Today I called the engineers at Preformed Line Products. At the end of my
work-oriented discussion, I said: "Hey, maybe you can
answer another question that has nothing to do with my project. I have heard
that Big Grips on tower guy wires can open up if a
large chunk of melting ice slides down the guy wire and slams into the Grip at
the bottom of the guy... and therefore some kind of
clip is needed to prevent this for towers in icy environments."
The engineer said, "Well, that's almost true." He went on to explain that
some years ago Preformed had received reports of grips
opening up from the field and had done an extensive study in the field and in
the lab. The engineers concluded that a properly
installed Grip could NOT be made to fail in this mode. Here, "properly
installed" means that the individual wires in the Grip must
be wrapped around the guy all the way to the end; i.e., no loose Grip wires
that didn't snap into place tight against the wire. If
the Grip was not snapped into place properly at the very tip, then a piece of
ice could pry open the Grip.
Preformed Line Products now provides two types of clips: an End Sleeve and
an Ear Clamp. The purpose of these clips is not to
keep the wire fingers of the guy grip from opening up when ice hits them -- at
least, not directly. It turns out that these End
Sleeves and Ear Clamps can NOT be installed over the tip of the Big Grip unless
the Big Grip has been properly installed (all the
wire fingers have snapped down against the guy). By requiring the construction
team to use End Sleeves or Ear Clamps, one is just
making sure the Big Grips were snapped into place properly.
This cleared up a tower myth in my mind... and maybe this information will
help someone else, too. (I thought it was an
interesting case of human engineering as well.)
-- Eric K3NA
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