What Is Working Load Limit (WLL) on a Towing Strap?

A working load limit is indicated on many different types of equipment, from lifting slings, shackles, and rigging hooks, some companies even indicate this on their towing and recovery straps. But do you know what this means, and do you know the difference between the WLL and the minimum breaking strength?

The working load limit (WLL) represents the amount of weight or force that that particular piece of equipment can handle safely, without the risk of it failing. This is always a set weight and is calculated from the minimum break strength, known as a Safety or Design Factor. 

This enables users to make sure the equipment they use is operated within a safe range, minimizing the risk of failing, especially important in industries where they are lifting and moving highly valuable machinery, or equipment.

However, as helpful as this is, this method can not be accurately determined with tow straps or recovery straps, and we believe that indicating a WLL will almost certainly lead to serious issues for users, both in terms of reliability and safety.

When carrying out a towing or recovery task, it's very easy to determine the gross vehicle weight, as this is shown in various locations on all types of vehicles. But this is not a true reflection of how much weight, or force is applied to the strap during different types of recoveries.

If you take the same vehicle, one is stuck on loose gravel, another is stuck on a beach which has soft dry sand, another is on a beach in winter and the sand is now harder, but holding water under the surface, and the next vehicle is stuck on some offroad track or field, where its wheels, axels, and brakes have sunk in deep, wet suctioned mud, there is physically no way you can accurately calculate the amount of resistance each of these vehicles has. If each were to use the same strap, one or two of them would likely succeed, but the others would either be unsuccessful in their attempts or more likely experience strap failure. 

This is why at Dawnerz, we focus solely on the minimum breaking strength and do not provide working load limits. We provide a range of information and resources to our customers, to provide them with enough knowledge to determine what type of strap suits them the best.

We have two clients who both operate the same types of vehicles, and both run their vehicles fully loaded 90% of the time. However the first company operates its fleet mainly on construction sites, even though the roads are unsurfaced, they have a solid base to operate on. So when they do experience issues in winter, it's usually in soft snow and ice, which creates mainly loss of traction. They have our 200,000 lb tow strap in every vehicle and have experienced no issues with this capacity.

However, our second customer operates in forestry and woodland, and in the winter months, the ground there is much more difficult to operate on. It's uneven, their vehicles can sink deeper at one side than the other, and the ground is much softer, causing an increased amount of resistance to recover. This company used the same 200,000 lb tow strap, but it failed within a week. They upgraded and now carry both our 260,000 lb and 380,000 lb tow straps, and in 18 months of operations, they have experienced no further issues. Their drivers then can evaluate the severity of each situation, and select the strap they think will best suit this specific task.

If you are unsure of how to choose the best tow strap or are unsure about lengths, and capacities, our team is always here to assist you through the process.