Special Metal Gaskets

They are especially suitable for flanges with worn or damaged RTJ grooves, where a standard metal ring would struggle to achieve proper sealing. The soft filler compensates for surface imperfections, ensuring tightness without requiring costly flange replacement or machining. Serrated RTJs are drop-in replacements and fit standard RTJ flange designs per API 6A or ASME B16.20/B16.5. They do not require modifications to the flange and are ideal for retrofitting in brownfield projects. Common applications include chemical and petrochemical plants, offshore facilities, refineries, and power generation.

The graphite or PTFE insert enhances sealing under thermal cycling and vibration, reducing fugitive emissions and the filler also prevents galling or damage to the flange face, extending the life of the connection. They are widely used in hydrogen, ammonia, hydrocarbons, and sour gas services, where leakage must be minimized. Material selection for the ring includes carbon steel, stainless steel, Inconel, Monel, and other alloys.

Filler choice depends on the medium: graphite is heat-resistant, PTFE is suitable for aggressive chemicals. The gasket can be produced in both oval and octagonal profiles, filled during the manufacturing process. While not included in API or ASME standards, they are manufactured to precise tolerances under custom specifications. Installation is straightforward and similar to standard RTJs, with added care for the filler during handling. In many cases, Serrated RTJs can restore sealing performance without shutting down the system for flange repair.

They are especially beneficial in critical service lines that have suffered mechanical wear or corrosion in the RTJ groove. Leak tightness is enhanced by the deformable filler, which reduces reliance on extreme bolt loads. 

These transition rings are used in situations where, along a pressurized line, there is a change in nominal diameter (DN), pressure class, or flange type, but a secure metal-to-metal seal is still required. They typically feature one side with an octagonal or oval profile and the other with a different profile (e.g., lens or 6BX), thus adapting to flanges that would otherwise be incompatible.

They are ideal for:

• Connections between API 6A 6B and 6BX flanges

• Transitions between ASME and API systems

• Plant modifications or revamping

• Situations where existing flanges cannot be replaced

Technical Features:

• Identical Pitch Circle Diameter (PCD) between the two flanges

• Combined metal-to-metal sealing faces

• Available with oval or octagonal profiles

• Not directly covered by API or ASME specifications, but manufactured according to specific dimensional requirements of the customer or project

Key Benefits:

• Mechanical compatibility between dissimilar flanges

• Effective solution for existing lines without replacing flanges

• Reduced leakage risk in critical connections

• Reliability under high pressure and intense thermal cycles

Unlike traditional tees or saddles, the Lens Branch uses a "lens"-type sealing surface to ensure a high-integrity metal-to-metal connection between the main pipeline and the branch. This component is widely used in industrial sectors where safety and reliability are paramount, such as in the chemical industry, petrochemical plants, nuclear power stations, high-pressure energy production, and cryogenic or high-temperature processes. Its design principle is based on the DIN 2696 standard, which governs lens gaskets that are also adapted for branch connections. The connection is achieved through two spherical surfaces in direct contact, tightened by dedicated tie rods or retaining flanges to ensure high resistance to pressure and thermal expansion, without the use of non-metallic gaskets.

Advantages of the Lens Branch

• Reliable sealing even under extreme conditions

• No gaskets subject to aging

• Compact profile, ideal for tight spaces

• Corrosion resistance selectable based on process fluid compatibility

• Easy inspection and replacement of the joint

The Lens Branch can also be manufactured as a single branch, in carbon steel, stainless steel, or special alloys (e.g., Inconel, Hastelloy), and is often customized according to nominal pressure (PN) or ANSI class (150 – 2500).

It consists of two metal discs joined by a central section resembling a bridge: one disc is solid (blind), and the other has a central hole (spacer). By rotating the flange around the bridge axis, the line can be either isolated or opened depending on the selected position. It is commonly used in piping systems to allow a physical and visual interruption of the flow, especially during maintenance or testing operations.

The component is designed according to the international standard ASME B16.48, which defines its dimensions, materials, and tolerances, in compliance with the pressure classes specified in ASME B16.5 (up to 24") or ASME B16.47 (above 24"). The materials used typically include carbon steels, stainless steels, and special alloys, selected based on the process fluid, temperature, and operating pressure.

If designed with an RTJ profile, the Spectacle Blind Flange may feature a recessed ring groove in the flange, where an RTJ gasket is inserted, or it may itself be machined in the RTJ shape. The reference standard for this type of connection is ASME B16.5 Appendix D. The Spectacle Blind Flange can also adopt a "Lens" sealing profile, in accordance with DIN 2696.

• M (Male): has a raised face that fits into the groove of the flange.

• F (Female): has a groove that mates with the male raised face.