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Frenchtown Ceramics in
Frenchtown, NJ, an alumina manufacturer made an
alumina that was pink in color. In addition to the normal 94%
alumina plus other oxides, they added a small addition of manganeese
oxide; their claim was that it increased the mechanical strength.
The alumina was used for making
Beryllium oxide is easy to tell from alumina; it's not as tough
to scratch as alumina, and it is usually light gray in color.
Beryllium-Oxide BeO is a very fast heat conductor. if you put a soldering iron on
one side of a BeO insulator you feel the heat come through to the
other side almost immediately.
In the 70th stores personnel
[unprotected] were in the habit of smashing the duds with a hammer
and/or burning them along with all sorts of A-Class items. That
piece of open ground was declared a hazard during a later era . Various Techs informed the Department of the potential dangers.
A few years later Technical Admin wrote to Eimac asking specifically
what 'dangerous' materials were in the range of tubes used. The
answer was very guarded and stated specifically that all of the
types in question should be returned to the manufacturer after use.
It is likely just alumina, BeO is used where high thermal
needed, and ranges from snow white to light grey. It is also denser
alumina, and the high thermal conductivity (about that of aluminum)
"feel" like a metal. It is used in thermal links, but in
tube applications. It is very irritating to the eyes and mucus
so be sure to wash before touching your eyes, etc. (This also go for
metallic beryllium, ask me how I know!) BTW, the pink ceramic is
with magnesia added for strength. Shows up in RCA tubes an RF power
semiconductors, as well as Svetlana and other Russian tubes).
In 1987, was asked an Eimac engineer in a telephone interview about
BeO in tubes. He quickly got hostile and huffy, and declared that NO
Eimac products contained BeO, but if they did -- he said that they would be marked as BeO and
all you needed to do was ship them back to the factory for proper
And I quoted him verbatim in the article.
I don't know whether that's still true about BeO disposal, but I
would expect that Eimac would still accept stray BeO pieces. As long
as you don't break or grind them, they're safer to handle than
bigger glas tubes.
After all, you can drop a BeO thermal link on the floor and probably
nothing will happen ....
Anyway, I expect that there's much more to the issue of BeO content
in Eimac products than they are willing to tell. But as long as you
don't smash their stuff, you should be fine.
The only Eimac tube that had BeO was a 416C and they marked it.
In the ceramic form the Beryllium Oxide c Ceramic is not hazardous,
unless you decided to ingest it. Lots of things used in many other
vacuum tubes are worse. Go look at any RCA tube book and read the
contents of their tubes. Now days the EPA restrictions on lead an
mercury are enough to move tube manufacturing over seas or shut it
down completely. BeO is NOT on the list of hazardous waste in the
ceramic compounds used, but if it is machined, or ground into a
freyable dust that can be inhaled there are EPA/OSHA protocols and
restrictions. I found out our city (Phoenix Az) has dangerous
amounts of Chromium 6 in it, along with all the other cities tested.
The manufacturing standards for making a florescent lamp tube are so
loose some have visible big blobs of mercury rolling around inside
them, and some have the "tiny insignifigant" small amount the comany
says is safe, and required to ignite the lamp. I would not loose any
sleep over BeO ceramics at all. They are not in the hazardous wate
list made up by the DEQ - EPA -ETC alphabet soup of govt reg comms.
The Eimac catalog shows the 4CS250R -
conduction cooled variant of the 4CX250 where it is clearly stated
that there is a BeO thermal coupling section to the anode.
Yes, it's safe to assume that the ceramic thermal links for
tubes will always be BeO, and probably will be marked as such. I've
a BeO thermal link that was an integral part of any electron device
that 416C photo. The Eimac engineer I spoke with in the 80s was
"no Eimac products contained BeO" -- I'm sure he meant the electron
not the accessories, like thermal links. But we've seen a pretty
of an Eimac device labeled "contains BeO." So go figure. Anyway,
important for our personal safety and the safety of others that we
be aware of
the potential hazard, and handle this stuff accordingly. For example,
of us have tubes with uranium glass?
I've noticed warnings on the datasheets for some high-powered
stating "contains BeO" but no indication where in the device. I's
the "pill" part is alumina and the BeO part is inside, between the
die and the
flange. I would like to look, but knowing how nasty berylliosis is,
there would inevitably be some dust released when the package was
opened, I just
haven't wanted to know THAT much.
Most if not all conduction cooled ceramic/metal tubes used a BeO
block between tube and heat sink. Eimac purchased theirs as did RCA
The most common tubes are the 8072, 8560, and 8873 which had no BeO
Several obscure ones also were made.