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Old 06-12-2018, 11:02 PM
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Bob Galanter
Join Date: Sep 2005
Location: Whitefish Bay, Wi (Milwaukee)
Posts: 988
Originally Posted by benman94 View Post
The surfaces we're trying to mate really aren't flat to begin with. The ultor flange sticks out from the glass portions at a 90 degree angle. We'd be filling in the cracks that occur near those joints. I doubt very much we'll ever stumble across a perfect material for sealing these tubes, so there is going to be some kludging in any case. The properties of the Epotek still look a bit more promising to me, except for the rather low temperature it can tolerate without breakdown.
It sounds like the Pelco material is designed to be used in between precision mating surfaces, like vacuum flanges or precision ground glass mating surfaces, however that is just conjecture on my part. It sounds like this material is similar to the VacSeal, which is also used between precision mating surfaces. Using VacSeal to just coat external surfaces is totally useless. Perhaps the Pelco product is pretty much the same.

The advantage of the 353ND from Epotech, is that it not only has a very high affinity to mating with metal and glass but it can be applied as an external coating. Although the 353ND has the disadvantage of not being able to withstand a 650F evacuation oven, it is possible to evacuate a crt at temperatures that the 353ND can tollerate, you just have to pump for a lot longer time.

Of course this has not been proven because so far we have not had the opportunity to try a low temperature pump down in practice with 353ND sealing a 15G. Sure would be nice if someone with an oven could give this theory a try before I die.
Vacuum tubes are used in Wisconsin to help heat your house.

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