Analyzing the Impact of a Falling Chain on a Round Sling in Marine Environments

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In summary, the falling chain will apply a force to the round sling, but it is not certain how much force will be applied. The sling is designed to resist this force.
  • #1
BasileDiver
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Hello everyone!

I am a commercial diver working in the Northsea. I happened to be very curious but unfortunately I forgot bits and pieces from my formal education and that stops me from answering my question.
I don’t think that this question will be a big problem for you and that is the reason I joined the forum.

I have two chains hanging from a ship. The plan is to secure one to the other and then cut the first one and then recover it. We are planing to secure the first chain with a 5m round sling to the second chain.
My question is: What will be the force applied by the falling chain to my round sling, and will it resist to it.

mass of the chain: 13 000kg.
Fluid surrounding the chain: sea water.
length of the round sling: 5m
Drag Coefficient of the chain: unknown.
Distance between the two chains: they are so close that we can consider that the fall will be vertical all the way.

Any idea?
 
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  • #2
Welcome to PF.
I assume the two chains are next to each other attached to the ship above the water line.
We need more information.
1. What height above the water line are they attached to the ship ?
2. What are the lengths of the chains ?
3. How far down each individual chain will you attach the sling ?
4. Is the mass of the chain: 13 000 kg each, or is that total of two.
 
  • #3
The chains are next to each other yes, almost touching. Everything is happening underwater. To put it like that: the saw is underwater so the cut is underwater as well.

We don’t have the exact length of the chain, but the scale on the winch measured around 13 tonnes from the cutting point.

Each attachement points will be at the same depth. The fall should not exceed the length of the sling (if it doesn’t break). The sling will be attached on the eye just under the cut. The other end should be attached on the other chain at the same depth.

13000kg is the mass of the chain that will be cut, from the cutting point.

Does this help you?
 
  • #4
BasileDiver said:
Each attachement points will be at the same depth. The fall should not exceed the length of the sling (if it doesn’t break). The sling will be attached on the eye just under the cut. The other end should be attached on the other chain at the same depth.
If you attach the sling to the top link of the chain to remain, and to half a sling below on the chain to be cut, the length of chain will fall for only one link maximum, with the upper few links of the cut chain inverting. Is that possible to arrange?

Does a "5m round sling" have a total circumference of 10 m if laid out in a circle ?
 
  • #5
BasileDiver said:
Hello everyone!
...
We are planing to secure the first chain with a 5m round sling to the second chain...
Welcome! :cool:

Since the sling seems to be the weakest link in this situation, resisting the yank of the second falling chain (as far as I can understand your description), how much can you tell us about it?

Do you know some specifications for that particular sling, such as load bearing material, load capacity, safety factor, number of strands, type of wrap (if any), minimum allowed bending, certification, etc.?
 
  • #6
BasileDiver said:
they are so close that we can consider that the fall will be vertical all the way.
I am not so sure that can be considered absolutely factual.
Length of chain is important.
As well as the viscous drag upon chain links ( which would or could be estimated somehow ).

Once the cut is made, the whole dropping chain does not fall immediately as one complete unit.
The first top link falls, then the first and the second, then the first second and third and so on as the support for each link farther down is removed. I can imagine some of these links will rotate with respect to one another due to the different velocities of fall of each link.
Depending on the length of the chain, the top link could be arrested from falling by the sling before the last bottom link in the chain has even begun to fall, or even ones farther up from the bottom link.
 
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1. Will my round sling break if I exceed the weight limit?

Yes, if you exceed the weight limit of your round sling, it is highly likely that it will break. It is important to always check the weight limit and never exceed it to ensure the safety and longevity of your round sling.

2. Can a round sling break from wear and tear?

Yes, like any other equipment, round slings can break from wear and tear over time. It is important to regularly inspect your round sling for any signs of damage or wear and replace it if necessary.

3. How often should I replace my round sling?

The frequency of replacement for your round sling will depend on several factors such as usage, weight limit, and wear and tear. It is recommended to follow the manufacturer's guidelines for replacement or to replace it if there are any signs of damage or wear.

4. Can a round sling break from improper use?

Yes, using a round sling improperly can increase the risk of it breaking. It is important to follow proper lifting techniques and always use the appropriate type and size of round sling for the load being lifted.

5. What should I do if my round sling breaks?

If your round sling breaks, immediately stop using it and replace it with a new one. It is also important to inspect the load being lifted for any damage and to ensure the safety of those around you.

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