Table of contents:

• Generell rope construction
• Classification according to the purpose
• Length of lay
• Direction of lay
• Strand types
• Stranding types
• Rotation characteristics of wire ropes
• Type of cores
• Compaction
• Wire ropes with plastic padding
• Transport, storage and handling
• Wire rope assembly
• Which direction of lay for which drum?
• Deflection angle
• Inspection of rope sheaves and rope drums
• Measuring wire ropes correctly:
• Discard criteria of wire ropes
• Lubrication of wire ropes
• Wire rope relevant abbreviations

Generell rope construction

Rope structure:
Wire ropes consist of several strands, which in turn consist of individual wires. Wires are therefore the load-bearing element of any wire rope.

The strand:
To make a strand, wires are helically wrapped around a core wire (here: center wire). Depending on the design, the number of wires in a strand and also the number of strands within a wire rope can vary.

The core:
The core supports the strands and gives the rope its shape. Depending on the intended use, the core can be made of fiber or steel.

Depending on the core, there are different advantages and disadvantages.fiber cores (NFC, SFC) are less expensive and are therefore often used for sling ropes. The disadvantage is that ropes with fiber cores have no transverse compressive stability and are therefore unsuitable for multi-layer spooling, for example.

Wire ropes with steel cores (WSC, IWRC) have a higher breaking load, better transverse pressure stability, better temperature resistance and are more suitable for maintaining the rope geometry in the long term

Classification according to the purpose

Running ropes are guided over drums, pulleys or sheaves and are constantly subjected to bending stress. For example, crane ropes, hoist ropes, elevator ropes, conveyor ropes, scraper ropes or haul ropes for ropeways.

Stationary ropes are not deflected and are mainly permanently installed. For example, guy ropes, guide ropes or holding ropes.

Carrying ropes perform the function of running rails. They are used to run pulleys of handling equipment such as cable cranes, suspension ropes for ropeways and cable scrapers.

Length of lay

The lay length of a wire rope is the distance of an outer strand measured parallel to the longitudinal axis of the rope up to one complete turn around the axis of the rope (according to EN 13385:2 3.7.11). The lay length can also be measured in the same way for strands by measuring the distance of an outer wire. A change in lay length can influence breaking strength, elasticity, torsional stability and fatigue behavior. Furthermore, the lay length can be used to determine whether a wire rope has been forcibly twisted during use.

Direction of lay

Lay directions (direction of lay) of the rope means the direction of the screw line of the outer strands. The first letter s and z is written in lower case and indicates the direction of lay of the wires in the strands. The second letter S and Z is written in capital letters and indicates the direction of lay of the strands. Basically, a distinction is made between cross lay and equal lay:

Crosslay right-hand (sZ) / Crosslay left-hand (zS):

The wires in the strands have opposite directions of rotation to the direction of rotation of the strand.

Crosslay right-hand (sZ)

Crosslay left-hand (zS)

Technical charateristics:

• Opposite direction of lay of the wires
• Each wire appears three times per stroke on the rope circumference
• Poorer pressure conditions
• Wire breaks are clearly visible from the outside, discard maturity is better recognisable

Langlay right-hand (zZ) / Langlay left-hand (sS):

The wires in the strands and the strand in the rope have the same direction of rotation.

Langlay right-hand (zZ)

Langlay left-hand (sS)

Technical charateristics:

• Same direction of lay of the wires
• Each wire appears once per lay on the rope circumference
• Better pressure conditions
• Wire breaks more difficult to recognise from the outside, discard maturity more difficult to recognise
• Good for multi-layer spooling as the wires in the outer strands have no crossover points with wires from upper or lower layers

Strand types

Filler (F):

• the outer layer has twice as many wires as the inner layer
• non-load-bearing cored wires lie in the groove formed by the inner wires
• the filler wires provide better support for the load-bearing wires

Warrington (W): 

• the inner layer consists of wires with the same diameter
• the outer layer consists of twice as many wires, but they differ in diameter, as there is always a thick and a thin wire alternately applied
• Increased rope flexibility

Seal (S):

• the number of wires in both layers is the same
• the wires in the outer layer are thicker than the wires in the inner layer
• better abrasion protection

Warrington- Seal (WS):

• Warrington strand is inside. A seal construction is hammered onto this
• Warrington strand provides an optimal support surface for the wires of the seal layer
• better abrasion protection (Seal) and increased flexibility of the rope (Warrington)

Stranding types

Cross-lay:

Cross stranding is also considered standard stranding. It is common for standard wire ropes according to EN12385-4. All wires and strands have different lay lengths. As a result, the superimposed layers cross and there is increased pressure at the crossing points. This can lead to early wire breaks on the inside of the rope and thus to an earlier discard point.

Parallel lay:

With parallel stranding, the superimposed layers do not cross because the lay lengths of the wire layers are the same. This avoids crossing points and the wire layers are loaded linearly, which leads to a more optimal load distribution. Parallel stranded wire ropes are often found in special wire ropes such as Casar Alphalift, Casar Paraplast, Casar Turbolift, Casar Betalift, Casar Parafit, Casar Doublefit or the Casar Superplast10 Mix.

Rotation characteristics of wire ropes

non-rotation wire ropes:

In non-rotational wire ropes, all rope layers run in the same direction. Thus, under load, the torque of a load is absorbed into the rope and the rope tries to close or open. If this effect occurs, the rope is defective and must be replaced. These ropes must not be used with swivels. 

rotation-resistant wire ropes:

The outer strand layer is opposite to the inner strand layer, thus the torque is greatly reduced. Examples of low-torque wire ropes are 18x7 (EN12385-4) or the 36x7 (EN12385-4). Attention: For these wire ropes, the torque is greater than 1 i.e. not greater than 4 turns/1000d when lifting a load corresponding to 20% of the minimum breaking load. A swivel may only be used in compliance with the recommendations of the rope manufacturer and/or with the approval of a competent person (definition according to EN12385:3 B1.5).

rotation resistant wire ropes:

In rotation resistant wire ropes, the outer strand layer is opposite to the inner strand layer and in addition there is a steel core that functions as a separate rope. These wire ropes are suitable for lifting unguided loads in single strand operation and for multiple strands with very large lifting heights. According to EN12385:3 B1.5, the rotation property is less than or equal to 1 rotation /1000d when lifting a load corresponding to 20% of the minimum breaking load. A swivel may be used with these wire ropes. 

ATTENTION: In common usage, twist-free and low-twist wire ropes are often erroneously referred to as low twist or low tension. However, the terms "low twist" and "low tension" do not provide any information about the twisting behavior, but describe a special treatment in the stranding process with the aim of ensuring that strands and wires do not, or only slightly, come out of the rope bond after the removal of bindings.

Type of cores

Depending on the rope construction, different materials with different structure are used for the rope core.

Fiber core:

According to EN12385-2, the fiber core is also abbreviated as FC = Fiber Core. Fiber cores can be made of natural fibers (NFC = Natural Fiber Core) or synthetic fibers (SFC = Synthetic Fiber Core). The fiber core supports the strands and dampens vibrations. It is impregnated with lubricant and releases this into the wire rope under load during operation. This has the advantage that wire ropes with fiber core are well protected against friction in the wire rope. However, this effect wears off over time, so the ropes should be relubricated regularly. A disadvantage is that the fiber core can not only store lubricant, but also moisture, which significantly increases the risk of corrosion. Due to the high deformability, ropes with fiber core have a low resistance to transverse forces, which can lead to rope deformation over time, making the rope ready for discard.

Steel core:

According to EN12385-2, the steel core is also abbreviated as WC = Wire Core. In the case of steel cores, a distinction is made between the wire strand core (WSC = Wire Strand Core) and an independently stranded wire rope (Independent Wire Rope Core). The wire strand core (WSC) consists of a core wire in the case of spiral ropes or of stranded wires in the case of stranded ropes. That of a round strand rope consists of a steel strand. The wire rope core (IWRC) consists of a stranded wire rope and is used particularly frequently because its design and diameter can be optimally adapted to the outer strands. One advantage of wire ropes with steel cores is their better dimensional stability and better resistance to transverse forces. In addition, the metallic cross-section is higher, resulting in a higher breaking load for the same rope diameter compared to ropes with fiber core. Furthermore, ropes with steel cores can be used up to 400°C degrees (take into account loss of load-bearing capacity!), while fiber cores can only be used up to approx. 100°C degrees.

Compaction

A basic distinction is made between wire ropes with compacted outer strands, hammered wire ropes and wire ropes without compaction.

Wire ropes with compact strands:

In the case of wire ropes with compacted outer strands, conventional round strands are previously drawn through a compaction apparatus. This deforms the wires in the strands, reducing the strand diameter. The strand surface is smoothed and the contact areas between the wires within a strand are increased, as well as between adjacent strands. The compaction process increases the metallic cross-section of the wire rope, resulting in increased breaking strength, more flexibility and increased transverse compressive stability. In addition, the smoother rope surface reduces the risk of negative impressions in sheaves and increases rope service life in multi-layer windings. Resistance to corrosion is also increased because it is more difficult for liquid to penetrate the rope than with conventional ropes without compaction.

Hammered wire ropes:

In the case of hammered wire ropes, the wire rope is first manufactured and then completely drawn into a compactor. This gives the wire rope extraordinarily high compressive stability and very high breaking forces are achieved. Due to the very round rope surface, hammered wire ropes are particularly suitable for multi-layer windings because the risk of interlocking between the individual layers is considerably reduced.

Wire ropes with plastic padding

In the manufacturing process, the steel core is covered with a plastic sheath. In the final stranding, the outer strands are optimally embedded by heating the plastic so that the plastic lies in the natural rope interstices and prevents contact between the strands. 

Furthermore, the plastic padding offers the following advantages:

• Protection against internal wire breaks
• Stabilization of the rope structure
• Encloses lubricant inside the rope
• Impedes the penetration of water and dirt particles
• Absorbs dynamic energy
• Resistant to chemical environmental influences

Transport, storage and handling

Transport: Transport packaging should be chosen to protect the ropes from mechanical damage. It is essential to ensure that the rope does not come into contact with sharp edges.

Storage: Ropes should be stored in a well-ventilated, dry and dust-free interior. If indoor storage is not possible, wire ropes should be protected with waterproof packaging. In addition, ropes should be protected from direct sunlight, high temperatures and chemical vapors. For traceability purposes, rope identification should not be lost. For storage removal, the "first in, first out" principle is recommended.

Handling: When handling ropes, wear suitable personal protective equipment in accordance with the operational risk assessment. Take care when removing strapping; reeled or coiled ropes are under tension, the end of the rope can "kick out" and cause injury. When unwinding and uncoiling, ropes must not be contaminated or twisted, but must be unwound or uncoiled in a straight line (see drawing); no counter-bending may occur. Under no circumstances may ropes be pulled sideways from the reel or ring.
from the ring. Ropes must be protected against mechanical damage and dirt when being laid. Guiding over sharp edges must generally be avoided!

Cutting-off: If cut-off is required, it is recommended that a cut-off wheel be used if the end of the rope must be welded or soldered. Please make sure that the room is adequately ventilated and to prevent the accumulation of vapors. The safety tie-off should be placed on both sides of the cut mark and should be at least twice the nominal rope diameter for stranded ropes.

Wire rope assembly

The rope must be reeved tension-free, untwisted and undamaged. Otherwise, there is a risk of rope damage after a short time, which can lead to immediate discarding.

Ropes must not be pulled off the side of rings or reels. Otherwise, this procedure will lead to twists resulting in loops in the rope. If the rope is pulled tightly, kinks can occur which lead to immediate discarding.

For this reason, wire ropes should be unrolled on the floor with the help of a turntable or like a tire. Caution: When unrolling on the floor, there is a risk that dirt will be absorbed by the lubricant of the wire rope and will subsequently work its way into the rope.

Turntables or racks for twist-free unwinding are also suitable for reels.

Since each wire rope is given a preferred bending direction in the production process, care must be taken during rewinding to ensure that both spools run in the same direction. This means that if the outgoing rope strand is above, the incoming rope strand must also be above, or if the outgoing rope strand is below, the incoming rope strand must also be below. Otherwise, there is a risk that the wire rope will twist between the two spools during the rewinding process or that it will try to regain its original bending direction by twisting during subsequent crane operation.

Which direction of lay for which drum?

Basically, you should follow the manufacturer's instructions. If nothing is specified by the manufacturer, the following procedure applies: 

Step 1:

Check how the rope runs from the drum into the reeving. There are two possibilities:

• Rope entry at the front (pictures on the right)
• Rope entry at the rear (pictures on the left)

Step 2:

Mentally place your hand on the piece of rope lying on the d

The forefinger points in the direction in which the rope runs off the drum.

The thumb points simultaneously to the rope fixed point on the drum.

Decision:

If the left hand is positioned according to the upper figures (A), it is a left-hand rope.

If the right hand is positioned according to the lower figures (B), it is a right-hand rope.

Deflection angle

The deflection angle (β) is the lateral inclination of a wire rope on a drum or reeving. Since the sheave is usually located centrally for the drum, the deflection angle is greatest on the two outer drum flanks. It should also be noted that the rope grooves on the drum also have a so-called pitch angle (α) which must either be added to the deflection angle or subtracted from the deflection angle. If the deflection angle is too high, the rope will not enter the sheave at the lowest point, but will first touch one of the two outer flanks and then roll into the bottom of the groove. The higher the deflection angle, the more the rope rolls over the flanks into the bottom of the groove, causing the rope to twist. It can also happen that the wire rope running off the drum is pulled against the secondary windings and the outer wires are damaged. For this reason, the deflection angle must be max. 4° for non-rotation-free ropes and max. 2° for rotation-free wire ropes (according to ISO16625).  The deflection angle for rotation-resistant ropes is smaller because they are more sensitive to violent twisting due to the counter-rotating core..

Inspection of rope sheaves and rope drums

Rope sheaves and drums play an important role in influencing rope service life. Special attention should be paid to the condition and dimensional accuracy. Rope sheaves should be smooth-running, the groove base must not be damaged and must not show rope marks from previous ropes. The optimum groove diameter should be rope diameter +6-8% or according to DIN 15020 rope diameter x 1.05 or at least 5% and at most 10% of the nominal rope diameter according to ISO16625. Values above and below these ranges can have serious consequences for rope service life. The groove depth should be at least 1.5 times the nominal rope diameter and the groove opening angle should be between 45-60°. If the groove diameter is too small, the incoming wire rope will be compressed, which can lead to wire breaks and deformation. In addition, the pressure of the lateral flanks may push outer strands further forward, causing strands to loosen permanently or resulting in the formation of a basket. If the grooves are too large, the contact part of the wire rope is subjected to strong surface pressure without the outer flanks being able to act as a support. This can lead to rope deformation and a reduction in rope service life.

Table for groove radii for rope sheaves according to DIN 15061 Part 1:

Notes on the table:

• Accuracy 1 = Standard rolled
• Accuracy 2 = rotated
• Accuracy 3 = finely turned e.g. for metallurgical/rolling mill cranes
• the following deviations of the rope diameter are ok:
  • up to 3mm 0-8%
  • between 3-6mm 0-7%
  • between 6-7mm 0-6%
  • from 7mm 0-5%

Table for groove radii for rope drums according to DIN 15061 Part 2:

Notes on the table:

• h≥0,375 * d due to the rope jump
• r2 gilt bis h≤0,4 * d

The use of so-called groove gauges is recommended for checking grooves. These are pressed into the grooves to be checked and should be in good contact over long stretches of the circumference. If the groove gauge only rests on the flanks and does not touch the bottom of the groove, the groove is too narrow.

Measuring wire ropes correctly:

The rope diameter is the diameter d of the circle drawn around the rope cross-section.

A distinction must be made between the nominal and the real rope diameter. The nominal rope diameter is a theoretical value while the real rope diameter describes the actual rope diameter. According to EN12385-4, the plus tolerance between the nominal and the real diameter is 0-5% for wire ropes from 8mm. A real rope diameter below the nominal rope diameter would therefore not conform to the standard. For rope diameters below 8mm, the tolerances are usually larger. Special rope manufacturers such as Casar or Diepa usually have plus tolerances between 2-4%. As a rule, rope diameters should be measured in the unloaded state.

Discard criteria of wire ropes

First and foremost, the discard criteria of the crane manufacturer listed in the manual apply. In addition, the discard criteria for wire ropes are based on DIN ISO 4309:

Visible broken wires:

Wire breaks that occur scattered in areas that run through sheaves that spool or unwind on drums or that meet in crossover areas during multi-layer spooling. The following two tables serve as discard criteria. In case of wire breaks in rope zones on a length of 6c which do not wind up or unwind on drums, it may be necessary to discard the rope if only one or two strands are affected, although the number is below the specifications in the following tables. In addition, a rope is discarded if two or more wire breaks are found in the strand valleys/strand shoulders in one lay length (or 6d) and if two or more wire breaks are present at end connections. Individual wires may break as a result of manufacturing, lay-up, handling, storage, and shipping. Since these wires have not been in use, for example, due to fatigue as a result of bending stress, these wire breaks are not usually considered in a test.

Table for single layer and parallel stranded ropes:

Table for low rotation ropes:

Notes on the table:

• for outer strands with seal type, the number is two rows lower than indicated in the table if the number of wires per strand is 19 or less
• filler wires are not counted
• each broken wire has two ends and is counted as one broken wire
• the calculated numbers are to be rounded up
• d stands for the nominal rope diameter
• the values for multi-layer spooling apply to damage in the crossover points and overlaps of windings. The values are not intended for rope zones which only run over sheaves and are not wound up
• for single layer and parallel lay ropes, twice the listed wire breaks apply as discard criteria for drive groups M5 to M8

Reduction of the rope diameter:

The following table indicates when a reduction of the wire rope diameter leads to discard maturity. Relevant for this are rope sections that wind up on single layer drums and/or run over sheaves. For rope sections that coincide with crossover points or with areas that are deformed as a result of winding onto a multi-layered drum. The reference diameter is determined in an area that is not pulled over sheaves and should be measured immediately after the rope is laid.

In case of a local reduction of the rope diameter due to, for example, failure of a rope core, the rope is ready for discard. The rope is also ready for discard if a complete strand breaks.

Corrosion:

When wire ropes are used outdoors or are exposed to moisture or seawater atmospheres, corrosion often occurs as a reason for discard. Basically, a distinction must be made between corrosion of the rope wires and corrosion of the rope surface. Before inspection, the wire rope should be cleaned and brushed if necessary. External corrosion that can be wiped off can be considered harmless. If the wire surface is badly affected or wires appear slack, the rope is ready for discard. Visible corrosion from the inside of the wire rope, for example, escaping corrosion particles found in the valleys between the outer strands, is always a discard criterion. Friction corrosion caused by dissolved steel particles when dry wires and strands rub against each other can also be a filing criterion if the particles penetrate into the rope interior and corrode there. Please note that fretting corrosion or corrosion inside the rope can lead to an increase in rope diameter.

Deformation and damage:

If a wire rope visually deviates from its original shape, this is referred to as deformation. Deformation can lead to uneven load distribution in the rope and is often found in limited areas. Possible deformations or damages can be corkscrew-like deformation, basket formation, protruding or deformed core or strand, loop formation, knots, local increase or decrease of rope diameter, flattening, chinking or tightened rope loops, kinks in the rope or damage due to heat. As a general rule, ropes should always be discarded immediately if their condition is considered hazardous.

Lubrication of wire ropes

Straight running wire rope should be lubricated. Special wire ropes for these applications are usually already intensively lubricated during the manufacturing process. However, lubrication does not last forever, so ropes should be relubricated regularly. In addition to protecting against corrosion, lubrication also performs other important tasks, such as reducing friction between the rope and the sheave and increasing work safety. In dry ropes, wires subjected to bending stress no longer slip smoothly, so that the wires absorb the bending stress to a greater extent. This leads to faster fatigue of the material and thus to wire breaks. Regular relubrication can therefore significantly increase rope service life compared to unlubricated ropes.

The choice of the optimum relubricant can vary depending on the rope type, application area and place of use. If you have any questions about which lubricant is right for your application, please contact us.

Wire rope relevant abbreviations