| Term | What it means | How to use it |
|---|---|---|
| Minimum breaking load (MBL/MBF) | Specified minimum force for a new rope | Confirm from the product standard or certificate |
| Working load limit (WLL) | Maximum permitted service load | Set by the responsible designer and governing code |
| Proof load | A specified verification load below failure | Use only when the applicable specification requires it |
For preliminary screening only:
Preliminary allowable load = verified MBL × termination efficiency ÷ required design factor
Example: if the verified MBL is 50 kN, the termination efficiency is 80%, and the governing design factor is 5, the preliminary value is 50 × 0.80 ÷ 5 = 8 kN. This is not final approval: bending fatigue, shock loading, corrosion, temperature, drum or sheave geometry and the weakest fitting may require a lower limit.
A 1×19 rope is relatively stiff, 7×7 provides intermediate flexibility, and 7×19 is designed for greater flexibility. The number and diameter of wires change the metallic cross-sectional area, so nominal diameter alone does not determine breaking strength.
304 and 316 stainless steels are selected primarily for corrosion conditions, while wire tensile grade and manufacturing route also affect capacity. Do not substitute a generic value for the certified breaking force of the ordered construction.
Swaged terminals, sockets, clips, thimbles and splices do not transfer the same percentage of rope strength. Small sheaves, poor groove geometry, misalignment, crushing and cyclic bending can reduce service life even when the static load is below the calculated limit.
Compare available stainless steel wire rope constructions. Final capacity must be approved for the complete assembly and service condition.