Jan.14.2025
In vacuum systems, vacuum flanges are key components for connecting pipes and equipment, which is crucial in ensuring vacuum sealing, system stability, and ease of assembly and disassembly. CF, KF, and ISO are three common types of vacuum flanges widely used in ultra-high and standard vacuum systems. Fleyenda will introduce the specifications and main features of these three types of vacuum flanges.
Part 1: CF Flange
The English name of the CF flange is "Conflat Flange." It is a type of flange connection used in ultra-high vacuum systems, featuring a metal static seal that can withstand high-temperature baking.
The nominal diameter sizes include: DN16, 40, 63, 100, 160, 200, 250.
The applicable vacuum level is up to 10^-12 mbar.
Flange sealing materials are typically Viton, PTFE, oxygen-free copper, etc., and the flanges are usually made of 304, 316 stainless steel.
Table of Common CF Flange Models and Sizes
The inner side of the CF flange has a raised sharp edge that seals the vacuum by compressing the oxygen-free copper gasket (or other soft metal) to deform it. This all-metal sealing method is widely used in ultra-high vacuum systems. CF flanges are also often referred to as ICF flanges. The number following "CF" indicates the standard inner diameter of the tube, while the number after "ICF" refers to the flange's outer diameter. The common CF flange models and sizes are listed in Table 1.
CF flanges come in two types: fixed and rotatable. Fixed flanges are integrated structures, while rotatable flanges consist of the sharp-edged sealing part and a bolt-fixing part. Flanges may have through holes or threaded holes. Flanges with through holes are fixed with bolts and nuts, while those with threaded holes are fixed directly with bolts. The flange material is primarily SUS304 (or SUS304L) because SUS304 has low outgassing and is easy to machine and weld.
Table 1: Common CF Flange Models and Sizes
| Flange Models | A/mm | B/mm | C/mm | T/mm | T₁/mm | n×d |
|---|---|---|---|---|---|---|
| ICF34 (CF16) | 34 | 16 | 7.5 | 3.3 | 6.5 | 4-6.5 |
| ICF70 (CF35) | 70 | 16 | 38.1 | 7.5 | 7.3 | 6-6.5 |
| ICF114 (CF63) | 114 | 67 | 90 | 16 | 8.8 | 8-8.5 |
| ICF152 (CF100) | 152 | 102 | 130 | 18 | 9.8 | 8-10 |
| ICF203 (CF150) | 203 | 152 | 180 | 20 | 10.8 | 8-12 |
| ICF253 (CF200) | 253 | 202 | 230 | 22 | 12.8 | 12-12 |
| ICF305 (CF250) | 305 | 253 | 280 | 24 | 14.8 | 12-14 |
| ICF356 (CF300) | 356 | 305 | 330 | 24 | 16.5 | 16-14 |
| ICF406 (CF350) | 406 | 355 | 380 | 28.6 | 18.5 | 16-16 |
Part 2: KF Flange ISO-KF
ISO-KF is a type of quick-release flange used in vacuum systems. It consists of the following components: two symmetrically distributed KF flanges, an O-ring, a centering ring, and a clamp. No other tools are required; simply turning the wing nut by hand can loosen or tighten the connection.
ISO-KF vacuum fittings are small-sized quick-release flanges. The nominal diameter sizes include: DN 10, 16, 25, 40, 50.
Manufacturing standards include: DIN 28403, ISO 2861.
The applicable vacuum level is up to 10^-8 mbar.
Flange sealing materials are typically Viton, Buna, Silicone, EPDM, aluminum, etc.
Flanges are usually made of 304, 316 stainless steel, etc.
ISO-KF vacuum fittings typically consist of a flange, clamp, O-ring, and centering ring, as shown in the figure below.
1—CF/NW adapter flange; 2—Clamp; 3—Centering ring; 4—O-ring; 5—NW adapter flange
Small-diameter piping uses rubber O-rings to seal the vacuum flange, which is called an NW (or KF) flange and is widely used in low, medium, and high vacuum systems. Its advantages include reusability, ease of operation, and cost-effectiveness. However, NW flanges have two major issues: one is their limited heat resistance during baking, and the other is the permeability to hydrogen and helium.
When using NW flanges, an O-ring equipped centering ring is placed between two NW flanges, and a clamp is used for quick installation and removal (see Figure 1). When using Viton O-rings, the baking temperature can typically reach 150°C.
Part 3: ISO Flanges
ISO flanges and pipes can be used for various applications, from atmospheric pressure to high vacuum, and are frequently assembled and disassembled. Generally, pipes with diameters larger than 50 mm (2 inches) are used. With Viton O-rings, they can withstand baking at 150°C.
The two common types of ISO flanges are ISO-K and ISO-F.
ISO-K and ISO-F vacuum fittings are large-sized vacuum fittings, and the nominal diameter sizes include: DN 63, 100, 160, 200, 250, 320, 400, 500, and 630.
Manufacturing standards include: DIN 28404, ISO 1609.
They are applicable in scenarios requiring a vacuum level of up to 10^-8 mbar.
Flange sealing materials are typically Viton, Buna, Silicone, EPDM, aluminum wire, etc.
Flanges are usually made of 304, 316 stainless steel, etc.
a. ISO-K vacuum fittings typically consist of a flange, clamp, O-ring, and centering ring, as shown in the figure below.
b. ISO-F vacuum fittings typically consist of a flange, O-ring, and centering ring, and unlike ISO-K, they are fixed with bolts, as shown in the figure below.
Fleyenda specializes in providing high-quality vacuum components, including CF, KF, and ISO standard vacuum flanges and valves. Our products are designed for ultra-high vacuum (UHV), high vacuum, and standard vacuum systems, ensuring reliable sealing and exceptional performance. With a focus on precision and durability, Fleyenda offers a comprehensive range of vacuum solutions, ideal for various industrial and research applications.
