Crane Wire Rope and Sheaves: Construction, Inspection and Replacement

Crane wire rope is the steel hoist rope that runs from the winch drum along the boom, over the sheave at the boom tip and down to the hook block. It carries every load the crane lifts on its winch; consequently, its condition, and the condition of the sheaves it travels over, determines whether the lift is safe. On a hydraulic truck mounted or marine crane, hydraulic cylinders raise and fold the boom, so the rope you inspect every day is usually this hoist rope.

We have built truck mounted cranes in Xuzhou since 2003, and every telescopic crane we ship lifts on a winch and a wire rope. This guide explains how crane rope is made, how it is reeved over sheaves to the hook block, what the inspection rules ask for, when a rope must be discarded and how to replace it with the right rope. It complements our crane winch guide, which covers the winch itself.

What is crane wire rope?

A crane uses two categories of wire rope. A running wire rope is, in the words of 29 CFR 1926.1401, “a wire rope that moves over sheaves or drums”. A standing rope, such as a boom pendant, remains stationary and only supports the structure. The hoist rope on a winch is a running rope, so it is bent over the drum and the sheaves thousands of times during its service life.

This repeated bending is the principal reason the rope wears out. Wikipedia’s wire rope article notes that running ropes are “stressed mainly by bending and secondly by tension”. The crane rope standard, ISO 4309:2017, therefore treats the rope on a crane as “an expendable component”, to be replaced when inspection shows that further use might be unsafe. The standard covers ropes on mobile cranes, deck cranes and floating cranes, among others, whether the winch is driven manually, electrically or hydraulically.

The hoist rope is a component of the crane, not a lifting accessory. Wire rope slings below the hook follow their own rules and removal criteria, which our crane rigging and slings guide explains.

Wire rope construction: wires, strands, core and lay

Every steel wire rope is manufactured in the same way: individual wires are twisted into strands, and the strands are laid around a central core. The steel wires are normally non-alloy carbon steel with a carbon content of 0.4 to 0.95 % [8]. Their exceptionally high tensile strength allows a relatively thin rope to carry a considerable load and still operate over a sheave of modest diameter.

Term	What it means	Why it matters on a crane
Wire	A single steel wire	Broken wires are the first sign of fatigue and are counted at every inspection
Strand	Wires laid around a centre wire	A broken strand is a Category III deficiency under the US rule
Fibre core (FC)	A core of natural or synthetic fibre	Flexible, but it can be crushed, so it suits single-layer spooling
Independent wire rope core (IWRC)	A small wire rope used as the core	Supports the strands in multi-layer spooling on a winch drum
Lay	The direction the wires and strands are twisted	Decides how the rope behaves under load and how it spins
Rope lay (length)	The length in which one strand makes a full turn	The reference length for counting broken wires
Grade	The tensile strength of the wire, in MPa	With diameter and core, it sets the breaking force of the rope

Sources: NSW Government dogging and rigging guide, Wikipedia “Wire rope” and the US crane rule on wire rope inspection, compiled November 2026.

Fibre core or steel core

The NSW Government dogging and rigging guide says a fibre core gives extra flexibility and is normally used in single-layer applications. A wire rope core gives extra strength and support in multi-layered applications to prevent crushing. Its page on multiple layers on drums goes further: steel-cored ropes should be used, and fibre-cored ropes are not recommended. Most crane winches spool the rope in several layers; consequently, an IWRC hoist rope is the usual specification.

Core type and grade alter the strength considerably. The same NSW guide gives a 16 mm fibre core rope of 1570 grade a breaking strain of 113 kN, against 161 kN for a 16 mm steel core rope of 1770 grade [4]. Two ropes of identical diameter are therefore not interchangeable, which is precisely why a replacement must match the crane manufacturer’s specification.

Ordinary lay and Lang’s lay

Lay is the spiral direction in which wires form strands and strands form the rope. In ordinary (regular) lay, the wires run opposite to the strands, so the outer wires lie almost along the rope; most general-purpose ropes are right-hand ordinary lay. In Lang’s lay, wires and strands run the same way, and the NSW guide notes it is used where both ends of the rope are fixed to prevent rotation. According to the NSW guide, lay does not change the working load limit of the rope, but it does determine characteristics such as spin.

Rotation-resistant rope

Every stranded rope tends to unwind under tension, which can rotate a load suspended on a single line. Rotation-resistant rope is rope with two or more layers of strands laid in opposite directions, so that the turning forces largely cancel out. The NSW guide, which calls them non-rotating ropes, notes that they are usually used as crane hoist rope, with typical constructions such as 18×7, 19×7, 32×7 or 35×7.

The US rule, 29 CFR 1926.1414, sorts it into three types. Type I has at least 15 outer strands, Type II at least 10, and Type III no more than nine [2]. All rotation-resistant ropes need an operating design factor of no less than 3.5, and the rule sets 5 as the normal minimum for each type. This construction is less tolerant of damage, so its discard limits for broken wires are considerably stricter, as the discard section below explains.

How the hoist rope runs on a truck mounted or marine crane

On a crane equipped with a winch, the rope leaves the drum, travels along the boom and passes over the boom head sheave to the hook. With a single line, the hook is suspended from one part of rope. For heavier loads, the rope is reeved repeatedly between the sheaves in the boom head and the sheaves in a hook block, so that several parts of line share the load.

This arrangement operates like a block and tackle. If friction is ignored, its mechanical advantage is the number of rope parts that support the moving block, according to Wikipedia’s block and tackle article. The NSW guide’s page on mechanical advantage adds three practical points:

• The load in each part equals the total load on the lower block divided by the number of parts, and that total includes the slings, shackles and blocks.
• Friction accumulates. It amounts to approximately 3 % to 5 % per sheave, so the lead rope to the winch carries the highest load [6]. In the guide’s worked example, 10 t on five parts produces 2 t per part, but approximately 2.7 t in the lead rope after seven sheaves.
• Reeve symmetrically. When parts of line are removed to obtain a faster hook, they must not all be taken from one side of the boom head sheaves and the hook block.

The winch itself is a separate subject. Our crane winch guide explains when a crane requires one, why at least two full wraps must remain on the drum, and how the anti two-block device prevents the hook block from being pulled into the boom head. In practice, the rope is only as reliable as the drum, the brake and the limiting devices surrounding it.

On our cranes, the winch and rope are standard on every telescopic model, from the 2,000 kg SQ2SA3 to the 20,000 kg SQ20SA5, and optional on knuckle boom models, where a J in the model code marks the winch. Our technical drawings specify the crane’s capacity, lifting moment, outreach and self-weight. They do not state the rope diameter, rope length or the winch’s line pull. We confirm those values for your particular model and application in the quotation, together with the load chart for the winch configuration.

Crane sheaves: grooves, D/d ratio and the rooster sheave

A sheave is “a grooved wheel or roller over which a rope or chain passes”, as the NSW rigging glossary puts it. On a crane, sheaves are located in the boom head, in the hook block and occasionally as lead sheaves between the drum and the boom. Every sheave bends the rope, so a sheave in poor condition rapidly reduces rope life. The same glossary defines the rooster sheave as “the head sheave for the auxiliary winch on the top of the boom head of a hydraulic boom crane”. Not every boom-tip sheave is a rooster sheave, therefore: the term refers to the extra sheave for a second, auxiliary hoist line.

Groove size and shape

ISO 4309 says the sheave groove diameter should be between 5 % and 10 % larger than the nominal rope diameter, and at least 1 % larger than the actual diameter of the new rope [3]. The NSW guide’s page on sheaves explains why. A groove that is too large allows the rope to flatten, whereas a groove that is too small pinches the rope and creates additional friction that can eventually cut it. The same page asks for a groove depth of at least 1.5 times the rope diameter and groove sides flared between 42° and 52° [5].

Sheave diameter and the D/d ratio

The D/d ratio is the sheave or drum diameter (D) divided by the rope diameter (d). The smaller the ratio, the more severely the rope is bent and the sooner it fatigues, and Wikipedia identifies the D/d ratio as a principal factor in rope drive design. The Machinery Directive, in Annex I, section 4.1.2.4, simply requires pulleys and drums to have “a diameter commensurate with the size of the ropes”. The US rule on rope selection quotes the ASME mobile crane standard, B30.5, for a minimum pitch diameter of 16 times the rope diameter for sheaves in multiple rope reeving. It raises that to 18 times when rotation-resistant rope is used for boom hoist reeving [2].

For an owner, the practical consequence is simple: the sheaves are designed for that particular crane, so never fit a larger rope to gain additional strength. The NSW guide states that “sheaves are designed for a particular crane or hoist” and that a replacement rope must have the same diameter and construction.

How to inspect a crane sheave

The NSW page on sheave inspection identifies four areas to examine regularly, and a fifth item comes from its page on fleet angles.

1. Flange: cracks or chips on the flange can cut the rope as it enters the groove.
2. Groove: wear reduces the groove diameter and leaves an uneven bearing surface. Check the profile with a gauge before fitting a new rope.
3. Bearings: a badly lubricated sheave adds friction and wears the rope, pin and bearing.
4. Pin: it must not turn with the sheave, because a rotating pin can cut through the cheek plate.
5. Fleet angle: the angle between the drum and the first sheave should not exceed 5° for a grooved drum or 3° for a plain drum [9]. Otherwise the rope spools badly and wears the sheave flange.

The sheaves in the hook block, often called the crane sheave block, are checked the same way, together with the side plates and the hook. Our crane hook guide covers hook blocks and hook inspection in detail.

Wire rope inspection: shift, monthly and annual

The clearest rope inspection rule in force is the US construction rule, 29 CFR 1926.1413. It establishes three levels of inspection, each with a different scope and a different responsible person.

Inspection	When	Who	What it covers
Shift	Begun before each shift the crane is used, completed before or during the shift	Competent person	Visual check of the ropes likely to be used that shift for apparent deficiencies; no opening of the rope or booming down needed
Monthly	Each month	Competent person	The shift inspection, plus any deficiency the annual inspector marked for monitoring; documented
Annual / comprehensive	At least every 12 months	Qualified person	The whole length of every rope in use, with attention to hidden sections, reverse bends and rope passing over sheaves; documented

Source: 29 CFR 1926.1413(a) to (c), eCFR, retrieved November 2026.

The rule also names critical review items that need particular attention. These are rotation-resistant rope, rope at drum flange points, crossover points and repetitive pickup points, rope at or near its terminal ends, and rope in contact with saddles, equalizer sheaves or other sheaves where rope travel is limited. Rope lubricants of a type that hinders inspection must not be used.

ISO 4309 takes a different approach to timing. It separates daily visual inspections from periodic inspections and leaves the periodic interval to the competent person. That person must weigh the national rules, the type of crane and its environment, earlier results, how long the rope has been in service, how often it is used and the crane manufacturer’s recommendations [3]. In Great Britain, regulation 9 of LOLER 1998 requires lifting equipment exposed to deterioration to be thoroughly examined at least every 12 months, or under an examination scheme.

The rope is only one element of the crane’s wider daily inspection routine. Our truck mounted crane inspection checklist puts it alongside the hydraulics, the hook, the limit devices and the outriggers.

Wire rope discard criteria: when to replace the rope

A rope must be removed from service when its deterioration reaches a discard criterion, not when it finally breaks. The US rule classifies apparent deficiencies into three categories, and each category requires a different response.

Broken wires and diameter loss

For a running rope, the US limit is six randomly distributed broken wires in one rope lay, or three broken wires in one strand in one rope lay [1]. Rotation-resistant rope is far stricter: two broken wires in six rope diameters, or four in 30 rope diameters. A diameter reduction exceeding 5 % of the nominal diameter is also classified as a Category II deficiency.

The NSW guide’s page on common causes of damage and failure adds detail that helps on the crane. Broken wires on the crowns of the strands are normal fatigue. Breaks that start in the valleys between strands are more serious, because they point to internal fatigue or core problems, and the guide says such ropes should be discarded. It also says to replace a rope when its outer wires are worn by one third or more of their diameter [7].

Measure the diameter correctly: the NSW guide recommends vernier callipers, rotated around the rope until the jaws reach the widest point across the strand crowns. ISO 4309 requires the diameter of the new rope to be measured and recorded as a baseline, so later readings show the real loss rather than a guess.

Kinks, birdcaging, corrosion and heat

Category I covers damage that a competent person must judge on the spot: kinking, crushing, unstranding, birdcaging, signs of core failure, significant corrosion, heat or electric arc damage, and faulty end connections. If the damage is a safety hazard, the rope stays out of service until it is replaced or the damaged length is cut off. ISO 4309 lists similar discard modes, including waviness, basket deformation, core or strand protrusion, flattened portions, kinks, and damage due to heat or electric arcing.

Category III, the most serious group, covers a broken strand, core protrusion in rotation-resistant rope and any prior contact with a power line. A rope that has touched an energized line must never be repaired; it is replaced. Our crane power line safety guide explains how to keep the crane and its rope clear of overhead lines.

Splicing is not an acceptable repair: the US rule prohibits joining lengths of wire rope by splicing, and the Machinery Directive allows no splices in ropes used directly for lifting, other than at their ends. When a damaged length is cut off, at least two full wraps must still remain on the drum with the hook at its lowest position.

Wire rope care on marine cranes and in salt water

Salt water and spray attack wire rope considerably faster than road dust. Significant corrosion is a Category I deficiency, and the NSW guide describes it as “noticeable pitting or loosening of outer wires”. On a marine crane, the rope additionally spends long periods wound on the drum, where moisture can remain trapped between the layers.

• Rinse and lubricate. After work at sea, rinse salt from the rope and the drum with fresh water, then dress the rope with a lubricant compatible with the rope manufacturer’s original lubricant. Avoid any lubricant that hides the wires, because the US rule bans lubricants that hinder inspection.
• Store spare rope dry. ISO 4309 asks for a cool, dry building, off the floor and away from chemicals and steam. Outdoors, cover the rope so that moisture cannot cause corrosion.
• Inspect the concealed sections. Pay out the rope and examine the sections that normally remain on the drum or rest over the boom head sheave while the crane is parked.
• Look inside when in doubt. External rust is easy to see, but internal corrosion is not. The 2017 edition of ISO 4309 introduced magnetic rope testing (MRT) as an aid to the internal inspection of wire ropes.

Corrosion protection of the crane itself is an essential part of selecting the appropriate model. Our guides to marine crane sizes and the deck crane cover painting, stowage and care for cranes that work on vessels and quays.

How to replace crane wire rope

Replacement begins with the specification, not with whatever rope is available in the warehouse. ISO 4309 requires a rope of the correct length, diameter, construction, type, direction of lay and strength, as specified by the crane manufacturer, unless an alternative has been approved. The US rule on rope selection says replacement rope must follow the recommendations of the rope manufacturer, the equipment manufacturer or a qualified person.

1. Confirm the specification. Read it from the crane manual, or send the crane manufacturer the model and serial number. The minimum breaking force must not be lower than the crane manufacturer specifies.
2. Check the new rope on arrival. Compare it and its certificate with the order, then measure and record its diameter in a straight section without tension.
3. Check the sheaves and drum. Gauge every groove, and repair or replace worn sheaves before they damage the new rope.
4. Cut correctly. Apply seizings on both sides of the cut, as the US rule requires, so that the rope cannot unlay.
5. Install without twist. Pay the rope out in a straight line from the reel, because any induced rotation can form loops and kinks.
6. Spool under tension. The NSW guide’s page on winch drums suggests a pre-tension of approximately 10 % of the winch line pull [10]. Loose lower layers can crush when a load is lifted.
7. Run it in and record it. Run the new rope in as the crane or rope manufacturer instructs, record its diameter as the baseline and file the rope change, as ISO 4309 asks.
8. Test before work. Check the limit switches and the anti two-block device with the new rope length before the first lift.

In Europe, the Machinery Directive sets the working coefficient of complete ropes and their endings at, as a general rule, 5 [11]. A rope chosen to the crane manufacturer’s specification keeps that margin, whereas a cheaper rope of the same diameter may not. If the job needs a test after the change, our crane load test guide explains what the standards ask for.

Example scenario (an illustration, not a customer record): a harbour contractor runs a telescopic marine crane on a work pontoon. At the monthly inspection, the competent person finds four broken wires in one rope lay just behind the hook block, plus light surface rust where the rope rests over the boom head sheave. Four is below the US limit of six for a running rope, so the rope stays in service, but the finding is recorded and that length is checked every week. Two weeks later the count reaches six, and the crane is tagged out. The contractor orders a rope to the crane manufacturer’s specification, gauges the boom head and hook block sheaves, and fits and runs in the new rope before work resumes. Had the rope been rotation-resistant, two broken wires in six rope diameters would already have stopped the crane.

Frequently asked questions

What type of wire rope is used on cranes?

Crane hoist ropes are usually steel core (IWRC) ropes, which resist crushing when spooled in several layers on the drum, and many are rotation-resistant to limit spin of the hook. The exact diameter, construction, lay and grade are set by the crane manufacturer for each crane.

How often should crane wire rope be inspected?

Under 29 CFR 1926.1413, a competent person inspects the rope before each shift and every month, and a qualified person inspects its full length at least every 12 months. ISO 4309 leaves the periodic interval to the competent person.

How many broken wires are allowed in a crane rope?

Under the US rule, a running rope is removed at six randomly distributed broken wires in one rope lay, or three in one strand in one rope lay. For rotation-resistant rope the limit is two broken wires in six rope diameters, or four in 30.

What is a rooster sheave on a crane?

A rooster sheave is the head sheave for the auxiliary winch, mounted on top of the boom head of a hydraulic boom crane. It carries the auxiliary hoist line, while the main boom head sheaves carry the main hoist rope.

Can a damaged crane wire rope be spliced?

No. The US rule prohibits joining lengths of wire rope by splicing. A localised defect may be cut out and the undamaged length reused, as long as two full wraps remain on the drum, but a rope that touched a power line must be replaced.

How we compiled this guide

We compiled the inspection and discard rules from the official eCFR text of the US crane rule, sections 1926.1401 to 1926.1417. The ISO 4309:2017 scope, introduction and clauses 3 and 4 come from the standard’s official sample pages. The construction, sheave, drum and inspection guidance comes from the NSW Government dogging and rigging guide, and the European and British rules from legislation.gov.uk, all as they stood in November 2026. Our crane figures come from the SQ2SA3 and SQ20SA5 technical drawings, and the winch facts from our technical department. Achord Chan, Product Operations Director, reviewed the guide. It does not replace your crane manual, the rope manufacturer’s instructions or the rules where you work.

1. 29 CFR 1926.1413, Wire rope: inspection
2. 29 CFR 1926.1414, Wire rope: selection and installation criteria
3. ISO 4309:2017, Cranes: wire ropes, care and maintenance, inspection and discard (sample pages)
4. NSW Government: construction of steel wire ropes
5. NSW Government: sheaves
6. NSW Government: mechanical advantage
7. NSW Government: common causes of damage and failure
8. Wikipedia: Wire rope
9. NSW Government: fleet angles
10. NSW Government: winch drums
11. Machinery Directive 2006/42/EC, Annex I

Get a crane with the right rope and sheaves

Tell us the heaviest load you will lift on the winch and the depth or height the hook must reach. Tell us also whether the crane will operate on a truck, a vessel or a quay. We will recommend a crane with a winch and send its drawing and load chart, and we confirm the rope diameter, rope length and line pull with the quotation. If you already own one of our cranes, send the model and serial number and we will confirm the rope specification for it. Every crane carries a 12-month warranty on the whole machine, common spare parts leave the factory within 48 hours, and our service team answers within 12 hours. Contact us for a quotation.