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Views: 0 Author: Site Editor Publish Time: 2026-01-30 Origin: Site
How many wires are allowed to break in a wire rope?
Note:
The lay length refers to the axial length of the wire rope corresponding to one complete helix of a strand around the rope.
For a typical six-strand wire rope, it is measured from the first strand to the seventh strand and is generally equal to eight times the nominal rope diameter.
Broken wires are randomly distributed along sections of single-layer wound wire ropes passing over one or more steel sheaves, sections where the rope enters or exits the drum, or sections of multi-layer wound wire ropes located in the cross-over overlapping zones.
Discard Criteria:
The minimum number of visible broken wires that constitutes discard in single-layer strand wire ropes and parallel-lay compacted wire ropes is shown in Table 1.
For wire ropes with Seale construction and 19 or fewer wires per outer strand (e.g. 6×19 Seale or WSRC), the value of n shall be taken as the number of load-bearing wires per outer strand, as shown in the second column.
One broken wire with two fracture points shall be counted as two broken wires.
These values apply to deterioration caused by interference between adjacent rope sections in cross-over zones or due to fleet angle effects. They do not apply to rope sections that only operate over sheaves without drum winding.
When the machine duty group is M5–M8, the allowable number of broken wires shall be half of the values listed in this table.
d refers to the nominal diameter of the wire rope.
The minimum number of visible broken wires that constitutes discard in rotation-resistant wire ropes is shown in Table 2.
For wire ropes with Seale construction and 19 or fewer wires per outer strand (e.g. 18×19 Seale-WSRC), the value of n used in the table refers to the number of load-bearing wires per outer strand, as specified in the corresponding row.
One wire with two fracture points shall be counted as two broken wires.
These values apply to deterioration caused by cross-over zones and fleet-angle-induced interference between adjacent rope sections. They do not apply to rope sections that only operate over sheaves without drum winding.
d denotes the nominal diameter of the wire rope.
Local Concentration of Broken Wires in Sections Not Passing Over Drums
Discard Criteria: If broken wires are concentrated in one or two adjacent strands, even if the number of broken wires within a length of 6d is below the values specified in Table 1 and Table 2, the wire rope must be discarded.
Broken Wires in Strand Valleys
Discard Criteria: If two or more broken wires are found within one lay length of the wire rope (approximately 6d), the rope must be discarded.
Broken Wires at Rope End Terminations
Discard Criteria: The wire rope shall be discarded if two or more broken wires are found at the rope end termination or anchorage.
Uniform diameter reduction along the rope length
For wire ropes wound in a single layer on a drum or passing over steel sheaves, the discard limits for uniform diameter reduction are given in the corresponding table (bold values).
These limits do not apply to cross-over zones or other sections where similar deformation results from multi-layer winding.
Local diameter reduction
If a noticeable local reduction in diameter is observed, such as that caused by damage to the rope core or the central region of the wire rope, the wire rope shall be discarded.
If an entire strand of the wire rope breaks, the rope shall be discarded immediately.
Discard criteria and corrosion severity classification are shown in the corresponding table.
When assessing the extent of corrosion, it is important to distinguish between:
Corrosion of the steel wires themselves, and
Surface corrosion of the wire rope caused by oxidation of foreign particles.
Any visible distortion that causes a wire rope to lose its normal shape is considered deformation. Deformation usually occurs locally and results in an uneven distribution of internal stresses within the affected section of the wire rope.
Deformation and damage may manifest in various forms. The following lists the more common types along with their discard criteria. If the condition of the wire rope itself is considered hazardous, it shall be discarded immediately.
Waviness
Under any of the following conditions, the wire rope shall be discarded:
a) In straight sections of the wire rope that have not passed over sheaves or been wound on a drum, if the gap g between a straightedge and the underside of the rope helix is
g ≥ 1/3 × d;
b) In sections of the wire rope that pass over sheaves or are wound on a drum, if the gap g between a straightedge and the underside of the rope helix is
g ≥ 1/10 × d.
d — nominal wire rope diameter;
g — gap.
Basket or Lantern Deformation
Wire ropes exhibiting basket-shaped or lantern-type deformation shall be discarded immediately, or the affected section shall be removed, provided the remaining rope length meets operational requirements.
Protrusion or Distortion of Core or Strands
Wire ropes with protruding or distorted cores or strands shall be discarded immediately, or the affected section shall be removed, provided the remaining rope length meets operational requirements.
Ring-Shaped Protrusion of Wires
Wire protrusion usually appears in groups on the backside of the wire rope where it contacts the sheave groove. Wire ropes with such protrusions shall be discarded immediately.
Note:
A single core wire protruding between the outer strands of the wire rope may not necessarily be grounds for discard if it can be removed or does not affect other parts of the wire rope during operation.
Local Increase in Rope Diameter
For steel-core wire ropes, a diameter increase of 5% or more, and for fiber-core wire ropes, a diameter increase of 10% or more, shall require investigation of the cause and consideration of discarding the wire rope.
Note:
An increase in wire rope diameter may affect a considerable length of the rope. For example, diameter increase caused by expansion due to excessive moisture absorption by a fiber core may result in uneven loading of the outer strands and prevent the rope from maintaining the correct lay direction.
Local Flattening
When flattened sections of a wire rope pass over sheaves, deterioration may be accelerated and broken wires may occur. In such cases, the wire rope may be considered for discard regardless of the degree of flattening.
Flattened sections of wire ropes used in standard slings may suffer more severe corrosion than normal rope sections, especially when the outer strands open and allow moisture to enter. If continued use is required, more frequent inspections shall be carried out; otherwise, discarding the wire rope is recommended.
Local flattening caused by multi-layer winding does not require discard if the number of broken wires associated with the flattening does not exceed the limits specified in Table 1 and Table 2.
Kinking
Wire ropes that have developed kinks shall be discarded immediately.
Note:
A kink is a type of deformation formed when a loop of wire rope is tightened while the rope is unable to rotate about its own axis. Kinking causes uneven lay length and excessive wear, and severe twisting can result in a significant reduction in wire rope strength.
Bending
Severely bent sections of a wire rope may deteriorate rapidly and develop broken wires when passing over sheaves. In such cases, the wire rope shall be discarded immediately.
If the degree of bending is not severe and continued use of the wire rope is required, more frequent inspections shall be carried out; otherwise, discarding the wire rope should be considered.
Note:
Bending is an angular deformation of a wire rope caused by external forces.
The severity of bending shall be determined by judgment. If a crease is present on the underside of the bend, it shall be regarded as severe bending, regardless of whether the rope passes over a sheave.
