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LOG NOTES

Know Your Tiedowns

Just a quick note to commend you on a well-written article [“Tiedown for Safety and Mission Accomplishment,” by Colonel Neal H. Bralley, USA (Ret.), in the July–August issue] on an often overlooked subject: chains and tiedowns. I find very little to argue with on your straightforward treatment of the subject.

One point that may need clarification is the drawing on page 32. I cannot tell from the drawing if the doubled front and rear forward restraint chains are actually four single chains, free to slide through the ATLAS’s tiedown loops, or two completely separate chains at each point, for a total of 8. [“ATLAS” is All Terrain Lifter Army System.] “Doubling” seems to be a common “workaround” when a rig is short a few chains. The bad news is, if the chains can slide through, they only count as one, not two—even though attached to the trailer at two points. A Department of Transportation safety inspector would rate that setup as 6 aft, but only 6 forward—not 10. A single chain can count for two (or more) only if positively, independently attached at each end of each run. (The same rule applies to another common mistake: having multiple chains run to a single clevis or shackle of insufficient total WLL!) [“WLL” is working load limit.]

I would suggest a few additional topics for a future piece, such as restraint of bulk materials, the use of non-metal straps, wood blocks and chocking, tire inflation (for both the load and the truck-trailer), and periodic load testing of chains and binders. While the ATLAS has hauling instructions, a lot of mission-related stuff does not.

I’m also a fan of using binders only on aft restraints, and keeping the bindered chains short, so if that “chin breaker” comes loose, the load can’t move far. These are lessons learned by observing others’ problems.

Agreed, 3/8-inch and 1/2-inch G70 chains are the best value; 5/8-inch and 3/4-inch chain are way too heavy to handle, but usually no one will steal them, either! One question: What is your source for the “rail” restraint factor? The numbers strike me as being too high, though the AAR [Association of American Railroads] is conservative.

Thanks again for good info. Every Army truck driver should read and heed. Our contractor drivers need reminding, too. Luck is a poor substitute for a strong chain, and the laws of physics self-enforce!

—William Ellis
Rock Island Illinois

[Mr. Bralley, the author of the article, provided the following response to Mr. Ellis’s letter.]

I appreciate Mr. Ellis’s comments. I completely agree on chains needing to provide stand-alone restraints. It is possible to use one chain for two separate restraints, but no part of the chain may be providing restraint support to both securement legs at the same time. (For example, if you have a 14-foot length of chain, you could have two 5-foot sections providing restraint, with 4 feet of slack chain between the two sections of chain providing restraint. Such a restraint may make use of the two grabhooks at the ends of the single chain and then use separate load binders to form the second ends of the two independent restraining legs of the single chain. This example provides one chain with four independent tiedown ends. What you do not want is a single chain that might loop twice (slide) through a tiedown ring but has only two tied-down points. Such an arrangement with one chain has no more strength than a single leg of chain.)

It is also critical that Soldiers not exceed the restraint capacity of any tiedown anchors on the load-bearing vehicle (the trailer) or the tiedown anchors on the load vehicle itself. Caution is necessary to ensure that two or more chains do not provide more restraint than a single anchor or other component may safely accommodate; to do this would result in an unsafe condition. The tiedown illustration in my article was reduced to fit on the printed page, but it reflects 10 chains for forward restraint using grade 70, 3/8-inch transport chains.

It is also critical for personnel securing loads to trailers with chain to fully understand working load limit (WLL) versus maximum breaking strength (MBS) so they do not exceed chain capacities. WLL is generally one-fourth of the value of the MBS of a chain. Many people use these terms almost interchangeably, but they mean very different things. The WLL is the critical number; for grade 70 transport chains, it is 25 percent of the MBS. For example, 1/2-inch grade 70 chain has an MBS of approximately 48,000 pounds; however, its WLL is only 12,000 pounds.

Readers may find all the current restraint factors for highway, rail, maritime, and air in Department of Defense Interface Standard for Transportability Criteria, MIL–STD–1366E, paragraphs 5.1.6 to 5.2.1. You can find this document at https://assist.daps.dla.mil/quicksearch/basic_profile.cfm?
ident_number=36714
. Rail restraints are high because railroad operators may couple cars within their rail yards at speeds of 4 to 6 miles per hour. Such coupling speeds will result in significant jarring of cars and their attached cargo loads. Normal truck operations do not join tractors to trailers at such speeds.

Highway transport restraint factors may also be found at the Federal Motor Carrier Safety Administration website at http://www.fmcsa.dot.gov/rules-regulations/administration/fmcsr/fmcsrruletext.asp?
rule_toc=762&section=393.102&section_toc=1929
.

—Neal H. Bralley
Fort Leavenworth, Kansas


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