In the field of vacuum technology, we often come into contact with flanges of different specifications such as CF, KF, NW, and ISO. These flange types play a crucial role in sealing connections in vacuum systems. However, many people may not be fully aware of the differences and applications of these flanges. Next, we will explore these issues and jointly deepen our understanding of the characteristics and usage methods of these flanges. Firstly, let's focus on the CF series flanges.

CF flange, full name Conflat Flang, is designed specifically for ultra-high vacuum environments, using metal static sealing technology and possessing high temperature baking resistance. This flange connection method is easy to identify due to its uniqueness and is mainly used for sealing work in ultra-high vacuum systems. Its core sealing mechanism lies in the metal sealing of copper gaskets. It is worth noting that the sealing effect of CF copper gaskets gradually decreases after the first use. Therefore, in high vacuum application scenarios, new gaskets must be replaced after each disassembly to ensure the sealing performance of the system.

The nominal diameter size range covers DN16, 40, 63, 100, 160, 200, up to 250mm. CF flanges of these sizes can operate stably under vacuum degrees up to 10-12 mbar. In terms of material selection, high-performance materials such as Viton, PTFE, or oxygen free copper are usually used for flange sealing, while the flange itself is mostly made of high-quality metals such as 304 and 316 stainless steel to ensure stable performance in high vacuum environments.

1、 KF series:

The KF series flanges are also suitable for high vacuum environments, with a wide range of nominal diameter sizes ranging from DN16 to DN250mm. These flanges are made of high-quality materials such as 304 or 316 stainless steel, as well as high-performance sealing materials such as Viton or PTFE. At vacuum levels of up to 10-12 mbar, KF series flanges can maintain stability, ensuring sealing and stability in high vacuum environments.

The KF series flange, as a common sealing connection method in high vacuum systems, has a wide range of specifications, ranging from KF10 to KF50. Under normal circumstances, the size of the pipeline connected by KF is set based on inch specifications. For example, KF25 corresponds to a pipe size of 25.41.65mm, and so on (the welding size of the flange can be customized for special pipe size requirements). Once it exceeds KF50 (with a piping size of 50.81.65mm), subsequent vacuum connections usually use the ISO series, including ISO-K and ISO-F types.

2、 ISO series flange

The ISO series flange is another important sealing connection method in vacuum systems, which includes two types: ISO-K and ISO-F. Similar to KF series flanges, ISO series flanges also have a wide range of specifications to meet different vacuum connection requirements.

ISO-KF vacuum connector is a convenient connection method in vacuum systems. It consists of two symmetrically distributed KF flanges, O-Ring sealing rings, centering brackets, and clamps. By simply twisting the disc nut, the tightness of the connection can be easily adjusted without the need for other tools. This type of joint is particularly suitable for small-sized vacuum connections, with nominal diameters ranging from DN 10, 16, 25, 40, and 50. In addition, it also has a wide range of manufacturing standards and applications, and can withstand a vacuum degree of up to 10-8 mbar. In terms of material selection, flanges are usually made of 304 or 316 stainless steel, while sealing materials include Viton, Buna, Silicone, EPDM, and aluminum. In addition, the design of ISO-KF vacuum joints is relatively simple, usually consisting of several components such as flanges, quick clamps, sealing rings, and center positioning rings.

Similarly, the ISO-K and ISO-F types in ISO flanges are widely used in various vacuum applications. They are large-sized vacuum joints with nominal diameter sizes covering DN 63, 100, 160, 200, 250, 320, 400, 500, and 630mm. These joints also comply with the manufacturing standards of DIN 28404 and ISO 1609 and are suitable for applications requiring a vacuum degree of up to 10-8 mbar. In terms of materials, flanges are usually made of 304 or 316 stainless steel, while sealing materials may include Viton, Buna, Silicone, EPDM, and aluminum wire. The design of ISO-K vacuum joints is more detailed, consisting of key components such as flanges, flange claws, sealing rings, and center positioning rings, providing a stable and reliable connection method for vacuum systems.

The ISO series accessories used for high vacuum systems have a specification range starting from ISO63 (piping size of 63.5 * 1.65mm), gradually increasing to ISO80, ISO100, ISO160, and even larger specifications. These joints adopt a double card head connection method, mainly involving two ISO flange plates, supplemented by a sealing ring in the middle, and fastened by four double card heads. It is worth noting that compared to the KF series, the sealing ring design of the ISO series includes an aluminum spring outer ring in addition to the center bracket and fluororubber material sealing ring. This design aims to prevent the sealing ring from slipping in larger pipelines due to machine vibration or temperature changes, ensuring that the sealing effect is not affected. In addition, ISO-F vacuum joints are usually composed of components such as flanges, sealing rings, and center locating rings. The flange connection adopts bolt fastening method, which is different from ISO-K joints.

3、 NW series:

The NW series vacuum accessories, as key components of high vacuum systems in Japanese standards, have a wide range of applications in Japanese enterprises and equipment. Unlike the ISO series, which is connected by two flange plates and four double hooks, the NW series adopts a design where two NW flanges are connected by chain clamps. It is worth mentioning that the N63 flange is similar in appearance to an enlarged version of the NW50 flange, which makes the NW series unique in the field of vacuum systems.