Ceramic insulator seals

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Richard Hull
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Ceramic insulator seals

Post by Richard Hull » Mon Jul 10, 2017 8:09 am

Adapting an odd based insulator to a usable conflat or KF SS flange can be tricky if you need to braze at or near the metal to ceramic seal. Such seals are, effectively, glass to metal seals and you do not want to overtemp this critical seal during a brazing operation. If the ceramic to metal seal is somewhat removed from the joint or if it has a thin sheet cross section all the way to the joint, then you might be in luck if you use a very low melting point brazing alloy.

In the end, it will be up to you. If you go ahead with a brazing operation, pre tin-braze the mating surfaces, if possible. Make sure all surfaces are bright and clean. I suggest using a prefluxed alloy paste if possible over a brazing rod. (Jewelers supply houses sell this)

Always heat the large massive part first and allow the thin section to the seal get its brazing heat from the more massive heated part. Once the brazing alloy flows, immediately stop heating the part.

One of the rules of brazing is to make sure the parts to be brazed touch each other over every surface. Air gaps will not be filled in by brazaing alloy like they will with common soldering.

Always try to figure a mechanical work-around that will not involve brazing near a metal to ceramic seal, first!

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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