▌ APPLICATION NOTE · OCTOBER 2026 · HOIST ROPE Hoist Rope: Inspection Intervals, Discard Criteria and Safe Replacement A hoist rope is a machine made of many small wires, and it fails in a way that is easy to miss. There is rarely a single dramatic break. Instead wires break one by one, corrosion thins the strands, and the rope that looked fine last week reaches its discard criteria without announcing it. The inspection routine exists because the rope cannot be trusted to fail visibly. This note explains how a hoist rope is made and reeved, how it wears, what an inspection should look for, the criteria that require replacement and how a replacement should be carried out. The crane maker’s manual and standards such as ISO 4309 set the discard criteria; this note explains how to apply them on site.
01 HOW THE ROPE IS MADE AND REEVED A hoist rope is a steel wire rope of a class and diameter specified by the crane maker. It is terminated with a certified ferrule or socket and reeved through the hook block and drum according to the machine’s parts of line. The construction, the lay direction and the termination all affect how the rope behaves and how it should be inspected. The reeving decides the load on the rope. With more parts of line, each rope section carries less load but runs over more sheaves, so it bends more often. Both the load and the bending have to be considered when judging wear. ▌ SPECIFIED CONSTRUCTION Rope class, diameter and lay come from the crane maker. ▌ CERTIFIED TERMINATION Ferrule or socket terminations must be certified and correctly made. ▌ REEVING SETS THE LOAD More parts of line means less load per rope but more bending. 02 HOW ROPE WEARS Rope wears in several ways at once. Individual wires break, especially where the rope runs over sheaves or spools onto the drum. Abrasion flattens the outer wires. Corrosion attacks the strands, often from the inside where it cannot be seen. Kinking and crushing damage the rope’s structure and cannot be repaired. The location of the wear matters. Rope that spends its life bending over the same sheave may wear at one zone far more than elsewhere. Inspection should therefore look along the whole length, with particular attention to the sheave zones and the termination. ▌ BROKEN WIRES Wire breaks cluster at sheaves and drum spooling zones. ▌ ABRASION AND CORROSION Flattened wires and internal corrosion both reduce strength. ▌ KINKS CANNOT BE FIXED Crushed or kinked rope is damaged structurally and must be replaced. 03 WHAT TO INSPECT AND HOW OFTEN Inspection should follow the interval set by the manual, which is often based on duty and rope condition. The inspection looks for broken wires over a defined length, wear of the outer wires, corrosion, kinking, crushing and damage at the termination. A rope that has been overloaded or shock-loaded should be inspected immediately, not at the next scheduled interval. The inspection should be recorded. Counting broken wires over a measured length is more reliable than a general impression, and a written record shows how the rope is deteriorating over time. ▌ FOLLOW THE INTERVAL Use the manual’s inspection interval, based on duty and condition. ▌ INSPECT AFTER OVERLOAD Any overload or shock load calls for an immediate inspection. ▌ COUNT AND RECORD Record wire breaks over a measured length to track deterioration.
04 DISCARD CRITERIA A rope is discarded when it reaches the maker’s criteria: a number of broken wires over a specified length, a level of wear or corrosion, or structural damage such as kinking or crushing. The criteria are not advisory. A rope that is close to the limit should be planned for replacement before it passes it. Replacement rope must match the original specification: same class, diameter, lay and termination. A rope of a different construction may fit the drum and sheaves and still behave differently under load and bending. ▌ THE LIMIT IS A LIMIT Discard criteria are mandatory, not a suggestion. ▌ PLAN AHEAD Rope near the limit should be scheduled for replacement before it fails. ▌ MATCH THE SPECIFICATION Replacement rope must match class, diameter, lay and termination. 05 REPLACING THE ROPE SAFELY Replacing a hoist rope is a planned job, not an emergency repair. The drum and sheaves should be inspected while the rope is off, the new rope should be reeved to the correct parts of line and the termination should be made by a competent person with certified fittings. The rope should then be run and checked before it goes back into lifting service. Cutting out a damaged section and re-terminating on site is not an acceptable repair for a hoist rope. It changes the rope’s certified condition and leaves a termination that may not be reliable. ▌ PLAN THE JOB A rope change is scheduled work, with the drum and sheaves inspected at the same time. ▌ COMPETENT TERMINATION Terminations must be made by a competent person with certified fittings. ▌ NO CUT-AND-REPAIR Cutting out a damaged section is not an acceptable repair for a hoist rope. PROCUREMENT IMPACT ● Order rope to the crane maker’s class, diameter and lay specification. ● Specify certified ferrules or sockets and the correct termination method. ● Ask for the maker’s discard criteria and inspection interval with the rope. ● Keep a spare rope of the correct specification for critical machines. ● Include sheave inspection in the rope replacement job. WHAT TO WATCH ● Watch broken wires at sheave zones and the drum spooling area. ● Watch for corrosion, especially internal corrosion that cannot be seen. ● Watch kinks and crushing; they cannot be repaired. ● Watch after any overload or shock load with an immediate inspection. ● Watch the termination, which is often where a rope fails first. ABOUT ZN Industrial (Shandong Zhinuo) designs and manufactures crane safety monitoring systems, positioning systems and mechanical auxiliary handling equipment for overseas construction, industrial and steel markets. Standards and regulations vary by market — local rules still govern your site. ▌ CONTACT shandongzhinuo@outlook.com +86 176 6371 0314 · en.znaqkj.com SOURCES · ISO 4309 · ISO 12480-1 · BS 7121 · crane maker’s manual |
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Hoist Rope: Inspection Intervals, Discard Criteria and Safe Replacement
The hoist rope is one of the highest-wear parts of a tower crane. This note explains how rope fails, what to look for during inspection, when it must be discarded and how to replace it safely.
