Differences Between WLL and SWL
WLL vs SWL
WLL and SWL are abbreviated terms commonly used in the field of engineering. “WLL” stands for “working load limit” while “SWL” stands for “safe working load.” The main differences between safe working load from working load limit is that “SWL” is the older term. Today, SWL is not used anymore because it has been completely replaced by the term WLL. Let us discover the reasons why engineers put an end to using the term “safe working load.”
“Safe working load” is also synonymous with “normal working load.” According to irata.org, “safe working load” is defined as “the breaking load of a component divided by an appropriate factor of safety giving a safe load that could be lifted or carried.” Safe working load is the amount of weight (load) that a lifting device can carry without fear of breaking.
Now, who sets the load capacity for certain lifting equipment? It is the lifting equipment’s manufacturer. The manufacturer recommends the maximum load capacity of his lifting equipment. The lifting equipment or device can be a rope, a line, a crane, hooks, shackles, slings, or any lifting device. To know the safe working load, the lifting equipment’s minimum breaking strength is divided with the safety factor that is constant or assigned to a particular type of equipment. Usually, the safety factor of a particular equipment ranges from 4 to 6. If the equipment poses a risk to a person’s life, the safety factor is raised to 10.
Since the definition of “safe working load” is not very specific and there are legal implications, the USA standards began to stop using this term. A few years after the USA standards began to stop using this term, the European and ISO standards began to follow suit. Later on, both the Americans and Europeans developed a more appropriate term and definition for the maximum load capacity of a particular lifting device. Both parties agreed to the use of the term “working load limit” or WLL.
Based again on the pdf file presented in itera.org, the specific definition for the working load limit is that it is the maximum mass or force which a product is authorized to support in general service when the pull is applied in-line, unless noted otherwise, with respect to the centerline of the product. This definition can also be added to refer to the following definitions: the maximum load that an item can lift; and the maximum load that an item can lift in a particular configuration or application.
The working load limit of a lifting equipment depends greatly on a competent and skilled manufacturer who can wisely designate its WLL value. It’s the responsibility of the manufacturer to determine the right or approximate WLL value for each lifting device. To come up with a WLL value, there are many factors to consider. This includes the speed of operation, the applied load, the length of each rope or line, size, number, and etc. Any factor that can affect the working load limit of a lifting device should be carefully observed.
Summary:
- WLL stands for working load limit while SWL stands for safe working load.
- WLL and SWL are terms often used in the field of engineering.
- Safe working load is the older term of working load limit.
- The definition for safe working load is the breaking load of a component divided by an appropriate factor of safety giving a safe load that could be lifted or be carried.
- The working load limit is that it is the maximum mass or force which a product is authorized to support in general service when the pull is applied in-line, unless noted otherwise, with respect to the centerline of the product.
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thanks. i appreciate you relative explanations and differences between both terms in their simplicities.
Our Swl is 10 ton. I’m a safty rep and just want to know. Who can change the swl up to 13 ton and down also with 3 tons. We had a incident and just wondering if a maintance electisian from our company may change the limits. Please if you can assist me.
You can have someone come in, load test and certify to a lower SWL, but never higher than the manufactures SWL.
No this article is completely wrong if you are talking about lifting tackle for tower cranes, certainly anywehere in Europe. WLL is the working load limit which is the maximum load which an accessory can by design lift. SWL safe working load is the load that can be lifted under particular service conditions. The SWL of sling chains depends on the included angle.
Correct
sorry sir,
But what you said is same with what written in article
best regards
This is incorrect, as LOLER inspector I use both the SWL and the WLL, obv the SWL is calculated by a safety factor depending on the application…as is also stated by other readers!!
Can I use a chain sling SWL 5 Ton Max. Test load 10 Ton to lift an item from 7.5 Ton to 9 Ton?
The difference between Swl and well is that if a crane’s capacity for lifting is 10 ton and than if crane’s lift 8 ton this is swl and if it’s lift 10 ton that is WLL
The explanations on this article is not clear. The easiest way is to look at the WLL as the accessories ‘ability’ (like a noun) and the SWL as the weight of load with some added weight (safety factor) in relation to the configuration/composition that will lift it. For instance, if a load is actually 5tonnes, the Safe Working Load SWL to be anticipated may be around 6 or 7 tonnes to be sure there is tolerance.
State 2 effects of a Slewing load that a slinger should be aware of
increase of radius
change of ground force
I am seeking information on features of lifting equipment for an assignment. I would appreciate it.Thanks
Minimum breaking streangh
Maximum force
WLL used is straigt lift only
SWL used is angular lift.
Hello
Interesting article. In the UK the term SWL is still widely used, although from reading other articles across the world some have deemed this ‘the old term’ and that WLL supersedes this.
In the UK if I were to buy a 1te SWL sling. I can then apply a mode factor to this depending on how I use the sling. This will then get me my WLL.
E.g If I choked a 1te sling then my WLL becomes 0.8te
however
If I doubled up the same sling my WLL becomes 2.0te
In that sense my WLL could be the same, lower or even higher than the SWL. It depends how I am using the sling
Can you please cite some standards or other references about this?
I am a Canadian construction engineer and I found British Columbia OHS uses working load limit (WLL) and does not use the safe working load anywhere. In the neighbouring province Alberta, it’s the opposite.
Most Canadian OHS jurisdictions will refer American standard ASME B30.9 “Slings” for using and maintaining slings. In B30.9, ‘working load limit’ is used with chains and ‘rated capacity’ is used with wire rope slings, metal mesh slings, synthetic web slings and synthetic roundslings. Web slings and roundslings (yes, its one word) are then referenced from WSTDA standards WSTDA -WS-1 and WSTDA-RS-1 respectively (which, by the way, are currently free downloads). They use ‘rated capacity’ but also define “Working Load Limit – See rated capacity.”
In both ASME and WSTDA, neither of them refer to SWL, even when talking about hitch types or sling angles.
Even when talking about lifting devices (ASME B30.20-2013 “Below-the-Hook Lifting Devices”) they use the term rated capacity and nothing else (neither WLL or SWL).
Nonetheless, I still find that my colleagues use both terms interchangeably, and we or the workers have no problem with it–its how much weight/force a worker is allowed to lift with the sling or device under specified conditions and/or sling angles.
Personally, I prefer to use the term WLL over SWL only because I do not want to indicate an extra level of ‘safety’ just by the words I use. I don’t use the term ‘rated capacity’ when designing lifting devices mostly because WLL (and even SWL) are a catchy/pithy term. When you paint the words “WLL = 9000 kg” in big letters on the side of a spreader beam or debris bin, the workers ‘get it’ right away.