Category Archives: WLL

Misconceptions About Tarp Straps and WLL

We’d like to clear something up: our rubber tarp straps don’t have a Working Load Limit (WLL) printed on them, and they’re not supposed to. Lately we’ve been catching a lot of flack for this. Our tarp straps are used to tension covers and tarps over loads, typically loads carried by flat bed trucks. The straps keep the tarps from flapping around during transport, something that would limit both their effectiveness and their service life. A working load limit applies to the maximum cargo weight a strap can be used to restrain. The problem is that tarp straps are not cargo restraint straps. They’re designed to stretch, which—while beneficial when holding down tarps—is a serious hazard when restraining cargo.

The problem arose when overseas manufacturers started printing WLLs on their tarp straps. What makes this situation all the more baffling is that there’s no way to test the tensionality of rubber. The Society of Automotive Engineers (SAE) and ASTM International (formerly the American Society for Testing and Materials) set the standards for these tests: how they are to be operated and the standards they are to adhere to. Neither of these bodies has ever put forth a method for setting a WLL for rubber tarp straps. Compounding this is the fact that all rubber inherently wears out—a natural rubber strap that’s been under sunlight for six months will have a lower breaking point than a new strap. Even if an accurate test were developed, the results wouldn’t hold firm over time.

We understand how this problem grew out of control. If you see a safety rating on one product, you start to wonder why a similar product by a different manufacturer doesn’t have the same rating. But in this case, it’s equivalent to stating the laser intensity your bicycle helmet can withstand (and we certainly hope you ride your bike in laser-free environments). It’s frustrating to lose business over an incorrect practice, but it’s downright distressing to know that companies are selling unsafe products that have the potential to hurt a lot of people. So please, when you’re buying tarp straps, use them only to hold down tarps, for the sake of your safety and the safety of everyone on the road.