Rigging | By Gisela Clark | Feb 26, 2013
What is the working load limit of a ½ “ – G80 2-legged chain sling when both legs are used in a choke?
The first thing that you want to do is to look at how the choke is rigged or rendered. Working load limits shown on charts or tags for vertical chokes are based on the angle of choke being 120 degrees or greater. If there is less than a 120-degree angle of choke, the choke rating must be reduced further. Once we determine the correct choke rating, we can take into account the angle of loading.
First, you take the choke rating and multiply it by the SIN of the angle x 2 = Rating of a two leg sling used in a choke.
Our charts show that ½” grade 80 chain is good for 9,600 lbs when pulled vertically with a choke hitch of 120 degrees or greater. Let’s assume when this double sling is rigged at a 60-degree angle it has a choke hitch of 120 degrees or greater. Our working load limit for this sling is 9600 lbs x .866 ( sin of 60 degrees) = 8314 lbs x 2 legs = 16628 lbs.
Another way is to take the rating of the sling at a 60-degree angle and reduce it by 20%. Again assuming 120-degree angle of choke, ½” Grade 80 double sling chain is good for 20,800 lbs (at a 60-degree angle) x .8 (20% reduction): rating: 16640 lbs.
Our first example is a little more conservative.
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