I just finished replacing the top level guy wires on my 33 y.o. 127 ft Rohn 25.
I was nervous because some of the 3/16 EHS guy cable had become very rusty, and
the outer strands appeared to be heavily pitted, to the point that I was
crossing my fingers at every significant wind storm.
Following the replacement, I examined the old guy wire; using a set of
bolt-cutters, I cut through it at several points where the cable appeared to be
in the worst shape. I was amazed at how good a condition that cable still is.
The rust appears to be almost entirely at the surface with all seven of the
strands of EHS still mostly sound steel. The inner strand still has the
majority of its galvanising intact. To make sure I wasn't smearing sound metal
over deeply rusted ends at the cut, I ground away at several of the ends using
a fine-grit emery wheel, and still found each strand to be almost entirely
sound other than a thin layer of surface rust. I suspect those rusty cables
would have lasted for years to come.
I still plan to replace the rest of the guy wires when good weather returns,
since once the protective coat of zinc is gone, the invasion of rust will only
accelerate, and if I waited till the cables did become dangerously rusty, I
might no longer be physically able to climb (I'm already 72 now).
Something else that amazes me is how non-uniform the rusting process is. From
the ground, the top two of the four sets of guys looked to be heavily rusted,
but the lower two hardly showed any deterioration at all. When I climbed the
tower the first time on my initial inspection tour, it appeared that all four
sets of guys were still in fairly good condition where they are attached to the
tower. But I had to lower one of the bottom guy wires because of a careless
goof-up when I let the hoisting rope that was pulling up one of the replacement
guys get hopelessly tangled in one of the bottom guys. Luckily, that also
happened to be the guy wire having a broken insulator for several years, so I
temporarily guyed at that point, dropped the guy cable, untangled the rope and
replaced the damaged insulator. Lo and behold, that guy, which appeared in very
good condition at the ground end and in pretty good condition at the top, was
just as badly rusted in the mid-section as were the top two cables that had me
worried. I would never have guessed that cable to be in such poor condition had
I not lowered it, since the rust wasn't visible from the ground, even using
binoculars. So now, all three of the remaining sets of guys are slated for
replacement as soon as I can do it.
When I erected the tower in 1981, someone at Rohn told me its life expectancy
should be about 40 years. It has seven years to go, but I believe by replacing
the guys and perhaps painting the tower, it should last for many more years,
and probably out-last me. It would probably be in much better shape than it is,
if it weren't for the acid rain, particularly with a coal-burning power plant
about 15 miles from here spewing out corrosive sulphur compounds for the past 5
or 6 decades. A friend of mine put up a similar tower on the other side of town
about the same time as I put up mine, and his hardly shows any signs of rust.
Don k4kyv
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