EXERCISE 1

Lifting Load Calculations

Master the critical physics of Safe Working Loads (SWL) and ensure every lift is engineered for safety

Interactive Whiteboard

3D Simulations

Real-world Scenarios

🎯 Learning Objectives

By the end of this exercise, you will be able to:

Understand Physics

Grasp the fundamental tension physics in rigging systems and how angles affect load distribution on lifting equipment.

Calculate Capacity

Accurately determine equipment capacity based on lifting angles using industry-standard load factor formulas.

Identify Limits

Recognize the weakest component in a rigging system and understand that safety is only as strong as the weakest link.

Determine Max Load

Confidently establish the final maximum safe working load for any rigging configuration you encounter.

📋 The Rigging Scenario

You're planning a critical lift with a 60-degree included angle. Let's analyze whether this rigging configuration is safe.

3D Interactive View

Controls: Click & drag to rotate • Scroll to zoom

Technical Diagram

Each sling is 30° from vertical (60° included angle total)

Wire Rope Slings

Quantity

2 Slings

Safe Working Load (Each)

4.0 T

Total Capacity: 8.0T (before angle adjustment)

Bow Shackles

Quantity

2 Shackles

Safe Working Load (Each)

3.0 T

Total Capacity: 6.0T (before angle adjustment)

📐 The Physics of Angles

                        Critical Principle: As the included angle increases (the rigging gets flatter),
                        the tension in each sling increases exponentially—not linearly. This is why angle matters so
                        much in rigging safety.
                    

0°

Vertical Lift

100% of load
✓ Ideal

60°

Moderate Angle

115% per sling
⚠ Acceptable

120°

Wide Angle

200%+ per sling
✗ Dangerous!

                        Industry Rule: Never exceed a 120° included angle. Most professionals aim for
                        60° or less for optimal safety margins.
                    

🧮 Understanding Load Factors

The Load Factor is a mathematical multiplier that accounts for increased tension due to lifting angles. It tells us how much harder each component is working compared to a vertical lift.

For a 60° Included Angle

LOAD FACTOR

1.154

                                The Formula: Load Factor = 1 ÷ cos(angle from vertical)

                                For 60° included angle: Each sling is 30° from vertical

                                Therefore: 1 ÷ cos(30°) = 1 ÷ 0.866 = 1.154

🔧 Step 1: Wire Rope Sling Capacity

The Calculation Formula

                                (Sling SWL ÷ Load Factor) × 2
                            

📊 Input Data

Sling SWL: 4.0 T
Load Factor: 1.154
Quantity: 2 Slings

Step-by-Step Calculation

Step 1:
                                            Divide SWL by Factor
4.0 ÷ 1.154 = 3.466
Step 2:
                                            Multiply by 2 slings
3.466 × 2 = 6.932
Final
                                            Capacity
6.93 T

🔗 Step 2: Bow Shackle Capacity

The Calculation Formula

                                (Shackle SWL ÷ Load Factor) × 2
                            

📊 Input Data

Shackle SWL: 3.0 T
Load Factor: 1.154
Quantity: 2 Shackles

Step-by-Step Calculation

Step 1:
                                            Divide SWL by Factor
3.0 ÷ 1.154 = 2.599
Step 2:
                                            Multiply by 2 shackles
2.599 × 2 = 5.198
Final
                                            Capacity
5.20 T

📊 Critical Comparison Analysis

                            Critical Safety Principle: In any rigging system, you are only as strong as
                            your weakest link. We must always select the LOWEST calculated capacity value to ensure safe
                            operations.
                        

Wire Rope Slings 6.93 T

✓ Sufficient

Bow Shackles (THE LIMIT) 5.20 T

⚠ CAPACITY LIMIT

Critical Finding

The shackles limit the entire system to 5.20 tonnes, even though the slings can handle more.

✓ Final Safety Determination

Maximum Safe Working Load

5.20T

RESTRICTED BY BOW SHACKLES

What Are Your Options?

Option A

Reduce the Load to 5.20 tonnes or less to safely use existing equipment.

Option B (Recommended)

Upgrade the Shackles to a higher SWL rating to match the sling capacity.

🎛️ Interactive 3D Load Simulator

Experiment with different angles and watch how the rigging system responds in real-time. Color-coded stress indicators show you exactly when configurations become unsafe.

Live Configuration

ACTIVE

Included Angle

60 °

10° Safe Vertical 140° Danger

Load Factor: 1.154

Status: SAFE

3D Visualization

Color Guide:
🟢 Green = Safe • 🟡 Yellow = Caution • 🔴 Red = Danger

WIRE ROPE SLINGS

6.93 T

2 × 4.0T slings adjusted for angle

BOW SHACKLES

5.20 T

2 × 3.0T shackles adjusted for angle

MAXIMUM SAFE WORKING LOAD

5.20T

Restricted by: Shackles