My 127' Rohn 25G tower has now been up for 29 years. I put it up myself,
single-handedly. It has 4 sets of guys, each using 3/16EHS guy cable, broken up
every 18' with strain insulators. I live in middle TN, so we are not subject to
salt spray, but we have had some pollution from a near-by coal burning power
plant. They claim to have cleaned up their sulphur dioxide emissions.
I have noticed that some sections of the guy cables are completely brown from
rust, while others appear only partially rusted and some still show few signs
of rust. The rusting seems to be completely random, although the sides of the
wires facing southwest, towards the prevailing precipitation seem to be worse.
The tower itself is in a similar rusty condition.
I have not climbed the tower for several years, so my observations are all made
from the ground. I am open to suggestions to what would be a good indicator
that it is time to replace the guy wires with new cable. I believe the rust is
still mostly on the surface, but I wouldn't want a cable to fail unexpectedly
because it has rusted through. I haven't tried scraping any of the rusted
spots to see how deeply the rust has penetrated before reaching bright metal.
I feel it would be a waste of time and money to replace the rusty guy wires on
a rusty tower, if the original guy wires are still mechanically sound, and I
don't have the physical stamina that I had 29 years ago, although I think I
could still do the job but at a slower pace.
I recall reading a few years ago from Rohn that corrosion of the u-bolt cable
clamps should not be a cause for concern, that even when they appear fully
rusted there is still some active galvanising protection, but they said nothing
about the guy wires themselves. One set of guys uses Guy-Grip pre-forms at the
strain insulators, but the rest use cable clamps.
I have seen severely rusted guy wires in which the strands appeared to actually
contain small cracks. I would be leery to even climb such a tower. Mine don't
appear to be in that condition yet.
Don k4kyv
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