cargo-working-load-limit-calculation

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.

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This skill is published under the X3 Compass open skills initiative. Contributions welcome at https://github.com/x3fleetsafety/skills