Ring Type Joint (RTJ) Flange

Ring Type Joint Flange (RTJ)

Ring Type Joint flanges are typically used in high-pressure (Class 600 and higher rating) and/or high-temperature services above 800°F (427°C). They have grooves cut into their faces and seat ring gaskets. The flanges seal when tightened bolts compress the gasket between the flanges into the grooves, deforming the gasket to make intimate contact inside the grooves, creating a metal-to-metal seal. An RTJ flange may have a stepped face with a ring groove machined into it. The raised face does not serve as a sealing mechanism. For RTJ flanges that seal with ring gaskets, the raised faces of the connected and tightened flanges may contact each other. As the compressed gasket cannot carry any additional load beside the bolt tension, vibration and movement cannot further crush the gasket and reduce the connecting tension.

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Ring Type Joint gaskets are metallic sealing rings, suitable for high-pressure and high-temperature applications. Ring Type Joint gaskets are designed to seal by “initial line contact” or wedging action between the mating flange and the gasket. By applying pressure on the seal interface through bolt force, the “softer” metal of the gasket flows into the microfine structure of the more rigid flange material creating a very tight and efficient seal. The most commonly used type is the style R ring that is manufactured by ASME B16.20 and used with ASME B16.5 flanges, class 150 to 2500. Style “R” ring-type joints are manufactured in both oval and octagonal configurations.

The octagonal cross section has a higher sealing efficiency than the oval and would be the preferred gasket. The sealing surfaces on the ring joint grooves must be smoothly finished to 63 micro inches and be free of objectionable ridges, tool, or chatter marks. They seal byby initialine contact or a wedging action as compressible forces are applied. The hardness of the ring should always be less than the hardness of the flanges.