ConFlat (CF) Fittings and Flanges: What Are They?

ConFlat (CF) fittings are flanges which utilize metal seals to attain vacuum conditions. The combination of a stainless-steel knife-edge flange and a copper gasket (OFHC) makes for a nearly impenetrable vacuum barrier.

For the seal, the integrity of the knife-edge on the stainless-steel flange is vital. The hardness of the stainless steel coupled with the softer copper gasket means that there are few configurations that would provide equally airtight capabilities. The stainless-steel knife-edge cuts an indentation into the softer copper gasket, as it is the sturdier, stronger metal.

The CF knife-edge system guarantees the best performing vacuum seal, permitting vacuum levels, which are over 10-12 mbar. CF flanges use a series of bolts, unlike other vacuum seals that use clamps and elastomers.

This guarantees a strong and uniform seal over the copper gaskets. Depending on the application, CF fittings can be supplied with both through-bolt and threaded holes.

The Appearance of CF Fittings

The gaskets are made from soft materials, while the majority of CF fittings are manufactured from high tensile metals like stainless steel. OFHC copper is the most common material utilized for the gaskets. Silver plated copper of aluminium gaskets provide a viable alternative where pure copper cannot be used.

The main advantages of using such robust materials are; increased durability and an elevated propensity for withstanding high temperatures. The seals can be baked to temperatures as high as 400 °C, which, consequently, enables the more efficient pumping of a system.

A certain level of flexibility is required because of the varied environment that CF fittings are used in. There is a variety of standard products, with rotatable and fixed flanges. Rotatable flanges are needed for bolt holes to align and permit components to interface with each other.

CF fittings are utilized for UHV application, but not exclusively, another common application is for high temperature processes. The all metal seal will withstand temperatures up to 400 °C making it a popular choice for coating systems and furnaces, amongst other applications.

When to use CF Fittings

Allectra’s team of specialists would recommend CF fittings in a high temperatures process or when the vacuum level requires it. The durability at high temperature, naturally low outgassing of metals, and the superior metal sealing technology make them the obvious choice for processes in demanding environments.

This information has been sourced, reviewed and adapted from materials provided by Allectra Limited.

For more information on this source, please visit Allectra Limited.

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