[R-390] Grounding and CAD Welding

[Tisha Hayes]

I was first introduced to CAD welding as a means of attaching a cathodic
protection lead to a pipeline. Our corrosion techs ran around everywhere
with a shovel a CADWELD kit and a half-cell.

Moving more into the comms side of the oil world we were cadwelding as a
cadweld is not considered a connection. It is a permanent means of attaching
two pieces of metal and does not have the same potential to cause an arc due
to an electrical fault.

Of course the act of creating a cadweld creates plenty of fireworks and can
scare the hell out of you the first time if you have never seen it done
before.

At least in the south, most of the electric utilities I work with (Southern
Co and TVA) prefer a cadweld connection in their facilities as it does not
need to be checked for corrosion annually.

If you are planning on cadwelding anything I suggest the use of the "one
shot" cadweld kits. They are good for making a connection between a round
conductor and the top of a ground rod. It gets E X P E N S I V E to buy all
of the molds and forms to do every different type of cadweld connection.
Also the molds have a lifetime limited by how many times they are used and
how what environment they are stored in (it looks like a pair of graphite
blocks with a set of handles and a latch). They hate getting left on a damp
floor and I have had molds crack in half due to the moisture content.

One of our warehouse guys decided to "clean up" one day and saw all of these
nasty looking black, scorched things on a shelf. Must have asked someone who
had no clue and decided to throw them out. When I found out a few weeks
later I just threw my hands up in the air and turned around and walked away.
I was not about to fill out a requisition for $2000 more in molds.

If you use a compression type attachment (copper to copper or even copper to
aluminum) use the anti-corrosive paste. It will keep you from creating a
diode connection that can make your ground system turn into a giant crystal
radio receiver.

-- 
Ms. Tisha Hayes