Understanding Chain Slings: Why Do Only 3 of 4 Chain Legs Take the Load?

5 comments

by  on July 16, 2015

Randy, an Instrument Technician in the energy industry and recent safety webinar attendee, asks:CM Rigging Quad Sling

“Why do only 3 of 4 chain sling legs take the load?”

Peter Cooke, Columbus McKinnon Training Manager and Safety Webinar Presenter, answers:

When using a chain to build a sling, tolerances for chain can make the legs slightly longer or shorter than one another. Because of this, the National Association of Chain Manufacturers (NACM) agreed to only count 3 of the 4 legs of a quad sling to be rated the same. When you first lift the load off the ground the legs that are under tension will stay under tension, so it is important for the rigger to visually see how many legs are loaded before lifting the load off the ground.

To do this, tension up the legs, but do not let the load leave the ground. Safely approach the sling being sure to stay out of the path of tension. You can then quickly check the legs by shacking them slightly. Although you may find all four legs are taking the load, only three are used for calculating the max working load limit of the sling.

It is important to always check the manufacturer’s load charts and safety information prior to making any lift. You must be qualified to lift the load you are rigging.

Want to learn more? View our Safety Webinar on How to Size Your Chain Slings.

{ 5 comments… read them below or add one }

Gisela Clark Gisela Clark August 24, 2015 at 1:03 pm

Hello Afzaal,
Sorry for the delay. I have spoken to our training manager, Peter Cooke, and here are his comments:

“ASME 30.9 is based off the NACM (National Association of Chain Manufacturers) which bases 3 of the 4 legs of the sling taking the load. I do not have the EN standard but it could be more conservative, taking only 2 of the 4 legs. You did not specify Grade 80 or Grade 100. Please send me the load charts for the EN standard and I can figure it out. You can send them to cmcolive@cmworks.com. Thank you! Peter”

Dyson August 8, 2015 at 6:11 am

Ensure that alloy steel chain slings not included in these tables are used only in accordance with the manufacturer’s recommendations. Do not use a component unless it is the proper shape and size to ensure that it is properly seated in the hook or lifting device.

Afzaal August 2, 2015 at 8:59 am

Dear Gisela,
Can you help me explain why there is such a big difference between ASME 30.9, for instance with a 5/8inch (16mm) 60 degrees with horizontal is 14 Tons (2000 lbs) and EN 13414-1, 16 mm, 4 leg sling, 30 degrees with vertical (=60degrees with horizontal) is 6.3 tonnes (7 T)?

“tolerances for chain can make the legs slightly longer or shorter than one another” how it come to a conclusion that we are going to use three legs of a 4 leg Chain sling? there can be 2 slings or may be even 1?

Afzaal

Gisela Clark Gisela Clark July 20, 2015 at 9:35 am

Hello Kwame,
Per Peter Cooke, what we have shared is a conservative approach to rigging.
Chain sling charts will show WLL or 3 legs for quad synthetic. Wire rope charts will use all 4 legs for WLL.
Please let us know if you have any further questions.
Thank you!
Gisela

kwame Murphy July 18, 2015 at 12:00 pm

In multi sling we calculate only two, i don’t know if the formula bis change.

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