RTJ Gaskets Explained: Ring Type Joints for Oil & Gas Flanges
When pressures climb into Class 900 and beyond — wellheads, christmas trees, high-pressure separators — soft gaskets give way to ring type joints. An RTJ gasket is a solid metal ring that seats into machined grooves in both flange faces, sealing by controlled plastic deformation of the ring against the groove walls. Done right, it's the most reliable seal in hydrocarbon service. Done wrong, it damages flanges that cost far more than the gasket.
R, RX, and BX Styles
Style R rings come in oval and octagonal cross-sections and fit standard ASME B16.5 and API 6B ring grooves through Class 2500. Octagonal is the modern default — it seats on the flat groove faces with better surface contact — while oval is required for older round-bottom grooves. Style RX is a pressure-energized, asymmetric ring that fits the same grooves as R but seals tighter as internal pressure rises. Style BX is for API 6BX flanges in 5,000–20,000 psi wellhead service; BX rings are not interchangeable with R or RX.
The Hardness Rule
The ring must always be softer than the flange, so the gasket deforms instead of the groove. Standard materials in ascending hardness: soft iron (armco), low carbon steel, 4–6% chrome, 304, 316, and exotic alloys for sour service. For H2S environments, specify rings meeting NACE MR0175 — typically soft iron with controlled hardness or 316 annealed.
Selection Basics
| Application | Ring | Typical material |
|---|---|---|
| Refinery piping Cl. 900–2500 | R octagonal | Soft iron, 316 |
| High-pressure pipelines | RX | Low carbon steel, 316 |
| Wellhead / API 6BX to 20k psi | BX | 316, Inconel, per API 6A |
Installation Practices
Never reuse a ring joint — the seal depends on virgin deformation. Clean and inspect grooves for scoring, install dry or with a light oil film only (never grease that traps debris), and torque in a star pattern to full flange bolt load; RTJ joints seat at higher bolt stress than spiral wound joints. If the flanges don't pull face-to-face gap per spec, stop and check the ring number.
Ring Joints From Stock
We supply R, RX, and BX ring joint gaskets in soft iron, carbon steel, and stainless, with material test reports on request. Put your ring number (or flange size and class), material, and quantity in the quote form at the top of this page — quotes back in 1–2 business hours.