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GOOD SLINGING PRACTICE<br />
BASIC RULES ... 4<br />
4.3. SAFE WORKING LOADS - TWO-LEG SLINGS.<br />
The modern method of rating slings is by their working load limit (WLL), which<br />
rates the sling in pure tension (that is, vertical). The safe working load (SWL)includrefers ed angles on sling loads.<br />
to the rigging system being used - that is, sling angles, reeving, number of sling legs,<br />
and the like.<br />
Using our Riggers' Guide, we find for<br />
this system:<br />
1. the SWL = 4500 kg.<br />
2. the WLL of each sling = 3200 kg.<br />
3. the load in each sling leg will be<br />
the actual load x 0.7.<br />
4. the SWL = WLL of ONE sling leg<br />
divided by 0.7.<br />
Note: Older slings will be<br />
rated as SWL for straight lift<br />
or pull. In this case, use the<br />
SWL in your calculations.<br />
As an example:<br />
1. Each leg of a two-leg sling has a WLL of 100 kg.<br />
The included angle between the legs of the sling<br />
is not more than 60°.<br />
<strong>Safe</strong> working load = (100 / 0.58) = 172 kg.<br />
2. Should the included angle between legs be<br />
increased to 120°;<br />
the S.W.L. = (100 / 1) = 100 kg.<br />
3. The load is 100 kg, and the included angle is 30°.<br />
Sling load = 100 kg x 0.52 = 52 kg per leg.<br />
Refer to the chart at right for the effect of<br />
included angles on sling loads<br />
90°<br />
Load<br />
10mm<br />
Chain<br />
Slings<br />
This chart is in the Riggers Guide<br />
EFFECT OF INCLUDED ANGLE<br />
ON SLING LOADS<br />
0.5 t 0.5 t<br />
Load<br />
in<br />
tonnes<br />
30°<br />
0.52<br />
60°<br />
0.58<br />
90°<br />
120°<br />
0.7<br />
1.0<br />
151° 2.0<br />
171° 6.0<br />
1 tonne load
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