Ring Joint Flanges

Metal-to-Metal Seal for High-Pressure and High-Temperature Service

What Is a Ring Joint Flange?

Ring Type Joint (RTJ) is a flange facing type, not a separate flange type. Any weld neck, blind, or slip-on flange can have an RTJ facing. The RTJ face has a precision-machined groove that accepts a metallic ring gasket (R, RX, or BX type). The ring gasket deforms under bolt load to create a metal-to-metal seal. RTJ flanges are designed per ASME B16.5, with ring gasket dimensions covered by ASME B16.20.

Key Design Features

  • Precision-machined groove on flange face
  • Metallic ring gaskets (softer than flange material) deform to seal
  • Self-energizing under pressure — higher pressure creates a tighter seal
  • Groove dimensions standardized per ASME B16.5 Table E3
  • Available ring types: R (oval/octagonal), RX (pressure-energized), BX (pressure-energized for API 6A)

Common Applications

  • High-pressure systems (Class 600 and above)
  • Subsea and offshore pipelines
  • Wellhead and Christmas tree connections (API 6A)
  • High-temperature refinery and petrochemical piping
  • Any application where zero leakage is critical

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Ring Gasket Types

R-type: Standard oval or octagonal cross-section. Octagonal is preferred because it provides more contact area with the groove faces.

RX-type: Pressure-energized design that looks similar to an R-type but is engineered so that internal pressure helps create the seal.

BX-type: Used with API 6BX flanges for pressures up to 20,000 psi.

Available Sizes and Pressure Classes

Per ASME B16.5, RTJ flanges are available in NPS 1/2 through 24, Classes 150 through 2500. RTJ facing is most commonly specified in Class 600 and above, though it is available in all classes.

Common Materials

Flanges:

  • Carbon Steel — ASTM A105
  • Stainless Steel — ASTM A182 F304 / F316
  • Alloy Steel — ASTM A182 F11 / F22 / F22V

Ring Gaskets: Soft Iron, 304SS, 316SS, Inconel 625. The ring gasket material must always be softer than the flange material.

Related References