Industrial-grade lifting-point verification: shackle WLL table with side-load derating, DIN 580 eye bolt checks with load-direction factors, thread engagement and shoulder seating verification, utilization verdict and full audit trail.
Decision:Run the stated engineering model, review its assumptions and warnings, then make the release decision against the governing standard and verified source data.
SectorCalc SC-032 verifies the two most common lifting points: anchor shackles from the standard G-209/2130-class WLL table and DIN 580 eye bolts. Both are direction-sensitive — a shackle loaded 90° off its pin axis keeps only half its rating, and an eye bolt pulled transverse to its eye plane is prohibited outright. The engine applies the published derating factors, checks thread engagement and shoulder seating for eye bolts, and returns a utilization verdict with next-size-up guidance. Tag and certificate always govern over table values.
Working load limits and the safety factor
Shackle WLLs carry a 5:1 or 6:1 design factor depending on class; DIN 580 values embed their own margin for C15E material. These factors cover material scatter and test verification — NOT misuse. Side loading, wear, deformation and corrosion eat the margin from the other side. Never add your own "extra safety factor" on top of WLL; derate for the actual conditions instead.
The derating comes from the shackle manufacturer association (Crosby published): a side-loaded shackle bends the pin and pries the bow ears apart — half the rating disappears at 90°. Multiple sling legs in one shackle must be checked leg by leg against the pin-axis rule: symmetric bridle legs at ±θ stay "inline" as long as the resultant runs through the pin centerline.
Eye bolt load directions
Eye bolt: axial ×1.00 · angled ≤45° ×0.50 · 90° in eye plane ×0.25 · transverse to eye plane: PROHIBITED
An eye bolt is a threaded cantilever. Axially it loads the thread in pure shear; angled it bends the shank against the shoulder; transverse to the eye plane the ring opens like a hook — DIN 580 forbids it entirely. For anything but vertical picks, use swivel hoist rings (rated for angled loads) instead of plain eye bolts.
Installation: engagement and seating
Thread engagement must reach ≥1.5×d in steel and ≥2×d in cast iron or aluminium — the WLL table assumes it. The shoulder must seat flat on a machined surface; a gap lets the shank bend under axial load and converts a straight pull into a fatigue failure. Shim washers under the shoulder are prohibited; counterbore or spot-face instead.
Multiple devices sharing a load
Equal sharing is assumed — valid for symmetric loads with identical devices at identical angles. With two eye bolts and a two-leg sling, each bolt sees the full leg tension at its own angle, not half the total: verify per-point loads from the sling calculation (SC-031) rather than trusting the arithmetic mean.
Frequently asked questions
The shackle pin is harder to turn after a lift — reuse it?
No. A stiff or distorted pin signals side-load yielding: the shackle is scrap. Cut it up so nobody reuses it, and record the destruction in the rigging register.
Can I weld an eye bolt to the load?
Never. Welding destroys the forged structure and the certification. Weld-on lifting points (DIN 580 is screw-in only) are a different product family with their own rated tables and welding procedure requirements.
Why is the transverse direction prohibited when 90° in-plane is allowed?
In-plane side loading still bears against the forged ring's strong section; transverse loading twists the ring open at its weld-free but weakest geometry. Tests show catastrophic opening at a fraction of axial WLL — hence prohibition, not derating.
DIN 580 vs collar-type (swivel) hoist rings?
Swivel rings rotate to align with the pull and carry full WLL at any angle in their rated cone — they cost 10× more and are mandatory wherever the pull is not axial. If this tool flags your eye bolt direction, the answer is usually a swivel ring.
