Today we took down 60 feet of rohn 25 that was 20' up on a roof. Everything
that could go wrong did.
I planed this out with my friend that is our tower climber/rigger about a week
in advance. We decided to drop the tower all at once rather than piece by
piece. This was to be accomplished by dropping the tower north after
releasing the back leg, and lowering it down using 2 ropes attached to the
top and mid section. The ropes were secured to the back of the 4WD truck
using a D ring.
Here's a diagram of the roof/site.
/ ________________________
/ | |
________ / | |
{R} | / | |
{O} | / | * Guy Anchors * | /|\
{O} | P | | N
{F} | O | |
{ } | W | |
{P} | E | # |
{E} | R | () ### Base |
{A} | L |Chimney |
{K} | I | |
| N | |
^^^^^^^^ E | * |
/ | |
neighbors / |________________________|
building /
/
/
The plan was to drop it north after cutting the south guy, and lower it by
taking the slack off the south ropes. We had tied another rope to the
north-east anchor, and we planed to pull on it to keep it from even comming
close to the NIPSCO Line.
We cut the South guys, and the top guys on all sides, and started to lower it.
At this time, the north-east anchor eye bolt broke, and the tower decided to
fall due West over the NIPSCO Line, and hook the top section over the roof
peak of the neighbors building. The fall was further compounded by the fact
the base plate, was not bolted at all to the roof!
Now the fun began! Luckily the tower hit the other building and did not break
the power line, just rested on it. At this time we assumed the line was
live, and the tower as well. We were able to shut off the power at the pole,
and killed the line. When the tower fell it came to rest on the chimney, so
the base was about 3 feet above the roof, so we could lever it to raise it
over the other building. The problem was, that 4 feet of mast and the top
section was hooked over the roof of the West building.
We had 2 men climb over on the west building and saw the top section off to
free the tower. the 3 of us on the base, pushed down on the base end, using
the chimney as a fulcrum, swung the tower up and over the NIPSCO lines and on
to the roof of the east building.
We were able to take the sections apart, and lower them off the roof safely at
this point.
The Results:
We inspected the roof of both buildings, and got lucky again, no damage to
either building. The NIPSCO line was fine, and we turned it back on.
As for the tower, we have 4 good sections, and 2 bent sections, and the top
was Bent in half!
Mistakes Made:
We assumed the tower base was bolted to the roof, and that the guy anchors
under the tar roof was in good repair. The problem with the eye bolts, which
the turnbuckles bolted to is they were covered up to the middle of the
turnbuckle with roofing tar. After inspecting the eye bolt that broke, it
looks like it sat in water for years and rusted away. I hypothesize the
roofing tar trapped this water in the eyebolt, and if it had been left
uncoated, it would still be like new.
Things we did right:
We went out to the site 3 times before today, and planed out exactly what we
were going to do. Today we had 5 men onsite, instead of the 3 we had planed.
I made sure each one knew exactly how this was going to go down, and most
importunely showed them where the NIPSCO kill switch was.
Well after all this, I am sunburnt, and feel like I am going to puke. I was
lucky today, it could have been much much worse. I am thankfull no one got
hurt, or killed.
I might get some pictures together in the next week of the eye bolt, and the
bent sections. I could not believe how the one section was twisted, and
bent, just looked like a noodle when it fell!
73's and God Bless,
--
Bryan Fields, KB9MCI
____________________
23:33:26 up 2 days, 1:55, 11 users, load average: 1.33, 1.40, 0.71
Oh wearisome condition of humanity!
Born under one law, to another bound.
-- Fulke Greville, Lord Brooke
|