After final heat treatment slings with accessories shall be tested as an assembly, multi- leg chain slings shall be tested in sections. Individual sections of the chain slings shall be subjected to 2.0 times the load to which the section will be subjected when the assembly is subjected to its working load limit in accordance with the plan.
Factors For Working load limit
PL1
PL2
PL3
1
1.4
2.1
Proof load (2xWLL)
2
2.8
4.2
Lifting capacity of sling / working load limit (MT)
Rating
Single Branch slings
Single branch slings shall have a working load limit equal to that of the Chain used in their construction
Multi Branch slings
Multi branch slings shall be rated at a uniform working load limit for an angle between branches of 90o-120o(45o- 60oto the vertical) or additionally a ta uniform working load limit for any angle between branches of 90o-120o(45o- 60oto the vertical ).
Uniform Load Method
Double branch slings
For all angles between branches from 0??- 90?? (0??- 45?? to the vertical) WLL = 1.4 x WLL of a single branch made from similar chain. When additionally marked for angles between branches of 90??- 120?? (45??- 60?? to the vertical) WLL = 1 x WLL of single branch made from similar chain.
Three and four branch slings
For all angles between branches from 0??- 90?? (0??- 45?? to the vertical) WLL = 2.1 x WLL of a single branch made from similar chain. When additionally marked for angles between branches of 90??- 120?? (45??- 60?? to the vertical) WLL = 1.5 x WLL of single branch made from similar chain.
Various Types of Slings for Different Requirement
How lifting angles reduce Working Load Limits? Varying lifting angles
Percentages shown are of the maximum Working Load Limit of chain
Dos
Select correct size of sling for the load, taking into account the included angle & possibility of unequal loading in case of multi- leg slings.
Ensure that chain slings are not twisted.
Ensure the load is fully supported in the bowl of the hook, not on tip.
Avoid snatch or sudden loads.
Get your slings inspected by competent person at regular intervals.
Keep register for all slings in use.
Dont???s
Leave slings on the floor when not in use. Hang them on hook.
Use sling over sharp corners without protective padding
Trap the sling under a load.
Use slings which are torn, bent, corroded, locked, stretched or damaged.
Knot a chain.
Heat treat grade 80 slings. This is unnecessary & could be dangerous.
Effect of Temp. on chain slings
Slings used at elevated temperatures
Sometimes Grade 80 slings may have to be used in conditions where the chain is subjected to higher temperature. The table below gives a general guideline of reduction in working load limit at elevated temperature. We do not recommend the use of chain 0 slings above 400 C.
