When lifting heavy loads using slings or rigging, the angle of the sling plays a crucial role in determining how much force each leg of the sling must support.
The smaller the angle between the sling and the horizontal, the higher the tension on each leg.
The Sling Angle Factor Calculator helps you quickly find the angle factor and the load per sling leg, ensuring safe lifting and accurate rigging calculations.
1. Formula for Sling Angle Factor
The Sling Angle Factor (SAF) is determined using the cosine of the sling angle (the angle between the sling leg and the horizontal plane):
Sling Angle Factor=2×cos(Angle)1
However, for each sling leg, the load increases as the sling angle decreases.
To simplify, the most commonly used formula for a 2-leg sling is:
Sling Angle Factor=cos(Angle)1
2. Formula for Load per Sling Leg
Once you know the angle factor, you can calculate the load on each sling leg using:
Load per Sling Leg=Number of SlingsTotal Load×Sling Angle Factor
Important Note:
As the sling angle decreases, the tension on each sling leg increases sharply.
- At 90°, the factor = 1.0 (no increase in load)
- At 60°, the factor = 1.155
- At 45°, the factor = 1.414
- At 30°, the factor = 2.0
- At 15°, the factor = 3.864
This means lifting at smaller angles is unsafe and should be avoided.
Example Calculation
Let’s calculate the load per sling leg for a 2-leg sling lifting a 2,000 lb load at a 60° angle from the horizontal.
Step 1: Find Sling Angle Factor
Sling Angle Factor=cos(60°)1=0.51=2.0
Step 2: Calculate Load per Sling Leg
Load per Sling Leg=22000×2.0=2000lb
Final Result:
Each sling leg must support 2,000 lb, which means the total force on both slings is 4,000 lb — double the weight of the load!
That’s why it’s important to always check the sling angle before lifting.
Why Use a Sling Angle Factor Calculator?
- Ensures safe lifting operations
- Prevents overloading of sling legs
- Helps determine proper sling capacity
- Saves time with accurate calculations
FAQs
1. What is a Sling Angle Factor?
A Sling Angle Factor (SAF) is a multiplier used to determine the extra load placed on each sling leg when the sling is at an angle. The smaller the sling angle (closer to horizontal), the greater the tension on each leg — increasing the risk of overload.
2. Why does the sling angle matter?
The sling angle affects how the load is distributed across the sling legs.
- At 90° (vertical) → Factor = 1.0 (no extra load).
- At 60° → Factor = 1.155 (about 15% more load).
- At 30° → Factor = 2.0 (double the load).
- So, smaller angles cause higher tension, which can make lifting unsafe if not accounted for.
3. What is the best sling angle for lifting?
Ideally, the sling angle should be between 60° and 90° from the vertical.
Angles less than 45° can put too much stress on the slings and lifting points, so it’s best to avoid shallow angles whenever possible.
4. How can a Sling Angle Factor Calculator help me?
A Sling Angle Factor Calculator quickly determines how much load each sling leg will carry based on your input angle and total weight. It ensures your lifting setup stays within safe working limits, preventing sling failure or load imbalance.
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