Ring Joint Flange

Product Overview

The Ring Joint (RTJ) Flange is a high-integrity pipe flange engineered for demanding high-pressure and high-temperature service conditions commonly encountered in the oil and gas industry. Its defining feature is a precision-machined circumferential groove on the flange face that accepts a solid metal ring gasket, creating a robust metal-to-metal seal that outperforms conventional soft-gasket face types under extreme operating conditions.

RTJ Groove Design and Ring Gaskets

The RTJ groove is machined to precise dimensional tolerances to ensure consistent seating and sealing performance. Two ring gasket profiles are compatible with RTJ flanges:

• Oval Ring Gaskets – A traditional profile with a rounded cross-section, suitable for lower pressure classes and offering good conformability to the groove surface.
• Octagonal Ring Gaskets – A flat-sided profile that provides greater contact area and higher sealing efficiency, preferred for higher pressure classes and critical service applications.

When the flange bolts are tightened, the ring gasket is compressed into the groove, deforming slightly to fill any micro-surface irregularities and establishing a leak-tight metal-to-metal seal. This mechanism makes RTJ flanges particularly effective in cyclic pressure and thermal cycling environments.

Material Options

Ring Joint Flanges are available in two primary material grades to suit a wide range of process media and environmental conditions:

• Carbon Steel (CS) – Cost-effective and widely used for standard oil and gas service where corrosion is managed through process control or coating. Suitable for non-corrosive and mildly corrosive environments.
• Stainless Steel 316L – Offers superior corrosion resistance, particularly against chloride-containing media and sour gas (H₂S) environments. The low-carbon "L" grade minimizes sensitization risk during welding.

Size Range and Pressure Class Ratings

These flanges are manufactured across a broad size range from 1/2" to 24" nominal pipe size (NPS), accommodating the majority of pipeline and process equipment connection requirements. Pressure class ratings span from Class 600 through Class 2500, covering moderate to extreme high-pressure service conditions. The combination of size flexibility and high pressure ratings makes RTJ flanges a versatile solution for wellhead, manifold, and process piping systems.

Applicable Standards

All Ring Joint Flanges are manufactured and tested in conformance with the following industry standards:

• API 6A (Wellhead and Christmas Tree Equipment) – Governs design, material, testing, and quality requirements for flanges used in wellhead and surface equipment applications.
• ASME B16.5 (Pipe Flanges and Flanged Fittings) – Defines dimensional standards, pressure-temperature ratings, materials, and testing for flanges in the NPS 1/2" through 24" range.

Typical Applications

RTJ flanges are the preferred choice in high-pressure oil and gas applications where joint integrity is critical. Typical service environments include:

• Wellhead and Christmas tree assemblies
• High-pressure manifolds and production headers
• Subsea and offshore pipeline connections
• Refinery and petrochemical process piping at elevated pressures
• Gas compression and injection systems

Installation and Sealing Notes

Proper installation is essential to achieving the full sealing performance of an RTJ flange assembly. The ring gasket must be inspected for surface defects prior to installation and should never be reused after compression. Flange faces and grooves must be clean and free of damage. Bolts should be lubricated and tightened in a cross-pattern sequence to the specified torque values to ensure uniform gasket compression. The hardness of the ring gasket must always be lower than that of the flange groove material to allow controlled deformation without damaging the precision-machined seating surface.