A rope with six broken wires in one lay might be fine to keep running — or it might already be well past its discard point, depending entirely on how that rope is built. Wire rope inspection isn't one universal number; the threshold that pulls a rope from service changes with construction, lay type and application. Here's the anatomy behind the criteria, the inspection tiers that catch deterioration in time, and exactly how to measure what you're looking at.
Which Discard Threshold Applies to Your Rope?
Pick a rope construction. See the broken-wire count that pulls it from service — because the same defect can be routine on one rope and a fatality risk on another.
Across all strands (3 in one strand) — the familiar threshold, but only for this construction class, per ASME B30.30.
Higher wire count spreads the same failure risk across more wires, so more individual breaks are tolerated before discard.
Dramatically stricter — internal wire contact in rotation-resistant construction hides damage that's already more advanced than it looks.
Standing ropes aren't measured over a lay length at all — any 3 broken wires anywhere, or 2 at one end fitting, means replacement.
Rope Anatomy: The Vocabulary Every Criterion Assumes
Every discard criterion in wire rope inspection is written using the same three reference points, so getting them straight first makes every threshold that follows make sense.
The smallest individual strand of steel. Multiple wires twisted together form a strand — a single broken wire is the base unit every removal count is built from.
A bundle of wires twisted around a center wire. Several strands, laid around a core, make up the finished rope — typically 6 or 8 strands in common construction classes.
The distance along the rope in which one strand makes a complete revolution around the core. Broken-wire counts are always expressed "per lay," not per foot or meter.
Short and long reference lengths used in modern discard tables, measured as 6 and 30 times the rope's own nominal diameter — this is why the same rope has two different broken-wire limits.
Three Levels of Wire Rope Inspection
Frequent Inspection
Daily, before use, by the operator. A visual check of the rope, end connections and anything reasonably visible during normal operation — no measurement tools required, but any obvious damage stops work immediately.
Periodic Inspection
Monthly to annually, by a qualified or competent person, matching OSHA 1926.1413's structure and ASME B30.5. A full run of the rope, measured broken-wire counts, diameter readings at multiple points, and a written, dated record.
Special Inspection
Triggered by an event, not a schedule — after overloading, shock loading, contact with a power line, or exposure to a corrosive environment. Treated with the same rigor as a periodic inspection regardless of when the last one happened.
This three-tier structure is consistent across the major frameworks — OSHA 1926.1413 and ASME B30.5 in the U.S., ISO 4309 internationally for cranes and hoists, and AS2759 in Australia — even where the exact terminology differs. Book a demo to see all three tiers scheduled per rope, with special inspections triggered automatically after a logged overload event.
Two Categories of Removal Criteria
- Kinking, crushing, birdcaging or unstranding
- Core protrusion or any sign of core failure
- Heat damage from a torch or electrical arc
- Corrosion causing visible pitting
- Damaged, cracked or improperly applied end fittings
Any single condition here means immediate removal — no broken-wire count needed, no judgment call.
- Counted over the 6d and 30d reference lengths
- Threshold varies by construction class (see calculator above)
- Two or more valley breaks in one lay — automatic removal regardless of total count
- Requires a full run of the rope, not a spot check
- Must be measured and recorded, not estimated
This is where most inspection errors happen — applying one rope's threshold to another.
Valley breaks deserve special attention: they occur between strands rather than on the visible crown, signal internal fatigue far more advanced than the surface suggests, and are treated as an automatic removal trigger across every major standard regardless of how few are found. Book a demo to see Category 1 and Category 2 conditions both captured on the same digital inspection, instead of relying on an inspector to remember which rule applies.
How to Measure What You're Looking At
A broken-wire count only means something if the diameter and location measurements behind it are done correctly — and this is where a rushed inspection quietly produces a wrong answer.
Diameter
Measure crown-to-crown across the rope, not strand valley to strand valley. Take 3 measurements on a 6-strand rope and 4 on an 8-strand rope, at different points, and compare against nominal — wear or core damage past roughly 5–10% reduction typically triggers replacement depending on the governing standard.
Broken Wire Location
Count separately by lay section, not cumulatively along the whole rope — a rope can pass a cumulative count and still fail because one lay section alone exceeds the threshold. Run the full length; damage concentrates at drum crossover points and sheave contact zones, not evenly.
Corrosion & Wear
Surface rust after light use often signals lubrication failure, not structural loss — but pitting that's visibly reduced a wire's cross-section is a Category 1 condition regardless of broken-wire count. Distinguish the two before deciding whether the rope needs replacing or just relubricating.
Sign up free to build measurement fields directly into your rope inspection template, so a diameter reading gets compared to nominal automatically instead of left to memory.
Documentation: The Wire Rope Inspection Record That Proves the Rope Was Sound
One published analysis of U.S. crane fatality data found rigging and cable failure behind roughly 27% of fatal load-drop incidents — and in nearly every one, the question that follows isn't just what failed, it's whether an inspection record exists showing the rope was sound the day before. A mill certificate documenting diameter, construction and working load limit at installation, a dated inspection log with inspector identity and measurements (not just "OK"), and photo evidence at each periodic inspection together form the record that either supports a maintenance program under scrutiny or leaves it exposed. Retention matters as much as the record itself — most standards expect periodic inspection records kept for the working life of the rope, not just the most recent cycle. Book a demo to see a full inspection history pulled up per rope in seconds, ready before an auditor or incident investigator asks for it.
What a Rigging Supervisor Actually Watches For
New guys almost always apply the standard 6-strand rule to everything, because it's the number everyone learns first. I've had to stop a lift because someone cleared a rotation-resistant hoist line using the wrong threshold entirely — two broken wires should have pulled that rope, and it passed under the wrong rule. Now every rope's construction is tagged and the inspection template pulls the right criteria automatically, so nobody's relying on memory under pressure.
The Takeaway
Wire rope inspection only works when the threshold applied matches the rope on the hook — a standard 6-strand count on a rotation-resistant line isn't a minor error, it's the exact mistake that lets a rope stay in service well past where it should have been pulled. Know your construction class, run the full length at every periodic inspection, measure diameter correctly, and treat Category 1 conditions as non-negotiable regardless of broken-wire count. Sign up free and put the right discard criteria behind every rope in your inventory automatically.
Frequently Asked Questions
How many broken wires mean a wire rope must be removed from service?
It depends entirely on rope construction. Standard 6-strand running rope is typically removed at 6 broken wires within a 6-diameter length or 12 within a 30-diameter length (3 in a single strand). Larger running ropes (8-strand and above) tolerate more — roughly 8 and 16 respectively. Rotation-resistant rope is far stricter, at around 2 and 4. Standing ropes such as guy or bridge ropes use a different rule entirely: as few as 3 broken wires total, or 2 at a single end termination, per ASME B30.30.
What's the difference between frequent, periodic and special wire rope inspections?
Frequent inspection is a daily visual check by the operator before use, requiring no tools. Periodic inspection is a scheduled, documented inspection by a qualified or competent person — monthly to annually depending on use and governing standard — involving a full run of the rope with measured broken-wire counts and diameter readings. Special inspection is triggered by a specific event, such as overloading, shock loading, or exposure to a corrosive environment, and is carried out with the same rigor as a periodic inspection regardless of the regular schedule.
What is a valley break and why does it matter?
A valley break is a wire that fractures between strands rather than on the visible outer crown of the rope, which means it's often harder to spot on casual inspection. Valley breaks indicate more advanced internal fatigue than the visible surface suggests, and under major standards including ASME B30.30, finding two or more valley breaks in a single lay length triggers automatic rope removal regardless of the total broken-wire count.
How should wire rope diameter be measured correctly?
Diameter should be measured crown-to-crown across the outer strands, not valley-to-valley between strands, since measuring the wrong reference point produces a falsely low reading. Standard practice is 3 measurements at different points along a 6-strand rope and 4 on an 8-strand rope, compared against the rope's nominal (not actual installed) diameter. A reduction of roughly 5–10% from nominal, depending on the governing standard, typically triggers removal regardless of broken-wire count.
What wire rope conditions require immediate removal with no broken-wire counting?
Category 1 conditions require immediate removal regardless of broken-wire count: kinking, crushing, birdcaging or unstranding, any core protrusion or sign of core failure, heat damage from a torch or electrical arc, corrosion causing visible pitting, and damaged, cracked or improperly applied end fittings. These conditions indicate structural compromise that a broken-wire count wouldn't capture, so no threshold applies — any one of them alone is sufficient grounds for removal.
Stop Relying on Memory for Construction-Specific Discard Criteria
HVI applies the correct removal thresholds by rope construction, captures measurements with photo evidence at every inspection tier, flags deficiencies automatically, and keeps a permanent, exportable inspection record for every rope in your inventory.
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