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Rigging Failure - Hong Kong 16

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If the load was off balance, that would have been obvious when they initiated the lift. Perhaps the hydraulics on the excavator experienced a malfunction during the lift.
 
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Notice the side to side spreader.
The four way, side to side and fore and aft spreader was the mistake on the failed lift.
There is more weight on the forward slings.
The trapezoidal arrangement of the rigging allowed the spreader to move too much away from horizontal.
As the spreader tipped, so did the excavator, until the CG passed the line of the forward slings.
The rigging was probably grossly undersized.
The fastening to the spreader was not secure.
The forward attachments can be seen slipping about 18" to 24".
When the attachments reach the end of their travel, they stop with an impact that triggers the major failures.
They should have listened to Juan.
He's done this before.
He probably snuck out just before the lift started so as to not share any responsibility.

Bill
--------------------
"Why not the best?"
Jimmy Carter
 
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I thought I heard something snap just before it started to shift. Is it possible that something broke, a cable or a shackle?

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without
 
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Obviously the rigging configuration was not stable. As waross points out the problem was the spreader bars and not that the attachments to the crane were below the center of gravity. The spreader spacing was like double the spacing of the hooks on the crane. So when the spreader bars tilted, the crane tilted twice as much. This transfered a lot of the load onto two chains rather than four, which tilted the spreader bars more. The spreader bar arrangement basically flipped the crane over. The crane was still supported by the upper hook while it was upside down until something in the rigging broke.

I don't know why chains would be taboo for lifting, there is nothing tougher against abuse. Everything wears and can break. Probably because there are many grades of chain and it is not easy to tell visually.
 
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Remember the old saying?
"Them as can, do.
Them as can't, teach."
With time that has changed to;
"Them as can, do.
Them as can't, write safety regulations."

Bill
--------------------
"Why not the best?"
Jimmy Carter
 
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@GregLocock. That bit about the turrets of tanks falling off if you turn them upside down is a myth. Trust me on this (but please don't ask how I know).

A.
 
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Most earth moving equipment and other equipment cranes and manlifts use slewing rings or rotation about a vertical axis. Slewing rings can handle substantial moment loads, and have been used to support loads hanging from them. I would expect that you could hold the excavator upside down without risk of the boom falling off. An attempt to use the boom as the lifting point would likely overload the connection to the point of damage, but likely would not pull the boom off the base on the first lift.

Choice of lift points and control of center of gravity is an important part of planning lifts. Factory installed lifting points and a rigging diagram can be provided by most OEM's.

Fred
 
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By far, the heavier part of an excavator is the part on top that rotates on the track carriage. I doubt there would be any problem lifting one from the boom or any other attachments on the top. The million dollar question is if that particular excavator has places to lift above the COG or if they were lifting from the only points available.

I tend to think they were lifting it from the only lifting points available.
 
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It could be the hydraulics of the bucket allowed it to swing forward, changing the centre of gravity by moving it forward.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?
-Dik
 
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ALL US battleships had turret clips which prevent the turret from falling in case of capsizing. The turret clips are arranged around the the electric deck. There are gaps for the buffer and the traverse pinions but other than that they go pretty much all around the turret ring. The Abrams tank has 48 fasteners that hold the turret on.

Excavators are also bolted to the base as shown on the pictures.

climbing excavator

stuck excavator



 
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Turrets on the German ship Bismark were held in by gravity. It did a complete roll underwater after being sunk. It's turrets lie up-side down on the bottom some distance from the main body of the ship which is upright.
 
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As it happens different navies had different ideas. Bis was famous and is the example I remembered, but Hood had clips, as did many American designs.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376
 
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Speaking of construction equipment and such, pretty soon you may no longer need to wear hard hats or steel-toed shoes:

The forklift truck drivers who never leave their desks


John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without
 
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I calculated a fall distance of about 150ft from a fall time of about 3 to 3.5s. Anyone see how deep it was in the links?
 
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I've never seen any reports about the distance of the fall, which is why I posted my calculations on 16 October.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without
 
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Who cares? Looked about 50m alright from the video but so what?

Something happened to make the digger start to dip, but it never looked good from the start of the vido and then just got worst.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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It looks like there was a spreader above. My guess is that there was a shallow angle on the chokers on the spreader due to head height -

stability__equilibrium_slide61_ikft16.jpg
 
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