The lift cable is the single component most likely to fail catastrophically and the easiest to misjudge by eye. This chapter shows what each damage mode looks like, when industry standards (ASME B30.30, B30.9, OSHA 29 CFR 1926.1413) say to remove the cable from service, and how to inspect with confidence.
A Sumner lift cable is aircraft cable — galvanized steel wire rope. Sumner specifies the cable by diameter:
Industry-standard construction for this diameter range is 7×19 (seven strands of nineteen wires each), though Sumner's customer-facing copy does not specify the construction. Three inspection terms are essential:
By the wire-rope industry rule of thumb (lay length ≈ 7× rope diameter for 7×19), one lay on a 1/8″ cable is roughly 0.875 in; on a 7/32″ cable, roughly 1.5 in. Mark a reference length on a ruler before you inspect.
For each mode below: what it looks like, what causes it, and what the industry standards say. The verdict tag is the bottom line — service, monitor, or remove.
Individual wires fractured at random points along the cable. Caused by fatigue, side-loading over a sheave, or overload events.
Industry threshold (running rope, ASME B30.30): 6 randomly distributed broken wires in one lay or 3 broken wires in one strand in one lay.
● Remove from serviceWires fractured at the bottom of the valley between two adjacent strands — the inner crown. Hard to see from outside the cable; usually evidence of internal core failure.
Industry threshold: 2 or more valley breaks in one lay = immediate removal. There is no monitor zone.
● Remove immediatelyCable measures smaller than nominal at a localized spot. Caused by core failure, internal corrosion, or crushing. Use calipers, not your fingers — you can't feel a 5% change.
Industry threshold: >5% reduction from nominal diameter at any point = remove. For 1/8″ cable, that's a measurement of 0.119″ or less. For 7/32″ cable (Sumner MX-equipped lifts), 0.208″ or less.
● Remove from serviceThe cable holds a permanent bend or wave that doesn't straighten under tension. Caused by improper handling during cable installation — pulling out a loop without unwinding it.
Verdict: any kink = remove. The strands at the kink have already yielded; the cable cannot be straightened back to original load capacity.
● Remove from serviceOuter strands have separated from the core, ballooning out from the cable axis. Caused by sudden tension release after stretching, or torsional shock loads.
Verdict: any birdcage = remove. The strands have permanently lost their helical relationship and the cable can no longer share load equally between strands.
● Remove from serviceDiscoloration (blue, straw, or black), localized melting, or pitting from welding-arc strike. Heat alters the wire's temper — even a brief touch from a stick electrode can ruin a cable.
Verdict: any evidence of heat or electrical-arc damage = remove. There is no inspection that can verify the remaining strength of a heat-affected cable.
● Remove from serviceSurface oxidation from moisture exposure. Light surface rust on a galvanized cable is normal as the zinc coating is consumed; severe corrosion with visible pitting of the steel underneath is not.
Verdict: light surface oxidation only = service (and improve storage). Pitting of the underlying steel, or any visible rust on broken-wire ends = remove.
● Monitor / Remove if pittingOuter wires of the cable show flat spots from repeated travel through a worn or sharp-edged sheave. Often the warning sign that the sheave needs replacement before the cable does.
Verdict: <1/3 of the original wire diameter remaining at the wear point = remove. Replace the sheave at the same time or the new cable will wear in the same spot.
● Monitor / Replace sheaveBefore each shift. Use a clean rag and a pair of leather gloves — broken wire ends are razor sharp and rags catch them before they catch you.
Unloaded cable is easier to inspect, and the sheave-side wear surfaces are exposed.
The rag will snag on broken wires before your fingers do. A rag that comes back clean and un-frayed is a strong positive signal — but it is not a substitute for visual inspection.
Concentrate on: the cable termination at the carriage, the sheave-contact zone (top of mast at full extension), and the first wrap at the winch drum. Most failures concentrate at one of these three.
Spot check three points along the cable. For 1/8″ nominal: 0.125″ is healthy, 0.119″ (−5%) is the threshold for removal. For 7/32″ nominal: 0.219″ is healthy, 0.208″ is the threshold (the 7/32″ cable is what most current Sumner contractor lifts use).
Check the swage stop on the drum end, and the thimble + anchor clip at the carriage. Cracks at terminations are a removal trigger by themselves — the cable might be fine but the connection has failed.
Verify the minimum cable wraps remain on the winch drum at full lift height. Sumner's operator's manuals specify per-series: 4 wraps for the Series 2100, 3 wraps for the Series 2400. Confirm against the operator's manual matched to your lift's serial range.
If you find any of the eight damage modes above at the listed thresholds, tag the lift out of service. Note the finding on the maintenance-record decal and order the appropriate replacement cable.
Sumner's operator's manuals reference industry standards rather than redefining them. Use this matrix when you need a direct citation for a removal decision.
| Damage Mode | Running Rope (B30.30) | Wire-Rope Sling (B30.9) | Source |
|---|---|---|---|
| Random broken wires | 6 in one lay | 10 in one lay | ASME B30.30 / B30.9 |
| Broken wires in one strand | 3 in one lay | 5 in one lay | ASME B30.30 / B30.9 |
| Valley breaks | 2 in one lay = remove | 2 in one lay = remove | ASME B30.30 |
| Diameter reduction | >5% from nominal | >5% from nominal | ASME B30.30 / B30.9 |
| Kinking / crushing / birdcaging | Any = remove | Any = remove | OSHA 1926.1413 |
| Heat / arc damage | Any evidence = remove | Any evidence = remove | OSHA 1926.1413 |
| End-attachment cracking | Any = remove | Any = remove | ASME B30.30 |