"gettering" material

[gfrat17]

Can someone explain how gettering material is applied to stainless steel vessels.

 

[iainuts]

They are generally put into a permeable bag of some kind, such as a nylon stocking, and put into the annular space of a vessel. They are not applied to steel like paint.

 

[EdStainless]

In some cases the reactive gettering material is actually placed into a holder that has a heating element. After vacuum pumps do all that they can you heat the material to scavenge the last gases out of the space.
You know, like inside of CRT tubes.

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Plymouth Tube

 

[iainuts]

Hi Ed,

In some cases the reactive gettering material is actually placed into a holder that has a heating element. After vacuum pumps do all that they can you heat the material to scavenge the last gases out of the space.

Interesting about the heating element on the getter, I'd not heard of that being done before. But shouldn't that regenerate the getter, not activate it? I know that vacuum pumping is always accompanied by heating the vessel or pipe, and this drives out moisture and other contaminants that are bound to the surface of the steel. But I believe the heat also regenerates getters (ie: it drives contaminants out of the getter as well). Once the vacuum space and getter is cleaned up by heating, it can be sealed and the getter is then fresh to pull in any additional contaminants that come off during the lifetime of the vacuum space.

 

[EdStainless]

The getters that I am thinking of are highly reactive and cannot be regenerated. If you are working with a sorbant or descant then you can regen. If you work with reactive metals (Nb, Zr, Ti, Al, rare earths) then when heated they will react with react with all moisture, oxygen and even nitrogen leaving a lump of slag.

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Plymouth Tube

 

[iainuts]

Interesting. Thanks.