In a message dated 4/12/2011 6:13:31 A.M. Pacific Daylight Time,
towertalk-request@contesting.com writes:
> I recently collected several rolls of old guy wire from a local ham
with the
intention of removing the strain insulators to use in my tower installa
tion.
He told me the guy wire had been sitting in his back yard for nearly 30
years and had been used in towers from a broadcasting station (size and
height unknown).
> While expecting to cut through rust to remove the insulators I saw that
the
cable was clean and shiny. The insulators are spaced every 11 feet and the
connection at each insulator is made with a crimped pressed fitting. I
spread the cable strands apart and it was equally clean and shiny inside.
> The cable is hard and inflexible; I can hold out about 1 meter
horizontally
and it won't bend. It is about 4.7mm (3/16" ?) diameter and has 7 strands.
Each strand is between 1.6-1.7mm in diameter.
> I began considering whether the cable could be used as is instead of
removing the insulators and installing hundreds of U-bolts on new cable
(there are dozens of insulators on the rolls).
> I therefore have the following questions:
> 1) What is the lifetime of steel cable used as guy wire? Is there
a
rule of thumb on how often guy wires should be changed? Should old guy wire
be replaced/not used even if it appears to be in good shape?
Interesting question - and I think a new topic.
I understand that when installing a used tower, commercial standard is
to use only new fasteners. I would imagine that the same might be said for
the guys.
I've seen guys and towers that were over 30 years old and the guy
wires were fine. I've also seen some that were marginal.
Commercial tower inspectors use an instrument that measures rust
depth. I don't know what it's called.
2) Same question as above for crimped pressed fittings. Does their
holding strength deteriorate with time?
Probably not. The crimps (typically Nicopress) are usually aluminum or
brass and thus don't rust like steel does. The compression of the pressing
actually fuses the materials together so there's not much of a chance of
them separating or oxidation taking place.
3) Can someone help identify the cable with the description given
above? My guying specs call for 3/16" EHS.
Sounds like EHS to me.
If you're ambitious, you might want to paint the guys with cold
galvanizing paint. Let it soak in and it should give you several more years of
life. In any case, they sound usable.
If you don't have 100% confidence in them, use new guys on the top
level (where most of the forces wind up) and the used ones on the rest.
Cheers,
Steve K7LXC
TOWER TECH
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