SWL, WLL, or MBS, MBL Which one is correct?

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A post shared by Tegnika (@tegnika) on Jun 21, 2019 at 7:27am PDT

Sometimes I don't understand what kind of term SWL, WLL, MBS or MBL. Looks similar, yet in reality which one is correct? 

it can be confusing for us if we do not know the term. Let us see source from Wikipedia :

Safe Working Load (SWL) sometimes stated as the Normal Working Load (NWL) is the maximum safe force that a piece of lifting equipment, lifting device or accessory can exert to lift, suspend, or lower, a given mass without fear of breaking. Usually marked on the equipment by the manufacturer. It is a calculation of the Minimum Breaking Strength (MBS) aka Minimum Breaking Load (MBL) divided by a safety factor, usually ranging from 4 to 6 on lifting equipment. The factor can be as high as 10:1 or 10 to 1, if the equipment has poses a risk to a person's life.

Working Load Limit (WLL), which is the maximum working load designed by the manufacturer. This load represents a force that is much less than that required to make the lifting equipment fail or yield. The WLL is calculated by dividing MBL by a safety factor (SF). An example of this would be a chain that has a MBL of 2000 lbf (8.89 kN) would have a SWL or WLL of 400 lbf (1.78 kN) if a safety factor of 5 (5:1, 5 to 1, or 1/5) is used.

As such:

WLL = MBL / SF

SWL is no longer used to identify the maximum capacity of equipment due to it being too vague and leaving it open for legal issues. The US and European standards switched to The Working Load Limit' standard shortly after.

Wikipedia said that SWL is no longer used to identity the maximum capacity.  the term SWL was changed to rated capacity for cranes, hoist and winches and Working Load Limit (WLL) replace that term which in describing the capacity of items such as hooks, Slings and Shackle.

About 23 years ago, the USA replace the term of SWL to WLL, because of legal impications and the European and ISO standards followed suit a few years later. I think that word Safe in lifting device should be avoided as a term. 

Australian Standard 1418.1 crane, Hoists and Winches details requirement for cranes. it was revised in 2002, and part of this revision included replacing the term "safe working load" with Rated capacity. 

The term SWL was changed to rated capacity which usually used for cranes, hoists, and winches. Working Load Limit (WLL) should replace safe working load (SWL) in describing the capacity of items such as hooks, Sling, Shackle, Spreader Bar, that is for lifting devices below the crane hook as reference AS4991:2004 Lifting devices. 

 When used on a crane, hoist or winch, the rated capacity includes the weight of any attachment. 

How About MBS ?

Minimum Breaking Strength (MBS) should known as Minimum Breaking load was originally used for the manufactures specified maximum load that the item could lift, because WLL is calculated by dividing MBL by a safety factor (SF). 
WLL = MBL/ SF

the safety factor (SF) may be different depends on what purpose of lifting, location lifting, or many others.

Try look at wire rope sling, has safety factor 5. so that the WLL is MBL/ 5 for Wire rope sling.

Thankyou

Source :
https://asseteng.com.au/do-you-know-the-difference-between-swl-wll-mrc-and-when-they-should-be-used/
https://en.wikipedia.org/wiki/Working_load_limit