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Octagonal Ring Type Joints

A ring-type joint is a metallic ring that is machined to sit between two mating surfaces, where it will be compressed to provide a high-quality and reliable seal.

Ring-type joints are vital components in various applications across multiple industry sectors, preventing leaks from gas or liquids.

In this article, we explore one particular type of RTJ further: the octagonal ring-type joint. We look at what this flange offers, its makeup, and which industries and applications it is most suited to.

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Octagonal ring-type joint flanges

Solid metal gaskets, an octagonal RTJ, provides an excellent sealing solution for applications that operate within extreme pressures.

Octagonal RTJ flanges were originally developed for the petroleum industry and oil field, where high-pressure and high-temperature applications required a suitable sealing solution to prevent leaks.

However, today, these ring type joints have been modified to provide a better sealing performance extending the numerous benefits that this type of ring type joint can offer, so that in fact you will find octagonal ring type joint flanges also used in pipework systems, valves, and more.

They are also suitable for use in ASME or API flanges with flat-bottomed grooves, providing a tight, reliable, and long-lasting seal.

You will also be accustomed to knowing the exact dimensions of the seating area, which allows you to calculate the exact torque values so that you can target your gasket seating stress levels appropriately. This can be vital for applications and systems within high-profile industries, where leaks and contamination must be avoided at all costs.

Compared to their counterpart oval RTJs, octagonal ring-type joints are often the preferred choice due to their higher sealing efficiency and ability to generate higher sealing stresses.

However, both oval and octagonal configurations are interchangeable on modern grooved flanges, and this is a significant benefit to bear in mind.

Benefits of Octagonal RTJs

  • Suitable for use on standard ring joint flat bottom groove flanges
  • Available in a range of sizes and diameters
  • Manufactured in a selection of various materials to suit the intended application. Materials such as:
    • Stainless, low carbon, and alloy steel
    • Iron
    • PTFE-coated metals.
  • Octagonal RTJ flanges are a modification of the oval design, extending its superior sealing functionality.
  • The RX design of an octagonal flange can handle extremely high-pressure applications, making these flanges a great option where vibration and shock loading are present in applications.
  • Due to the various different types and sizes, there are ring-type joint flanges to suit a range of budgets.
  • Due to their broader sealing contact surface, these flanges sit tightly into the sides of the grooves they’re compressed against as the gasket ring comes into contact with the mating groove face, ultimately providing a resilient seal.
  • Octagonal RTJs are less sensitive to minor flaws and any imperfections that may be found on the application’s seating surface.

Points to consider

With all flanges, including oval and octagonal, it’s important to bear in mind you must avoid:

  • Overtightening the valve
  • Yielding the studs
  • Rotating the flange
  • Damaging the gasket’s surface.

This is to ensure a tight seal and secure fit with the gaskets and groove.

Specialist Sealing Products (SSP)

At SSP, our quality ring-type joints are precision-engineered from the right materials suited to the intended application and manufactured in accordance with ASME B16.20, API 17D, and API 6A.

We’re specialists in ring joint types, and we help you find the right solutions to ensure the most appropriate and successful outcome.

Why SSP?

We offer full product certification for all our products, which includes material specifications, cure dates, batch numbers, and more.

We also have testing and inspection facilities available as we want to provide full assurances that all of our products meet British and International standards and specifications.

We understand the vital role that gaskets, valves, flanges, and more play in critical applications, and we know the importance across industries for the need to avoid leaks and contamination.

That’s why we work with you and our manufacturers to ensure the supply of the most appropriate products of the highest quality.

All of our team are qualified and knowledgeable in our sector, and we know our products inside and out.

For further information or to ask us a question or advice, please drop us an email at or call us at 01535 274 776, and we’d be happy to help.

Read next article: Flange Faces



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