single layer wire rope free sample

Rotation resistant wire rope refers to a series of steel ropes which minimizes the tendency to spin or rotation under load. These wire ropes boast special design - the outer layer is twisted in the reverse direction of inner layers for counteracting torsional forces generated from multi-layers of strands.

To achieve the resistance against the spin and rotation, all wire ropes are composed of at least two layers of strands. In general, more layers a rotation resistant wire rope has, more resistance it will boast. For example, 2-layer ropes is much easier to spin and rotate than 3-layer ones. Meanwhile, if one end of free rotation is allowed, 2-layer rope can only develop 55% to 75% of its breaking strength comparing with 95% to 100% of 3-layer ropes.

The 3-layer rope with more outer strands is capable to distribute more radial pressure onto inner layers and ideal for larger mobile such as all tower cranes.

Wire ropes with 8 to 10 strands & 2-layer constructions without reversely twisted inner strands have very similar appearance to rotation resistant wire ropes, but they are not.

Rotation resistant wire ropes are considered to be less stable needing to be handled and installed with great care. They must be taken to avoid high loads with small diameter sheaves.

Asteel wire rope is defined not only by its basic elements (wires, strands, core), but also by the way in which the individual wires are laid together to create a strand and the way in which the strands are laid around the core, etc. The steel wire rope’s construction is ­defined when the following criteria have been determined:

The steel wire rope is designated according to the number of strands, the number of wires in each strand, the design (type) of the strand, and the type of core.

The number of wires in a strand varies between three and approx. 139, although there are most commonly 7, 19, 24 or 36 wires. The number of wires and their thickness depend on the design of the strand and affects the characteristic of the steel wire rope.

The type of strand is characterised by the way in which the wires in the strand are arranged. There are four basic types of strand design that are used in all steel wire ropes, either in their original form or as a combination of two or more types. The four basic types are:

The Standard construction (fig. 3) is characterised by the fact that all wires are of equal thickness, although the core wire may be thicker. The wires are also laid together in such a way that all of them, with the exception of the centre wire, are of equal length. In this way all the wires are subjected to an equal distribution of load when pulled straight.

The geometric wire distribution consists of one centre wire, onto which one or more layers are laid. Each layer is produced in a separate operation. If there are several layers, the number of wires increases by six for each layer.

The designation for a Standard strand with e.g. seven wires is (1-6), i.e. one centre wire with six external wires in one operation. If there are 37 wires it is known as (1-6/12/18), i.e. one centre wire with six external wires from the first operation, 12 from the second operation and 18 from the third operation.

The Seale construction (fig. 5) is characterised by the way in which the strand consists of two layers of wire produced in one operation. Also, the number of wires in the first and second layer is identical.This construction is somewhat stiffer than a corresponding Standard construction (with the same number of wires). This is because the outer wires in the Seale construction are considerably thicker.

The Filler construction (fig. 7) is characterised by a strand ­consisting of two layers of wires produced in one operation. Also, the number of wires in the second layer is twice the number in the first layer. This is, however, only possible if filler wires are inserted between the first and the second layers, to prevent the strand becoming hexagonal in shapes.

This construction is more flexible than a corresponding Standard construction and considerably more flexible than a corresponding Seale construction (with the same number of wires excluding filler wires).

A Filler strand with e.g. 25 wires ­(including 6 filler wires) is known as (1-6+6F-12), i.e. one centre wire with six wires in the first layer and 12 wires in the second layer. There are six filler wires between the first and the second layers.

The Warrington construction (fig. 9) is characterised by a strand consisting of two layers of wire produced in one operation. The second (outer) layer contains wires of two dimensions, and the number of wires in the second layer is twice the number in the first.

This construction is very compact and flexible. A Warrington strand with e.g. 19 wires is known as (1-6-6+6), i.e. one centre wire with six wires in the first layer and a total of 12 wires of two dimensions in the second layer. The centre wire may be replaced by several wires or a fibre core (fig. 10).

The Warrington-Seale construction is characterised by a strand consisting of three layers of wire produced in one operation. The number of wires in the third (outer) layer matches the number of wires in the second layer. Also, the layers below the outer layer are built as a Warrington construction.

A Warrington-Seale strand with e.g. 36 wires is known as (1-7-7+7-14), i.e. one centre wire with seven wires in the first layer, 14 wires made up of two dimensions in the second layer, and 14 wires in the third layer.

The strands and the wires in the strands do not necessarily have to be round. Examples of this are shown in fig. 12. The strands are special strands (i.a. with profiled wire), designed to meet extremely unusual requirements.

The number of strands in a steel wire rope varies between three and approx. 36, although most commonly there are six strands. The more strands a steel wire rope contains, the more rounded and flexible it is, although the wires in the strand are also thinner (less durable).

Fibre cores are the most commonly used, as not only do they provide a good, elastic base but also enable lubrication of the rope from the inside, since it is possible to add oil and/or grease to the fibre core during production. This reduces the risk of rust attacking from the inside. The fibre core is normally produced from polypropylene (PP) or sisal. PP can withstand weaker acids and alkalis and it does not rot. The advantage of a sisal core is that it can absorb oil/grease to a greater degree for lubrication of the steel wire rope from the inside.

Randers Reb recommends the use of a steel core, in the event that it is not certain that a fibre core will provide satisfactory support for the strands, e.g. if thesteel wire rope is spooled on to a drum in several layers under a considerable load, or at high temperatures.

The word “lay” has more than one meaning in this context. It is used to describe the process of interweaving the wires and strands and also to describe the appearance of the finished steel wire rope. The four most common terms to describe the lay of a steel wire rope are:

Right hand regular lay steel wire rope. In this instance the wires in the strand are laid in the opposite direction to the strands in the rope. The wires are laid helically left, while the strands are laid helically right (see fig. 13).

Right hand Lang lay steel wire rope. Here the wires are laid in the same direction as the strands in the rope. The wires in the strands and the strands are laid helically right (see fig. 15).

Multi layer steel wire rope (low rotation/rotation resistant). Here there are usually two layers of strands, the inner layer as a rule a left hand Lang lay, while the outer layer is a right hand regular lay.

Cable laid steel wire rope. The strands are normally 6-lay steel wire rope with a fibre or steel core. The core is a fibre core or a 6-lay steel wire rope with a fibre or steel core.

Flat braided steel wire rope. This steel wire rope is flat braided from strands or consists of parallel strands or steel wire ropes that are bound together by sewing (belt strap).

Right hand lay steel wire rope is also known as Z-lay, and left hand as S-lay. Similarly, a right hand lay strand is known as z-lay and left hand as s-lay. Fig. 17 shows why. Of the types of lay described, right hand regular lay is the most common.

“Preformed” refers to steel wire ropes in which the strands have been permanently formed during the laying process (see fig. 18), so that they are completely stress-free within the unloaded steel wire rope.

All Randers Reb steel wire ropes are supplied preformed, with the exception of certain individual special constructions (e.g. low-rotation/rotation resistant).

The actual diameter of a wire rope is the diameter of a circumscribed circle that will enclose all the strands. It’s the largest cross-sectional measurement as shown here. You should make the measurement carefully with calipers.

The rope diameter should be measured on receipt for conformity with the specification. British Standard (B.S. 302:1987, standard steel wire rope, Part 1. Clause 5.1) allow for a tolerance of - 1% to 4 % of the nominal rope diameter.

The generally accepted method of measuring rope diameter for compliance with the standard is to use a caliper with jaws broad enough to cover not less than two adjacent stands. The measurement must be taken on a straight portion of rope at two points at least 1 meter apart. At each point two diameters at right angles should be measured. The average of the four measurement is the actual diameter.

After the rope has made the first few cycles under low load, the rope diameter should be measured at several points. The average value of all the measurements at each point must be recorded and will form the basis of comparison for all future measurements.

The measurements of the rope diameter an essential part of all inspections and examinations. It ensures the maximum diameter reduction does not exceed the recommended figure. As stated in 5.2 British standard 6570 recommends that a wire rope should be discarded when the diameter of the rope is reduced to 90% of the nominal diameter.

A comparison of the measured data with the recorded previous values can detect an abnormal rate of reduction in diameter. Coupled with assessment of previous rope examination data, the probable date of rope renewal can be predicted.

If we examine the cross-section of a six-stand wire rope, we will find that measuring the thickness of the rope over the crowns (Fig-a) will produce a higher value than measuring it over the valleys (Fig-b). The actual diameter of the rope is defined as the diameter of the circumscribing circle.

When using a conventional caliper, wire rope with an even number of outer strands (four-, six, eight-, and multi strand) ropes must be measured from crown to crown. The advantage of a proper wire rope caliper with measuring plates is that even if the measurement is carried out "incorrectly", adjacent crowns are always included, so that the actual diameter is determined at any section. (Fig-c)

Measuring the diameter of wire rope with an uneven number of outer strands (three, five, seven, or nine-strand ropes) is more complicated: a crown on the one side of the wire rope always has a valley as a counterpart on the other side of the wire rope. A conventional caliper, therefore, has to be applied diagonally to the axis of the rope, so that at any time a crown adjacent to a valley is covered. Again a wire rope caliper with measuring plate is definitely to be preferred as it always includes strands crowns.

In all cases during periodic examinations where the measurements are to be recorded, the rope should be measured as already described. Where the roundness is being checked to detect potential faults, two diameters, one at right angles to the other can be taken and noted in the records. The entry into the records might read rope diameter : 20.4/20.5mm.

After a rope has been fitted to the appliance, its length cannot be measured again accurately, with out a great deal of trouble. The purpose of measuring the length of lay is to detect any increase in the rope length which may have been caused by corrosion, core deterioration or rope rotation (unlaying). With n new rope the wire and strands should be allowed to settle into their permanent position. Six or seven lifting cycles with a light to medium load are recommended before measuring error, the measurement should be made over four lays and the length divided by four lays and the length divided by four to find the average lay length.

On eight strand ropes the eight, sixteen, twenty-four and thirty-second strands must be marked. Using a straight length of the rope and with the rope under no load, first mark any strand on the crown with a piece of chalk; this strand now become"" crown zero"". Excluding this strands, count the next eight strands and mark the eight strand with chalk. Exclude the eight strand and repeat the procedures further two times. The measured length between the outer chalk marks is then divided by four to give the lay length.

As a rough check on the overall accuracy of the chalk marking, the length of lay for eight strand ropes is approximately between 6.25 and 6.5 x the diameter of the rope e.g. using a lay length of 6.5 x rope diameter, four lay length of a 32mm diameter rope will be 32mm x 6.5 x 4=832mm.

An alternate method of measuring the rope lay is to secure the free end of the roll of adding machine paper to the rope with adhesive tape. The paper is rolled out over the rope and simultaneously the wax pencil is drawn over the paper, providing a clear print of the outer wires of the rope. The finished print can be field for comparison with later measurements.

A third method is to wrap typing carbon papers round the rope under the roll of paper. By rubbing along the paper with a piece of cardboard, the carbon marking on the underside of the paper can be confined to the tops of the strand crowns.

Wire rope and cable are each considered a “machine”. The configuration and method of manufacture combined with the proper selection of material when designed for a specific purpose enables a wire rope or cable to transmit forces, motion and energy in some predetermined manner and to some desired end.

Two or more wires concentrically laid around a center wire is called a strand. It may consist of one or more layers. Typically, the number of wires in a strand is 7, 19 or 37. A group of strands laid around a core would be called a cable or wire rope. In terms of product designation, 7 strands with 19 wires in each strand would be a 7×19 cable: 7 strands with 7 wires in each strand would be a 7×7 cable.

Materials Different applications for wire rope present varying demands for strength, abrasion and corrosion resistance. In order to meet these requirements, wire rope is produced in a number of different materials.

Stainless Steel This is used where corrosion is a prime factor and the cost increase warrants its use. The 18% chromium, 8% nickel alloy known as type 302 is the most common grade accepted due to both corrosion resistance and high strength. Other types frequently used in wire rope are 304, 305, 316 and 321, each having its specific advantage over the other. Type 305 is used where non-magnetic properties are required, however, there is a slight loss of strength.

Galvanized Carbon Steel This is used where strength is a prime factor and corrosion resistance is not great enough to require the use of stainless steel. The lower cost is usually a consideration in the selection of galvanized carbon steel. Wires used in these wire ropes are individually coated with a layer of zinc which offers a good measure of protection from corrosive elements.

Cable Construction The greater the number of wires in a strand or cable of a given diameter, the more flexibility it has. A 1×7 or a 1×19 strand, having 7 and 19 wires respectively, is used principally as a fixed member, as a straight linkage, or where flexing is minimal.

Selecting Wire Rope When selecting a wire rope to give the best service, there are four requirements which should be given consideration. A proper choice is made by correctly estimating the relative importance of these requirements and selecting a rope which has the qualities best suited to withstand the effects of continued use. The rope should possess:Strength sufficient to take care of the maximum load that may be applied, with a proper safety factor.

Strength Wire rope in service is subjected to several kinds of stresses. The stresses most frequently encountered are direct tension, stress due to acceleration, stress due to sudden or shock loads, stress due to bending, and stress resulting from several forces acting at one time. For the most part, these stresses can be converted into terms of simple tension, and a rope of approximately the correct strength can be chosen. As the strength of a wire rope is determined by its, size, grade and construction, these three factors should be considered.

Safety Factors The safety factor is the ratio of the strength of the rope to the working load. A wire rope with a strength of 10,000 pounds and a total working load of 2,000 pounds would be operating with a safety factor of five.

It is not possible to set safety factors for the various types of wire rope using equipment, as this factor can vary with conditions on individual units of equipment.

The proper safety factor depends not only on the loads applied, but also on the speed of operation, shock load applied, the type of fittings used for securing the rope ends, the acceleration and deceleration, the length of rope, the number, size and location of sheaves and drums, the factors causing abrasion and corrosion and the facilities for inspection.

Fatigue Fatigue failure of the wires in a wire rope is the result of the propagation of small cracks under repeated applications of bending loads. It occurs when ropes operate over comparatively small sheaves or drums. The repeated bending of the individual wires, as the rope bends when passing over the sheaves or drums, and the straightening of the individual wires, as the rope leaves the sheaves or drums, causing fatigue. The effect of fatigue on wires is illustrated by bending a wire repeatedly back and forth until it breaks.

The best means of preventing early fatigue of wire ropes is to use sheaves and drums of adequate size. To increase the resistance to fatigue, a rope of more flexible construction should be used, as increased flexibility is secured through the use of smaller wires.

Abrasive Wear The ability of a wire rope to withstand abrasion is determined by the size, the carbon and manganese content, the heat treatment of the outer wires and the construction of the rope. The larger outer wires of the less flexible constructions are better able to withstand abrasion than the finer outer wires of the more flexible ropes. The higher carbon and manganese content and the heat treatment used in producing wire for the stronger ropes, make the higher grade ropes better able to withstand abrasive wear than the lower grade ropes.

Effects of Bending All wire ropes, except stationary ropes used as guys or supports, are subjected to bending around sheaves or drums. The service obtained from wire ropes is, to a large extent, dependent upon the proper choice and location of the sheaves and drums about which it operates.

A wire rope may be considered a machine in which the individual elements (wires and strands) slide upon each other when the rope is bent. Therefore, as a prerequisite to the satisfactory operation of wire rope over sheaves and drums, the rope must be properly lubricated.

Loss of strength due to bending is caused by the inability of the individual strands and wires to adjust themselves to their changed position when the rope is bent. Tests made by the National Institute of Standards and Technology show that the rope strength decreases in a marked degree as the sheave diameter grows smaller with respect to the diameter of the rope. The loss of strength due to bending wire ropes over the sheaves found in common use will not exceed 6% and will usually be about 4%.

The bending of a wire rope is accompanied by readjustment in the positions of the strands and wires and results in actual bending of the wires. Repetitive flexing of the wires develops bending loads which, even though well within the elastic limit of the wires, set up points of stress concentration.

The fatigue effect of bending appears in the form of small cracks in the wires at these over-stressed foci. These cracks propagate under repeated stress cycles, until the remaining sound metal is inadequate to withstand the bending load. This results in broken wires showing no apparent contraction of cross section.

Experience has established the fact that from the service view-point, a very definite relationship exists between the size of the individual outer wires of a wire rope and the size of the sheave or drum about which it operates. Sheaves and drums smaller than 200 times the diameter of the outer wires will cause permanent set in a heavily loaded rope. Good practice requires the use of sheaves and drums with diameters 800 times the diameter of the outer wires in the rope for heavily loaded fast-moving ropes.

It is impossible to give a definite minimum size of sheave or drum about which a wire rope will operate with satisfactory results, because of the other factors affecting the useful life of the rope. If the loads are light or the speed slow, smaller sheaves and drums can be used without causing early fatigue of the wires than if the loads are heavy or the speed is fast. Reverse bends, where a rope is bent in one direction and then in the opposite direction, cause excessive fatigue and should be avoided whenever possible. When a reverse bend is necessary larger sheaves are required than would be the case if the rope were bent in one direction only.

Stretch of Wire Rope The stretch of a wire rope under load is the result of two components: the structural stretch and the elastic stretch. Structural stretch of wire rope is caused by the lengthening of the rope lay, compression of the core and adjustment of the wires and strands to the load placed upon the wire rope. The elastic stretch is caused by elongation of the wires.

The structural stretch varies with the size of core, the lengths of lays and the construction of the rope. This stretch also varies with the loads imposed and the amount of bending to which the rope is subjected. For estimating this stretch the value of one-half percent, or .005 times the length of the rope under load, gives an approximate figure. If loads are light, one-quarter percent or .0025 times the rope length may be used. With heavy loads, this stretch may approach one percent, or .01 times the rope length.

The elastic stretch of a wire rope is directly proportional to the load and the length of rope under load, and inversely proportional to the metallic area and modulus of elasticity. This applies only to loads that do not exceed the elastic limit of a wire rope. The elastic limit of stainless steel wire rope is approximately 60% of its breaking strength and for galvanized ropes it is approximately 50%.

Preformed Wire Ropes Preformed ropes differ from the standard, or non-preformed ropes, in that the individual wires in the strands and the strands in the rope are preformed, or pre-shaped to their proper shape before they are assembled in the finished rope.

This, in turn, results in preformed wire ropes having the following characteristics:They can be cut without the seizings necessary to retain the rope structure of non-preformed ropes.

They are substantially free from liveliness and twisting tendencies. This makes installation and handling easier, and lessens the likelihood of damage to the rope from kinking or fouling. Preforming permits the more general use of Lang lay and wire core constructions.

Removal of internal stresses increase resistance to fatigue from bending. This results in increased service where ability to withstand bending is the important requirement. It also permits the use of ropes with larger outer wires, when increased wear resistance is desired.

Outer wires will wear thinner before breaking, and broken wire ends will not protrude from the rope to injure worker’s hands, to nick and distort adjacent wires, or to wear sheaves and drums. Because of the fact that broken wire ends do not porcupine, they are not as noticeable as they are in non-preformed ropes. This necessitates the use of greater care when inspecting worn preformed ropes, to determine their true condition.

Wire rope is a complex mechanical device that has many moving parts, all working in tandem to help support and move an object or load. In the lifting and rigging industries, wire rope is attached to a crane or hoist and fitted with swivels, shackles or hooks to attach to a load and move it in a controlled matter. It can also be used to lift and lower elevators, or as a means of support for suspension bridges or towers.

A wire rope is a machine with many moving parts. It has a unique design consisting of steel wires that form individual strands laid in a helical pattern around a center core.

Wire rope is a preferred lifting device for many reasons. Its unique design consists of multiple steel wires that form individual strands laid in a helical pattern around a core. This structure provides strength, flexibility and the ability to handle bending stresses. Different configurations of the material, wire, and strand structure will provide different benefits for the specific lifting application, including:

However, selecting the proper wire rope for your lifting application requires some careful thought. Our goal is to help you understand the components of a wire rope, the construction of wire rope and the different types of wire rope and what they might be used for. This will allow you to select the best performing and longest-lasting wire rope for the job at hand.

A finished wire rope is comprised of individual wires, which make up individual strands, which are then laid in a helical pattern around a synthetic or steel core.

A wire rope is a machine with many moving parts. From childhood, many of us have been conditioned to think of a machine as some device with gears, shafts, belts, cams and assorted whirring parts. Yet, by the rules of physics, an ordinary pry bar is a simple machine, even though it has only one part.

A wire rope is, in reality, a very complicated machine. A typical 6 by 25 rope has 150 wires in its outer strands, all of which move independently and together in a very complicated pattern around the core as the rope bends. Clearances between wires and strands are balanced when a rope is designed so that proper bearing clearances will exist to permit internal movement and adjustment of wires and strands when the rope has to bend. These clearances will vary as bending occurs, but are of the same range as the clearances found in automobile engine bearings.

Understanding and accepting the “machine idea” gives a rope user a greater respect for rope, and enables them to obtain better performance and longer useful life from rope applications. Wire rope is a complex piece of mechanical machinery with a number of different specifications and properties that can affect its performance and service life.

A finished wire rope is comprised of individual wires, which make up individual strands, which are then laid in a helical pattern around a synthetic or steel core. There are four basic components that make up the design of a finished wire rope:

Wires are the smallest component of wire rope and they make up the individual strands in the rope. Wires can be made from a variety of metal materials including steel, iron, stainless steel, monel, and bronze. The wires can be manufactured in a variety of grades that relate to the strength, resistance to wear, fatigue resistance, corrosion resistance, and curve of the wire rope.

Strands of wire rope consist of two or more wires arranged and twisted in a specific arrangement. The individual strands are then laid in a helical pattern around the core of the rope. Strands made of larger diameter wires are more resistant to abrasion, while strands made of smaller diameter wires are more flexible.

The core of a wire rope runs through the center of the rope and supports the strands and helps to maintain their relative position under loading and bending stresses. Cores can be made from a number of different materials including natural or synthetic fibers and steel.

The construction of wire rope falls into one of these strand pattern classifications. The number of layers of wires, the number of wires per layer, and the size of the wires per layer all affect the strand pattern type. Wire rope can be constructed using one of the following patterns, or can be constructed using two or more of the patterns below.

Filler Wire – Two layers of uniform-size wire around a center with the inner layer having half the number of wires as the outer layer. Small filler wires, equal to the number in the inner layer, are laid in valleys of the inner wire.

Seale – Two layers of wires around a center with the same number of wires in each layer. All wires in each layer are the same diameter. The large outer wires rest in the valleys between the smaller inner wires.

Warrington – Two layers of wires around a center with one diameter of wire in the inner layer, and two diameters of wire alternating large and small in the outer later. The larger outer-layer wires rest in the valleys,and the smaller ones on the crowns of the inner layer.

Remember, wire rope is a complex piece of mechanical machinery. There are a number of different specifications and properties that can affect the performance and service life of wire rope. Consider the following when specifying the best type of wire rope for your lifting application:

When you select a piece of rope that is resistant to one property, you will most likely have a trade-off that affects another property. For example, a fiber core rope will be more flexible, but may have less crushing resistance. A rope with larger diameter wires will be more abrasion resistant, but will offer less fatigue resistance.

A rope with larger diameter wires will be more crush resistant and abrasion resistant, while a rope with smaller diameter wires will be more bendable and fatigue resistant.

On a preformed wire rope, the strands and wires are formed during the manufacturing process to the helical shape that they will take in a finished wire rope. Preformed rope can be advantageous in certain applications where it needs to spool more uniformly on a drum, needs greater flexibility, or requires more fatigue-resistance when bending.

Direction and type of lay refer to the way the wires are laid to form a strand (either right or left) and how the strands are laid around the core (regular lay, lang lay, or alternate lay).

Regular Lay – The wires line up with the axis of the rope. The direction of the wire lay in the strand is opposite to the direction of the strand lay. Regular lay ropes are more resistant to crushing forces, are more naturally rotation-resistant, and also spool better in a drum than lang lay ropes.

Lang Lay – The wires form an angle with the axis of the rope. The wire lay and strand lay around the core in the same direction. Lang Lay ropes have a greater fatigue-resistance and are more resistant to abrasion.

A steel core can be an independent wire rope or an individual strand. Steel cores are best suited for applications where a fiber core may not provide adequate support, or in an operating environment where temperatures could exceed 180° F.

The classifications of wire rope provide the total number of strands, as well as a nominal or exact number of wires in each strand. These are general classifications and may or may not reflect the actual construction of the strands. However, all wire ropes of the same size and wire grade in each classification will have the same strength and weight ratings and usually the same pricing.

Some types of wire rope, especially lang lay wire rope, are more susceptible to rotation when under load. Rotation resistant wire rope is designed to resist twisting, spinning, or rotating and can be used in a single line or multi-part system. Special care must be taken when handling, unreeling, and installing rotation resistant wire rope. Improper handling or spooling can introduce twist into the rope which can cause uncontrolled rotation.

Compacted strand wire rope is manufactured using strands that have been compacted, reducing the outer diameter of the entire strand, by means of passing through a die or rollers. This process occurs prior to closing of the rope.This process flattens the surface of the outer wires in the strand, but also increases the density of the strand. This results in a smoother outer surface and increases the strength compared to comparable round wire rope (comparing same diameter and classification), while also helping to extend the surface life due to increased wear resistance.

A swaged wire rope differs from a compacted strand wire rope, in that a swaged wire rope’s diameter is compacted, or reduced, by a rotary swager machine after the wire rope has been closed. A swaged wire rope can be manufactured using round or compacted strands.The advantages of a swaged wire rope are that they are more resistant to wear, have better crushing resistance, and high strength compared to a round strand wire rope of equal diameter and classification. However, a swaged wire rope may have less bending fatigue resistance.

A plastic coating can be applied to the exterior surface of a wire rope to provide protection against abrasion, wear, and other environmental factors that may cause corrosion. However, because you can’t see the individual strands and wires underneath the plastic coating, they can be difficult to inspect.

Plastic filled wire ropes are impregnated with a matrix of plastic where the internal spaces between the strands and wires are filled. Plastic filling helps to improve bending fatigue by reducing the wear internally and externally. Plastic filled wire ropes are used for demanding lifting applications.

This type of wire rope uses an Independent Wire Rope Core (IWRC) that is either filled with plastic or coated in plastic to reduce internal wear and increase bending fatigue life.

Rope Services Direct supplies a variety of anti-spin non rotating wire rope (also called rotation resistant wire-rope). All standard rope wirehas a tendency to develop torque and therefore prone to rotation, whereas non-rotating wire ropes are designed so that the wire-rope outer rotational force naturally counteracts the inner strands rotational force. This is in the event that a rope is subjected to a load.

Rope elongation and rotation occurs on standard ropes when loaded, which can therefore spin the load, quite possibly out of control, which can be dangerous. When the rope rotates in this way the strands will begin to unravel. This causes the rope to lose strength and will undoubtedly fail, which could be catastrophic. It is for these reasons that non rotating wire rope is commonly used for many types of lifting applications including main hoist rope, whip rope,crane rope, off-shore and deck rope and more.

Non rotating wire rope or rotation resistant wire rope has a different construction to standard. as wires and strands are not laid in the same direction like they would be on standard rope. Inner and outer strands of wires are laid in opposite directions. For example the inner may be constructed in left hand lay whilst the outer layer is in right hand lay. The nature of this construction means that torsional forces on the inner and outer wires/strands will counteract each other and therefore minimising the risk of unraveling.

It is worth noting that the number of strand layers will have an effect of the resistance of rotation. A 2 layer rope has less resistance than a 3 layer rope. Therefore the more layers the rope has the greater rotation resistance it will have.

These types of ropes can be classified as spin resistant, rotation resistant or non rotation resistant. Classed on the basis of the number of rotations a certain length of rope does when a force of 20% of the MBF is applied; with 1 turn or less the rope will be classified as non rotating; with rotations between 1 & 4 the rope is classed as low rotation and for rotations between 4 & 10 the rope will be classified as spin resistant, any higher and the rope is NOT rotation resistant at all.

Correct usage and care with handling will prolong the working life. This is due to the friction on the inner wires caused by the strand crossover’s which will eventually cause the inner wires to break up. This is more apparent on non rotating wire rope with two layers. Ropes with 3 or more strand layers will distribute the radial pressures more evenly. Which will reduce friction and stress on the inner wires.

Regular,thorough inspectionsof non rotating rope are essential due to the fact that it is the inner strands that often break first and broken internal wires often go unnoticed as they are difficult to see.Rope Services Direct offer inspectionson all rope with certification issued on completion.

Holding both ends of the rope will prevent unraveling. Correctly fitted terminations will help to prevent damage. Kinking and unraveling may occur and they can also have an effect on the rotational balance if not fitted correctly.

Lifting operations are performed in every area of the iron and steel plant. In these operations, safety is a critical factor, which requires reliable materials. Steel wire ropes are a key element of the lifting operations, since everything depends on their performance.

Steel wire rope is also known as steel cable.  It is a type of rope which consists of several strands of steel wire laid (twisted) into a helix. It is a preferred lifting device for several reasons. Its unique design consists of multiple steel wires which form individual strands laid in a helical pattern around a core. This structure provides strength, flexibility, and the ability to handle bending stresses. Different configurations of the material, wire, and strand structure provide different benefits for the specific lifting applications. These benefits include strength, flexibility, abrasion resistance, crushing resistance, fatigue resistance, corrosion resistance, and rotation resistance.

Wires are the basic building blocks of a wire rope. They lay around a ‘centre’ in a specified pattern in one or more layers to form a strand. The strands are helically laid together around a centre, which is typically some type of core, to form a wire rope. The strands provide all the tensile strength to the wire rope. Properties like fatigue resistance and resistance to abrasion are directly af­fected by the design of strands. Selection of the proper wire rope for a lifting application needs some careful considerations.

Modern wire rope was invented by the German mining engineer Wilhelm Albert in the years between 1831 and 1834 for use in the mining operations. It was quickly accepted because it proved superior to metal chains and ropes made of hemp which were used earlier. Wilhelm Albert’s first ropes consisted of three strands with each strand having four wires. With the change in the needs, the designs of the wire ropes have also undergone major changes with respect to the core, overlay, and the weight requirement etc.

A wire rope is, in reality, a very complicated machine. It consists of a number of precise moving parts, designed and manufactured to bear a definite relation to one another. In fact, some wire ropes contain more moving parts than many complicated mechanisms. For example, a six strand wire rope laid around and independent wire rope core, each strand and core with 49 wires, contains a total of 343 individual wires. All these wires are to work together and move with respect to one another if the rope is to have the flexibility necessary for successful operation. The wires in a wire rope move independently and together in a very complicated pattern around the core as the rope bends. Clearances between wires and strands are balanced when a rope is designed so that proper bearing clearances exist to permit internal movement and adjustment of wires and strands when the rope has to bend. These clearances vary as bending occurs, but are of the same range as the clearances found in the automobile engine bearings.

The primary factor in wire rope performance is selecting a wire rope with the best combination of properties for the job. The service life of that rope can be greatly extended by following a planned program of installation, operation, maintenance, and inspection to avoid its failure. The appropriate time to replace a wire rope in service is frequently determined by counting the number of broken wires in the length of one rope lay.

The terms which help to define the construction and properties of the wire rope are length, size, pre-formed or non pre-formed, direction and type of lay, finish of wires, grade of rope, and type of core. The length of the wire rope is the total number of meters (cut to size) when wrapped around the spool and the size is the specified nominal diameter of the wire rope and is specified in millimeters.

There are three basic components which make up the design of a steel wire rope. These are (i) wires made from steel which form a singular strand, (ii) multi- wire strands laid around a core in a helical pattern, and (iii) the core.

Wires– Wires are the basic and smallest component of the wire rope and they make up the individual strands in the rope. Wires can be made from a variety of metal materials including steel, iron, stainless steel, Monel, and bronze but in the steel wire rope they are made from steel. The wires can be manufactured to predetermined physical properties and sizes and in a variety of grades which relate to the strength, resistance to wear, fatigue resistance, corrosion resistance, and curve of the wire. A pre-determined number of finished wires are helically laid together in a uniform geometric pattern to form a strand. The process is carried out with precision and exactness to form a strand of correct size and characteristics. The wires themselves can be coated but are most commonly available in a ‘bright’ or uncoated finish.

Strands – Strands of the wire rope consist of two or more wires arranged and twisted in a specific arrangement. The individual strands are then laid in a helical pattern around the core of the wire rope. Strands made of larger diameter wires are more resistant to abrasion, while strands made of smaller diameter wires are more flexible. Strands are designed with various combinations of wires and wire sizes to produce the desired resistance to fatigue and abrasion. Normally, a small number of large wires are more abrasion resistant and less fatigue resistant than a large number of small wires. The required numbers of suitably fabricated strands are laid symmetrical with a definite length of lay around a core to form the finished wire rope.

The core – The core of a wire rope is the foundation of a wire rope. It runs through the centre of the rope. Its primary function is to support the wire strands in the rope and to maintain them in their correct relative positions during the operating life of the wire rope. The core supports the strands and helps to maintain their relative position under loading and bending stresses. Cores can be made from a number of different materials including natural or synthetic fibres and steel but in the steel wire rope, the core is made from steel. Steel core provides more support than the fibre core. Steel cores resist crushing, are more resistant to heat, reduce the amount of stretch, and increase the strength of the wire rope.

Steel cores are normally of two types. The first type is wire strand core (WSC). This type of the core is used in case of small diameter ropes and in some rotation resistant wire ropes. The second type of steel core is independent wire rope core (IWRC). The IWRC can be made in a separate operation or during the closing operation of the wire rope. IWRC normally provides increased strength to the rope, greater resistance to crushing, and resistance to excessive heat. IWRC increases the strength of the wire rope by 7 %, increases its weight by 10 %, and decreases the flexibility slightly. These ropes are recommended for use on installations where severe loads are placed on ropes running over sheaves or wound on drums. The wire core can also have a plastic coating.

Cores made of compacted strands have the additional designation (K). An independent wire core made of compacted strands is hence called IWRC (K). A rope closed in a single operation and made out of compacted strands both in the core and the outer strands is called PWRC (K).

Wire ropes and their free rope end rotate to a greater or lesser extent around its longitudinal axis under the influence of tension. Wire ropes having a core lay direction opposite to the lay direction of the outer strands and 3-strand or 4-strand regular lay wire ropes rotate considerably less than wire ropes with the same lay direction of the wire core and the outer strands and wire ropes with fibre cores.

According to VDI 2358, a wire rope is semi rotation-resistant when ‘the wire rope which turns around its longitudinal axis when subjected to unguided load and / or hardly transmits a torque to the attachment at the end in the event of guided rope ends’. According to ISO 21669 and DIN EN 12385-3 ‘a rope is considered to be semi rotation resistant if it rotates at least once and at most four times around its axis at a length of 1,000 x d under a load of 20 % of the minimum breaking force. In terms of rotation angle, the defined limits are between 360 deg and 1,440 deg’.

According to the regulation of VDI 2358, a wire rope is rotation-resistant, when ‘the wire rope, which hardly turns around its longitudinal axis when subjected to unguided load and / or hardly transmits a torque to the attachment at the end in the event of guided rope ends’. According to ISO 21669 and DIN EN 12385-3 ‘a rope is considered to be rotation resistant if it rotates around its axis at most once at a length of 1,000 x d under a load of 20 % of the minimum breaking force. The rotation can be exhibited here in rope closing or rope opening sense. For the rotation angle, this implies between -360 deg and 360 deg’.

A distinction is made between the nominal rope diameter and the actual rope diameter. The nominal wire rope diameter is an agreed theoretical value for the diameter of the smallest circle enclosing the outer strands. The effective diameter of the wire rope, also called actual rope diameter, is the diameter of the smallest circle enclosing all outer strands, as measured on the rope itself. The tolerance range for the effective rope diameter is specified in related national and international standards. In order to define the correct effective rope diameter, the correct measuring device has to be used. The measurement is to be strictly done over the round ends (circumscribed circle of the rope). If the measurement is done in the strand valleys, the result is inaccurate. For ropes with an uneven number of outer strands, it is important that the measuring surface covers several strands. Fig 1 shows components of a wire rope and measurement of its diameter.

Wire ropes are identified by a nomenclature which is referenced to (i) the number of strands in the rope, (ii) the number (nominal or exact) and arrangement of wires in each strand and (iii) a descriptive word or letter indicating the type of construction i.e. the geometric arrangement of wires.

In the stranding process, initially straight wires are forced into a helical or double-helical form. Hence, the wires in a rope are always under tension, even in an unloaded rope. Such a rope is to be sealed very tightly left and right of the joint before cutting the rope since otherwise the free ends of the wires spring open.

By using a ‘pre-forming tool’, the wires and strands can be heavily plastically deformed during the stranding, so they are laying nearly without tension in the rope, the rope now is pre-formed. The rope producers consider such ropes to be ‘dead’. Pre-formed ropes can be cut much easier, also secured by seizings of course, than non pre-formed ropes.

The wire rope lay is the helix or spiral of the wires and strands. The word ‘lay’ has got three meanings in the rope design. The first two meanings are descriptive of the wire and strand position in the rope. The first meaning describes the direction in which strands rotate around in the wire rope i.e. right lay or left lay. If the strands rotate around the wire rope in a clock wise direction, the rope is said to be right lay. When the strands rotate in the counter-clockwise direction, the wire rope is left lay. The second meaning shows the relationship between the direction strands lay in the wire rope and the direction wire lay in the strands. The third meaning is a length measurement used in manufacturing and inspection. In the third meaning it is the linear length along the rope that a strand makes one complete spiral around the rope core. Lay length is measured in straight line parallel to the centre line of the rope, not by following the path of the strand.

Direction and type of lay refer to the way the wires are laid to form a strand (either right or left) and how the strands are laid around the core (regular lay, lang lay, or alternate lay). Fig 2 shows direction and types of wire rope lay.

Regular lay in the wire rope denotes that the wires are twisted in one direction, and the strand in opposite direction to form the rope. The wires in regular lay line up with the axis of the rope. The direction of the wire lay in the strand is opposite to the direction of the strand lay. Regular lay wire ropes are distinguished between right hand ordinary lay (RHOL) and left hand ordinary lay (LHOL). Due to the difference in direction between the wires and strand, regular lay ropes are less likely to untwist or kink. Regular lay roes are also less subject to failure from crushing and distortion because of shorter length of exposed outer wires. Regular lay ropes are naturally more rotation-resistant, and also spool better in a drum than lang lay ropes. The advantages of regular lay ropes are (i) better structural stability, (ii) higher number of broken wires is allowed, and (iii) identification of broken wires is easier.

Lang lay in the wire rope is the opposite. The wires form an angle with the axis of the rope. The wire lay and strand lay around the core in the same direction. The wires and strands appear to run at a diagonal to the centre line of the rope. Lang lay wire ropes are distinguished between left hand lang lay (LHLL) and right hand lang lay (RHLL). Due to the longer length of the exposed outer wires, lang lay ropes have greater flexibility. These ropes are more likely to twist, kink, and crush. Lang lay ropes have a greater fatigue-resistance and are more resistant to abrasion. The advantages of lang lay ropes are (i) better contact in the groove of the sheaves, (ii) superior resistance to wear, (iii) longer lifetime in case of high dead loads, and (iv) considerably better spooling behaviour on a multi-layer drum

As regards lay direction of a wire rope, a distinction is made between right hand and left hand lay ropes. The lay direction is left hand, when the strands (moving away from the beholder) are rotated counter-clockwise. The lay direction of a rope is right hand, when its strands (moving away from the beholder) are rotated clockwise. The lay direction of a rope is frequently given by a capital S for the left hand lay rope and by a capital Z for the right hand lay rope. Others frequently use abbreviations are RH for right hand lay ropes and LH for left hand lay ropes.

One strand is normally made up of seven to several tens of wires with similar, or differing, diameters in single or multi-layers. In the method where the wires are positioned to form more than two layers, there is the cross lay where the wires of each layer are in the same lay angle, and the parallel lay where one process is used to lay the wires so that the wires of each layer are of the same pitch. For strands of the same diameter, the more is the number of wires, the smaller is the diameter of each wire and the greater is the flexibility of the strand. However, conversely, the rope becomes inferior in its wear resistance nature and its shape deformation nature.

Cross lay – The cross lay is referred to as the point contact lay, as each wire is in contact with each other. The laying of the wires is carried out in such a way that the lay angle is almost equal for each layer of wire of the same diameter. The length of the wires in each layer is also to be the same and the wires of each layer are in contact with each other. Hence, the tension stress which works on the wire becomes uniform, but the bending stress due to the contact points is added and so the fatigue resistance is not as great.

Parallel lay – Parallel lay is also referred to as equal lay. It is also called one operation lay from the number of stranding processes and also as linear contact lay as each wire is in contact with each other. In the parallel lay, the wires of each layer are positioned in such a way that there is no space between them so that the upper layer wires fit neatly into the groove of the lower wires of the strand. For this, wires of differing diameters are positioned at the same time so that each wire layer has the same pitch and is in contact with each other. Hence, parallel lay rope differs from the cross lay rope, although the lay angle of each wire layer and the length of the wires are not uniform, as each wire is in contact with each other, it is superior in its fatigue resistance nature.

The fill factor of a rope is defined as the ratio of the metallic cross section of the rope (or a simplified calculation of the sum of the single wire cross sections) related to the nominal rope diameter. The fill factor specifies the amount of space the wires and strands take in the rope. The fill factors of the most common ropes are between 0.46 and 0.75. This means, that the amount of steel in the rope volume is around 46 % to 75 %. Wire ropes with a wire rope steel core have higher fill factors than ropes with a fibre core. The fill factor of the strand is the proportion of the metallic cross sections at the metal cross section area of the minimum circumscribed circle. Wire ropes which are made of compacted strands have higher fill factors than ropes of un-compacted strands. By compacting and rotary swaging of the rope itself the fill factor can further be increased.

The basic parallel lay are basically of five types namely (i) single layer type, (ii) Seale type, (iii) Warrington type, (iv) filler type with filler wire, and (v) combined pattern type. Fig 3 shows types of basic parallel lay wire rope.

The single layer type wire rope has the basic strand construction of having wires of the same size wound around a centre. The most common example of the single layer construction is a 7 wire strand. It has a single-wire centre with six wires of the same diameter around it.

The Seale type wire rope construction has two layers of wires around a centre with the same number of wires in each layer. All wires in each layer are of the same diameter. The strand is designed so that the large outer wires rest in the valleys between the smaller inner wires. In Seale type, the number of wires of each layer is shown as 1+n+n and the number of wires of the inner and outer layers is the same. The wires of the outer layer fit completely into the grooves of the inner layer wires. The outer layer wires of the Seale type rope is thicker when compared to other parallel lays and so it is superior, particular in its wear resistance and is mainly used for elevators.

The Warrington type wire rope construction has two layers of wires around a centre with one diameter of wire in the inner layer, and two diameters of wire alternating large and small in the outer layer. The larger outer-layer wires rest in the valleys, and the smaller ones on the crowns, of the inner layer. In the Warrington type, the number of wires of each layer is shown as 1+n+(n+n) and there are two types of wires for the outer layers, one being large and the other being small. The number of wires of the outer layer is double that of the inner layer and through a combination of the inner and outer layers the spaces between the wires are kept small. The Warrington type rope is not being used to a great extent these days.

The filler wire type wire rope construction has two layers of uniform-size wire around a centre with the inner layer having half the number of wires as the outer layer. Small filler wires, equal in number to the inner layer, are laid in valleys of the inner layer. In the filler type (with filler wire), the number of wires of each layer is shown as 1+n+(n)+2n and the number of wires of the outer layers is double that of the inner layer. The inner wires and the same number of thin filler wires are used to fill the spaces in the inner and outer layers. This filler type rope has a good balance between the flexibility, fatigue resistance, and wear resistance and has the widest range of use among parallel lay ropes.

The combined patterns type wire rope construction has strand which is formed in a single operation using two or more of the above constructions. As an example, the wire rope can have a Seale construction in its first two layers and a Warrington construction in the third layer, and a Seale construction in the outer layer. The combined pattern type of wire rope construction is very superior in its fatigue resistance nature. It also has high flexibility and is superior in its wear resistance and hence has a wide range of uses.

Flat type – In flat type wire rope, the strands are combined in such a way that the outer circumference of the rope is flat in shape. This rope has a smooth surface and hence the surface pressure due to coming into contact with the groove of the drum and the sheave is smaller than that of ordinary ropes. It is also superior in its wear resistance nature. In general, the triangular strand and the shell strand are used the most. The flat strand is also being used at certain places.

Lubrication is applied during the manufacturing process of the steel wire rope and penetrates all the way to the core. Wire rope lubrication has two primary benefits namely (i) it reduces friction as the individual wires and strands move over each other, and (ii) it provides corrosion protection and lubrication in the core, inside wires, and outside surface.

Lubrication of wire ropes is a difficult proposition, regardless of the construction and composition. Wire rope lubricants have two principal functions namely (i) to reduce friction as the individual wires move over each other, and (ii) to provide corrosion protection and lubrication in the core and inside wires and on the exterior surfaces.

There are two types of wire rope lubricants namely (i) penetrating and (ii) coating. Penetrating lubricants contain a petroleum solvent which carries the lubricant into the core of the wire rope then evaporates, leaving behind a heavy lubricating film to protect and lubricate each strand. Coating lubricants penetrate slightly, sealing the outside of the cable from moisture and reducing wear and fretting corrosion from contact with external bodies. Both types of wire rope lubricants are used. But because most wire ropes fail from the inside, it is important to make sure that the centre core receives sufficient lubricant.

A combination approach in which a penetrating lubricant is used to saturate the core, followed with a coating to seal and protect the outer surface, is normally recommended. Wire rope lubricants can be petrolatum, asphaltic, grease, petroleum oils or vegetable oil-based. Petrolatum compounds, with the proper additives, provide excellent corrosion and water resistance. In addition, petrolatum compounds are translucent, allowing the technician to perform visible inspection. Petrolatum lubricants can drip-off at higher temperatures but maintain their consistency well under cold temperature conditions. Asphaltic compounds normally dry to a very dark hardened surface, which makes inspection difficult. They adhere well for extended long-term storage but crack and become brittle in cold climates. Asphaltic compounds are of coating type.

Various types of greases are used for wire rope lubrication. These are the coating types which penetrate partially but normally do not saturate the rope core. Common grease thickeners include sodium, lithium, lithium complex, and aluminum complex soaps. Greases used for this application normally have a soft semi-fluid consistency. They coat and achieve partial penetration if applied with pressure lubricators. Petroleum and vegetable oils penetrate best and are the easiest to apply since proper additive design of these penetrating types gives them excellent wear and corrosion resistance. The fluid property of oil type lubricants helps to wash the rope to remove abrasive external contaminants.

Wire ropes are lubricated during the manufacturing process. In case of wire rope with a steel core, the lubricant (both oil and grease type) is pumped in a stream just ahead of the die which twists the wires into a strand. This allows complete coverage of all the wires.

After the cable is put into service, re-lubrication is required due to loss of the original lubricant from loading, bending, and stretching of the cable. Field re-lubrication is necessary to minimize corrosion, and to protect and preserve the rope core and wires, and thus extend the service life of the wire rope.

The term ‘bright’ refers to a wire rope manufactured with no protective coating or finish other than lubricant can provide.  These wire ropes are normally manufactured from high carbon steel. The chemistry of the steel used and the practice employed in drawing the wire are varied to achieve the ultimate combination of tensile strength, fatigue resistance, and wear resistance in the finished wire rope.

Bright finish is suitable for most of the applications. Galvanized finish is done for corrosive environments. Galvanized finished wire ropes have improved corrosion resistance. These wire ropes are produced from the drawn wires which have been galvanized. Wire ropes are normally produced in three grades as given below.Improved plow steel (IPS) -Th