1.Identify the Sling Type and Material
Slings vary by material and design, each with unique load capacities:
- Chain Slings: Durable for heavy loads but sensitive to shock forces.
- Wire Rope Slings: Flexible and heat-resistant but prone to kinking.
- Synthetic Slings (Nylon/Polyester): Lightweight and corrosion-free but degrade with UV exposure.
- Metal Mesh Slings: Ideal for sharp-edged loads.
Check the manufacturer’s tag for the rated SWL, which is based on vertical lifting (straight pull).
2.Understand Sling Configuration
The angle of the sling’s legs drastically affects capacity. Use this formula:
SWL = (Rated Load) × (Angle Factor)
| Sling Angle (Degrees) | Angle Factor |
| 90° (Vertical) | 1.0 |
| 60° | 0.866 |
| 45° | 0.707 |
| 30° | 0.5 |
Example: A sling rated for 2,000 lbs at 90° will only safely lift 1,414 lbs at a 45° angle (2,000 × 0.707).
3. Calculate Load Distribution
For multi-leg slings (e.g., 2-leg, 3-leg, or 4-leg bridles):
- Divide the total load by the number of legs.
- Adjust for uneven weight distribution (use the weakest leg’s capacity as the limiting factor).
Example: Lifting a 6,000 lbs load with a 4-leg sling at 60°:
- Load per leg = 6,000 lbs / 4 legs = 1,500 lbs
- Adjusted SWL per leg = 1,500 lbs / 0.866 (angle factor) ≈ 1,732 lbs
Ensure each sling leg is rated for at least 1,732 lbs.
4. Consider Environmental Factors
- Temperature: Synthetic slings lose strength in extreme heat (>194°F/90°C for nylon).
- Chemicals/Oils: Can degrade synthetic fibers or corrode metal slings.
- Abrasion/Sharp Edges: Use edge protectors to prevent cuts or wear.
5. Inspect Slings Regularly
Before use, check for:
- Metal Slings: Cracks, rust, deformed links, or stretched hooks.
- Synthetic Slings: Cuts, fraying, melting, or UV damage.
- Wire Rope: Broken wires, kinks, or crushed strands.
Key Takeaways
- Never exceed the SWL on the sling’s tag.
- Use angle factors to adjust for sling configuration.
- Always prioritize balanced loads and proper rigging techniques.
