"Ignoramus5533" wrote in message
...
I came into possession of a few used 400-600A circuit breakers. Each
is the size of a milk jug. While researching prices on them and such
(they sell for $150-200 on ebay), I learned that some cost many
thousands of dollars new. I saw numbers from $2,500 and higher.

I am curious just what makes them so expensive. Do they have any
precious materials inside? Or what?

i

My experience in refining precious metals taught me that high amperage
contacts are usually made from a compound of silver and some other element,
often tungsten. You can expect the breakers to contain silver, but that
hardly explains the high cost, particularly when a contact is generally well
under a troy ounce in size. Cost is likely attributed to a high
degree of engineering and limited production.

That's my story, and I'm stickin' too it! g

Harold

In article , Harold and Susan Vordos says...

My experience in refining precious metals taught me that high amperage
contacts are usually made from a compound of silver and some other element,
often tungsten. You can expect the breakers to contain silver, but that
hardly explains the high cost, particularly when a contact is generally well
under a troy ounce in size. Cost is likely attributed to a high
degree of engineering and limited production.

At one time they contained cadmium as well as sliver. The guy I
used to work with at GTE Labs was working on replacing the cad
with, among other things, Wo.

Anyone taking older breakers like that apart should be alert for
cadmium in the items, including that which was vaporized and sprayed
around inside the housing.

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

"jim rozen" wrote in message
...
In article , Harold and Susan Vordos says...

My experience in refining precious metals taught me that high amperage
contacts are usually made from a compound of silver and some other
element,
often tungsten. You can expect the breakers to contain silver, but
that
hardly explains the high cost, particularly when a contact is generally
well
under a troy ounce in size. Cost is likely attributed to a high
degree of engineering and limited production.

At one time they contained cadmium as well as sliver. The guy I
used to work with at GTE Labs was working on replacing the cad
with, among other things, Wo.

Anyone taking older breakers like that apart should be alert for
cadmium in the items, including that which was vaporized and sprayed
around inside the housing.

Jim

I often encountered small contacts that were silver/cadmium. I have no
clue why the cadmium, but it was always a surprise to find the yield lower
than expected, thanks to the cad content. Interestingly, cad and silver
are quite similar in appearance, so there is no outward sign of the alloy.
That's very unlike the tungsten type, which often have a waffle pattern on
the back side, and are considerably heavier than the other alloy types.

Harold

"Ignoramus5533" wrote in message
...
Tungsten feels very strangely heavy when I hold it. I have a pack of
10 3/16" electrodes, the little box weighs about a pound (did not
weigh it).

i


Oh, yeah! Specific gravity, as I recall, is something like 18-19. Not too
many elements are heavier. Gold (19.3) , Platinum (21.37), Iridium
(22.42). Silver (10.4+) languishes down with lead, about 11.

Harold

In article , Harold and Susan Vordos says...

I often encountered small contacts that were silver/cadmium. I have no
clue why the cadmium, but it was always a surprise to find the yield lower
than expected, thanks to the cad content.

Apparently breaker contacts have a tough job to do. They have to
resist oxidation to some large degree, but there is always some
surface oxide present to interfere with the making of the contact
when the breaker closes. The cadmium, having a relatively high
vapor pressure, does vaporize to some degree every time the
contact opens, and leaves a surface that is favorable to re-closing
the breaker.

The man I knew was a technician who was responsible for formulating
different kinds of sintered contacts out of different materials,
to research the idea of getting the Cad out of the product. At the
time GTE was well aware that it was not the best material to have
in their products, and wanted to be one step ahead of any regulation
about the issue.

I think by the time I met him (this was about '81 or so) they had
already decided on tungsten as a likely replacement. I always
though it was very ironic that this man was toiling away quietly
doing work that would benefit the public, and the environment as well,
greatly. Yet each night he would bring home two one-gallon jugs
of water from the lab (we received our water from the metropolitian
district commission) because his own public water supply for his
town (woburn, mass) had been badly polluted by W. R. Grace, and he
did not want to drink or cook with that water.

As a side note, the guy who first figured out what was going on
was indeed another GTE Labs employee, who ran a sample of his
tap water through a Mass Spec Gas Cromatograph anaysis machine (which
was what he did there at the labs) just as a lark. "Hmm, let's
see what's in this, just for fun."

Holy Sh%t.

Lots of chlorinated solvents, like TCE and Benzine.

And then the shouting began.

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

"jim rozen" wrote in message
...
In article , Harold and Susan Vordos says...

I often encountered small contacts that were silver/cadmium. I have no
clue why the cadmium, but it was always a surprise to find the yield
lower
than expected, thanks to the cad content.

Apparently breaker contacts have a tough job to do. They have to
resist oxidation to some large degree, but there is always some
surface oxide present to interfere with the making of the contact
when the breaker closes. The cadmium, having a relatively high
vapor pressure, does vaporize to some degree every time the
contact opens, and leaves a surface that is favorable to re-closing
the breaker.

The man I knew was a technician who was responsible for formulating
different kinds of sintered contacts out of different materials,
to research the idea of getting the Cad out of the product. At the
time GTE was well aware that it was not the best material to have
in their products, and wanted to be one step ahead of any regulation
about the issue.

I think by the time I met him (this was about '81 or so) they had
already decided on tungsten as a likely replacement. I always
though it was very ironic that this man was toiling away quietly
doing work that would benefit the public, and the environment as well,
greatly. Yet each night he would bring home two one-gallon jugs
of water from the lab (we received our water from the metropolitian
district commission) because his own public water supply for his
town (woburn, mass) had been badly polluted by W. R. Grace, and he
did not want to drink or cook with that water.

As a side note, the guy who first figured out what was going on
was indeed another GTE Labs employee, who ran a sample of his
tap water through a Mass Spec Gas Cromatograph anaysis machine (which
was what he did there at the labs) just as a lark. "Hmm, let's
see what's in this, just for fun."

Holy Sh%t.

Lots of chlorinated solvents, like TCE and Benzine.

And then the shouting began.

Jim

Interesting. Reminds me of a product I used to make for Univac, that
required cadmium plating with an iridite finish. Zinc was substituted for
the cad almost immediately. This was back in the 70's, so the movement away
from cadmium use was already in motion. Almost everything that got plated
was done with cad those days----at least in the missile facility. I
became well acquainted with its use and appearance.

Harold