This EVAC Chain Clamp for NW25 KF25 flanges is for converting Elastomer (Viton/Buna) rubber seals to UHV (Ultra High Vacuum) metal seals. This allows for a lower vacuum compared to elastomer (Viton/Buna) rubber seals. Other benefits include: reduced outgassing, no permeation , no hydrocarbons, and resistance to radiation and higher heat. The resultant UHV seal has a helium leak rate of of less than 1 X 10 -11 standard cc/sec. They can also be baked repeatedly to 150°C (302°F). The EVAC chain clamp and an aluminum knife edge seal form the UHV vacuum seal between the connecting KF flanges. (please see far right graphic above - click to enlarge).

This is a uncoated version that is the preferred choice for sealing standard KF flanges with aluminum metal seals. This chain clamp has aluminum links. This is a KF25 NW25 chain clamp only, the aluminum knife edge seal IS NOT included but available on this website. For a complete explaination of this UHV Seal and dimensions of the chain clamp, download the EVAC FLange Brochure .pdf below. See page 4.