KEVOS® MAKEOS · Mechanics
Lifting Beam and Spreader Beam Check
Is this lifting beam or spreader bar strong and stiff enough for the load, and what are the sling tensions?
Check of a below-the-hook beam: a lifting beam (one top lug, load hung from two points, beam in bending) for bending stress and deflection, or a spreader beam (top slings to the ends, beam in compression) for the compression from the sling angle and Euler buckling, with the sling leg tensions, using a dynamic factor on the load.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Beam type | choice | A lifting beam carries the load in bending from one central lug; a spreader beam keeps slings apart and is in compression. |
| Load mass | kg | Mass of the load (plus rigging below the beam). |
| Dynamic factor | Factor for lifting dynamics (from the lifting standard; about 1.1–1.3). | |
| Spacing of the load lift points | mm | Distance between the two load lift points. |
| Top sling angle from vertical (spreader) | ° | Angle of each top sling leg from vertical (spreader beams). |
| Section | ||
| Elastic section modulus | mm³ | Section modulus of the beam about the bending axis. |
| Second moment of area (least, for buckling) | mm⁴ | Second moment of area (the least one for spreader buckling). |
| Elastic modulus | GPa | Elastic modulus of the beam. |
| Allowable bending or compressive stress | MPa | Allowable stress from the lifting equipment standard. |
| Section area (spreader) | mm² | Cross-section area of a spreader. |
| Required buckling factor (spreader) | Factor required against Euler buckling. | |
Method and formulas
- Design load W = mass × g × dynamic factor; each load point carries W ÷ 2.
- Lifting beam: M = W S ÷ 4; stress = M ÷ Z; deflection = W S³ ÷ 48 E I (central lug, end loads, equivalent to a centrally loaded simple span).
- Spreader: top sling tension = W ÷ (2 cos θ); compression = (W ÷ 2) tan θ; buckling P_cr = π² E I ÷ S² (pinned ends).
- Example: a 5000 kg load on a 3000 mm lifting beam gives 153.23 MPa bending stress.
Limitations
- Lifting equipment must be designed, proof-tested and certified to the applicable standard.
- Lug, weld and local flange checks are separate.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check a fabricated lifting beam before use
- Choose a section for a spreader bar
- Find sling tensions for a two-point lift
Who it is for
- Rigging supervisors
- Structural engineers
- Lifting equipment designers
What you get
- Design load and sling tension
- Bending stress and deflection (lifting beam)
- Compression and buckling factor (spreader)
Interpreting the result
- Flatter top slings (larger angles) raise both sling tension and spreader compression quickly.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2613–2625, 281–285. Topic reference; no source tables or recommended settings are reproduced.
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