Shackles working load limit

[sam62]

Can someoone help me with this problem?

I am trying to calculate shackles' working load limits for 4 lifting chains. How many chains are to be considered in the caculation to allow a good safety margin?

Thank you,

Sam62

 

[Ussuri]

The working load limit for a shackle is published by the manufacturer, Crosby, Van Beest etc. The factor of safety on the shackle is dependent on the type of shackle you are using but typically is 4.5:1 to 6:1, and is also given by the manufacturer. So a 25 tonne shackle has a WLL of 25 tonnes and a minimum breaking load of 112.5 - 150 tonnes.

Now, if you actually mean you want to size the shackle then there are a number of different approaches. First you need to calculate the loads in each of the legs of your slings. This is dependent on lifted object COG, object weight, sling lengths and sling angles. You also need to consider any dynamic effects.

Some people assume that one of the four sling legs is slack and only three of the legs carry any load. Others prefer to distribute the load over all four legs and then skew the load with a load factor to take account of the manufacturing tolerance on lengths of the slings.

Once you know the maximum static and dynamic load in the slings/shackles you can then size the components accordingly.

The factors of safety you adopt depend on which code you are designing the lift rigging to. That will be dependent on country, industry, best practice where you are.

 

[ishvaaag]

http://www.elephantlifting.co.za/pdf/products/welded_link_steel_chain.pdf

http://www.usmra.com/repository/category/chains_ropes_and_slings/Safetybulletin-chainsafety.pdf

http://www.scc-chain.com/PDF/Cat_pg_50.pdf

http://www.thecrosbygroup.com/html/en-US/pdf/pgs/244_245.pdf

http://www.ohiobwc.com/downloads/blankpdf/OAC4123-1-3-08.pdf

this last has info of capacity of a number of slings at an angle

Hope some of this helps. Since I didn't search this one through google, give it a try for more info.

 

[sam62]

Thanks Ussuri and ishvaaag. That was very helpful.