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*