17.1 Lifting Beams, Spreaders and Configuration Ratings
Key Takeaways
A compression spreader is not automatically rated for a central top pick.
Use the rating for the actual adjustable span.
Device weight adds to upper-system demand.
Testing requirements are device and application specific.
Match the structural function
A spreader commonly uses an upper bridle at its ends and lower connections to the load. In a simple symmetrical arrangement with vertical lower drops, the upper bridle’s inward components produce compression in the member. A lifting beam commonly uses an upper connection nearer its center and separated lower picks, producing significant bending.
These descriptions explain common arrangements; actual devices can combine functions. Select the manufacturer’s approved configuration rather than assuming any member called a “beam” can be suspended from any point. Applying a central top pick to a compression-only spreader creates a different structural load path that may be unapproved.
A spreader’s inclined upper bridle usually needs more headroom than a low-headroom lifting beam. A beam may have greater self-weight for a particular design, but there is no universal three-to-five-times weight ratio. Use actual weight and dimensions when calculating clearance and crane demand.
Keep lower force geometry explicit
Vertical lower drops can avoid inward sling components at the payload in the simple model. If lower slings incline, inward forces remain. A spreader does not automatically eliminate all crushing or provide stability for every load. The lower attachments, contact and support geometry still need approval.
For a symmetrical ideal spreader carrying W through vertical lower drops, upper angle θ from horizontal gives an inward component at each end of W/(2 tan θ), excluding member-weight effects not included in that simplified model. At lower upper angles, compression increases. This calculation explains why the manufacturer’s minimum upper angle matters; it does not qualify a homemade compression member.
| Configuration item | Selection consequence |
|---|---|
| Upper pick arrangement | Determines the structural load path |
| Lower span | May change rating and payload reactions |
| Upper sling angle | Changes tension and compression |
| Device weight | Adds to upper system and crane demand |
| Lower sling direction | Determines payload attachment forces |
| Stability | Requires the complete assembly geometry |
Read span and adjustment ratings
Adjustable beams can have different capacities at different spans or connection positions. Use the rating for the actual installed condition. Pins, bolts, stops and detachable components must match the manufacturer’s assembly. A sliding lug does not permit attachment at any unmarked point.
A training beam rated 20,000 lb at a 10-ft span and 14,000 lb at a 16-ft span cannot carry an 18,000-lb payload at 16 ft under those supplied conditions. The headline 20,000-lb rating belongs to another configuration. The upper slings and crane must also carry the beam and lower gear weight.
Marking and device information
The B30.20-2018 structural/mechanical excerpt in the CCO manual specifies rated-load marking and identification, including manufacturer information, serial number, design category and service class. It specifies lifter weight marking when over 100 lb, with applicable electrical data. Do not claim that every device must universally have the same riveted metal plate or every listed data item regardless of category.
Design category and service class describe design assumptions and fatigue-related service. They do not increase WLL or authorize shock loading. The responsible design and manufacturer information determine suitability for the intended duty. A rigger should recognize required markings and restrictions, not assign a new design category in the field.
Testing requirements depend on the device
Follow applicable B30.20, manufacturer and legal testing requirements. OSHA 1926.251(a)(4) specifically requires proof testing certain special custom-designed lifting accessories at 125% of rated load before use. That specific requirement must not be generalized into a claim that every below-the-hook product always requires one identical 125% test after every change.
A proof test is a controlled qualification activity, not a routine trial lift or permission to overload equipment at a job. The responsible entity must determine the applicable test, inspection, records and release to service. Missing required evidence is a reason to resolve the device’s status before lifting.
Evaluate suspended stability
A simple rigid assembly pivoting from one upper connection is unstable if its combined CG is above that pivot axis. Actual lower slings, constraints and articulation can introduce additional rotation modes. Evaluate the complete device-load system rather than assuming a spreader is inherently stable or a beam always flips if any individual pick lies below CG.
Weight-accounting example
A payload is 18,000 lb, lower rigging 600 lb and beam 1,400 lb. The upper connection carries 20,000 lb in the simplified static inventory. If the beam’s payload rating is 20,000 lb and its instructions define how lower rigging is included, follow that definition. Do not compare the upper 20,000-lb total with a rating intended only for payload without reading the basis.
Inspect members, welds, holes, bails, pins and adjustable connections before operation and through the applicable program. Stop for damage or a configuration discrepancy. Never weld a new pick onto a rated device or drill an extra adjustment hole without approved engineering and manufacturer procedures.
Sources: CCO B30.20 reference excerpt, OSHA custom-designed accessories.
A supplied beam is rated 20,000 lb at 10 ft and 14,000 lb at 16 ft. Can it carry an 18,000-lb payload at 16 ft?
No; the actual-span rating is only 14,000 lb
Yes; the largest rating always applies
Yes if the upper slings are stronger
Yes if the payload remains level
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