A Detailed Comparison of the Advantages, Disadvantages, and Applicable Scenarios of Various Types of Vacuum Flanges

　　Below, I will provide a detailed breakdown of the advantages and disadvantages of various types of vacuum flanges along with their applicable scenarios, followed by a summary table for quick reference.

　　The selection of vacuum flanges is mainly based on factors such as vacuum requirements, frequent disassembly and assembly, cost budget, size, and whether baking is needed.

　　1、 Ultra High Vacuum (UHV) Flange Series

　　This type of flange is dominated by metal sealed flanges, with its core features being the ability to bake and extremely low leakage/gas release rates.

　　1. CF flange

　　Description: The gold standard in the UHV field. Composed of stainless steel flange, a copper gasket with a central opening, and a set of bolts/nuts. There is a sharp 'knife edge' on the flange sealing surface.

　　Working principle: When tightening the bolt, the blade bites into the soft copper gasket, causing it to undergo plastic deformation, filling all micro unevenness and forming a certain airtight metal seal.

　　Advantages:

　　Excellent sealing performance: extremely low leakage rate (<10 ⁻¹² mbar · L/s), capable of achieving ultra-high vacuum and extremely high vacuum (XHV).

　　High temperature baking: It can usually withstand baking temperatures of 150 ° C to 450 ° C to accelerate gas desorption from the inner walls of the system.

　　Extremely low material gas release rate: all metal structure, no organic material pollution.

　　High degree of standardization: complete size range (from DN10CF to DN500CF or even larger), good compatibility with products from different manufacturers.

　　Disadvantages:

　　High cost: Both flanges and bolts are precision machined parts, which are expensive.

　　Disassembly and assembly are cumbersome: a torque wrench is required to gradually tighten the bolts in diagonal order, which takes a long time.

　　Gasket disposable: Each time it is disassembled, a new copper gasket must be replaced and cannot be reused.

　　Applicable scenarios:

　　Any system that requires achieving and maintaining UHV/XHV.

　　Particle accelerators, synchrotron radiation beamlines, surface science experiments (such as XPS, AES, STM), molecular beam epitaxy (MBE), high-energy physics experiments, etc.

　　2. ISO-K/LF flange (ISO Large Flange)

　　Description: Another mainstream UHV metal sealing flange, commonly found in Europe and Japan. Unlike CF flanges, it uses a grooved flange with solid aluminum wire (or copper wire) as the sealing ring.

　　Working principle: Place the aluminum wire into the groove of the flange. When tightening the bolt, the flange plane compresses the aluminum wire, causing it to deform and form a seal.

　　Advantages:

　　The sealing performance is comparable to CF flanges and can also achieve UHV/XHV.

　　Easy to align: The groove design makes it easier to align with the center when connecting large-diameter pipelines.

　　Disadvantages:

　　The cost is even higher: the processing is more complex, and the placement of aluminum wire is not as convenient as copper gaskets.

　　Disassembly and assembly are equally cumbersome.

　　Aluminum wire is softer than copper gaskets and can be easily damaged if not handled properly.

　　Applicable scenarios:

　　Similar to CF flanges, it is particularly common in large UHV systems, such as large vacuum chambers, main pump connections, etc.