Choosing a Gasket

Quick pick (TL;DR)

RF flange → spiral-wound (316 winding + flexible graphite) for most service up to ~600°C; kammprofile for tighter sealing.
RTJ flange (Class 900+) → metal ring joint (soft iron / 316 / Inconel).
FF cast-iron/FRP → full-face soft sheet.
Choose filler by temperature, ring metal by corrosion.

Step 1 — Match the facing first

The facing dictates the gasket family — start there, then pick materials.

Flange facing / class	Gasket family
RF, Class 150–600	Spiral-wound / kammprofile.
RTJ, Class 900–2500	Metal ring joint (R/RX/BX).
FF (cast-iron / FRP)	Full-face soft sheet.
Hygienic / clean	PTFE envelope.

Step 2 — Materials by temperature & fluid

Filler: PTFE ≤200°C / chemicals; graphite for steam/hot.
Metal: 316 general; 316L/Inconel for Cl/sour.
Inner + outer rings for vacuum / anti-blow-out.

Step 3 — Seating: m & y factors

Bolt-up must reach the seating stress y and maintenance factor m (ASME BPVC App. 2) — links to bolting.

Typical values

Spiral-wound m ≈ 3.0 , y ≈ 10,000 psi CNAF sheet m ≈ 2.75 , y ≈ 3,700 psi PTFE m ≈ 2.0 , y ≈ 1,200 psi (low seating — easy to seal) Use higher y → need more bolt load → check bolting

Failure modes

Symptom	Cause & fix
Leak after start-up	Under-bolted / relaxation → re-torque.
Crushed / extruded	Over-bolted → correct type/rings.
Chemical attack	Wrong filler → reselect.

Requisition & datasheet

Flange size/class/facing; type; metals; filler.
Standard; confirm bolting reaches y.

Frequently asked questions

What should I know about Choosing a Gasket?

RF flange → spiral-wound (316 winding + flexible graphite) for most service up to ~600°C; kammprofile for tighter sealing. RTJ flange (Class 900+) → metal ring joint (soft iron / 316 / Inconel). FF cast-iron/FRP → full-face soft sheet. Choose filler by temperature, ring metal by corrosion.

Which standards or codes apply?

ASME B16.20 (metallic — spiral-wound, RTJ, kammprofile), ASME B16.21 (non-metallic sheet); ASME BPVC Sec VIII App. 2 (m & y).

Standards — ASME B16.20 / B16.21; ASME BPVC App. 2.