c,
> I just cannot figure out why such an apparatus would so drastically 
> fail, especially after two guys were involved.  But then there were 
> plenty of engineers who went over the Titanic designs.
As Eric mentioned there is a difference between a permanent rig and a 
temporary rig. A permanent rig I am used to calling a house rig. A 
permanent rig is kind of incorporated into the building system. Usually 
it was installed when the building was built. There are lot of different 
configurations.

What I am used to seeing is on the roof to the inside of the parapet 
there will be a rail that runs above the roof and that at intervals will 
be supported on steel posts that go into the roof that I assume are 
anchored to the building structure. You will then have posts that roll 
around on the rail that support outriggers that support the scaffold 
itself. It is usually designed in such a way that you can swing the rig 
out over the parapet, or swing it in and move it around to another 
location on the roof. There will be wires going to the house rig. Should 
be different sorts of safety controls.

Window washers do not maintain these rigs. The rigs are maintained by 
elevator service companies. In order to operate a rig you need to be 
certified by the mechanics that work for the elevator company. That 
process takes like a half hour on the site. So you can easily imagine 
that the window washers might now have much of a clue about the 
condition of the equipment. For those who work on temporary rigs they 
are more apt to be intimate with the system as they assemble and 
maintain their equipment on a regular basis. A temporary rig may also be 
a bit less complicated of a system than a house rig and easier to 
understand by a user.

The reason a house rig would fail is probably not that it was 
particularly poorly engineered to begin with, though it could have been, 
but likely has more to do with if it was stored in a manner to keep it 
intact, or if it was maintained properly. Such things as cutting off 
wires and leaving them dangling the guy from the elevator company may 
feel just fine about that but it does not mean that it is safe. If you 
do not understand the system and you are told by some guy that it is 
safe the tendency is to believe them. Knowledge in this case is life.

Though the building owner may claim no responsibility it also has to do 
with if they were willing to pay for an elevator maintenance company 
that that was not into going the cheap way... at least when a wire is 
cut that could be a safety override tape up the end of it and tie it off 
so that it does not swing around in the air. As I recall, and I can be 
corrected on this, there is not an independent inspection of house rigs 
in the way that there is an inspection of elevators. I believe, if I am 
not incorrect, that the elevator maintenance folks are supposed to look 
at them once a year. A house rig can be forgot to be checked. I tends to 
be up to the building engineer (maintenance) to keep track of these 
maintenance issues. Though the building staff may not directly be 
responsible for the hands-on maintenance they are responsible to make 
sure the inspection schedule is kept up.

Though from Ralph's Xmas Party conversation it sounds like it may have 
been a swing stage (temporary rig).

Later,
][<en

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