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DN50CF (3.375″ OD) 316LN SS Standard ConFlat® (CF) UHV Flanges

Overview of ConFlat Flanges for High Vacuum and UHV Applications

ConFlat (CF) flanges are highly favored for high vacuum (HV) and ultra-high vacuum (UHV) systems due to their reliability and versatility. These flanges support a wide range of vacuum components, including gauges, instruments, feedthroughs, and accessories, making them integral to complex vacuum systems.

Blank (Blind) Flanges

A blank, or blind, flange is a solid, disc-shaped fitting designed to close off unused ports or sections in a vacuum chamber. They can also be machined to create custom fittings or adapted for various configurations within vacuum systems.

CF Flange Sealing Mechanism

The sealing mechanism of CF flanges is based on a knife-edge structure machined just below the flange’s flat surface. When a pair of flanges is bolted together, these knife-edges press into a soft metal gasket, forming grooves that compress the gasket material. This process fills surface defects, creating a reliable, leak-tight seal. CF seals can withstand pressures ranging from 760 torr (103 mbar) to ultra-high vacuum levels as low as <1 x 10⁻¹³ torr (<1.3 x 10⁻¹³ mbar) and operate effectively across temperatures from -196°C to 450°C, depending on the material.

Size Nomenclature

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

Types of ConFlat Flanges

CF flanges are available in two primary configurations:

  • Fixed Flanges: These flanges are a one-piece design where the bolt-hole orientation is set relative to the fitting. Fixed blank flanges are commonly used to seal off ports that are not in use, providing a leak-tight assembly. Fixed bored flanges, on the other hand, are designed to accept standard tube sizes and can be welded onto components.
  • Rotatable Flanges: Rotatable flanges consist of two parts—an inner weld ring and an outer bolt ring. This design allows the bolt ring to rotate freely around the inner ring, facilitating easy alignment with mating flanges. Rotatable bored flanges are ideal for systems where bolt-hole alignment is crucial, as they can accept standard tube sizes and be welded onto various components.

Both fixed and rotatable versions can be ordered with clearance-holes or tapped holes.

Hole Types

  • Clearance-Holes: These are through-holes that provide sufficient clearance for bolts to pass through both flanges, secured by nuts or plate nuts.
  • Tapped Holes: These holes are machined with imperial or metric threads, allowing the flange to be fastened without the need for nuts or plate nuts. It is essential to consider bolt-hole orientation when selecting tapped flanges to ensure proper alignment with system components.

316LN Stainless Steel: Key Features

For enhanced performance, CF flanges made from 316LN stainless steel offer several benefits:

  • Increased Hardness: With a hardness rating of 170 on the Brinell scale, 316LN is more durable than 304L stainless steel, making it ideal for applications that involve frequent disassembly and reassembly.
  • Electro-Slag Remelting (ESR): This process improves the homogeneity of the metal, reducing the presence of macro segregation and enhancing overall material quality.
  • Low Magnetic Permeability: 316LN stainless steel has a magnetic permeability (µ) of ≤1.005, significantly lower than that of 304L (µ = 1.03), making it better suited for applications sensitive to magnetic interference.

These features make ConFlat flanges a critical component in ensuring the stability and integrity of high-performance vacuum systems across various industries.

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FAQ

Tube fittings are designed for tubes (measured by outside diameter and wall thickness) used in high-pressure and instrumentation applications, whereas pipe fittings are for pipes (identified by nominal pipe size) primarily used in fluid transport.

 

Common valve types include ball valves, gate valves, check valves, butterfly valves, and globe valves. Each serves a specific function—from quick shutoff (ball/gate valves) to flow regulation (globe valves).

 

  • For tubing, measure the outside diameter; for pipes, refer to the nominal pipe size (using conversion charts if needed). Always match the valve or fitting size to your pipe’s dimensions and flow requirements.

  • Frequently used thread types include NPT (National Pipe Tapered), BSP (British Standard Pipe), and UNC, along with slip-fit options that rely on compression or fusion rather than threads.

Interchangeability depends on manufacturer specifications and certification. Always verify compatibility via manufacturer guides or certified interchangeability charts.

 

  • A coupling is a short, straight fitting used to join two pipes or tubes. It provides a secure, leak-tight connection and can sometimes serve to extend or repair piping runs.

Consider valve type, pressure and temperature ratings, material compatibility with your fluid, actuation method (manual or automatic), and maintenance requirements.

 

  • Valves regulate flow by opening, closing, or partially obstructing the pathway. Their mechanisms (such as the rotation of a ball or the linear movement of a gate) determine the speed and precision of flow control.

  • A flange is a flat, circular component used to connect pipes, valves, or other equipment. Bolted together with gaskets, flanges provide a secure, leak-proof joint that facilitates both assembly and maintenance.

  • Manual valves require physical operation via handles or levers, whereas actuated valves use mechanisms—pneumatic, electric, or hydraulic—to open and close automatically or remotely.

  • Issues include leaks caused by improper installation, over-tightening, degraded seals, material incompatibility, and fatigue from repeated cycling. Regular inspection and proper installation practices help mitigate these problems.

Regular maintenance involves periodic inspections, cleaning or replacing worn seals, ensuring proper torque during installation, and adhering to manufacturer guidelines and local plumbing codes to preserve system integrity.

 

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