I can only tell you what I've done in the past.
I'm not a professional, but I've been climbing for many years and had to
do
so at work as well.
This information is all well and good ... it rings with a bell of
caution ... BUT , how do you know .. ????
First you do a thourough visual inspection of the tower, tower bolts,
guys,
and guy anchors looking for any damage, irregularities (is it straight,
bent, twisted, or dented. How about cross braces no longer attached.), and
*signs* of rust. Rusty bolts, or signs of rust around the bolt holes. I'd
even go so far as to remove at least one bolt from the bottom of each
tower
leg. Is the bolt rusty or is the bolt good but has signs of rust being
deposited on it, particularly as a stain. (pull the top bolt of the pair
and
use a light to inspect the lower bolt in place if possible)
Guy wires may or may not rust from the inside. I've taken down towers
where
the guy wires were completly coated with rust, but proved to be plenty
strong. Be wary of small guy wires. Wire rope showing rust is likely to
be
bad or at least seriously compromised and particularly the smaller
diameter
stuff. It can be tensioned to near it's working strength as a test using a
Loos gage. If it passes back off to the normal 10% of the rated strength.
I *always* use temporary guys on any older tower. Even use extra temporary
guys if there is any doubt.
I shold note that the tensioning of the guy wires doesn't necessiarily
prove
the tower is good. It's only a test of the guys and the atach points.
Remember a tower can have some serious damage and still have sufficient
strength in the vertical plane while having very little in the horizontal
at
spots.
Internal rust may be completely invisible from the outside, hence the
reason
for checking the bolts for signs of rust. It may be stains which are a
warning sign, but not necessiarily and indication the tower is ready to
fail. OTOH if there is loose, granular rust laying on the bolts or visible
at the base of the tower it's time to call a crane in. I'd definately not
climb in that case.
At one time I had an electronic thickness gage that worked on steel and
aluminum. It only needed to be calibrated for the material to be tested.
We
used it on pressure vessels. How well that would have worked on tower
legs,
I don't know.
BUT even after a thourough inspection there is still a fair amount of
intuition involved because as I said above, some serious damage may be
completely invisible and with no outward signs elsewhere. I've put up
and
taken down a lot of towers, but when it comes to older towers I become
very
picky. As I said earlier, I also use temporary guys so even if a guy broke
or a secion buckled it'd not fall far unless it broke off completely.
In this case the climber felt all was well until the tower came down
with him on it .. but now how in the world do you test and determine
all is OK before you climb.?? Or what steps do you use to protect
your self ...
Certainly the professional tower people who partake in this forum
will have a degree of in site for us .. but it needs to be
discussed.!!! We've got guys here with 5-10-20 plus years old towers
http://www.rogerhalstead.com/ham_files/tower9.htm The tower shown is well
over 30 years old and had been up at 3 different locations. It showed no
signs of rust and was climbed regularly. However it was reaching the point
where there were many small irregularities in it. IE it was no longer
straight. Not bad, but not straight either and that was when I decided it
was time to replace it. After it was taken down there were no signs of
rust
damage inside.
....What is the answer??
As a personal opinion, climbing is risky even with the proper equipment.
Climbing old towers can be down right dangerous and I'd not recomend it
for
a casual climber unless they can get some one "in the know" to do a good
apraisal of the tower. Even then there are no gurantees.
Roger (K8RI)
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