Jim Thomson wrote:
>>Typically we'd blow out about one of those every day of two. The
>>transports that moved through vacuum seals also used Teflon insulation.
>>There was always a bunch of those stacked up waiting to be rebuilt. When
>>we'd have an arc over at the base of a transformer there'd be a lot of
>>black smoke and soot along with a smell similar to Chlorine and most
>>likely part of the gas was Chlorine.
There is no chlorine in Teflon (PTFE, poly-tetrafluoroethylene). When
Teflon is burned, the gas given off is hydrogen fluoride (HF). It does
smell a little like chlorine, but it's much more biting in the nose and
throat... believe me, I've breathed my share of both.
Teflon by itself is chemically inert and non-flammable. It has to be
either burned by an electrical arc or involved in a fire, but the fire
has to be fueled by something else.
>>The gas given off is very poisonous
>>which we didn't find out until a bit later. After they found out what
>>it gives off when burnt, any arc usually resulted in all the operators
>>deciding to take a break at the same time.
>>
>>The gas isn't good for you, but unless in a closed space or you stick
>>you nose in the smoke it's unlikely to cause any problems.
>>
Yes, that's exactly right. Even in very small concentrations, hydrogen
fluoride is biting in the nose and throat, so after the first sniff
people just leave.
The classic hydrogen fluoride victims were machinists who were making a
lot of very fine Teflon dust, which then get into their cigarettes. When
they lit up, the Teflon burned along with the tobacco, and they drew in
a deep double lungful.
>## My understanding is... Teflon is normally rated to run at 200 deg C
>CCS. It's max rated for 250 deg C. It decomposes at 335 deg C.
>
>## when Teflon turns into gas [dunno what temp it liquefies at]
>the gas given off is called Phosgene gas. This is extremely
>dangerous !
Wrong - phosgene (carbonyl chloride) is something completely different.
There is no chlorine in PTFE, and no fluorine in phosgene.
The persistent chlorine/phosgene myths that are attached to Teflon
should really belong to polyvinyl chloride (PVC): non-flammable but a
biting odor when burned, and a much closer chemical relationship to
phosgene. Yet somehow we never hear this same "phosgene gas" story about
PVC.
>## I didn't realize that Teflon could generate gas...from
>an arc?
Only if it's actually being burned by the arc... or if fine Teflon dust
gets into an open flame or a cigarette.
--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|