HD W.L.L.

To begin our conversation about heavy-duty rigging, it’s important to understand that regardless of the amount of force applied to the rigging or the winch line, the operator understands that every piece of rigging has a specific purpose, it has a specific design factor, and it has a specific breaking strength. All are subject to all of the conditions present in the recovery setting. 

To begin our conversation about heavy-duty rigging, it’s important to understand that regardless of the amount of force applied to the rigging or the winch line, the operator understands that every piece of rigging has a specific purpose, it has a specific design factor, and it has a specific breaking strength. All are subject to all of the conditions present in the recovery setting. 

To begin our conversation about rigging, let’s talk about a factor that we call the Working Load Limit. Working Load Limit is the amount of force that that product is authorized to support in general service. This is directly related to how that piece of rigging, or that product, was engineered and designed by the manufacturer. 

The next thing that we talked about is Ultimate Load. When a piece of rigging was engineered and designed by the manufacturer, they want to test it to find out how much force that it will absorb before it breaks. Testing on these pieces of rigging and rigging components are done in a controlled environment. It’s important to understand that the manufacturer  designs each piece of rigging to be utilized in a specific way. For example, when a chain is designed and tested it is pulled in a straight line with no twists in the chain. In order to come up with repeatable results in load testing and testing to failure that piece of chain is loaded and pulled until it breaks. 

The conditions in the field will often be different than those present during manufacturers testing, So it’s important that has operators and riggers that when installing a piece of rigging, we install it in a way that most closely resembles that in which it was tested in order to get specific tensions and specific values associated with its breaking strength and it’s working load limits. 

A design factor is an industry term that denotes a theoretical reserve. Design factor is often set or identified by the industry that’s using it. For the most part the design factor associated with hard rigging such as shackles, hooks, or chain links is 4:1. Meaning that we identified that the breaking strength is 4 times greater than the theoretical reserve. So when we identify a design factor of 4:1 we can come up with a Working Load Limit. The Working Load Limit of most hard rigging is 1/4 that piece of rigging’s breaking strength.