Know the Direct and Indirect Tie-Downs with Aggregate WLL

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Tie-down solutions are not usually that simple, and if you don’t know what you’re doing when it comes to securing your loads on your trailer, you risk damaging your cargo and, in some cases, fines and warnings from DOT roadside inspections if they notice something is wrong. Knowing how to properly secure your loads, the difference between indirect and direct tie downs, as well as understanding working load limits (WLL) and what they mean for your cargo can go a long way and guarantee every trip you make is a safe one.

Difference between Direct and Indirect Tie-Downs

What is Direct Tie Down?

A direct tie-down is a tie-down that is put in place to provide direct and strong resistance to shifting by attaching one end of your strap or transport chain to the cargo itself and the other to the trailer. For example, heavy machinery or vehicles use direct tie-downs to prevent damage from shifting. If vehicles were strapped using an indirect tie-down, significant damage would occur to the vehicle the moment excessive force was applied to it.

What is Indirect Tie Down?

An indirect tie-down is when straps or chains go over, through, or around the cargo and the tension from the cargo is being put on the deck of the trailer. Indirect tie-downs are the most common type of tie-down and are usually seen on trailers carrying palletized cargo. Essentially, indirect tie-downs help applies pressure around the cargo to prevent the shifting of individual items. If a direct tie-down was used for these types of loads, either you’d have to connect several straps or chains to each individual item which wouldn’t be ideal.

How to Secure Direct and Indirect Loads

Like what was mentioned before, direct tie-downs involve going from one side of the load to the same side of the load. One end of the chain or strap is connected to a tie-down point on the trailer, run through a securement point on the load such as a wheel, spoke, or rod, and then runs right back to the same side of the trailer. In this case, the working load limit is cut down in half because it doesn’t evenly distribute the force of the securement to the whole tie-down.

Indirect tie-downs, again, are the most common type of tie-down you’ll see, and are secured by having one end of the strap or chain connected to the trailer at a tie-down point, up and or around the load, and connected to the trailer on the other side of the load. The working load limit is not affected by this type of tie-down, as the full force of the load is put on the strap or chain.

No matter what cargo securement method you use, it’s important to make sure that it’s enough to hold your cargo in place with no possibility of equipment failure. Though the best way to prevent equipment failure is to know and understand working load limits.

What is Working Load Limit (WLL)?

Working load limits are put in place to determine the amount of force that can be put on cargo control equipment without the possibility of failure. The aggregate WLL is the total overall load limits for each cargo control device used in the securement. When it comes to how many chains or straps you should use, the FMCSA suggests that the aggregate WLL must equal one-half the weight of what is being secured.

This is not to be confused with breaking strength. WLL is the safest amount of force that can be exerted without causing equipment failure while the maximum breaking strength is the maximum amount of force that can be applied to it before it fails. To prevent long-term damage and the possibility of failure, no one should exceed working load limits.

Calculating Aggregate WLL

To get the aggregate working load limit of your securement, take 50% of the working load limit of each chain or strap connected to an anchor point on your trailer, and add 50% of the working load limit of each strap or chain connected to your trailer and go over, through, or around your cargo.

It’s important to remember that the aggregate working load limit for any tie-down solution needs to be 50% of the cargo’s weight.

Cargo Control from Mytee Products

At Mytee Products, we carry an extensive range of cargo control equipment from Winch Straps to Ratchet Straps, and Chains and Chain Binders. All of our products are tested in-house to make sure that they live up to the working load limits printed on them. We don’t just sell straps either, we carry specially designed and durable tarps to help protect your cargo.

You can get your straps, chains, tarps, and more from Mytee Products or by calling us at 1-888-705-8277. Get your cargo control from us at excellent prices so you can haul safely, and earn more!

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