DN75CF (4.625″ OD) 316LN SS Standard ConFlat® (CF) UHV Flanges

Overview of ConFlat Flanges

The ConFlat (CF) flange is the industry standard for high vacuum (HV) and ultra-high vacuum (UHV) systems. These flanges are widely used in conjunction with various gauges, feedthroughs, instruments, and accessories, offering excellent compatibility and reliability in vacuum applications.

Blank (Blind) Flanges

Blank or blind flanges are solid, disc-shaped components used to close off unused sections of tubing or ports in vacuum chambers. They can be machined to create custom fittings or simply serve to block unused areas in a system.

CF Flange Sealing Mechanism

The CF flange’s sealing mechanism relies on a knife-edge design, machined below the surface of the flange. When two CF flanges are bolted together, the knife-edges create annular grooves in a soft metal gasket, ensuring a tight seal. The extruded metal fills any machining marks and surface imperfections, providing a reliable, leak-proof seal. CF seals can function at pressures ranging from atmospheric levels (760 torr, or 103 mbar) down to ultra-high vacuum levels below 1 x 10⁻¹³ torr (<1.3 x 10⁻¹³ mbar). They can also handle a wide temperature range from -196°C to 450°C, depending on the materials used.

Flange Size Nomenclature

In North America, CF flange sizes are typically determined by their outside diameter (O.D.). However, in Europe and parts of Asia, the nomenclature is often based on the nominal internal diameter (nominal I.D.) of the largest tube that can be welded to a bored flange.

Types of ConFlat Flanges

ConFlat flanges are available in multiple configurations to suit different vacuum system requirements:

• Fixed Flanges: These are single-piece flanges where the bolt-hole orientation is fixed relative to the fitting. Fixed blank flanges are used to seal off ports, while fixed bored flanges are used for welded connections to standard tubing.
• Rotatable Flanges: These consist of an inner weld ring and an outer bolt ring, allowing the bolt ring to rotate around the weld ring. This rotation makes it easier to align bolt holes during installation. Rotatable bored flanges are designed for welding to standard-sized tubes.

Both fixed and rotatable designs come with options for clearance-holes or tapped holes.

Hole Options

• Clearance-Holes: These are through-holes designed for bolts to pass through the flange, secured by nuts or plate nuts on the other side.
• Tapped Holes: Tapped holes are either imperial or metric threads machined directly into the flange. This allows bolts to be secured without using nuts. When selecting tapped flanges, the bolt-hole orientation should be considered for proper alignment with mating components.

316LN Stainless Steel Features

ConFlat flanges are often manufactured from 316LN stainless steel, which offers several benefits for demanding vacuum applications:

• Increased Hardness: With a Brinell hardness rating of 170, 316LN is harder than 304L stainless steel, making it more suitable for systems that require frequent disassembly and reassembly.
• Electro-Slag Remelting (ESR): The ESR process improves the material’s homogeneity, reducing imperfections such as gross macro segregation.
• Low Magnetic Permeability: 316LN has a magnetic permeability of µ ≤ 1.005, compared to 1.03 for 304L stainless steel, making it ideal for use in environments sensitive to magnetic interference.

These properties make ConFlat flanges an excellent choice for vacuum systems that demand both performance and durability in high vacuum and UHV conditions.

Ordering Table