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Difficulty: EasyCargo Securement: Tie-Down Rules and WLL

A flatbed driver is transporting an unblocked piece of manufacturing equipment that is 15 feet long and weighs 20,000 lbs. If the driver secures the cargo using tie-downs with a Working Load Limit (WLL) of 4,000 lbs each, what is the minimum number of tie-downs required to safely and legally secure this load?

  1. A
    1 tie-down
  2. B
    2 tie-downs
  3. 3 tie-downsAnswer
  4. D
    5 tie-downs

Answer

3 tie-downs
Federal cargo securement rules require that the aggregate Working Load Limit (WLL) of all tie-downs must equal at least 50% of the total cargo weight, and unblocked cargo between 10 and 20 feet long requires at least 2 tie-downs. For a 20,000-lb item, the required aggregate WLL is 10,000 lbs. Two 4,000-lb straps only provide 8,000 lbs of WLL, so a third strap is required (giving 12,000 lbs of aggregate WLL), which satisfies both the weight and length requirements.

Step-by-Step Solution

1
Determine the minimum tie-downs required by cargo length
2 tie-downs required
Cargo that is unblocked and between 10 and 20 feet in length requires a minimum of 2 tie-downs (1 tie-down for every 10 feet or fraction thereof).
2
Calculate the required aggregate Working Load Limit (WLL) based on cargo weight
10,000 lbs aggregate WLL
Federal regulations mandate that the aggregate WLL of all securement devices must equal at least 50% of the cargo's total weight (0.50 × 20,000 lbs = 10,000 lbs).
3
Calculate the number of tie-downs needed to meet the aggregate WLL and compare with length requirements
3 tie-downs needed
Dividing 10,000 lbs by 4,000 lbs per strap gives 2.5 straps, which rounds up to 3 tie-downs. Since 3 tie-downs satisfy both the weight (12,000 lbs aggregate WLL >= 10,000 lbs) and length rules, 3 is the minimum required.

Key Concept

Cargo securement requires satisfying both length-based tie-down counts and the 50% aggregate Working Load Limit (WLL) rule.
Estimated Time:45s
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Topics

Cargo Securement: Tie-Down Rules and WLL

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