Pipe Gaskets — Spiral Wound, RTJ, PTFE
ASME B16.20 metallic and B16.21 nonmetallic gaskets for pipe flanges, Class 150–2500, with Fig. 8 and flat line blanks per B16.48.
Fig. 8 Spectacle Blank
Open / closed line isolation without removing the blank, NPS 1/2–24.
Standards & Materials
Metallic gaskets follow ASME B16.20: spiral-wound (Class 150–2500), ring-joint RTJ (Class 600–2500) and metal-jacketed types, with winding strip and rings in 304 / 316 / 321 / 347 stainless, Inconel 600 / 625 or Monel 400 and fillers in flexible graphite or PTFE. Nonmetallic gaskets follow ASME B16.21 (Class 150–900) in rubber, PTFE and non-asbestos fiber. Line blanks follow ASME B16.48, NPS 1/2–24, Class 150–2500.
Gaskets are matched to the flange face type: raised-face (RF) flanges use flat-ring or spiral-wound gaskets, flat-face (FF) flanges use full-face gaskets, and ring-joint flanges use RTJ rings. EN 10204 3.1 certificates and third-party inspection are available on request.
FAQ
Which gasket do I need for raised-face flanges?
For raised-face (RF) flanges use a spiral-wound gasket (Class 150–2500) or a flat-ring gasket (Class 150–900); match the gasket to the flange class and service.
When is an RTJ ring gasket required?
RTJ ring gaskets are used on ring-joint flanges in high-pressure service, typically Class 600 and above. The metal ring seals by deformation into the flange groove.
What is the maximum pressure class for B16.21 nonmetallic gaskets?
Class 900. Above Class 900 the standard provides no size tables — use metallic or semi-metallic gaskets per ASME B16.20.
Is PTFE suitable for high temperatures?
PTFE is best for chemical resistance up to roughly 260°C; above that use flexible-graphite or metallic gaskets.
Fig. 8 blank or flat blank — which do I specify?
Specify a Fig. 8 spectacle blank when the line needs periodic isolation without removing the blank; a flat blank or paddle for fixed isolation during shutdown.
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