Gefahren / Danger


©  Tube Museum / Collection
Udo Radtke,  Germany

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Beryllium ist in Bezug auf seine Gefährlichkeit nicht zu unterschätzen. Vor Jahren habe ich mal eine Metall-Keramik-Röhre der Wehrmacht mühevoll aufgeschliffen um das Innenleben zu sehen. Als ich dies später Professor Dieminger am Ionosphäreninstitut Lindau / Harz erzählte, meinte er, das könnte mein Tod sein.

Es gäbe Leute, die den Kontakt mit dem Feinstaub schadlos überstünden, andere würden jämmerlich daran sterben. Vielleicht gehöre ich zur ersten Gruppe, oder es war kein Beryllium.

Hier ein Link zur Berylliose

Deshalb Vorsicht im Umgang mit Metall-Keramik-Röhren, sie könnten Beryllium-Oxyd enthalten.

Wanderwellen-Röhren von Siemens, wie die RW1127 tragen einen gelben Warnaufkleber.

Berylliumoxy BeO ist ein guter Isolator mit extrem guter Wärmeleitung. Die Keramik sieht leicht gräulich aus. Das Besondere daran, ist die gute, dichte Verschmelzung mit metallischen Dichtflächen.

Reines Beryllium ist oft auch als Austrittsfenster an alten Röntgenröhren zu finden. Bitte nicht berühren und falls doch, bitte nicht damit an den Augen reiben. Es ist sehr giftig.

Eine rötlich bis bläulich aussehende Keramik besteht aus "Aluminia" + Farbpigmenten und Magnesium zur Erhöhung der Festigkeit. Derart gefärbte Keramik findet man auch häufig bei russischen Koax-Trioden.

In den 70 Jahren wurden viele dieser BeO enthaltenden Röhren einfach zerschlagen und entsorgt. Später bestanden Firmen, wie Eimac, auf Rückgabe zur sicheren Entsorgung.



Please see text, containing several contributions from collectors.

For Medical informations please try Google by search word Berylliose.


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 ceramic-metal seals.

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 conductivity is needed, and ranges from snow white to light grey. It is also denser than alumina, and the high thermal conductivity (about that of aluminum) makes it "feel" like a metal. It is used in thermal links, but in semiconductor and tube applications. It is very irritating to the eyes and mucus membranes, 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 Alumina 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 disposal.

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 conduction-cooled
tubes will always be BeO, and probably will be marked as such. I've never seen
a BeO thermal link that was an integral part of any electron device -- until
that 416C photo. The Eimac engineer I spoke with in the 80s was adamant that
"no Eimac products contained BeO" -- I'm sure he meant the electron devices and
not the accessories, like thermal links. But we've seen a pretty clear example
of an Eimac device labeled "contains BeO." So go figure. Anyway, it's more
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, how many
of us have tubes with uranium glass?

I've noticed warnings on the datasheets for some high-powered semiconductors
stating "contains BeO" but no indication where in the device. I's assuming that
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, and that
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 thermal
block between tube and heat sink. Eimac purchased theirs as did RCA and

The most common tubes are the 8072, 8560, and 8873 which had no BeO in them.
Several obscure ones also were made.


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