Many of the products we sell come with an assigned Working Load Limit, commonly abbreviated as WLL
(also referred to as Safe Working Load, abbreviated as SWL).
Example products include Rigging Shackles
, Eye Bolts
, Nylon / Polyester Slings
, Alloy Chain and Components
, and many others to be sure.
While all of these items are detailed with numerous specifications, no particular piece of information is more important than the item’s WLL.
Simply stated, the WLL of an item represents the absolute maximum load the item should ever be subjected to.
Whether in a slow static lift, or a more chaotic dynamic load (try to avoid these), the item should never bear a force greater than its assigned WLL.
A WLL is a reflection of several things:
- The material the item is made of (e.g., alloy or carbon steel)
- The intended use (e.g., general rigging or life support)
- The Safety Factor (sometimes called Design Factor, this is a percentage of the item’s breaking strength represented in a ratio such as 5:1)
Whether lifting or pulling, it’s important to know the WLL of the rigging product you are using. Based on years of experience in the rigging industry, I can confidently say that many rigging accidents can be avoided by working within, and never exceeding, the WLL.
Also, keep in mind that a given item, such as a nylon lifting sling, may have multiple WLL figures on its identification tag.
One may represent a vertical lift, one a choker hitch (the lowest of the three) and the third for a basketed load (the highest of the three).
Make sure you identify the type of hitch you are using and reference the proper WLL.
Additionally, keep in mind that angular loading reduces the WLL of an item.
This often comes into play with rigging bridles (aka multiple leg slings).
When lifting at an angle, slings bear a higher load than when lifting vertically.
Please reference this handy Guideon Angular Lifting
Lastly, do not rig with any rigging products that do not have a clearly defined WLL. Some inexpensive products, particularly those from overseas, do not have a WLL or product trace code. This makes them hard to identify and unsafe for use. At the same time, there are many excellent domestic and foreign manufacturers that make easily identifiable, safe and legally compliant rigging gear. You will find no shortage of them on our site.
At the end of the day, safe rigging starts with you! Inspect your gear before performing a lift or rigging up for a climb. If you supervise a crew, then remember that you are responsible for providing them with safe rigging gear and teaching them how to use it. Aside from obvious concerns about personnel safety and protection of expensive equipment and machinery, there are liability concerns for those that directly or indirectly ignore Working Load Limits.
Questions or comments…please, post below or contact us directly!