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Crane drops vessel into sea.
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Previously:
https://www.homemadetools.net/forum/...951#post187196
https://www.homemadetools.net/forum/...114#post180236
https://www.homemadetools.net/forum/...901#post156534
https://www.homemadetools.net/forum/...587#post159055
https://www.homemadetools.net/forum/...259#post141967
All too often riggers either miscalculate or don't have the proper sling lengths or capacities for the lift they are tasked with doing. The longer the slings are and the closer to vertical they can be used the lower the stresses each sling will be under during the lift. 2 slings at 90° to a load of 1000 lbs. will each have half the load or 500 lbs but, at 60° each will have 577 lbs of stress. At a 45° angle both slings will have a load of 707 lbs. and at an extreme angle of 30° each sling will have double the loading stresses compared to the vertical loading angle even though the actual weight of the lift remained the same. Whenever possible we always tried to keep our sling angles between 75 and 85°s because the additional loading stresses in any of the slings was negligible. Baring that if there simply was no possibility of using long slings a spreader bar was always the weapon of choice
Attachment 43746
Yup. Sounds plausible. Lets make the assumption that the lifting lugs are placed roughly square on the deck of that boat. Looking from the side those slings look roughly 45 degrees. But if you work out the angles in 3D, what looks like 45 degrees from the side is actually about 35 degrees with respect to the plane of the rope. Then there's a whole ton of dynamic loads that they almost certainly didn't take into account with that thing sloshing all over the place. And they probably overloaded one of those slings like crazy when they impacted the deck of the crane vessel. It's hard to tell from the video, but I don't see any softeners on that hook either. And what are they in the middle of a hurricane? Ever lift I've ever been on has been shut down if there's more than a stiff breeze.Quote:
Originally Posted by Frank S
So a comedy of errors and incompetence.
Right U are Frank. That's the first thing I noticed as well, I just didn't have all the specifics along with pics.
Another thing I noticed it looked like only 2 slings were used for the lift, Maybe I'm assuming too much here but to me logic would tell me if a small cargo craft such as that one had been designed to be hauled from the sea via crane, it would most likely have had 4 lifting lugs for hoisting it out of the water, not 2. All of the work and crew barges I had ever been on or worked around, all had a minimum of 4 lifting lugs. It is very difficult to guarantee a flat lift of anything even if the weight is perfectly distributed with only 2 lifting points
