Thanks to all who responded to my question regarding the use of the
exothermic process to bond radials. I got many requests to post a summary so
one is enclosed.
I would like to add some comments that may be valuable in helping others to
understand the process. I am still learning myself.
Webster's New Collegiate Dictionary defines exothermic to
mean,"characterized by or formed with evolution of heat."
Cadweld is the patented name for this process and ERICO at 1-800-842-7437,
is the parent company. I visited their web page and found the following
description.
"An exothermic connection is actually a molecular bond formed between 2
metals such as copper and steel. Copper oxide and aluminum are combined and
ignited. The result is an exothermic reaction that produces molten copper and
aluminum oxide slag. The molten copper melts the objects being connected
together forming the molecular bond. This bond will not loosen overtime or
deteriorate with age. The connection's current carrying capability is to that
which it is being connected. In other words, there is no increase in
resistance in an exothermically welded connection as there is in most pressure
connections."
I called and ordered a catalog. Unfortunately there were no engineers
available to answer questions. Tomorrow I am going to visit a local
distributer.
Thanks again to all,
Joe AA6WG
Joe,
I am interested in your comment on exothermic bonding and would be grateful
for a copy of any replies you get.
The only comment I can make as a contribution is that the specifications
state that all underground bonding should be hard soldered, ie. silver
solder. I doubt if this is what you are referring to but would be
interested in what it actuall means.
Best Regards
Bob Parkes
4S7RPG
Joe,
I would like to have used exothermic welding on my tower grounding system.
A friend, who is a telecom engineer, explained the process, for which the
materials are available locally and in most cities.
In the end, I settled for silver soldering, which can be done with a $30
kit available from Burnzomatic. It uses Map Gas and Oxygen cylinders (the
size you can hold in your hand) and a small torch. Works very well.
Brad KV5V
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Joe, I haven't used them for radials (wire too small for molds) but use them
alot for ground wires (big wire). The common name is Cadweld and you can
get the shot cartridges and mold blocks at most good electrical supply
houses. If you know an electrical contractor you can maybe borrow his mold
blocks. Cadweld makes one-shot kits for ground rods that you might be able
to adapt to your needs. Their stock numbers are GR1-161X, X represents the
specific application size. There is also a GT1-161X for attaching multiple
wires to a ground rod.
Hope this helps.
Gary K7FR
At 10:46 PM 2/11/97 -0800, you wrote:
>Has anyone used the "exothermic" process to bond their radial system
together?
>It is prefered over the usual soldered bond because solder will melt with the
>first lightning strike. Is there anyone who is familar with the process and
>can describe the tools and materials that are used. Also does anyone know of
a
>good supplier or 2 who sells the tools and materials?
>
>Thanks,
>Joe AA6WG
>
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>FAQ on WWW: http://www.contesting.com/topband.html
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>
Hello,
I read your request for exothermic bonding information. Rest assured, that
what you have heard about it protecting the radial system against lightning
damage is an old radio engineering tale. I have seen exothermic bonds
completely shattered due to lightning hits. In fact, I have seen solder
fair better than exothermic in commercial AM broadcast installations because
the ground, being an excellent heat sink, does not allow the solder to flow
or stay molten long enough to do so. Once an exothermic bond shatters, its
finished and can not return to a semblance of working order. Personally, I
hope you are not serious with this posting. If you have a direct hit that
carries enough amperage (10^8) to melt solder bonds, you have some much more
serious problems in your shack to worry about than the radial system buried
in your yard.
Very 73, Rob WS7U
PS. Last summer lightning hit tower number 2 on KID and the radial systems
melted the soil around them to a dirty rough glass consistancy. It also
welded every rack cabinet closed inside the transmitter building.
Joe;
That process is available under the brand name "Cadweld"; the parent
company is "ERICO", and you can find some info at
http://www.therfc.com/cadweld.htm (Info on cadweld from distributor)
http://www.erico.com/ (Info from parent company of Cadweld)
I have used Cadwelding in several projects and there is nothing better!
But it is not cheap.
73,
Pete, N5TP
Joe AA6WG
The reason is _not_ that a soldered connection will melt due to heat
generated during a stroke. It because the welded connections are the only
ones that can survive reliably underground for long periods due to
dissimilar metal reactions. Above ground, clamped or soldered connections
are fine as long as the connection is a good one. Not much heat is really
involved unless the connection has deteriorated so that there is a high
connection resistance.
Actually, there is now a pressure bonding system (made by Burndy) that is
claimed to be as good as the welded connections. But I have no experience
with these yet. The crimping tool for it costs about 2500 bux.
It sounds like you really do want to do this correctly. Here is the
address for a source for the exothermic process materials. Contact them
for process info and local distribution sources. If you design your system
to make use of one size conductor (that needs welding due to being below
grade) and one class of connection, you should be able to get away for a
bit over $5 per weld.
ERICO Products Inc. (Lightning Grounding Hardware & Welding Eqpt)
34600 Solon Road
Cleveland (Solon) Ohio 44139
(800)-248-9353
(216)-248-0100
248-0723
Barbara Gaskins
Sales Correspondent
Cadweld Electrical Div.
Samuel B Barnes
Regional Manager
P.O. Box 3225
Newport Beach, CA 92663
It has been a while since I contacted these people. So the names may have
changed. Good luck. If you liked fireworks as a kid, you'll love this
stuff.
73, Eric N7CL
Joe, if exothermic welding is what I recall from 31 years ago, it's what we
used to bond the grounding system at a tropo station in Vietnam. Pretty
good grounds were needed for 80-foot dish antennas on a mountaintop in a
lightning-prone area. Thing is, I recall that we called it cadwelding,
which may be the same as exothermic welding. I work as an electrician, and
the other day there was a discussion about grounding systems in which
someone mentioned cadwelding. It is apparently the bonding method of
choice. It welds the copper conductors together.
You can probably get info and materials from any large electrical supply
house, since they are supplying it to electrical contractors for large
grounding systems. Another source might be your local electric company.
Many electric utilities will sell supplies, and all would certainly have
anything you might need for grounding or bonding. Try contacting their
supply warehouse people.
73
Larry
N9DX
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