Rigging safety help, what's wrong?

[lazarus1337]

Morning all,
Just looking for some advice on the setup of this rig. An undergrad is setting this up and knows just enough to be dangerous. Looking for some sound feedback on the safety implications as it doesn't look right to me to bring up to management.

Firstly, the truss is angled in a v-shape on a sloped roof, does that pose any additional risk? I would assume it would be safer to hang them perpendicular to the slope to have equal tension on the points.
I also noticed the slings have no choke in the basket which also seems unconventional.
Supposing he loaded these up with a few hundred lbs each do the span of the chain hoists appear correct in distance without doing load calculations?
Lastly, the hoists are at angles to the points which also seems problematic to me.

Thanks in advance.

 

[RonaldBeal]

The short answer: You need a qualified rigger to plan and supervise that install. There are real world life/safety issues that can arise from DIY rigging.
The slightly longer answer... You will need to consult the instructions from the truss manufacture, and a building structural engineer. With out knowing allowable roof loads, no one can make a determination from the pictures you provided as to if your structure is safe to load on the beams in the fashion shown.
Without knowing the final truss loads, and the mfg specs for the truss, no one can determine if the amount of spanset toe is acceptable. (They do appear to be slung around the truss in a manner that many manufactures do not endorse, but again, with out the manufactures specs, we can not know that.)

Are the hoists built for overhead suspension? Again, not enough information, but I suspect not.

The "V" shape is of little concern (but again without knowing the roof loading specs it could be a huge concern)

The reality is that someone could hang hundreds of pounds of gear on this, and get away with it, BUT, that is just a "normalization of deviance" and horrible practice.
Doing something wrong a hundred times does not guarantee that the 101st time won't lead to a catastrophic failure.

 

[lazarus1337]

The short answer: You need a qualified rigger to plan and supervise that install. There are real world life/safety issues that can arise from DIY rigging.
The slightly longer answer... You will need to consult the instructions from the truss manufacture, and a building structural engineer. With out knowing allowable roof loads, no one can make a determination from the pictures you provided as to if your structure is safe to load on the beams in the fashion shown.
Without knowing the final truss loads, and the mfg specs for the truss, no one can determine if the amount of spanset toe is acceptable. (They do appear to be slung around the truss in a manner that many manufactures do not endorse, but again, with out the manufactures specs, we can not know that.)

Are the hoists built for overhead suspension? Again, not enough information, but I suspect not.

The "V" shape is of little concern (but again without knowing the roof loading specs it could be a huge concern)

The reality is that someone could hang hundreds of pounds of gear on this, and get away with it, BUT, that is just a "normalization of deviance" and horrible practice.
Doing something wrong a hundred times does not guarantee that the 101st time won't lead to a catastrophic failure.

Thank you this is what I have been trying to tell them.

 

[Van]

It's hard to see if those are level, lens and angles might be throwing that off. there are couple thing that stand out to me but the most obvious is the placement of that House Right sling. it should be directly below the hoist. I can see that it appear a bit far in so maybe they thought they could more distance that way but I'd change the angle by moving the span-set or the pick point. Beyond that I don't think anyone is going to give you better advice than "Have a real rigger look at it. There should NEVER be guessing in Rigging."

 

[StradivariusBone]

The hoists look very similar to Pro-X chain hoists. We have a few of those and they're decent little 1 ton manual hoists. That said, I wholeheartedly agree with everything said. It could be fine, it could fail as soon as it's loaded. Depending on where you're located, you might find some local help through CB, but I'd push to have another set of eyes on it if I were in your position.

 

[brucek]

I'll inject that the roof trusses are often ONLY rated for a compression load from the top, not a tension load pulling down from the bottom member

 

[TimMc]

I'll inject that the roof trusses are often ONLY rated for a compression load from the top, not a tension load pulling down from the bottom member

Yep, and it's why we have to order new engineering studies when superior tension loading is to be applied. A room I work currently took 24 years to get engineering sign off such a load.

 

[Malabaristo]

A room I work currently took 24 years to get engineering sign off such a load.

I'm now picturing someone signing off on this during their retirement party after going back and forth on it for practically their entire career.

 

[StradivariusBone]

A society grows great when old men hang truss whose lights they know they shall never focus.

 

[TimMc]

I'm now picturing someone signing off on this during their retirement party after going back and forth on it for practically their entire career.

Yeah, I wanted to ask what part of physics had changed because there had been no change to the structure over the years. I suspect what changed was the amount of risk aversion, whose, I do not know.

That aspect of the production space is above my battle station.

 

[TimMc]

A society grows great when old men hang truss whose lights they know they shall never focus.

Happens to me. I rig, and I'm a Noizeboi/HummHead by craft. I hang truss... and... focus? What, do I look like a lighting guy?