What is ISO 4309? Scope of Steel Wire Rope Inspection

ISO 4309 (Cranes — Wire ropes — Care and maintenance, inspection and discard) is an international reference standard for the maintenance, inspection and disposal of steel wire ropes used in cranes. The current edition of the standard is ISO 4309:2017.

The standard covers lifting and conveying ropes used in mobile cranes, tower cranes, overhead cranes, gantry cranes, and similar lifting machinery. The aim is to systematically evaluate the condition of the rope throughout its service life and to determine, using objective criteria, the moment when the safe limit is exceeded.

ISO 4309 classifies ropes according to their structure with a Rope Category Number (RCN) and treats rotation-resistant and non-rotation-resistant ropes with different criteria. The crane's operating class (e.g., M1-M8 mechanism groups) is also taken into account in determining the casting criteria.

  • Scope: Crane carriers and lifting ropes (mobile, tower, bridge, gantry, etc.)
  • Current edition: ISO 4309:2017
  • Structural classification by Rope Category Number (RCN)
  • Separate evaluation for rotationally resistant and non-rotating resistant ropes.

Rope Discarding Criteria: When is a Rope Taken Out of Use?

ISO 4309 stipulates that the decision on whether a rope should be discarded should not be based on a single finding, but rather on the combined assessment of multiple types of degradation. The criteria are derived from the standard's tables according to the rope's composition (RCN) and application; therefore, the numerical thresholds are not the same for every rope and must be verified against the relevant table.

Visible wire breaks are the most common criterion for a rope to break. The number of broken wires is counted over reference lengths defined as multiples of the rope diameter (typically 6d and 30d, where d is the nominal diameter). When the same number of breaks are concentrated in a narrow area, it is considered far more dangerous than when they are spread over a long distance; the standard defines separate, stricter criteria for localized break concentrations and valley breaks.

In addition to wire breakage, diameter reduction (due to wear, corrosion, or core/material damage), surface and internal corrosion, and deformations that distort the rope geometry are also evaluated. End connections (sockets, wedge-holes, clamping pliers, etc.) and contact areas with the pulley/drum are specifically examined. If a certain percentage of diameter reduction is exceeded, the rope may be discarded for this reason alone.

  • Apparent wire breakage: count at 6d and 30d reference lengths.
  • Separate, stricter criteria for local rupture concentration and valley ruptures.
  • Diameter reduction: a certain percentage threshold due to wear, corrosion, or internal damage.
  • Deformations: birdcage, pulling/detaching, crushing, tangling, bending
  • Condition of end connections and roller-drum contact areas
  • Numerical thresholds vary according to the rope's RCN (Relative Capacity Generator); these are verified from the relevant ISO 4309 table.

What is ISO 12482? Crane Design and On-Time Monitoring.

ISO 12482 (Cranes — Monitoring for crane design working period), in its current edition ISO 12482:2014, defines a method for monitoring the actual working load of a crane during its long-term use and comparing it to the working load predicted during the design phase.

The standard is based on the Design Working Period (DWP) concept. Determined by the crane's classification, this period provides a benchmark for estimating the accumulated fatigue and remaining lifespan of the mechanisms. As the crane approaches its design limits, the probability of danger increases, and logging and monitoring of usage allows for timely inspection of critical areas.

ISO 12482:2014 applies to cranes that remain permanently in the structure for their entire lifespan. Mobile cranes and tower cranes (excluding permanently mounted tower cranes) are outside the scope of this standard. The standard includes steps such as recording operational data, evaluating design lifespan, special assessment, and general overhaul.

  • Current edition: ISO 12482:2014
  • Comparing Design Runtime (DWP) with actual usage.
  • Work data recording, special evaluation and general overhaul
  • Scope: Permanent cranes; mobile and (non-permanent) tower cranes are excluded.

Remaining Safe Working Period (SWP) Assessment

When a crane approaches its design service life limits, a conditional continuation decision may be considered, rather than simply decommissioning it. At this point, an engineering assessment based on accumulated fatigue and actual usage data can determine a new period during which the crane can safely continue operating. In practice, this is referred to as the remaining safe working period (SWP).

SWP (Surface-to-Wheel) assessment may include analysis of the crane's operating history and load cycles, specific inspection of critical structural components and mechanisms, and planning of a general overhaul if necessary. The aim is to ensure, based on objective data, that the equipment can continue to operate within safe limits for a foreseeable future period.

These assessments require a competent engineering approach to the fatigue behavior of mechanisms and crane classification; the results provide input for the company's maintenance and refurbishment decisions.

  • Accumulated fatigue analysis based on real load cycles
  • Special inspection of critical components and mechanisms.
  • Planning for a general overhaul, if necessary.
  • Conditional and limited continuation decision based on objective data.

Why is it important? Security and early detection.

In lifting equipment, the snapping of steel wire ropes or unexpected damage to crane structures/mechanisms due to fatigue can have serious and often fatal consequences. The sudden failure of a rope or support component under load directly threatens both worker safety and the facility and equipment.

The shared value of ISO 4309 and ISO 12482 is that they enable early detection of deterioration using measurable and repeatable criteria, before it becomes an advanced failure. Knowing how close the rope is to its breaking limit and where it is in the crane's design life makes planned maintenance and timely replacement decisions possible.

This approach contributes to business continuity by reducing unexpected downtime and helps direct maintenance resources to truly critical components.

  • Cable breakage and crane fatigue pose a deadly risk.
  • Early detection through measurable criteria enables intervention before a failure occurs.
  • Reducing unexpected downtime through planned maintenance and timely replacement.

The Turkish Context: Mandatory Periodic Inspection and the Role of ISO

ISO 4309 and ISO 12482 are international standards and do not constitute a legal obligation on their own. In Türkiye, the periodic inspection of lifting and conveying equipment is mandatory under the Regulation on Health and Safety Conditions in the Use of Work Equipment (first published in the Official Gazette dated 25.04.2013 and numbered 28628).

The amendments made to this regulation by the Official Gazette dated 23.12.2025 and numbered 33116 have brought to the agenda provisions such as the definition of equipment inspection body, registration via ISG-KATIP, and the transition date of 1/1/2027 for accreditation under TS EN ISO/IEC 17020. For current obligations, the current text of the legislation should be taken as the basis.

In this context, ISO 4309 and ISO 12482 are used as internationally accepted technical methods and references in mandatory periodic inspections and engineering assessments: they provide a methodological framework for answering questions such as rope breaking limits and crane remaining life. It should be noted that the inspections required by the legislation regarding the application of the standard complement each other, but are not the same thing.

  • Periodic inspection requirement: Work Equipment Regulation (25.04.2013/28628)
  • Amendment 23.12.2025/33116: Inspection organization, ISG-KATIP, 17020 transition (1/1/2027)
  • ISO 4309 / ISO 12482: International technical reference/method for regulatory controls.
  • Current obligations must always be verified from the current text of the legislation.

Information Note

This page is for informational purposes only and constitutes a general technical guide; it does not replace an engineering decision, inspection result, or declaration of conformity relating to a specific piece of equipment, project, or situation. The discarding criteria and evaluation approaches described in this text are summaries; precise numerical thresholds and methods should be based on the current full texts of ISO 4309:2017 and ISO 12482:2014 standards and applicable national legislation.

AES Innovation can provide technical assessment and information services under ISO 4309 and ISO 12482 standards; the relevant reviews are handled in a technical report form prepared by an authorized engineer (mechanical engineer). These studies do not constitute an accredited inspection report. AES Innovation's TÜRKAK accreditation scope is limited only to the 6.1 Electrical Installation area; the steel wire rope and crane remaining life assessments described on this page are outside the scope of this accreditation.

For information on the general periodic inspection of steel wire ropes, slings and lifting accessories, or cranes, please refer to the relevant pages on our website (see Periodic Inspection of Slings, Chains, Ropes and Lifting Accessories and Crane Inspections). This page focuses specifically on the technical depth of ISO 4309 rope throwing criteria and ISO 12482 remaining safe working period (SWP).

  • This content is for informational purposes only; it does not substitute for engineering decisions or declarations of conformity.
  • For precise criteria, the full text of ISO 4309:2017 and ISO 12482:2014, as well as applicable legislation, are essential.
  • The assessments are presented as a technical report by an authorized engineer (mechanical engineer); they are not accredited inspection reports.
  • AES Innovation's TÜRKAK accreditation scope is limited solely to category 6.1 Electrical Installations.

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Frequently Asked Questions

What is ISO 4309?

ISO 4309 is an international reference standard for the maintenance, inspection, and decommissioning of steel wire ropes used in cranes. The current edition is ISO 4309:2017, and it aims to determine, using objective criteria, the moment when the rope's safe limit is exceeded.

When is a steel wire rope discarded (what are the discarding criteria)?

The decision is based not on a single finding, but on the combined assessment of multiple deteriorations: visible wire breaks (counted at 6d and 30d reference lengths), localized fracture concentrations and valley breaks, diameter reduction, corrosion, abrasion, deformations (birdcage, crushing, pulling, entanglement), and the condition of end connections. Numerical thresholds vary according to the Rope Category Number (RCN) of the rope and must be verified against the relevant ISO 4309 table.

What is the Remaining Safe Working Period (SWP)?

SWP (Surface-Time Operating) is the new, time-bound period during which equipment can continue to operate safely, determined by engineering assessment based on actual usage and accumulated fatigue data, when a crane approaches its Design Operating Time (DWP) limits. ISO 12482:2014 provides a framework for this assessment, including monitoring, specific assessment, and general revision steps.

Which cranes does ISO 12482 cover?

ISO 12482:2014 applies to cranes that remain permanently in place for their entire lifespan. Mobile cranes and tower cranes that are not permanently mounted are outside the scope of this standard. Permanently mounted tower cranes are covered.

Is the implementation of ISO 4309 / ISO 12482 mandatory in Türkiye?

ISO 4309 and ISO 12482 are international standards and do not constitute legal obligations on their own. In Türkiye, periodic inspections of lifting equipment are mandatory under the Work Equipment Regulation (25.04.2013/28628; amendment 23.12.2025/33116). ISO 4309 and ISO 12482 are used as internationally accepted technical methods and references in these inspections. Current obligations should be verified from the current text of the legislation.

Does AES Innovation conduct these evaluations?

AES Innovation can provide technical assessment and information services referenced in ISO 4309 and ISO 12482; these studies are addressed in the form of a technical report prepared by an authorized engineer (mechanical engineer) and do not constitute an accredited inspection report. AES Innovation's TÜRKAK accreditation scope is limited only to the 6.1 Electrical Installation area; rope and crane remaining life assessments are outside the scope of this accreditation.