The difference between the three common vacuum flange specifications (CF, KF, ISO)

1, CF flange

The English name for the CF flange is Conflat Flang. It is a flanged connection for ultra-high vacuum and is a metal static seal that can withstand high temperature baking.
Nominal diameter dimensions include: DN16, 40, 63, 100, 160, 200, 250
Suitable for vacuums up to 10-12 mbar

Flange sealing materials are usually Viton, PTFE, oxygen-free copper, etc.
The flange is usually 304, 316 stainless steel, etc., as shown in the figure below:

CF flange for vacuum standard:

GB/T 6070-2007 Vacuum Technology Flange Size
GB/T 6071-2003 ultra high vacuum flange

2, ISO-KF

ISO-KF is a quick release flange for use in vacuum systems. He consists of the following components: two symmetrically distributed KF flanges, O-Ring, centering brackets, and clamps. No need to use other tools, just loosely press the disc nut by hand to loosen or press the coupling.

ISO-KF vacuum fittings are small size quick flange fittings. The nominal diameter dimensions include: DN 10, 16, 25, 40, 50.
Manufacturing standards include: DIN 28403, ISO 2861
Suitable vacuum levels up to 10-8 mbar.
Flange sealing materials are usually Viton, Buna, Silicone, EPDM, aluminum, etc.
The flange is usually 304, 316 stainless steel, etc.
ISO-KF vacuum joints are usually composed of a flange, a clamp, an O-Ring, and a centering ring, as shown in the following figure.

ISO-KF applies vacuum standards:

Vacuum technology – Quick release connectors – Dimensions – Part 1: Clamping type
Vacuum technology – Quick release connectors – Dimensions – Part 2: Tighten type

3, ISO flange

ISO flanges and piping can be used in a variety of applications from atmospheric to high vacuum, often in assembly and disassembly. Typically the diameter of the tube exceeds 50 mm (2 inches). If you use a fluoro rubber O-ring, you can withstand baking at 150 °C.
The two common forms of ISO flanges are ISO-K and ISO-F.

ISO-K and ISO-F vacuum fittings are large-size vacuum fittings with nominal diameter dimensions including: DN 63, 100, 160, 200, 250, 320, 400, 500 and 630
Manufacturing standards include: DIN 28404, ISO 1609
Can be used where vacuum is required up to 10-8 mbar.

Flange sealing materials are usually Viton, Buna, Silicone, EPDM, aluminum wire, etc.
The flange is usually 304, 316 stainless steel, etc.

(1) ISO-K vacuum joints usually consist of a flange, a flange, an O-Ring, and a centering ring, as shown in the following figure.

(2)ISO-F vacuum joints usually consist of flanges, O-Rings, and centering rings. Unlike ISO-K, flanges are bolt-on. See below.

ISO flange for vacuum standards:

JB/T 1090-1991 Type J vacuum sealing ring type and size
JB/T 109l-1991 Rubber seal type and size for JO type and skeleton type vacuum
JB/T 1092-1991 O-type vacuum rubber seal type and size

tags: Spare Parts
Edited by Catherine Qin / EVP Vacuum Solution

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