[Milsurplus] Capacitor issues

[Kenneth G. Gordon]

On 2 Jun 2016 at 11:48, Nick England wrote:

> Not trying to re-hash the usual PCB merry-go-round, but this section from "Radio Transmitters" 
> by Gray and Graham (ITT) seems like reasonable advice -

Agreed.

> ==================================
> 14-8. Chemical Hazards. Most chemical hazards associated with
> radio transmitters occur as a result of failure or overheating of a component.
>    Insulating Oils. It is necessary to use nonflammable oils in transformers,
> capacitors, and other components which do not operate in a
> concrete vault. These chemicals are usually chlorinated biphenyls.

PCBs.

> Toxic fumes are liberated when this material is heated, and the maximum
> safe concentration is 1.0 to 2.0 mg per cu m of air. Transformers and
> chokes fitted with "breathers" should be vented to the outside. The
> liquid can be absorbed through the skin; so hands should not be immersed
> unless they can be washed fairly quickly afterward.

I see I was wrong about heating the stuff up. Thank you for the correction. And, yes, using 
those latex examination gloves, available in boxes at most pharmacies, is always a good 
idea. I think at this point, I would advise Ray to wear a pair of those gloves, take the caps 
outside, open up the bottoms with a Dremel, drain the oil, remove the guts, clean the cans 
out, and "restuff" with some high-quality modern electrolytics, then close them back up with 
JB Weld.

When I was still working, I once had an occasion to ask our local EPA how to dispose of 
PCB filled caps. They told me to simply drain the oil onto the ground somewhere, and 
discard the caps, or simply discard the caps without draining. The quantity of PCBs in any 
small cap is below the requirements to do anything more drastic with them.

>    Teflon. Teflon insulation releases vapors when heated to a point
> above 400°F. It is not particularly dangerous, but inhalation can cause
> an attack similar to influenza which has been called polymer fume fever.
> Symptoms do not occur until several hours after exposure, and the attack
> passes after 36 to 48 hr.
>    Selenium. A selenium rectifier which has been overheated should be
> approached with caution. The allowable concentration of selenium is
> 0.1 ppm in air. The material resembles arsenic both chemically and
> physiologically. It causes respiratory irritation, abdominal pain, and
> irritation to the brain (27).

Whenever I find any selenium rectifiers in anything I own, I remove them and replace those 
with silicon and an added series resistor. It is simply not worth the hazard to continue to try 
to use them. Besides, at this late date, they are barely more than what amounts to two 
resistors of slightly different values, depending on the direction of current flow.

>    Carbon Tetrachloride. Carbon tetrachloride is frequently used for
> maintenance purposes and is a dangerous chemical at room temperature.
> The maximum allowable concentration in air is 25 ppm. It causes eye
> inflammation and damage to the liver, kidneys, heart, and nervous
> system. Absorption of 3 to 4 ml can be fatal. The toxic symptoms may
> not appear until 2 to 8 days after exposure.
> ===================================

As far as I know, Carbon-Tet is simply no longer available except from chemistry stores at 
universities and then only for very special purposes.

MEK which is available from most hardware stores is better, but still should be used with 
caution.

> This generally useful book is at
> http://www.introni.it/pdf/Gray%20-%20Graham%20-%20Radio%20Transmitters%201961.pdf

An excellent source. Thank you, Nick.

Another somewhat common chemical which should be handled with caution is HF, or 
hydroflouric acid. Although it is very handy for moving certain types of crystals like FT-243s 
up in frequency or to clean crystals, in high concentrations, it is absorbed through the skin 
and can dissolve bone even in living tissue. It is also tremendously hygroscopic and 
evaporates in air extremely easily. As I have stated on the ARC5 list, the common 
household rust remover, Whink, contains only 1% HF, but is still capable of moving or 
cleaning crystals, and should also be handled carefully.

Common sense should prevail.

Ken W7EKB