[TowerTalk] Exothermic Welding?

[Eric Gustafson]

Hi Doc,

Exothermic reaction (or Cadweld) welding is definitely the
superior way to make the connection.  Particularly if there are
many connections to make.

If the connections in question will untimately be located below
grade and be coverd with earth, clamped connections are
inappropriate for dissimilar materials (steel ground rod to
copper conductor, etc.).  If the subgrade connections will be
copper conductor to copper conductor, there is a relatively newly
qualified clamp type connection (made by Burndy Inc. and possibly
others) that can be used.  But this connection requires extremely
clean conductors and a hydraulic crimper to generate the pressure
required to guarantee the desired connection quality.  The crimp
tool costs between $300 (hand pump) and $2500 compressor
operated).  I considered using these (before deciding on Cadweld)
only because the local distributor offered to lend me the tool
at no cost.

Both of the above methods require that you get some component
that matches _exactly_ the size and shape of the items to be
bonded.  This increases the possibility of additional costs due
to mistakes in estimation of the connection requirements.

If there are relatively few connections to make, there is a third
alternative which you may want to consider.  If done properly, a
brazed connection is as good as an exothermic reaction welded
one.  All that is required is a brazed connection that has
approximately the same solid bullk as the Cadwelded connection
would have had.  So, if you can do brazing (its a lot like
soldering - but hotter), or if you have a friend who can, you can
make perfectly adequate connections between randomly sized
objects fairly cheaply.  More time required, but far less
planning and a lot cheaper.

73, Eric  N7CL




>From: "Richard Spindler" <spindoc@digital.net>
>Date: Sun, 24 Oct 1999 08:50:24 -0400
>
>I am getting ready to install some ground rods for the tower.
>
>The PolyPhaser literature and, I believe, the NFPA literature
>talks about welding the ground wire to the rods with "exothermic
>welding."
>
>It sounds a little like witchcraft starting with some aluminum
>oxide powder and copper powder and an ignition powder with a
>form to put it all in.
>
>Anybody acquainted with exothermic welding?
>
>Doc, N9AM

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