Exercises: Advanced

Progression: 0/3

Advanced Principles Guide

Spreader Beams

Used to convert angled forces into vertical ones. The "Top Slings" carry the full load at an angle, while "Bottom Slings" carry only vertical share.

Tandem Lifting Formulas

Load on Crane A
Load x (Dist B / Total Dist)

Load on Crane B
Load x (Dist A / Total Dist)

1. Flexible Load (4-Leg Equalized)

A flexible load ensures weight is shared by all 4 legs. Calculate the Total Max Safe Load.
SWL = 3T per leg. Angle = 45°. Factor = 1.414.

Step 1: Vertical Capacity per Leg

SWL ÷ Factor = 3 ÷ 1.414 ≈ 2.12 Tonnes

Step 2: Total Capacity

Since load is flexible, all 4 legs work.

2.12 × 4 = 8.49 Tonnes

2. Spreader Beam Tension

Calculate the tension in the Top Slings (Red).
Total Load + Beam = 50 Tonnes.
Top Angle = 90° Included (Factor 1.414).

Hint: Calculate share per side (25T) then apply factor.

Step 1: Vertical Share per Side

50T Total ÷ 2 Sides = 25 Tonnes vertical load.

Step 2: Apply Angle Factor

25T × 1.414 = 35.35 Tonnes tension.

(Note: This is per sling set if using 2-leg top bridle)

3. Tandem Lift (2 Cranes)

Calculate the load shared by Crane A (Red).
Distances are from the lifting points to the Center of Gravity.
A to COG = 5m. B to COG = 15m. Total Span = 20m.

The Inverse Distance Rule

The crane closest to the COG takes more load.

Formula for A: Total Load × (Dist B ÷ Total Span)

Calculation

Load × (15m ÷ 20m) = 100 × 0.75 = 75 Tonnes