Spreader Bar — Animation
Spreader bar rigged between crane hook and load — keeps sling legs vertical to eliminate angle factor loss
Anatomy of a Spreader Bar
Main Beam
The structural member — either a tubular section or I-beam profile. Carries the full load in compression (spreader bar) or bending (lifting beam).
Top Lug
The upper attachment point connecting the spreader bar to the crane hook via a shackle or master link. Must be centred on the beam for balanced loading.
Bottom Lugs
Lower attachment points where slings connect to the load. May be fixed at set positions or adjustable via pin holes to suit different load widths.
End Plates
Welded plates at each end of the beam that house the bottom lug pin holes. Reinforce the beam ends and transfer sling forces into the main member.
Purpose & Key Advantages
- Eliminates sling angle forces — sling legs hang vertically from the bottom lugs, so each leg carries only its share of the load with no angular derating
- Prevents crushing of load — slings pull straight down instead of squeezing inward, protecting fragile or wide loads
- Distributes load evenly — spreads the lifting force across the full width of the load, reducing point loads
- Keeps slings vertical (0°) — each sling uses 100% of its WLL, vs only 50% at 120° included angle without a spreader
- Controls load orientation — prevents the load from rotating or tilting during lift
The Angle Problem a Spreader Solves
Without spreader @ 120°: each leg = 100% of load
With spreader @ 0° (vertical): each leg = 50% of load
When sling angles would exceed 120° without a spreader, the spreader bar keeps legs vertical, using 100% of sling WLL.
Always Check Data Plate & Manufacturer Specs
- The spreader bar data plate shows WLL, self-weight, span, and manufacturer
- Always refer to the manufacturer’s specifications for rated capacity at specific configurations
- The spreader bar’s self-weight must be included in total lift weight calculations
Spreader Bar vs Lifting Beam
These terms are often used interchangeably but they are structurally different:
| Feature | Spreader Bar | Lifting Beam |
|---|---|---|
| Primary stress | Compression | Bending |
| How it works | Slings from hook attach at each end — beam pushes outward | Single attachment at top — load hangs from lugs below the beam |
| Sling arrangement | Slings above and below the beam | All slings hang below the beam |
| Headroom required | More (slings above + below) | Less (only slings below) |
| WLL calculation | Based on compression buckling | Based on bending moment |
| Weight | Lighter for same span | Heavier (must resist bending) |
Critical Difference
- A spreader bar loaded in bending will fail — it is designed for compression only
- A lifting beam used as a spreader bar may buckle — different failure mode
- Never interchange them without engineering verification of the WLL for the actual loading mode
Selection Criteria
Select the correct spreader bar for each lift based on these factors:
- WLL rating — must be rated for at least the total weight of the load being lifted
- Length — must match or exceed the load width so sling legs hang vertical or near-vertical
- Attachment points — bottom lugs must suit the sling type (shackle size, pin diameter) being used
- Adjustable vs fixed — adjustable models allow different load widths but must be checked at the selected pin position
- Self-weight — add the spreader bar weight to the total lifted load when calculating crane capacity
- Number of pick points — some beams have 2, 4, or more bottom lugs for distributing load across multiple sling legs
Remember
Total lifted load = Load weight + Spreader bar weight + Sling weight
Always include the spreader bar and all rigging hardware in your gross load calculation.
Inspection & Rejection Criteria
Inspect spreader bars before every use. Remove from service if ANY of the following are found:
Reject Immediately If
- Bent beam: any visible bow, twist, or deformation in the main member
- Cracked welds: any cracks at lug-to-beam welds, end plate welds, or gusset welds
- Worn lugs: pin holes elongated, lug faces worn, or lug thickness reduced
- Damaged threads: on adjustable models, stripped or cross-threaded adjustment mechanisms
- No markings / WLL plate: missing, illegible, or removed identification plate
- Corrosion: significant pitting, rust scale, or material loss on any load-bearing section
- Unauthorised modifications: additional holes drilled, field welding, or attachments not on the original design
Good Condition Indicators
- Beam straight with no visible deformation
- All welds intact, smooth, and crack-free
- Pin holes round and not elongated
- WLL plate legible with current test date
- Adjustment pins/bolts in serviceable condition
- Paint/coating intact — no exposed corroding steel
When to Use a Spreader Bar
- Wide loads: when the load width would cause sling angles to exceed 120° included angle
- Fragile loads: glass panels, cladding, precast panels — prevent crushing from inward sling forces
- Long loads: steel beams, pipes, trusses — control balance and prevent bowing
- Loads requiring level lift: when the load must stay perfectly horizontal during the lift
- Multiple pick points: when the load has specific engineered lifting points that must be used
Never Use a Spreader Bar If
- The spreader bar WLL is less than the total load weight
- The attachment points do not suit the slings or shackles available
- The spreader bar has not been inspected and tagged
- It would exceed the crane’s capacity when added to the load weight
Standards & Compliance
| Standard | Covers |
|---|---|
| AS 4991 | Lifting equipment — design, manufacture, testing of spreader bars and lifting beams |
| AS 2550 Series | Cranes, hoists and winches — safe use (includes below-the-hook lifting devices) |
| AS 1418.1 | Cranes, hoists and winches — general requirements |
- All spreader bars must be proof-tested to at least 2× WLL before first use
- Must be permanently marked with WLL, identification number, self-weight, and manufacturer
- Must be included in a register of lifting equipment with inspection records
- Designed and manufactured by a competent person — never fabricated on site without engineering
- Periodic inspection intervals as per manufacturer or AS 4991 requirements