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Difficulty: MediumCargo Securement: Tie-Down Rules and WLL

A flatbed motor carrier is hauling a packaged industrial water filtration skid measuring 22 feet22\text{ feet} in length and weighing 14,000 pounds14,000\text{ pounds}. The unit is positioned on the deck without front-end blocking or contact against a bulkhead. If synthetic web straps rated at a Working Load Limit (WLL) of 2,500 pounds2,500\text{ pounds} each are used as indirect tie-downs, what is the minimum number of straps required to meet federal cargo securement regulations?

  1. A
    3 straps3\text{ straps}
  2. 4 straps4\text{ straps}Answer
  3. C
    6 straps6\text{ straps}
  4. D
    2 straps2\text{ straps}

Answer

The minimum number of straps required is 4 straps4\text{ straps}.
Securing unblocked cargo measuring 22 feet22\text{ feet} in length requires 2 tie-downs for the first 10 feet10\text{ feet}, 1 tie-down for the next 10 feet10\text{ feet}, and 1 tie-down for the remaining 2 feet2\text{ feet}, totaling 4 tie-downs. Four straps rated at 2,500 pounds2,500\text{ pounds} WLL provide an aggregate WLL of 10,000 pounds10,000\text{ pounds}, which satisfies and exceeds the mandatory 50%50\% weight threshold of 7,000 pounds7,000\text{ pounds} (14,000 lbs×0.5014,000\text{ lbs} \times 0.50). Thus, 4 straps4\text{ straps} is the governing minimum.

Step-by-Step Solution

1
Calculate the length-based tie-down requirement for unblocked cargo.
4 straps4\text{ straps} required by length.
Federal regulations mandate that unblocked cargo requires 2 tie-downs for the first 10 feet10\text{ feet} of length, plus 1 additional tie-down for every additional 10 feet10\text{ feet} or fraction thereof (2 straps for 0–10 ft+1 strap for 10–20 ft+1 strap for 20–22 ft=4 straps2\text{ straps for } 0\text{--}10\text{ ft} + 1\text{ strap for } 10\text{--}20\text{ ft} + 1\text{ strap for } 20\text{--}22\text{ ft} = 4\text{ straps}).
2
Calculate the weight-based Working Load Limit (WLL) requirement.
Minimum aggregate WLL of 7,000 pounds7,000\text{ pounds}, requiring at least 3 straps3\text{ straps}.
The aggregate WLL of all tie-downs must equal at least 50%50\% of the total cargo weight (0.50×14,000 lbs=7,000 lbs0.50 \times 14,000\text{ lbs} = 7,000\text{ lbs}). With 2,500 lb2,500\text{ lb} straps, 7,000/2,500=2.87,000 / 2,500 = 2.8, which rounds up to 3 straps3\text{ straps}.
3
Determine the governing requirement to satisfy both federal rules.
The final requirement is max⁡(4 straps by length,3 straps by WLL)=4 straps\max(4\text{ straps by length}, 3\text{ straps by WLL}) = 4\text{ straps}.
The securement system must simultaneously meet or exceed both the length-based spacing minimums and the aggregate WLL requirements.

Key Concept

Cargo Securement: Tie-Down Rules and Working Load Limit (WLL)
Estimated Time:1m 15s
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Topics

Cargo Securement: Tie-Down Rules and WLL

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