I do vaguely recall an older Rohn catalog (if memory serves, it was spiral
bound and thick as a phone book) that showed guy anchor foundations that
did prevent soil contact with the guy anchor. Do any of you have one of
those old catalogs?
Yes, I have a Rohn spiral-bound catelog from the late 1980s. I'm away until
the weekend. Contact me then if you still need this info. The soil placed
on top of the guy foundation is indeed part of the structural spec. Did
Mark mention a reason for the corrosion in those cases?
Back in 1979, we installed 300 ft of Rohn 55 to support a 3-bay commercial
FM antenna. As we were coring holes for the guy anchors, a geo-engineer
from ARCO Gas & Oil stopped by. He informed us that a large gas pipeline
ran directly under the tower site. The gas company placed an electric
current onto the pipe to retard corrosion. But that same current would have
eaten away at the guy anchors in a few short years if a reverse current was
not applied. At the gas company's expense, they installed an anti-galvanic
current circuit along with meters to measure current flow into the guy
anchors.
Before dirt was back-filled into the anchor holes, Rohn suggested (actually
insisted) that all exposed metal must be coated with a tar-like substance
that does not break down over time. My memory has faded over time, but
there was a specific product we used.
Anyone know of a method used today to measure the presence of harmful
current into guy anchors? I could see situations where someone installs a
tower not knowing that a pipeline runs under the land. That's exactly what
happened to us -- even with our due-diligence.
Paul, W9AC
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