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Tie-Down Traps

by Jim Park

There's a chain or a strap every eight feet or so, the boomers are all secured, and nothing's even close to coming loose. The chains are so tight a fiddler could play a tune on them. Yet, the creeper cop is writing you a ticket for an improperly secured load. What gives?

Well, there's this little section of the load-securement regulations that outlines, in pretty muddy English, the number of tie-downs that you must use to keep the cargo where it belongs. It's not enough to simply throw a few chains or straps over the top and hope for the best.

The January 2000 edition of the Insurance Corporation of British Columbia (ICBC) driver's handbook on load security says, "The aggregate safe working load of the tie-downs must not be less than the weight of the load secured." The equivalent handbook from Ontario's Ministry of Transportation says pretty much the same thing: "Tie-downs used to secure loads shall have an aggregate working load limit equal to the weight of the articles being secured."

How the heck are you supposed to know what the aggregate working load limit (WLL) of your tie-downs is?

Chains, straps, binders or boomers and even grab hooks all have limits to what they can do. The manufacturers use a prescribed formula to rate the WLL of their products, then they mark the device to indicate its rated strength. You need to refer to the manufacturer's rating, usually stamped into every few links of a chain, sewn or stenciled into the webbing of a strap, and embossed onto a grab-hook or the handle of a binder, to determine its WLL.

The inspectors add up the WLL for each tie-down to determine the total for all the tie-downs on a particular article. That total is called the aggregate working load limit (AWLL), but is sometimes referred to as the Rated Load Value (RLV), the Safe Working Load (SWL), or the Resultant Safe Working Load (RSWL).

Here's where it gets a bit tricky. A chain secured to the trailer and running once over the cargo and fastened again to some point on the trailer with a binder, counts as two separate tiedowns. That same chain fastened this time to the trailer with a binder and then directly to a tie-down point on the cargo, counts as only one tie-down. A single chain counts as two tie-downs when both ends are secured to the trailer, but as a single tie-down when secured directly from the cargo to the trailer.

Here's an example: four chains with binders were used to secure a 33,000-lb electrical transformer to a trailer. Each was attached to a tie-down point on the transformer, then secured to the trailer. The WLL of each tiedown was 4700 lb. In this case, each chain/hook/binder assembly counts as a single tie-down assembly, so the inspector calculated the total, or aggregate working load limit of the four assemblies, which equaled 18,800 lb (4 x 4700 = 18,800) - a shortfall of 14,200 lb.

Had the driver looped each of the same four chains over the transformer and secured it to the trailer in the usual fashion, he would have had an aggregate WLL of 37,600 lb. (8 x 4700 = 37,600). More than enough to secure the transformer according to the regulations. In order to meet the requirements using the first method, the driver would have needed three more chains and binders with a WLL of at least 4700 lb.

While the process for determining whether cargo is properly secured isn't terribly complicated, drivers often get into hot water because they're using insufficient, under-rated or damaged tie-down devices.

The Weakest Link

You've heard that expression before. The way it applies to cargo securement is as plain as the nose on your face. You can have a 5400-lb WLL chain and a 5400-lb WLL binder, but the whole assembly is really no better than the 3900-lb WLL grab hook at the end of it all. The inspectors will rate the tie-down assembly according to the lowest WLL of any of its components.

If a tie-down assembly consists of a length of 5/16 G7 chain with a WLL of 4700 lb, a binder rated at 5400 lb and a 5/16 HT grab-hook with a WLL of 3900 lb, then the entire assembly will have a WLL of only 3900 lb.

Here's an example: a marine container and its contents weighing 42,800 lb was secured on a flatdeck by two chains wrapped through the lower ends of the container at the front and rear, and two four-in. cargo straps placed at even intervals along the trailer. The two straps provided an AWLL of 20,000 lb, but one of the two chains had a WLL of only 1900 lb. The other, along with the binders and hooks, was rated at 4700 lb.

The inspector noted that the straps and chains were used in a way that gave the driver credit for eight tie-down assemblies, but the AWLL of the two chains was only 13,200 lb. The combined AWLL for all the securement devices was only 33,200 lb - a shortfall of 9600 lb.

It's obviously pretty important for a driver to understand the correct method of using the tie-down devices to achieve the maximum WLL for the assembly, but it's equally important for the driver to understand the WLL ratings of the equipment he's using. But just knowing the ratings isn't quite enough. You must be able to prove it.

Default Ratings

All proper tie-down equipment is stamped with the manufacturer's WLL rating (see chart). If the inspector is unable to determine what the rating is, either because the rating stamp can't be found or it's unreadable, he'll rate the tie-down at the lowest rating (Grade 3) for that size of chain. A driver might assume he's using a piece of 5/16 Grade 7 chain with a WLL of 4700 lb, but if the inspector is obliged to down-rate the assembly to the default rating of a Grade 3 chain, the maximum WLL would be only 1900 lb. That would have a large impact on the AWLL of all the tie-downs.

The same applies to webbed straps. If the WLL rating can't be identified, a 4-in. 5000-lb WLL strap will be downrated to a default rating of 1000 lb/in. of width, or 4000 lb.

Here's where it gets really brutal. Both strap and chain are subject to damage through normal use. When an inspector discovers a damaged chain, he'll discount it completely from the AWLL, just like it wasn't even there. Since a single chain can be counted as two tie-downs if used properly, a damaged chain could strip as much as 10,800 lb from the aggregate WLL of your tie-downs.

Strapping that's torn, cut, burnt or has holes or crushed areas in the webbing totaling more than 25% of its width will not be counted in the aggregate WLL. Minor cuts or holes will force the inspector to downrate the strap to the equivalent of the remaining width. If a 4-in. strap has a 3/4 in. tear, the strap will be rated at the WLL of a 3-in. strap.

It pays to know what you're doing in the flatdeck business, because not knowing can really cost you a bundle. Take a little time to inspect your chains, binders and grab hooks for the proper stamps and ratings. Check for damage while you're at it, and make darned sure you're using equipment that's rated for the job. But more importantly from a compliance perspective, make sure the rating stamps on your gear are readable. That's what the creeper cops are going to look at first.

A New Standard

Load-securement regulations are easily among the most complex of all the laws we have to comply with. There are dozens of local interpretations, many, many more cargo-specific requirements that vary across jurisdictions, and some cargoes that simply defy definition.

The soon-to-be-released North American Cargo Securement Standard should make compliance considerably easier to achieve. The proposed new standard outlines all the requirements for every element of cargo securement, including many new cargo-specific requirements. That will make the enforcement of the regulations considerably more uniform throughout North America.

Along with the detailed standards, officials will be introducing a comprehensive training program for drivers and a detailed booklet describing all the securement methods. It might take a bit of getting used to, but at least every jurisdiction will be required to comply with the same set of standards. That's got to be a step in the right direction.

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