| name | cargo-working-load-limit-calculation |
| description | Use this skill to calculate Working Load Limits for cargo tiedowns. Covers manufacturer ratings, deration, and total tiedown WLL.
|
Working Load Limit (WLL) Calculation
The Working Load Limit (WLL) is the maximum load a tiedown can safely handle. § 393.100 requires total tiedown WLL ≥ 50% of cargo weight.
Manufacturer WLL
- Every chain, strap, hook, and tiedown component has a stated WLL
- WLL is the maximum continuous load
- Working margin: 1/2 to 1/4 of breaking load
- Stamped or labeled on the component
Common chain WLL examples
- 3/8" Grade 70 chain: WLL 6,600 lbs
- 3/8" Grade 80 chain: WLL 7,100 lbs
- 1/2" Grade 70 chain: WLL 11,300 lbs
- 5/8" Grade 70 chain: WLL 18,100 lbs
Common strap WLL examples
- 4" strap: WLL ~5,000 lbs
- 6" strap: WLL ~9,000-13,000 lbs
Deration factors
- Wear: damaged chains/straps are derated (lower WLL)
- Wet conditions: ratings may reduce
- Knots/folds: significantly reduce WLL
- Sharp edges: contact with cargo edges reduces WLL
Total tiedown WLL
- Sum of all tiedown WLLs on the load
- Must be ≥ 50% of cargo weight
- Example: 10,000 lb cargo requires ≥ 5,000 lb total WLL
- Distribute across multiple tiedowns
Common errors
- Assuming higher-rated tiedown without verification
- Counting damaged tiedowns (should be removed)
- Single high-WLL tiedown instead of multiple distributed
- Tiedown attachment point WLL not considered (must also be rated)
Anchor point WLL
- Trailer anchor points have their own WLL
- Total cargo tiedown limited by lowest WLL in the system
- Attachment to weak anchor = WLL limited by anchor, not tiedown
Compass cargo securement
- WLL calculator built-in
- Tiedown configuration scoring
- Alert if total WLL insufficient for cargo
- Common commodity ratings referenced
CFR citations
- 49 CFR § 393.100
- WLL Standard
How Compass surfaces this
Searchable in Compass Ask. Runs against carrier fleet data when invoked from the relevant tracker. Read-only; no actions without explicit user approval.
Built by X3 Compass
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