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Posted By Mark S B
we have a container lifting frame (Chandelier) with a SWL of 40t. atttached on each corner are 4 x 8t Chains with container hooks at the ends.
my question is this would that give us a SWL of 32t for the lifting frame (4x8t)
or is that a SWL of 8t
thanks for your help
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Posted By Vrick
Hi Mark
If you are using the frame with the chains i.e 4 X 8T, then the SWL is automatically reduced to 32T because the weakest point you have on your lifting equipment is this value; Any weight above this, the risk of the chain breaking is very high.
Should you decide to change the chains and instead use 4 X 10T, you can still use the frame since it is rated SWL 40 T
Please note any weight under the frame is to be taken into consideration.
Thanks
Vrick
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Posted By Flic
Mark, I am not convinced that it is either 8t or 32t, but somewhere between. There are some good scientific reasons for believing this.
First, when you have two chains it is fairly easy to ensure the load is almost equally shared between them. This is also true for three chains, but when you get to four, just like a wobbly table with one leg shorter than the others, the equal distribution of the load is less certain.
Second, the frame takes the chains out at an angle, and for a given load this increases the forces in the chains. Thus it is important to derate the arrangement to take account of this.
Unfortunately I have been unable to run to earth a document that gives you formulae for calculating the SWL of such an arrangement. I suggest you contact the person who does the formal inspections to ask their advice.
Flic
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Posted By Vrick
Mark/Flic
From my experience and understanding, the chains are link to the container frame at the four corners and usually the chains and hooks are perpendicular to the load.
Flic, any SWL for a sling is for a perpendicular lift, yes i agree with you that if there is a change in the angle of lift, then the SWL is automatomatically reduced and thus the manufacturer guidelines and not the examiner advice which must be followed for the SWL at any particular angle of lift.
Yes, if it the load is perpendicular to the chains, then the SWL is 32T. Any deviation from 90 degrees, reduces the SWL.
You must look at the lifting plan which is an essential document.
Thks
Vrick
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Posted By Flic
Vrick
Although you say the load is perpedicular to the chain I think you mean that the line of action of the weight of the load is in the axial direction relative to the chain.
As Mark describes it, this equipment has chains going to the corners of the frame and it follows that it is not possible for the load still to be applied in the axial direction of all four chains.
The angle that the chain is set at, relative to the vertical, will therefore have to be taken into account.
Flic
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Posted By Mark S B
the frame fits onto a 20" container reachstacker spreader unit and is designed to lift 20" containers or tanks. the chains would only be used for straight lifts only.
thanks for your comments keep em coming
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Posted By Vrick
Flic
We are on the same wavelength at least!!!
Any deviation from 90 degrees, the SWL is REDUCED, and that's the most critical issue to determine the use or not of that particular equipment with a maximum load of 32T.
As Mark just confirmed, these are staright lifts,and taking into consideration the safety factor, the SWL of this equipment is 32T
I think Mark can make his own assessment now based on our contribution.
Thanks
Vrick
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Posted By Flic
Aha!
I think I have spotted the fundamental question here:
Are the chains between the crane hook and the spreader (in which case the chains will be at an angle)
or
Are the chains between the spreader and the load? (in which case the chains could be vertical).
I had assumed the former, but on re-reading it is likely to be the latter.
Flic
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Posted By Mark S B
i think i have the answer i expected,thank you
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