We see cases of berylliosis (the beryllium lung disease) around here
because there were a couple of aerospace manufacturers in the area.
Beryllium is widely used in aerospace applications because of its light
weight and high rigidity. Like aluminum, it forms an oxide layer quickly
which helps it resist further oxidation. I have seen beryllium parts that
are black anodized so without a warning label, you would not know it (these
were used in the optical equipment for the Apollo spacecraft). The Apollo
command module optical unit that housed the sextant and scanning telescope
and the Alignment Optical Telescope used in the Lunar module were mostly
beryllium. Unfortunately, scrap dealers found this out and equipment that
was sold off as excess after the Apollo program was canceled was scrapped
for the beryllium. I saw the results of this myself, so I know it happened.
I visited a surplus dealer who also scrapped stuff. I found the
non-beryllium remnants of three of the Apollo command module optical units
and four of the LM AOTs. He still had the transit cases for the telescopes.
All of this was brand new stuff. Kollsman Instrument was the contractor
for the Apollo optical equipment and he had purchased it from them.
Beryllium was scrapping at about $120 a pound then. The Command Module
optical unit weighed about 70 pounds and at least 60 pounds of that was
beryllium. The method of scrapping was not disassembly - it was to smash
things with hammers. Sad.
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On Thu, Jul 2, 2020 at 11:10 Chuck Harris <cfharris@...> wrote:
Beryllium ceramic is fascinating stuff. We all would use it a lot
more but for the liability issues.
It feels a lot like aluminum in that it draws the heat away from your
skin very quickly, making it feel perpetually cool when all but the
part that is touching you, is at room temperature. Most other
ceramics are pretty good insulators, so they feel warm and cozy as
their surface warms quickly to your skin temperature.
Another fun ceramic is the foamed stuff used for the space shuttle's
heat shield. This stuff heats up instantly bright yellow when you
play a propane torch on its surface, but take the flame off of the
tile, and you can touch it immediately, and it doesn't even feel more
than warm.
-Chuck Harris
Bruce Griffiths wrote:
I have some pink tinted alumina TO3 insulators as well as some blue
tinted beryllia ones from the 1970's.
The beryllia ones are much colder to the touch than the alumina ones.
Bruce
On 03 July 2020 at 02:19 stevenhorii <sonodocsch@...> wrote:
Beryllium and compounds have an unusual toxicity profile. Beryllium is
not
directly toxic as, say, arsenic is. However, how it harms you is to
cause
an intense allergic reaction. In the lungs, this results in fibrosis
from
the inflammation and severely affects lung function. Chuck is correct in
that most companies tinted BeO parts pink but I have certainly seen
non-tinted parts. I once found some long white pipes in a surplus yard.
Though they were not pink, they had a warning label on them. I alerted
the
owner to this and he said he¡¯d be careful, but he was somewhat pleased
because beryllia scraps out at a higher price than alumina.
Chuck is also correct in that beryllium and its compounds are safe if
you
don¡¯t create dust or fumes from them (no grinding or welding). Slivers
of
beryllium can cause an allergic reaction in your skin around the sliver.
You should be safe using the heatsink pad as intended but it does need
heatsink compound to be effective.
Steve H.
On Thu, Jul 2, 2020 at 09:19 Chuck Harris <cfharris@...> wrote:
It has been reported that Tektronix used BeO ceramic all
over the place.
Some common examples are the heat sink insulators for
the 5000 series H and V output transistors.
They also used it as the heat sink bar that fits under
the EHT for the 657 scopes.
This particular heat sink insulator looks probable to me.
Some more responsible companies tinted their BeO ceramics
pink or purple as a warning, but not tektronix, as far as
I have seen.
You needn't be terribly fearful, though. If you aren't
machining it into a fine dust, you should be ok.
Regardless of what it is, you will need heatsink compound.
The pieces you have are probably still serviceable, as I
doubt there is enough voltage there to jump the thickness
of the pad even if it were free air. Goop them up with
compound, and screw the device back down.
About the only stuff that doesn't need heatsink compound
are silicone heatsink pads... which are made out of heatsink
compound.
-Chuck Harris
John Gord via groups.io wrote:
Toby,
If it is a hard, brittle ceramic-like slab, it is probably alumina
(aluminum oxide). It is a good electrical insulator and a reasonably
good
thermal conductor. Beryllium oxide looks similar, but is unlikely here
because of its hazards.
--John Gord
On Wed, Jul 1, 2020 at 08:52 PM, <toby@...> wrote:
Hi,
In preparation for testing/replacing components on the HV & regulator
board, I removed it, and seem to have accidentally broken one of the
heatsink pads under a bottom transistor (see pic).
What is this material?
/g/TekScopes/photo/249616/0?p=Created,,,20,2,0,0
Should it be used with thermal paste or not?
Thanks
--Toby
