Load Securement

freedhardwoods · Jul 25, 2012

CAXPT said: ↑

Autocar, I remember now why I use WLL instead of MBS for computations.

freedhardwoods, I love a challenge, so here goes. Your statement, like many truckers, is based on A section. The reason it's important to learn the FMCSR's (green and white book) is because the regulations have overlapping applicability. For instance, the metal coils section §393.120 you are referencing is an example of a commodity-specific rule, that can only supersede the general requirements of § 393.106What are the general requirements for securing articles of cargo? when additional requirements are given for a commodity listed. This doesn't mean instead of the general requirements it means, additional. (i.e. through the eye in this coil securement case)

The section(s) you'll find your answer(s) in are § 393.106(a), (b), (c) and (d)

(a) Applicability. The rules in this section are applicable to the transportation of all types of articles of cargo, except commodities in bulk that lack structure or fixed shape (e.g., liquids, gases, grain, liquid concrete, sand, gravel, aggregates) and are transported in a tank, hopper, box, or similar device that forms part of the structure of a commercial motor vehicle. The rules in this section apply to the cargo types covered by the commodity-specific rules of §393.116 through §393.136. The commodity-specific rules take precedence over the general requirements of this section when additional requirements are given for a commodity listed in those sections.
(b) General. Cargo must be firmly immobilized or secured on or within a vehicle by structures of adequate strength, dunnage or dunnage bags, shoring bars, tiedowns or a combination of these.
(c) Cargo placement and restraint. (1) Articles of cargo that are likely to roll must be restrained by chocks, wedges, a cradle or other equivalent means to prevent rolling. The means of preventing rolling must not be capable of becoming unintentionally unfastened or loose while the vehicle is in transit.
......
(skipping condition for multiple pieces restraint requirement)....
......
(d) Aggregate working load limit for tiedowns. The aggregate working load limit of tiedowns used to secure an article or group of articles against movement must be at least one-half times the weight of the article or group of articles. The aggregate working load limit is the sum of:
(1) One-half the working load limit of each tiedown that goes from an anchor point on the vehicle to an anchor point on an article of cargo;
(2) One-half the working load limit of each tiedown that is attached to an anchor point on the vehicle, passes through, over, or around the article of cargo, and is then attached to an anchor point on the same side of the vehicle.
(3) The working load limit for each tiedown that goes from an anchor point on the vehicle, through, over, or around the article of cargo, and then attaches to another anchor point on the other side of the vehicle.

Especially note section (d) that specifies the types of tiedowns and their value with regard to meeting the "must be at least one-half times the weight of the article" and you'll see that you get to use the whole value of the WLL for a chain that goes from one side of the trailer to the other, or through the eye for our purposes. So for a 5,000 lb coil, the 2 would be enough for forward and rearward restraint according to the regs, but the heavier the coil, the more chains required and those will still be subject to this following section:

§ 393.120What are the rules for securing metal coils?
(a) Applicability. The rules in this section apply to the transportation of one or more metal coils which, individually or grouped together, weigh 2268 kg (5000 pounds) or more. Shipments of metal coils that weigh less than 2268 kg (5000 pounds) may be secured in accordance with the provisions of §§393.100 through 393.114.
....
(skipping sections for coils loaded eye to the sky and in rows)
....

(c) Securement of coils transported with eyes crosswise on a flatbed vehicle, in a sided vehicle or intermodal container with anchor points'(1) An individual coil. Each coil must be secured by the following:
(i) A means (e.g., timbers, chocks or wedges, a cradle, etc.) to prevent the coil from rolling. The means of preventing rolling must support the coil off the deck, and must not be capable of becoming unintentionally unfastened or loose while the vehicle is in transit. If timbers, chocks or wedges are used, they must be held in place by coil bunks or similar devices to prevent them from coming loose. The use of nailed blocking or cleats as the sole means to secure timbers, chocks or wedges, or a nailed wood cradle, is prohibited;
(ii) At least one tiedown through its eye, restricting against forward motion, and whenever practicable, making an angle no more than 45 degrees with the floor of the vehicle or intermodal container when viewed from the side of the vehicle or container;and
(iii) At least one tiedown through its eye, restricting against rearward motion, and whenever practicable, making an angle no more than 45 degrees with the floor of the vehicle or intermodal container when viewed from the side of the vehicle or container.
(2) Prohibition on crossing of tiedowns when coils are transported with eyes crosswise. Attaching tiedowns diagonally through the eye of a coil to form an X-pattern when viewed from above the vehicle is prohibited.

---emphasis/underlining added

Now, don't forget, there is also another section that puts further requirements on the computations. § 393.102 What are the minimum performance criteria for cargo securement devices and systems?

(2) Working Load Limit. Tiedown assemblies (including chains, wire rope, steel strapping, synthetic webbing, and cordage) and other attachment or fastening devices used to secure articles of cargo to, or in, commercial motor vehicles must be designed, installed, and maintained to ensure that the forces acting on the devices or systems do not exceed the working load limit for the devices under the following conditions, applied separately:
(i) 0.435 g deceleration in the forward direction;
(ii) 0.5 g acceleration in the rearward direction; and
(iii) 0.25 g acceleration in a lateral direction.
(b) Performance criteria for devices to prevent vertical movement of loads that are not contained within the structure of the vehicle. Securement systems must provide a downward force equivalent to at least 20 percent of the weight of the article of cargo if the article is not fully contained within the structure of the vehicle. If the article is fully contained within the structure of the vehicle, it may be secured in accordance with Sec. §393.106(b).

So, this means the one chain restraining the forward movement has to be able to restrain that 5,000 lbs coil by not exceeding the WLL of each device by .435 g deceleration forward, which for a 6500 lbs WLL of an anchor point would be 2827.5, since this is more than the required half of the weight of the article to be secured in aggregate (per §393.106 (d)), as long as the remaining chains and binders are capable of the same or better WLL's for this direction. this is the only chain minimally required by the regs. Add the chain for the rearward restraint and you have the minimum, until you notice that §393.102 (b) points out that you have to add at least one more chain to the minimum of 2 for the coil to control upward movement of 20% of the article weight on a flatbed. (not contained within structure, and no, a conestoga is not considered a structure for this purpose of coil securement.)

This brings the total minimum count of chains to 3, and that's just for a 5,000 lb coil, and all these minimums I've based on at least grade 70 chain/binders and anchor points rated at 6500 lb WLL for an anchor point and 6600 lb WLL for 3/8" chains. Grade 30, although initially meeting minimum standards to do the job, means recalculating everything for the different pieces and determining the true "weakest link" in the setup....and I don't know of any one that wants chains that are weaker then their binders.

That said, looking at that demonstration, it occurred to me, that maybe they were using Grade 30 chains, and as I watched their meter (thanks for that youtube link btw), I noticed where the breaking point was. First the actual meter isn't completely visible because of the handle in the way, which prevents us from accurately being able to tell what the guage reading measurements were. It was either "X=100", "X=1000", etc, couldn't tell. Also, the scale to read wasn't clear either as the inside scale may have been a metric equivalent to the outside scale, or a subcount etc.

Assuming, the outside scale was "X=100" and the inside scale was a subguage of "X=1000" it looked like the first chain was breaking at 2,265 lbs which is close to Grade 30 3/8" (they looked like) WLL of 2,650 lbs. So the video only raised more questions than it thought it was answering. In addition, the "coil" was a welded reinforced drum with no edge protection for the chains (a major violation on a real coil), and it had a hydraulic cylinder with constant and increasing pressure. The only reason the other chains over the top didn't pop, is because they were longer and had more elasticity because of that length.... but because of that longer length and elasticity, they really aren't holding anything down either because they don't actually get engaged by the pump, until the first chain snaps.

Sorry, like the other guy said, at $640 a set up, I'll buy extra chains and over chain the dang thing, by the time it walks through all those chains, the truck would have long since stopped.
Click to expand...

CAXPT said: ↑

So, this means the one chain restraining the forward movement has to be able to restrain that 5,000 lbs coil by not exceeding the WLL of each device by .435 g deceleration forward, which for a 6500 lbs WLL of an anchor point would be 2827.5,
Click to expand...

A WLL rating does not have mass, therefore it can't contribute to g forces created in a given situation. .435 x 5000 not 6500.

Third chain not needed to meet minimum requirements. Long explanation why later.

More points to make. No time now.

Log in or Sign up

Forums

Find Trucking Jobs

Load Securement

freedhardwoods Light Load Member

Trucking Jobs in 30 seconds

Wait, employers can't reach you!

Log in or Sign up

Useful Searches

Find Trucking Jobs

Load Securement

freedhardwoods Light Load Member

Wait, employers can't reach you!