Ring Type Joint (RTJ) Flanges — ASME B16.5 & B16.47

What is a Ring Type Joint (RTJ) Flange?

In an RTJ flange the sealing face is a trapezoidal groove. A metal ring gasket, oval or octagonal (R type) or pressure-energised (RX type), sits in the grooves of both flanges. When the bolts are tightened the softer ring deforms plastically into the harder groove, giving a metal-to-metal seal. RTJ joints are used for high pressure and high temperature service, typically Class 600 and above, and in hydrocarbon lines where a robust, fire-resistant seal is needed. The groove must be harder than the ring, and its surface finish is specified more tightly than an RF face.

Key features

• Groove dimensions and ring numbers per ASME B16.5 / B16.20
• Groove surface finish typically 63 µin Ra max
• Groove harder than the ring; ring material chosen accordingly
• Available on weld neck, blind, and other flange types
• Ring gaskets supplied with flanges on request

Specification

Applications

• Wellhead-adjacent and production piping (to ASME classes)
• High-pressure hydrocarbon and gas lines
• Hydrocracker and hydrotreater service
• High-temperature steam and process lines
• Compressor and pump discharge piping

RTJ vs raised face flange

A raised face flange seals with a softer gasket (spiral wound, graphite, PTFE) on a serrated face and is easier to make up. An RTJ flange seals metal-to-metal with a solid ring in a groove; it tolerates higher pressure, temperature and fire exposure, but needs tighter machining, harder groove material and careful assembly. RTJ is common in Class 900 and above and in critical hydrocarbon service.