Each Flexitallic Ring Type Joint is crafted from fully traceable materials and can be provided in accordance with NACE standards upon request. The joints are marked with low-stress stamping, displaying the style, ring number, API license, material specification, Product Specification Level (PSL), a unique Flexitallic material ID, and the date of manufacture. This thorough traceability—from certified raw material to final product—is a key component of the company’s rigorous quality control practices and surpasses the requirements of API 6A PSL 4
MATERIALS
Gasket materials should be chosen based on the specific service conditions. It’s generally advisable to use a gasket material that is softer than the connecting flange surfaces. Commonly used Ring Type Joint materials—along with their recommended maximum hardness levels and identification according to API 6A—are listed in the table below. For more demanding or specialized environments, Ring Type Joints can also be produced from DUPLEX steels and high-performance alloys such as Monel®, Inconel®, Incoloy®, and Hastelloy®. The Technical Team is available to provide guidance on alternative material options.
Originally designed for high-pressure and high-temperature conditions typical in the petroleum sector, Ring Type Joints were mainly used on drilling and well completion equipment in the oilfield. Today, their applications have expanded to include valves, piping systems, and certain high-integrity pressure vessel joints. Standard Style R Ring Type Joints are produced in compliance with API 6A and ASME B16.20 size and pressure ratings. They come in both oval and octagonal shapes, and both designs are compatible with modern grooved flanges designed for octagonal rings.
The RX Style is a modified version of the standard R Style, featuring a self-energizing effect during assembly. It is engineered to fit into the same groove as the standard R Style, allowing both types to be used interchangeably. However, attention should be paid to the variation in the final make-up distance. This enhanced design leverages assembly-induced activation to deliver improved sealing performance. Variants of this design are also available for subsea operations.
Style RX Ring Type Joints can be equipped with PTFE inserts to minimize turbulent flow and prevent erosion of the gasket and flange surfaces. These inserts are precisely engineered with radial pressure passage holes to maintain the self-energizing function of the RX Ring Joint.
As shown on the right, the insert is positioned between the inner diameter of the Ring Type Joint and the flange bore. When assembled, the insert becomes fully enclosed, occupying the space between the flange bore and the gasket.
Style BX energized Ring Type Joints, produced in line with API 6A standards, are specifically engineered for high-pressure systems reaching up to 20,000 psi. When properly installed, the BX gasket enables near face-to-face contact between the flanges, ensuring the gasket is completely enclosed along both its inner and outer edges. Each BX gasket also features a pressure equalization hole, designed to balance any pressure that might become trapped within the grooves.
SPECIALIZED RING TYPE JOINTS
RUBBER COATED RING TYPE JOINTS
This is an oval-shaped Ring Type Joint that is fully encased in a nitrile rubber coating. Typically, the core material consists of soft iron or low carbon steel. This gasket serves three primary purposes:
• It is commonly used during pressure testing to help prevent flange surface damage.
• The rubberized contact areas enhance sealing performance while also safeguarding the flange faces.
• It offers better protection against corrosion, which may develop between conventional Ring Type Joints and the flange groove surfaces.
A broad selection of standard sizes is available, and custom sizes can be produced upon request.
BLIND RING TYPE JOINTS
Custom Ring Type Joints can be produced to seal off flanges and piping systems. These are essentially standard Ring Type Joints modified with solid metal centers. Blind Ring Type Joints are available in all common materials as well as a variety of high-performance alloys.
For more details on these specialized Ring Type Joint options, please reach out to Flexitallic’s Technical Department.
In cases where traditional ring-type flange sealing is challenging, the specially designed Flexitallic “CG-RJ” Spiral Wound gasket may be a suitable alternative.
TRANSITION RING TYPE JOINTS
These are hybrid rings made up of two different sizes that share the same pitch circle diameter. They are designed to seal Ring Type Joint flanges when the connecting flanges have differing groove diameters.
Transition Ring Type Joints can be produced using both standard materials and high-performance alloys. They are available in either oval or octagonal configurations, although they are not covered under the API specifications.
SUBSEA GASKETS
Flexitallic offers subsea wellhead, mudline, and tree equipment that are safe and fully interchangeable in terms of dimensions and function, in accordance with API standards. These sealing solutions meet stringent requirements for pressure and thermal integrity, appropriate material selection, and ensure zero visible leakage.
To differentiate them from topside Ring Type Joints, the letter “s” is added as a suffix, indicating the inclusion of a pressure relief passage within the ring’s cross-section. This feature is essential to avoid pressure lock during underwater connections.
WELD RINGS
Another gasket design that originated in the German industrial sector is the welded gasket. Generally, there are two main types: Welded Membrane gaskets, which follow the DIN 2695 standard, and Weld Ring gaskets
WELDED MEMBRANE GASKETS
The Welded Membrane gasket is made up of two identical rings, each with a thickness of 0.157 inches. To maintain chemical compatibility, ensure proper thermal conductivity, and support weldability, the gasket material must match the flange material. Each ring is first welded individually to its corresponding flange. After the flanges are brought together, a second welding process joins the outer edges of the two rings, forming a completely welded seal.
WELDED RING GASKETS
Similar to Membrane Welded Gaskets, Weld Ring Gaskets are used in matched pairs. Each ring typically has a thickness of 0.591 inches and is made from materials compatible with the flange to ensure full material compatibility. All welding is performed on the outer surfaces of the gasket and flange, which simplifies positioning—particularly in tight or limited-space applications. There are two main types available: Style SR and Style SRL.
LENS RING
Flexitallic Lens Rings, produced in line with DIN 2696 standards, offer engineers a highly reliable sealing solution for demanding high-pressure and high-temperature applications.
These rings feature a spherical sealing surface and are intended for use with conical flange faces (other variants are available upon request).
It is standard practice to use a gasket material softer than that of the flange to ensure that compression causes deformation of the Lens Ring rather than damaging the flange surface.
Applying higher compressive loads increases the contact area between the ring and flange, helping to avoid overstressing the gasket.
As with all metallic gaskets, Lens Rings are not recommended for reuse. The material undergoes work hardening during installation and operation, and reusing them may require excessive bolt load to achieve the same sealing effect—potentially damaging the flange surfaces.
