Crane wire ropes are subject to considerable loads during operation and therefore suffer considerable mechanical damage throughout their service life. In addition, studies have shown that the main causes of wire rope failure are excessive deterioration and corrosion, lack of maintenance and inspection, and misuse leading to premature scrapping, reduced safety, and increased replacement costs.
Therefore, wire ropes should be inspected and maintained by appropriate personnel to ensure that they are in a safe state for use. Proper inspection can ensure high performance, long service life, safety of personnel and equipment, and reduced operating costs.
Daily inspection (visual)
The rope should also be checked to ensure that it is properly secured to the drum and over the sheaves and has not moved out of its normal operating position.
Any noticeable change in condition should be reported and the rope inspected by a competent person in accordance with the periodic inspection.
If the rigging arrangement is modified at any time, such as when the crane is moved to a new location and re-rigged, the rope should be visually inspected as described in this clause.
The driver/operator of the crane may be designated to carry out daily inspections, provided that the driver/operator is adequately trained and deemed competent to perform this operation.
2. Periodic Inspections
2.1 General
Periodic inspections should be performed by a qualified person.
The information obtained from the periodic inspections will be used to help determine whether the crane rope is safe to continue in use and should be subject to the next periodic inspection at the latest, or needs to be withdrawn immediately or within a specified time.
The severity of deterioration should be assessed by appropriate assessment methods, i.e. by visual means and/or measurement, or using MRT, and expressed as a percentage (e.g. 20 %, 40 %, 60 %, 80 % or 100 %), or in words (e.g. "mild", "medium", "high", "very high" or "discard").
Any damage that may have occurred to the rope should be assessed by a qualified person before it is put into operation and put into service, and the observations recorded.
The following table lists the types of damage to be inspected for wire ropes and whether each type of damage can be easily quantified or requires subjective assessment by a qualified person.
2.2 Frequency of periodic inspections
The frequency of periodic inspections shall be determined by the competent person who shall take into account at least the following factors:
a) statutory requirements applicable in the country of use;
b) the type of crane and the environmental conditions in which it operates;
c) the classification group of the organization;
d) the results of previous inspections;
e) experience gained from inspections of ropes on similar cranes;
f) the length of time the rope has been in use;
g) the frequency of use;
h) the recommendations of the crane manufacturer.
NOTE 1: The competent person may find it prudent to initiate or recommend more frequent periodic inspections than required by legislation. This decision may be influenced by the type and frequency of operations. In addition, depending on whether there has been any change in the condition and/or circumstances of the rope at any time, such as an accident or change in operating conditions, the competent person may deem it necessary to reduce or recommend a reduction in the intervals between periodic inspections.
NOTE 2: In general, ropes will develop broken wires more rapidly later in their service life than in the early stages of their service life.
2.3 Scope of periodic inspection of wire ropes
Each rope should be inspected along its entire length.
However, in the case of longer lengths, at the discretion of the competent person, only the working length plus at least five turns on the drum may be inspected. In this case, if a greater working length is foreseen after the previous inspection and before the next inspection, the additional length of rope should also be inspected before it is used.
Nevertheless, special attention should be paid to the following wire rope inspection checklist:
a) Drum anchorages;
b) Any section at or near the end of the rope;
c) Any section passing through one or more pulleys;
d) Any section passing the safe load indicator containing the pulley;
e) Any section passing through the hook block;
f) Any section of the rope that is on the pulley when the crane is under load if the crane performs repeated operations;
g) The section of the rope that is located above the compensating pulley;
h) Any section passing through the winding device;
i) Those sections wound on drums, especially the cross-over areas associated with multi-layer winding;
j) Any section subject to abrasion by external features (such as hatch combs);
k) Any part of the rope that is exposed to heat.
NOTE: See the following image for areas that require extra close inspection.
2.4 Periodic inspection records
After each periodic inspection, the supervisor should provide a record of the rope inspection and state the maximum time interval that should not be exceeded before the next periodic inspection. It is best to keep operation records.
3. Inspection of wire ropes in special conditions
3.1 Inspection after an accident
If an incident occurs that may cause damage to the rope and/or its terminal, the rope and/or its terminal should be inspected regularly before resuming work or as required by the competent person.
Note: In the case of a two-rope lifting system, it is usually necessary to replace both ropes even if only one rope has reached scrap status, because the new rope is larger than the remaining rope and has different elongation characteristics, and both ropes will have an effect depending on the corresponding amount of rope paid out from the drum.
3.2 Inspection during crane out of service
If the crane has been out of service for more than three months, the wire rope should be inspected regularly as specified in the periodic inspection before resuming work.
4. Wire rope scrapping standards
4.1 Visible wire breakage
Crown wire breaks
Valley wire breaks
4.2 Decrease in rope diameter
Local reduction in rope diameter (sunken strand)
4.3 Fracture of strands
If a complete strand fracture occurs, the rope shall be immediately discarded.
4.4 Corrosion
External corrosion: Signs of surface oxidation but can be wiped clean.
Wire surface rough to touch, heavily pitted and slack wires.
Enlargement of External corrosion
Internal corrosion: Obvious visible signs of internal corrosion.
corrosion debris exuding from the valleys between the outer strands.
4.5 Deformation and damage
Visible distortion of the rope from its normal shape is classified as deformation. It usually results in an uneven stress distribution in the rope in the area of the deformation, often found to be localized.Deformation and damage can manifest themselves in a number of ways.
Waviness
Basket deformation
Ropes with a basket or lantern deformation shall be immediately discarded or, provided the remaining length of rope is in a serviceable condition, have the affected section removed.
Core protrusion - Single-layer rope
Protrusion of inner rope of rotation-resistant rope
Strand protrusion/ distortion
Wire protrusion
Ropes with protruding wires, usually occurring in groups on the opposite side of the rope to that which is in contact with a sheave groove, shall be immediately discarded.
Local increase in rope diameter due to core distortion
If the rope diameter increases by 5 % or more for a rope with a steel core or 10 % or more for a rope with a fibre core during service, the reason for this shall be investigated and consideration given to discarding the rope.
Flattened portion(1)
Flattened portions of rope which run through a sheave are likely to deteriorate more quickly and exhibit broken wires. In such cases, but depending on the extent of the flattening, consideration may be given to discarding the rope.
Flattened portions of rope in standard rigging can suffer a greater degree of corrosion than other no affected portions, more so when the outer strands open up and allow ingress of moisture. If retained in service, they shall be inspected more frequently; otherwise, consideration should be given to discarding the rope.
Flattened portion(2)
Kink (positive)
Ropes with a kink or tightened loop shall be immediately discarded.
Kink (negative)
Kink
Bend in rope
Portions of rope with a severe bend which run through a sheave are
likely to quickly deteriorate and exhibit broken wires. In such cases,
the rope shall be immediately discarded.
If the degree of bend is not considered to be severe and the rope is
retained in service, it shall be inspected more frequently; otherwise,
consideration should be given to discarding the rope.
Damage due to heat or arcing
Ropes that do not normally operate at these temperatures but that are
subject to unusually high thermal effects, identifiable from the outside by the associated heat colour produced in the wires and/or obvious loss of grease on the rope, should be discarded immediately.
If two or more wires are locally affected by arcing, such as by welding leads that are not properly grounded, the rope should be discarded. This can occur at the point where the current enters or leaves the rope.
