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Quick Reference Guide

Load Factors (Sling Angle)

  • 90° (Vertical): Factor 1.000
  • 60° Included: Factor 1.154
  • 90° Included: Factor 1.414
  • 120° Included: Factor 2.000

Key Formulas

Load Factor
1 / cos(Angle from Vertical)
SWL Calculation
(Wll x Legs) / Factor
1. The "Weakest Link" Principle
UNKNOWN LOAD MASS SWL 4 TON SWL 3 TON Included Angle: 60°

Calculate the Maximum Safe Working Load (SWL) for this configuration.
Note: Consider both the Sling Capacity and Shackle Capacity. Angle Factor for 60° Included is 1.154.

Step 1: Identify the "Weakest Link"

The Slings are 4 Tonnes. The Shackles are 3 Tonnes.
The calculation must be based on the 3 Tonne Shackles.

Step 2: Determine Angle Factor

For an included angle of 60°, the factor is 1.154.

Step 3: Calculate System Capacity

Formula: (Lowest Capacity × Legs) ÷ Factor

(3T × 2) ÷ 1.154 = 5.20 Tonnes

2. Rigid Loads (3D Visualization)

A rigid box is being lifted by 4 legs. The slings are rated at 5 Tonnes each. Because the load is rigid, it may rock, placing weight on only 2 diagonal legs.
Calculate Safe Load assuming 90° Included Angle (Factor 1.414).

Step 1: The Rigid Load Rule

For rigid loads with 4 legs, we assume the load is carried by only 2 legs (diagonal pair).

Step 2: Calculation

Capacity = (5T × 2 Legs) ÷ 1.414

= 10 ÷ 1.414 = 7.07 Tonnes

3. Center of Gravity Shift
C.O.G Leg A Leg B Beam Length: 6m

The Center of Gravity is much closer to Leg B. Which leg will experience more tension?

Principle of Moments

The leg closest to the Center of Gravity (COG) always carries the greater share of the load.

Since the COG is shifted to the right, Leg B takes more weight.