what is the most abrasion resistant wire rope free sample

In selecting the right steel wire rope, it is important to determine how important the various properties are in relation to the application and then to assign priorities to these. It is also important to be aware of the relevant standards and regulations. If you are in any doubt, please contact our sales consultants or our Technical Department.

The tensile strength of the steel wire rope depends on the rope’s dimensions, the tensile strength of the wires and the construction. The minimum guaranteed tensile strength for the different kinds of rope is shown in the Randers Reb product catalogue.

The design of the steel wire rope does not significantly affect the tensile strength (up to approx. 5%). A change of core from fibre to steel makes slightly more difference (approx. 10%). The greatest change is achieved by changing the dimensions, usage of Compacted steel wire ropes or tensile strength of the wires (see also fig. 28).

It is often required that the steel wire rope must have a specific SWL value (Safe Working Load), also known as a WLL value (Working Load Limit). This means the steel wire rope’s tensile strength divided by the safety factor required for the relevant application.

Steel wire ropes with thick outer wires (e.g. 6x7 Standard or 6x19 Seale) provide good abrasion resistance. Lang lay ropes provide better abrasion resistance than regular lay steel wire ropes (see also fig. 28). Abrasion resistance can also be increased by using wires with greater tensile strength.

The greater the number of wires in the strand, the greater the bending fatique resistance and flexibility. Lang lay ropes provide better bending fatique resistance than regular lay steel wire ropes. Bending fatique resistance can also be increased by using pre-formed steel wire ropes (see also fig. 28).

Galvanised and rustproof wires provide excellent protection against corrosion. Lubrication with special types of grease or oil will also increase resistance to corrosion. If the steel wire rope is subjected to significant corrosive influences, it is recommended that strands with thick outer wires are used.

Steel wire ropes with fewer wires (e.g. 1x7 Standard and 1x19 Standard) are subject to the least elongation (have the greatest elasticity modulus). This type of steel wire rope is ideally suited for guy ropes, but is not suitable to be run over sheaves/blocks. If only a small degree of elongation when running over sheaves is required, 6x7 or 6x19 steel wire rope should be used, in each case with a steel core or with certain special constructions. For larger dimensions, 6x36 steel wire rope with a steel core can also be used (see also Elongation and Pre-stretching, page 8-28).

Standard 6-lay and 8-lay steel wire ropes will rotate when they hang free and carry a load. Regular lay steel wire rope provides greater resistance to rotation than lang lay steel wire rope. A steel wire rope with a steel core rotates less than a steel wire rope with a fibre core. The type of rope that provides greatest resistance to rotation is, as the name suggests, low-rotation and rotation-resistant steel wire rope (special constructions, see also ”Low-Rotation and Rotation-Resistant Steel Wire Rope”, page 8-10).

A steel core provides better support for the strands than a fibre core, which is why the risk of flattening is less in a steel wire rope with a steel core. Strands with fewer, thicker wires have greater resistance to flattening/crushing. Also, a 6-lay steel wire rope has greater crushing resistance than an 8-lay rope (see also fig. 28).

Vibrations, from wherever they might come, send shock waves through the steel wire rope, which will be absorbed by the steel wire rope at some point, and in some cases they may cause localised destruction of the steel wire rope (not necessarily on the outside). This may, for example, be at places where the steel wire rope comes into contact with a sheaf/block, or enters the drum, and by the end terminals. In general, those steel wire ropes with the greatest flexibility also have the greatest vibration resistance.

Changes in the tension of a steel wire rope, depending on the size and frequency, will reduce the rope’s life expectancy. In general, steel wire ropes with the greatest flexibility can cope better with intermittent loading. Great care should be taken in the use of end terminals or fittings, as their pulsation resistance is equally as important as the selection of the right steel wire rope.

Lang lay steel wire ropes are the ones most suited to running over sheaves and are the most durable, but if they are to be used, three things must be observed:

The reason for Lang lay steel wire ropes’ excellent qualities of abrasion resistance and pliability is that the wires are affected/loaded in a different way and have a larger load-bearing surface than a regular lay steel wire rope (see fig. 29). Note that the largest wearing surface is on the Lang lay steel wire rope.

As a wire rope is used, the outer wires wear through abrasion and so the rope suffers loss of cross-sectional area – this obviously reduces the breaking strength of the wire rope. Resistance to abrasive wear is therefore an important property of a wire rope.

Abrasion resistance is directly related to the design of the rope, in particular the design of the strands of the rope. In general, ropes with fewer larger wires will be more abrasion resistant than a similar rope made up of smaller wires – a 6 x 19 rope will therefore be more abrasion resistant than a 6 x 36 rope.

In a later article in this technical series we will discuss fatigue resistance in great detail but for the purposes of this discussion, we must recognise that a cyclic stress reversal occurs when a body is subjected to alternating tensile and compressive loads.

In a drilling operation, wire ropes run through sheaves constantly and so are constantly subjected to alternating tensile and compressive loads – i.e. cyclic stress reversals.

Figure 1 illustrates a wire rope bending over a sheave. It is clear that the outer parts of the rope running over the sheave are in tension and the inner parts of the rope running over the sheave are in compression and as the rope moves over the sheave these stresses reverse.

It should be obvious that the smaller the diameter of the sheave the greater the magnitude (amplitude) of the stress reversal and so the more rapidly fatigue will occur in the rope.

Wire ropes experience external forces that will tend to alter or distort the shape of the rope. Crushing prevents wires and strands moving easily over one another during normal operation and this can lead to accelerated wear and reduced rope life.

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 fiber core can be made of natural or synthetic polypropylene fibers. Fiber cores offer greater elasticity than a steel core but are more susceptible to crushing and not recommended for high heat environments.

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.

The 6 x 19 classification of wire ropes includes standard 6 strand, round strand ropes with 16 through 26 wires per strand. The 6 x 36 classification of wire ropes includes standard 6 strand, round strand ropes with 27 through 49 wires per strand. Although their operating characteristics vary, all have the same weight per foot and the same nominal strength, size for size.

While the 6 x 19 ropes give primary emphasis to abrasion resistance in varying degrees, the 6 x 36 ropes are important for their fatigue resistance. This fatigue resistance is made possible by the greater number of small wires per strand.

Although there are exceptions for special applications, the constructions in 6 x 36 classification are primarily designed to be the most efficient for each rope diameter. As the rope size increases, for instance, a large number of wires can be used to achieve required fatigue resistance, and still those wires will be large enough to offer adequate resistance to abrasion.

In this construction, each strand has nine outer wires over nine smaller inner wires over one large center wire. A comparison of cross-sections shows that these outside wires are larger than those of the 6 x 25FW or 6 x 26WS. Therefore, its resistance to abrasion is increased, but its fatigue resistance is decreased. This is a good rope to withstand abrasion or crushing on the drum.

To most wire rope users, 6 x 19 means 6 x 25 filler wire. It is the most common rope in the 6 x 19 classification. This rope has a good balance between both abrasion resistance and fatigue resistance in relation to other ropes.

This construction has better resistance to abrasion than a 6 x 25FW. It also features a compact construction with solid support for the wires; hence, it has a high resistance to crushing. Its number and relative size of the inner wires add to the stability of the strand and gives it a fatigue resistance comparable to a 6 x 25FW.

A standard 6 x 26WS construction provides the best rope for a wide range of applications. In general, we recommend the use of a 6 x 26WS in any application where a 6 x 25FW is used.

In most rope sizes, only one 6 x 36 classification rope is made. These constructions were selected to provide fatigue resistance without having wires that are too small.

The greater number of wires in the 6 x 36 classification makes these ropes more susceptible to crushing. This can be minimized, however, by specifying an Independent Wire Rope Core (IWRC) and by using well-designed sheaves, grooved drums and proper operating techniques.

Rotation-resistant ropes can frequently provide the best and most economical service in specific applications when you choose, handle and use them properly.

Contra-helically laid, rotation-resistant ropes are different from standard ropes because they"re designed to reduce rope torque. Modes of failure and wear for rotation-resistant ropes can differ from those for standard rope constructions. The very nature of these ropes requires special handling, selection and usage not encountered with standard constructions. They are susceptible to kinking, crushing and unbalancing in the form of "core pops" and "birdcages" Use extreme care to avoid operational practices that can possibly lead to these conditions.

Rotation-resistant ropes should not be used with swivels that allow rope rotation -- or in single part lifts where the load can rotate. Rotation will cause a reduction in strength, unequal loading in the rope and possible rope unbalance. If any significant change in diameter is found in a short length of a rotation-resistant rope, the rope needs to be replaced.

These ropes should be replaced when you see two randomly distributed crown wire breaks in six rope diameters -- or four randomly distributed crown wire breaks in 30 rope diameters.

Because rotation-resistant ropes are special, there are separate design, maintenance, inspection and removal criteria established for them by applicable industry regulations and standards.

In an application where a single-part hoist rope is used to lift a free load -- or where rotation-resistant properties are essential for rope performance -- the 19 x 7 can be used. Its rotation-resistant characteristic is achieved by laying six strands around a core strand in one direction, then laying 12 strands around the first operation in the opposite direction. Thus, when the rope is in tension, opposing rotational forces are created between the inner and outer layers.

In addition, frequent and regular inspection for broken wires is critical when using this rope. Due to its design, the 19 x 7 construction has a relatively low reserve strength. This can result in short service life between the point in time when the broken wire removal criteria are met and when actual rope failure occurs.

In a multi-part wire rope system where the blocks have a tendency to twist -- or for a single-part hoist line that doesn"t require the degree of rotation-resistant properties found in a 19 x 7 rope -- the 8 x 25 Resistwist rope has found successful application. The rotation-resistant characteristic is achieved by laying the eight outer strands around an independent wire rope core so these strands are in the opposite direction to the lay of the core. Thus, when the rope is in tension, opposing rotational forces are created between the core and the outer strands.

Though not as rotation-resistant, the 8 x 25 Rotation Resistant rope is more stable than a 19 x 7 rope. It also has increased resistance to bending fatigue and crushing. This is achieved through the use of eight-strand construction with an independent wire rope core.

Like any application where an installation"s rope type is changed, the 8 x 25 Rotation Resistant rope should be substituted only after carefully comparing specifications and strength requirements.

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.

Cables designed with 3×7, 7×7 and 7×19 construction provide for increasing degrees of flexibility but decreased abrasion resistance. These designs would be incorporated where continuous flexing is a requirement.

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.

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High strength 6-strand rope for applications which require a crush resistant rope to be used on multiple layer winding systems. Because constructional stretch is near zero it can be used where a "pre-stretched" rope would be required.

Super-8R is the next step up from regular 8x36 wire rope for overhead cranes with the ability to operate with fleet angles up to 4°. The 8-strand construction provides an excellent combination of flexibility and performance.

Super 8C is a classic "upgrade" rope for all overhead crane types for increased rope service life performance while maintaining the ability to operate with fleet angles up to 4°. The 8-strand construction provides an excellent combination of flexibility, fatigue life and abrasion resistance. This rope is also the idea choice for container- and port cranes. We can provide this rope in "dual-tensile strength" by which the outer strand wires are made from higher fatigue resistant steel.

Super 8V is an upgrade rope for all overhead crane types which require a stronger rope to increase the crane capacity while maintaining the ability to operate with fleet angles of up to 4°. The 8-strand construction provides an excellent combination of flexibility and abrasion resistance. Also used in looping- or accumulator tower applications.

Developed for maximum performance on overhead cranes. This rope features a plastic coated core for extended fatigue life performance and permanent core lubrication. Python® Multi is spin resistant to reduce block twisting on overhead cranes. Recommended for looping- or accumulator tower applications.

All steel high strength type for overhead cranes. This rope is swage compacted to enhance abrasion characteristic and to reduce sheave- and drum wear. Up to 40% strength increase over standard 6-strand constructions.

Ultra high strength type mainly used as high fatigue resistant rope for engineered cable assemblies. Up to 55% strength increase over standard 6-strand constructions. Sensitive to introduced rotation so call before you select this rope for overhead crane applications.

Very robust 4-strand wire rope which is compacted resulting in flat outer strands for increased abrasion resistance. This rope is spin-resistant and is used as hoisting rope for bulk ship cranes as well as on heavy duty construction equipment like pile drivers.

Same design geometry as 19x7 but due to a larger number of individual wires it is more flexible. The rope is strand compacted to provide for better drum spooling and less mechanical interlocking at the cross-over points. Recommended as standard rope type for Grove-, Terex-, National-, Century- and other US made truck- and mobile cranes. Python® Compac 18 is a rotation resistant rope and should only be used where these demands are low or moderate. NOT to be used in high cycle- high fatigue applications and NOT to be used with a swivel.

Recommended to be used on tower- and european type mobile cranes. Available in left- and right hand lay as well as in regular- and lang"s lay constructions. Recommended to be used in single line applications. ALLOWED to be used with a swivel.

Medium strength, high fatigue resistant non-rotating type. Compacting increases strength and sheave contact area. The plastic coated core increases fatigue life and prevents premature inner wire breaks as well as providing for permanent core lubrication. ALLOWED to be used with a swivel.Popular as ship crane main hoist rope.

High strength super flexible true non-rotating rope. Oval outer strands provide for excellent sheave and drum contact area. Lift has very successfully been used in multiple drum layer applications. Needs special attention during installation. ALLOWED to be used with a swivel.Used on many Manitowoc cranes.

Dyneema, a popular brand of multi-strand HMPE rope made by the Dutch multinational DSM, is offered in a range of fiber types and weaves-from SK 99 down to SK 25, with the smaller number indicating lower density, lower strength fibers. DSM has factories in the U.S. as well as China, where a line of generic HMPE ropes-identified only by tensile strength (bearing neither the Dyneema name or SK number)-are made. Other name-brand HMPE products include Spectra by Honeywell, and Acera by Timm/Willhelmsen.

In this report, we will compare the characteristics of conventional Dyneema to that of heat-set Dyneema, which is stronger and stretches less than conventional Dyneema of the same dimension and weave. We will also compare generic HMPE to the Dyneema brand SK cordage.

In any assembled rope, stretch comes in two forms: construction stretch, when knots, splices, and the braids tightens under load; and fiber stretch, when the rope fibers elongate. During heat setting, the fibers are stretched and heated in a carefully regulated process, which effectively accelerates the construction stretch that normally occurs under load. New England Ropes STS (stronger than steel) is a heat-set Dyneema.

We limited our testing to New England Ropes Dyneema products (New England Ropes) and one generic HMPE (Dyneema) product marketed through Amazon as winch cable.

In the lab, testers compared strength by pulling to failure a short length of each rope sample with eye splices at each end. Abrasion resistance was tested using a 75-pound weight swinging like a pendulum and dragging the unprotected rope across a cinder block about 20 times per minute for 10 minutes (see photo).

There is also an ongoing lifeline test. In 2012, we fitted a PS test boat with New England Ropes STS Dyneema lifelines for a long-term test. At present, the lifelines are showing no significant wear, nor do they reveal any indication that they’ve lost any significant strength. We plan to load test them in the future.

Shortly after the test began, after a few racing failures, World Sailing (then ISAF) restricted the use of Dyneema lifelines to inshore racing (Categories 4 and 5). Their concern was the lack of field data. Eventually, the risk factors were identified. Most commonly, stanchions that previously held bare wire cable had developed burrs at the edges.

In 2015 World Sailing once again allowed HMPE lifelines, though only for multihulls and near-shore racing (Categories 4 and 5). To combat chafe, World Sailing increased the specified diameters for smaller lines. Data collected so far suggests these lifelines will remain as strong as steel through a five- to eight-year lifespan, depending on use. The World Sailing specifications for sailing boat lifelines are available online at https://www.sailing.org/specialregs

Although World Sailing permits smaller diameter lines, we recommend a minimum of -inch Dyneema for the top lifeline. This guarantees a longer service life for just a few dollars more. The most important installation step-other than following splicing instructions-is to very carefully prepare the stanchion holes, removing all burrs and polishing with 1200 grit sandpaper. Chafe guards can also be inserted, made from 2-inch lengths of plastic tubing or nylon tubular webbing (see Fiber Protection Plan, PS September 2015).

New England Ropes STS (heat set Dyneema) is quite firm. It reminded us of the Amsteel cables used in our pull testing rig, which have seen hard use. New England Ropes HTS 78 and Endura 12 (conventional Dyneema) are a very supple line with the same braid as STS. Safeway Lines Tow Cable (generic Dyneema, aka HMPE) has a considerably looser weave and is slightly more prone to snagging. By the time of publication, we could no longer find this brand, although nearly identical products are offered under other brand names. All of the tested ropes spliced very easily.

Strength. Heat-set Dyneema has a slight advantage over normal Dyneema in initial strength, the result of the fibers and the molecules within them being better aligned. However, data from ropes suggest that this process also happens naturally under high load, and were inclined to believe that. We’ve see the changes that occur in highly loaded rigging and in cables that have been repeatedly loaded to high fractions of breaking strength on test stands; the rope becomes firm, like heat set, and stretch is reduced.

Fatigue. The argument against heat setting is that it is just a carefully controlled, accelerated aging process. The rope is made stronger and less stretchy, but lifespan is curtailed. Manufacturers of heat-set rope emphasize that heat-set ropes are stronger and thus have an inherently longer fatigue life. We’ve found no third party data comparing heat set vs. conventional HMPE fatigue life.

As a practical matter, it probably doesn’t make much difference. Correctly sized ropes will fail from chafe or UV damage long before fatigue becomes an issue. Colligo performed a 10-year study of Dynice Dux (heat-set Dyneema) that showed a straight-line decay from full strength to half strength in eight years. Obviously, usage and climate has an effect, so the recommendation for cruisers in the tropics is for replacement in five to seven years-fine considering the overspecified sizes for Dux. However, at the rate that Dyneema loses strength, the only thing keeping up the mast at 15 years will be wishful thinking. If you have Dyneema standing rigging, respect the replacement schedule.

Abrasion. Several riggers told us heat set Dyneema was less abrasion resistant than conventional Dyneema when used with a turning block, tackle, or adjustable backstay. However, during the pendulum torture test, none of the samples showed any appreciable damage after being tested for an hour across wood. Not a fiber was out of place, implying that even cheap Dyneema has a very long service life if properly installed. Polyester double braid showed 10-20 percent chafe damage under the same conditions.

The cinder block, on the other hand, was highly damaging to all of the samples. In all cases, some of the strands were chafed more than 50 percent through, but no strand chafed completely through. The accompanying photos reflecting chafe can be misleading because the weave of the heat set Dyneema remains tight, while the looser weave of the generic cable show damage more readily.

However, when corrected for differences in fiber strength, there was relatively little difference in abrasion or strength loss between the heat-set Dyneema and the cheap tow cable. The tow cable was abraded a bit more, but it was SK 65 fiber versus SK 78. The looser weave may also have contributed to the additional chafe.

The other interesting result was the performance of polyester double braid. In previous research (Abrasion and Break Testing, PS March 2015), Dyneema was much more durable in linear, push-pull testing than polyester, but in side-to-side testing over rough surfaces, the tightness of the braid is more important than the material. This is why polyester mooring bridles, such as Yales well-respected Maximoor, often outperform Dyneema pendants.

The best product depends on the job to be done. For standing rigging and other applications where minimal stretch and maximum strength are required, heat-set Dyneema from a reputable rope manufacture is the top choice. However, where flexibility and abrasion resistance are important-split backstays, lifelines, and low friction ring tackles, for example-conventional Dyneema will run much more smoothly.

Is there a difference in fatigue life? Were not sure. The heat set Dyneema does not like flexing around a pulley and the minimum recommended bend radius is greater.

The only clear advantage of heat set Dyneema is that when used for standing rigging, there is less construction stretch, making installation and rig tuning quicker and more predictable. In our experience, after a few months of hard use, regular Dyneema does seem to behave like heat set rope.

What about non-critical and low strain applications? The HMPE tow cable packs a lot of strength in a small space and offers a strength/dollar ratio that no other fiber can touch. On smaller boats Dyneema is nearly always over specified because the smaller sizes are just too difficult to handle. Dyneema is commonly used in low friction ring systems not because it is amazingly strong, but because it glides around turns so well.

We’ve also found many applications related to anchoring and mooring loops and pendants, where generic Dyneema delivers incredible strength in minimal space, and incredible durability if covered with a chafe guard. However, the difficulty in identifying the manufacturing source of some brands and confirm quality control keeps us skeptical. Although our field experience with generic HMPE rope has been very good to date, cost savings would be quickly erased by a failure in some critical application.

During the chafe testing, wear ranged from 20 to 50 percent of the original diameter, and breaking strength testing after chafe testing was generally proportional to the amount of damage.

None of the twisted strands comprising the woven rope chafed through completely. In the adjacent images, the weave was separated for closer inspection.The Endura 12-strand held 42 percent of its strength after chafe testing.

Compared to the damage caused by the cinder block (images 1-3), the wood-chafe was far less aggressive. The generic Safeway Tow Cable, is shown here after the wood test.

With each application, your choices of wire ropes can be many. How do you know which one works best for you? Ropes include a combination of characteristics that give them specific performance abilities. Before you choose, it pays to look closely at each rope’s special characteristics.

All wire ropes feature design characteristic tradeoffs. In most cases, a wire rope cannot increase both fatigue resistance and abrasion resistance. For example, when you increase fatigue resistance by selecting a rope with more wires, the rope will have less abrasion resistance because of its greater number of smaller outer wires. When you need wire rope with greater abrasion resistance, one choice is a rope with fewer (and larger) outer wires to reduce the effects of surface wear. But that means the rope’s fatigue resistance will decrease. That’s why you need to choose your wire rope like you would any other machine. Very carefully. You must consider all operating conditions and rope characteristics.

How do you choose the wire rope that’s best suited for your job? Following are the most common characteristics to be considered when selecting a rope for an application.

Wire rope strength is usually measured in tons of 2,000 lbs. In published material, wire rope strength is shown as minimum breaking force (MBF) or nominal (catalog) strength. These refer to calculated strength figures that have been accepted by the wire rope industry. When placed under tension on a test device, a new rope should break at a figure equal to – or higher than – the minimum breaking force shown for that rope. Certain standards allow for an acceptance strength that is 97.5% of the nominal strength to allow for testing variables. The values in this handbook apply to new, unused rope. A rope should never operate at – or near – the minimum breaking force. During its useful life, a rope loses strength gradually due to natural causes such as surface wear and metal fatigue.

Fatigue resistance involves metal fatigue of the wires that make up a rope. To have high fatigue resistance, wires must be capable of bending repeatedly under stress – for example, a rope passing over a sheave.

Increased fatigue resistance is achieved in a rope design by using a large number of wires. It involves both the basic metallurgy and the diameters of wires. In general, a rope made of many wires will have greater fatigue resistance than a same-size rope made of fewer, larger wires because smaller wires have greater ability to bend as the rope passes over sheaves or around drums. To reduce the effects of fatigue, ropes must never bend over sheaves or drums with a diameter so small as to bend wires excessively. There are precise recommendations for sheave and drum sizes to properly accommodate all sizes and types of ropes.

Every rope is subject to metal fatigue from bending stress while in operation, and therefore the rope’s strength gradually diminishes as the rope is used.

Crushing is the effect of external pressure on a rope, which damages it by distorting the cross-section shape of the rope, its strands or core – or all three. Crushing resistance therefore is a rope’s ability to withstand or resist external forces, and is a term generally used to express comparison between ropes. When a rope is damaged by crushing, the wires, strands and core are prevented from moving and adjusting normally during operation. In general, IWRC ropes are more crush resistant than fiber core ropes. Regular lay ropes are more crush resistant than lang lay ropes. Six strand ropes have greater crush resistance than 8 strand ropes or 19 strand ropes. Flex-X® ropes are more crush resistant than standard round-strand ropes.

Metal loss refers to the actual wearing away of metal from the outer wires of a rope, and metal deformation is the changing of the shape of outer wires of a rope. In general, resistance to metal loss by abrasion (usually called “abrasion resistance”) refers to a rope’s ability to withstand metal being worn away along its exterior. This reduces strength of a rope. The most common form of metal deformation is generally called “peening”– since outside wires of a peened rope appear to have been “hammered” along their exposed surface. Peening usually occurs on drums, caused by rope-to-rope contact during spooling of the rope on the drum. It may also occur on sheaves. Peening causes metal fatigue, which in turn may cause wire failure. The hammering – which causes the metal of the wire to flow into a new shape – realigns the grain structure of the metal, thereby affecting its fatigue resistance. The out-of-round shape also impairs wire movement when the rope bends.

When a load is placed on a rope, torque is created within the rope as wires and strands try to straighten out. This is normal and the rope is designed to operate with this load-induced torque. However, this torque can cause loads to rotate. Load-induced torque can be reduced by specially designed rotation resistant ropes. In standard 6 and 8 strand ropes, the torques produced by the outer strands and the IWRC is in the same direction and add together. In rotation resistant ropes, the lay of the outer strands is in the opposite direction to the lay of the inner strands, thus the torques produced are in opposite directions and the torques subtract from each other. Depending upon your application, other wire rope characteristics such as stability, bendability or reserve strength may need to be considered.

This construction is used where ropes are dragged on the ground or over rollers, and resistance to wear and abrasion are important factors. The wires are quite large and will stand a great deal of wear. In fact, this construction is sometimes called “coarse laid” because of the large wires. The 6x7 is a stiff rope and needs sheaves and drums of large size. It will not withstand bending stresses as well as ropes with smaller wires. Because of the small number of wires, with the resulting higher percentage of load carried by each wire, a larger factor of safety should be considered with 6x7 ropes than with ropes having a larger number of wires.

The 6x19 Classification of wire rope is the most widely used. With its good combination of flexibility and wear resistance, rope in this class can be suited to the specific needs of diverse kinds of machinery and equipment. The 6x19 Seale construction, with its large outer wires, provides great ruggedness and resistance to abrasion and crushing. However, its resistance to fatigue is somewhat less than that offered by a 6x25 construction. The 6x25 possesses the best combination of flexibility and wear resistance in the 6x19 Class due to the filler wires providing support and imparting stability to the strand. The 6x26 Warrington Seale construction has a high resistance to crushing. This construction is a good choice where the end user needs the wear resistance of a 6x19 Class Rope and the flexibility midway between a 6x19 Class and 6x37 Class rope.

The 6x36 Class of wire rope is characterized by the relatively large number of wires used in each strand. Ropes of this class are among the most flexible available due to the greater number of wires per strand, however their resistance to abrasion is less than ropes in the 6x19 Class. The designation 6x36 is only nominal, as in the case with the 6x19 Class. Improvements in wire rope design, as well as changing machine designs, have resulted in the use of strands with widely varying numbers of wires and a smaller number of available constructions. Typical 6x37 Class constructions include 6x33 for diameters under 1/2", 6x36 Warrington Seale (the most common 6x37 Class construction) offered in diameters 1/2" through 1-5/8", and 6x49 Filler Wire Seale over 1-3/4" diameter.

Alternate Lay, sometimes referred to as reverse lay, is a stranded rope where the type of lay of the outer strands is alternately regular lay followed by lang lay such that three of the outer strands are regular lay and three are lang lay. Alternate lay wire rope has the extra flexibility of lang lay in combination with the structural stability of regular lay. It unites the best features of both types of wire rope. Alternate lay is made with relatively large outer wires to provide increase of abrasion resistance to scrubbing against sheaves and drums. Finer inside wires and flexibility enable alternate lay ropes to absorb severe bending stresses. It is well suited to winding applications where abrasion and crushing can occur. Alternate lay wire rope applications include boom hoists and numerous types of excavating equipment like clamshells, shovels, cranes, winches and scrapers.

The 8x19 Classification rotation resistant ropes are recommended for hoisting unguided loads with a single-part or multipart line. The eight outer strands are manufactured in right lay, with the inner strands being left lay. These ropes are slightly stronger and significantly more rugged than the 19x7 construction. However, the rotation-resistant properties of the 8x19 rotation-resistant ropes are much less than those of the 19x7 construction. These ropes are manufactured in right regular lay in the 8x19 Seale and 8x25 Filler Wire constructions.

19x7 is recommended for hoisting unguided loads with a single-part line. The rotation-resistant properties of this rope are secured by two layers of strands. The inner strands are left lay, while the 12 outer strands are right lay, which enables one layer to counteract the other layer"s rotation. The rotation-resistant characteristics of the 19x7 wire ropes are superior to those of the 8x19 Class wire ropes.

SFP 19 is recommended for both multipart load and single-part fast line applications where rotational stability of the lifted load is needed, such as for use as a long fall on offshore pedestal cranes, rough and all terrain cranes, and crawler cranes. SFP 19 provides:

Fatigue Resistance. Improved fatigue properties are derived through the combination of the flexible 19x19 construction and die drawn strands. The drawn strand surfaces minimize the interstrand and interlayer nicking that take place in round rotation resistant ropes.

Abrasion Resistance. Die drawn ropes provide improved abrasion resistance as compared with round wire ropes because of the greater wire and strand bearing surfaces contacting sheaves and drums.

Resistance to Drum Crushing. SFP 19 wire ropes are resistant to the effects of drum crushing due to the compacted strands and smoothness of the rope surface.

Superior Rotation Resistance. The SFP 35 rope is the most rotation resistant rope manufactured by WW. Due to its rotation resistant properties, SFP 35 may be used with a swivel in both single part and multipart reeving.

Flexibility. SFP 35"s multiple strand construction provides increased flexibility which improves service life and high speed spooling. The compacted compacted multiple strand construction also reduces sheave and drum abrasion and provides excellent resistance to drum crushing.

6-PAC is recommended for use where the rope is subjected to heavy use or where conditions are extremely abusive, such as offshore pedestal, crawler and lattice boom equipped truck crane boom hoist applications. 6-PAC is also recommended for winch lines, overhead cranes, multipart hoist lines where rotation-resistant ropes are not required, and other applications where flexibility, high strength and resistance to crushing are important, and a cost-effective 6-strand rope is desired.

Fatigue Resistance. Improved fatigue properties are derived from the combination of 6-PAC"s flexible constructions and the compacted strands. The compacted strand surface minimizes the interstrand and interlayer nicking that take place in standard 6-strand ropes.

Abrasion Resistance. 6-PAC"s compacted strand design provides improved abrasion resistance as compared to standard 6-strand ropes because of the increased wire and strand surfaces contacting sheaves and drums.

Drum Crushing. 6-PAC dramatically increases the amount of wire contact with the drums and sheaves, reducing the wire rope, sheave and drum wear normally associated with standard wire rope.

Recommended for applications where abrasion and fatigue resistance is required, such as for winch lines, chokers, skylines, and haul backs, as well as any application where a swaged rope is used

8-PAC is recommended for hoist ropes for steel mill ladle cranes and hoist and trolley ropes for container cranes, or other hoisting applications with heavy duty cycles or where severe bending occurs.

Superior Performance. 8-PAC has higher breaking strength and gives superior performance in difficult hoisting applications compared to standard 6-strand and 6-strand compacted ropes.

Abrasion Resistance. 8-PAC compacted strand design provides improved abrasion resistance as compared to standard 6 and 8 strand ropes because of the increased wire and strand surfaces contacting the sheaves and drums.

SUPER-PAC is a double compacted product ideal for applications where abrasion and drum crushing are an issue. When compared with standard ropes, SUPER-PAC provides: Better resistance to multi-layer drum crushing. SUPERPAC dramatically reduces the damage at cross over points on smooth face drums, such as those found on many boom hoist systems on mobile cranes. This is achieved by compaction of the strands and the rope, making a tough but flexible product.

Superior Fatigue Resistance. SUPER-PAC is engineered for overall performance, its wire tensile strength being the key to its superior fatigue resistant properties. In addition to contribution to SUPERPAC’s EEEIP breaking strength, the wire used in the manufacture of SUPER-PAC remains ductile, minimizing the occurrences of external and internal wire breaks caused by operating stresses.

TRIPLE-PAC was developed for the most demanding hoist applications. TRIPLE-PAC offers the extra high strength and crushing resistance needed for applications such as boom hoist ropes, boom pendants and multipart load lines.

TRIPLE-PAC provides superior abrasion and fatigue resistance as compared with most compacted ropes due to WW’s unique design of compacting the IWRC, individual strands and the rope itself. Other benefits include:

High Strength. TRIPLE-PAC is designed to provide a nominal strength of 35% above EIP. WW achieves this strength through selected grades of steel and TRIPLEPAC’s unique design and manufacturing processes.

Superior Resistance to Multilayer Drum Crushing. TRIPLE-PAC provides superior resistance to crushing through its design. Its triple compaction provides a den