets (RTJ), and metal flat gaskets. It defines dimensions, tolerances, materials, and marking for gaskets used with flanges per ASME B16.5 and B16.47.
Gasket Types Covered
- Spiral-Wound Gaskets (SWG) — with inner ring, outer ring, or both; metallic winding strip + soft filler (graphite / PTFE)
- Ring-Joint Gaskets (RTJ) — R, RX, and BX styles; solid metal rings for Class 150 through Class 2500
- Metal Flat Gaskets — solid flat metal, plain or serrated
Materials
| Part | Common Materials |
|---|---|
| Spiral winding strip | 304, 316, 321, 347, Inconel 600 / 625, Monel 400 |
| Filler (soft) | Flexible graphite, PTFE, non-asbestos fiber |
| Ring joint rings | Soft iron, carbon steel (A105), 304 / 316 / 321, Inconel, Monel |
| Inner / outer rings | Carbon steel or stainless, matching pipe material |
Pressure Classes
Gaskets are supplied for flanges of Class 150 through Class 2500, matching the flange rating of ASME B16.5 / B16.47.
Related Standards
- ASME B16.5 — Flanges (NPS 1/2–24)
- ASME B16.47 — Large-Diameter Flanges (NPS 26–60)
- ASME B16.21 — Nonmetallic Flat Gaskets
- Our Gasket Range
FAQ
What is a spiral-wound gasket used for?
Spiral-wound gaskets are used on raised-face flanges in high-temperature and high-pressure piping — typical in oil & gas, chemical, and power plants. The metallic winding provides strength while the soft filler seals the joint.
When should I use an RTJ gasket?
Ring-joint gaskets are for RTJ flanges in high-pressure service (commonly Class 600 and above). The metal ring seals by deformation into the flange groove.
Which filler is best for high temperatures?
Flexible graphite handles the highest continuous temperatures; PTFE suits chemical resistance up to about 260°C. Consult us for your exact service conditions.
Need This Standard for Your Project?
We manufacture and export flanges, fittings and gaskets to ASME standards. Send your standard, size, material, and quantity — we reply within 24 hours.