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Difficulty: MediumCargo Securement: Tie-Down Rules and WLL

A flatbed trailer is transporting a skid-mounted industrial generator measuring 17 feet17\text{ feet} in length and weighing 32,000 pounds32,000\text{ pounds}. The unit is positioned without front-end blocking or a header board. If the driver secures the cargo using tie-downs each rated at a Working Load Limit (WLL) of 3,000 pounds3,000\text{ pounds}, what is the minimum number of tie-down straps required to meet federal cargo securement standards?

  1. A
    3 tie-down straps3\text{ tie-down straps}
  2. 6 tie-down straps6\text{ tie-down straps}Answer
  3. C
    2 tie-down straps2\text{ tie-down straps}
  4. D
    11 tie-down straps11\text{ tie-down straps}

Answer

6 tie-down straps6\text{ tie-down straps} are required to legally secure the cargo.
Federal Motor Carrier Safety Administration (FMCSA) cargo securement rules dictate two independent criteria: cargo length and aggregate Working Load Limit (WLL). For unblocked cargo measuring 17 feet17\text{ feet}, length rules mandate 3 tie-downs3\text{ tie-downs} (22 for the first 10 feet10\text{ feet} plus 11 for the additional 7-foot7\text{-foot} fraction). For weight, aggregate WLL must equal at least 50%50\% of the 32,000-pound32,000\text{-pound} total weight, or 16,000 pounds16,000\text{ pounds}. With straps rated at 3,000 pounds3,000\text{ pounds} WLL each, 5 straps5\text{ straps} provide only 15,000 pounds15,000\text{ pounds} (insufficient), requiring a minimum of 6 tie-down straps6\text{ tie-down straps} (18,000 pounds18,000\text{ pounds} aggregate WLL) to satisfy both legal requirements.

Step-by-Step Solution

1
Calculate the minimum number of tie-downs required by cargo length for unblocked cargo.
3 tie-down straps3\text{ tie-down straps}
Federal regulations mandate that unblocked cargo requires 2 tie-downs for the first 10 feet10\text{ feet} plus 1 additional tie-down for each additional 10 feet10\text{ feet} or fraction thereof (17 feet=10 feet+7 feet17\text{ feet} = 10\text{ feet} + 7\text{ feet}, requiring 2+1=3 tie-downs2 + 1 = 3\text{ tie-downs}).
2
Calculate the required aggregate Working Load Limit (WLL) based on total cargo weight.
16,000 pounds16,000\text{ pounds}
The aggregate WLL of all securement devices must equal at least 50%50\% (1/21/2) of the total cargo weight (0.50×32,000 pounds=16,000 pounds0.50 \times 32,000\text{ pounds} = 16,000\text{ pounds}).
3
Determine the number of 3,000-pound3,000\text{-pound} WLL straps needed to meet or exceed the aggregate WLL requirement.
6 tie-down straps6\text{ tie-down straps}
Dividing 16,000 pounds16,000\text{ pounds} by 3,000 pounds/strap3,000\text{ pounds/strap} gives 5.335.33 straps. Because partial straps cannot be used and 5 straps provide only 15,000 pounds15,000\text{ pounds} (under the required threshold), rounding up to 6 straps (18,000 pounds18,000\text{ pounds} total WLL) is necessary.
4
Select the greater of the length-based requirement and the weight-based requirement.
max⁡(3,6)=6 tie-down straps\max(3, 6) = 6\text{ tie-down straps}
Both length and aggregate WLL requirements must be simultaneously satisfied.

Key Concept

Federal cargo securement standards require meeting both length-based tie-down counts (at least 2 for the first 10 feet of unblocked cargo plus 1 for each additional 10 feet or fraction) and an aggregate Working Load Limit (WLL) of at least 50% of the cargo weight.
Estimated Time:1m 15s
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Topics

Cargo Securement: Tie-Down Rules and WLL

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