gasket (copper)


Gaskets for sealing UHV flanges are often made from high purity oxygen free copper. In a standard, so called conflat flange, the sealing is achieved by the flange knife edges cutting into the soft copper. The picture below shows a new (left) and used (right)


Given the high price of copper gaskets, one may want to re-use them. In principle this is possible if the knife edges have not cut in too far into the copper, i.e. if you can still drive them further in the second time you use the gasket. Re-using gaskets is certainly not the recommended procedure unless you are experienced with this because the risk of leaks is quite high.

Sometimes it can be difficult to get used gaskets out of the flange because they are squeezed in so tightly. When trying to remove them anyway, it is advisable to use a special gasket removal tool rather than a screwdriver or something similar because of the risk of damaging the knife edge of the flange.

For some very big flanges, the sealing is often just achieved by placing a copper wire loop between two polished, flat areas of the mating flanges. It can be tricky to place the wire such that it does not overlap with the screw holes and that it stays in place when the flanges are brought together. One can hold the copper loop in place by very thin gold wire which is then fixed to the outside of the flange by scotch tape. When the two sides come together, the soft gold is pressed in the copper and does not affect the sealing properties.


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