Hoists attached to another hoist to rotate load

[Isaac G.]

I wanted to get a quick sanity check on this one.

I have a load that needs to be rotated. The plan is to use two correctly rated hoists attached to it to lift it off the ground in one orientation, rotate it in air, then set it down in the other orientation. Nothing unusual here.

Can I attach these hoists, to another hoist? The setup would be; big overhead crane to a master link, master link to two portable air hoists, each connected to the load. All components would be under their WLL.

My thought is,
- the overhead crane doesn't care what's on its hook, doesn't matter if it is hoists, or rocks. The load would be about 25% of WLL, so a little more with acceleration when lifting the object, but no more than the hoist would see when it would accelerate the item if it were lifting it (assuming same speed/acceleration of hoists).
- the smaller air hoists don't care if they are attached to a hook or a beam, as long as it is rated for their load, everything is fine.

Is there any codes/requirements that would allow or disallow this?

Terrible drawing included below, blue are the air hoists, red is load, overhead crane is overhead crane.

Thanks In Advance!

 

[SWComposites]

well, among other things, you need a stable, more than two point, connection; as it is the block can rotate about a line connecting the two hoist attachments.

hopefully there is nobody and nothing important underneath this equipment.

aren't there specialty lifting companies for this type of thing?

 

[CWB1]

Sure. Rollover slings/attachments normally hang from a spreader bar, which hang from the crane.

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[LittleInch]

CofG will always be right under the hook.

What is the sequence of the lift? The drawings show the connecting points ,moving ??

Suggest you draw it better.....