types of wire rope breaks free sample

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.

Easy-to-read, question-and-answer fact sheets covering a wide range of workplace health and safety topics, from hazards to diseases to ergonomics to workplace promotion. MORE ABOUT >

Maintain a record for each rope that includes the date of inspection, type of inspection, the name of the person who performed the inspection, and inspection results.

Use the "rag-and-visual" method to check for external damage. Grab the rope lightly and with a rag or cotton cloth, move the rag slowly along the wire. Broken wires will often "porcupine" (stick out) and these broken wires will snag on the rag. If the cloth catches, stop and visually assess the rope. It is also important to visually inspect the wire (without a rag). Some wire breaks will not porcupine.

Measure the rope diameter. Compare the rope diameter measurements with the original diameter. If the measurements are different, this change indicates external and/or internal rope damage.

Visually check for abrasions, corrosion, pitting, and lubrication inside the rope. Insert a marlin spike beneath two strands and rotate to lift strands and open rope.

Assess the condition of the rope at the section showing the most wear. Discard a wire rope if you find any of the following conditions:In running ropes (wound on drums or passed over sheaves), 6 or more broken wires in one rope lay length; 3 or more broken wires in one strand in one rope lay. (One rope lay is the distance necessary to complete one turn of the strand around the diameter of the rope.)

Corrosion from lack of lubrication and exposure to heat or moisture (e.g., wire rope shows signs of pitting). A fibre core rope will dry out and break at temperatures above 120°C (250°F).

Kinks from the improper installation of new rope, the sudden release of a load or knots made to shorten a rope. A kink cannot be removed without creating a weak section. Discarding kinked rope is best.

Although every effort is made to ensure the accuracy, currency and completeness of the information, CCOHS does not guarantee, warrant, represent or undertake that the information provided is correct, accurate or current. CCOHS is not liable for any loss, claim, or demand arising directly or indirectly from any use or reliance upon the information.

In stricter senses, the term wire rope refers to a diameter larger than 9.5 mm (3⁄8 in), with smaller gauges designated cable or cords.wrought iron wires were used, but today steel is the main material used for wire ropes.

Historically, wire rope evolved from wrought iron chains, which had a record of mechanical failure. While flaws in chain links or solid steel bars can lead to catastrophic failure, flaws in the wires making up a steel cable are less critical as the other wires easily take up the load. While friction between the individual wires and strands causes wear over the life of the rope, it also helps to compensate for minor failures in the short run.

Wire ropes were developed starting with mining hoist applications in the 1830s. Wire ropes are used dynamically for lifting and hoisting in cranes and elevators, and for transmission of mechanical power. Wire rope is also used to transmit force in mechanisms, such as a Bowden cable or the control surfaces of an airplane connected to levers and pedals in the cockpit. Only aircraft cables have WSC (wire strand core). Also, aircraft cables are available in smaller diameters than wire rope. For example, aircraft cables are available in 1.2 mm (3⁄64 in) diameter while most wire ropes begin at a 6.4 mm (1⁄4 in) diameter.suspension bridges or as guy wires to support towers. An aerial tramway relies on wire rope to support and move cargo overhead.

Modern wire rope was invented by the German mining engineer Wilhelm Albert in the years between 1831 and 1834 for use in mining in the Harz Mountains in Clausthal, Lower Saxony, Germany.chains, such as had been used before.

Wilhelm Albert"s first ropes consisted of three strands consisting of four wires each. In 1840, Scotsman Robert Stirling Newall improved the process further.John A. Roebling, starting in 1841suspension bridge building. Roebling introduced a number of innovations in the design, materials and manufacture of wire rope. Ever with an ear to technology developments in mining and railroading, Josiah White and Erskine Hazard, principal ownersLehigh Coal & Navigation Company (LC&N Co.) — as they had with the first blast furnaces in the Lehigh Valley — built a Wire Rope factory in Mauch Chunk,Pennsylvania in 1848, which provided lift cables for the Ashley Planes project, then the back track planes of the Summit Hill & Mauch Chunk Railroad, improving its attractiveness as a premier tourism destination, and vastly improving the throughput of the coal capacity since return of cars dropped from nearly four hours to less than 20 minutes. The decades were witness to a burgeoning increase in deep shaft mining in both Europe and North America as surface mineral deposits were exhausted and miners had to chase layers along inclined layers. The era was early in railroad development and steam engines lacked sufficient tractive effort to climb steep slopes, so incline plane railways were common. This pushed development of cable hoists rapidly in the United States as surface deposits in the Anthracite Coal Region north and south dove deeper every year, and even the rich deposits in the Panther Creek Valley required LC&N Co. to drive their first shafts into lower slopes beginning Lansford and its Schuylkill County twin-town Coaldale.

The German engineering firm of Adolf Bleichert & Co. was founded in 1874 and began to build bicable aerial tramways for mining in the Ruhr Valley. With important patents, and dozens of working systems in Europe, Bleichert dominated the global industry, later licensing its designs and manufacturing techniques to Trenton Iron Works, New Jersey, USA which built systems across America. Adolf Bleichert & Co. went on to build hundreds of aerial tramways around the world: from Alaska to Argentina, Australia and Spitsbergen. The Bleichert company also built hundreds of aerial tramways for both the Imperial German Army and the Wehrmacht.

In the last half of the 19th century, wire rope systems were used as a means of transmitting mechanical powercable cars. Wire rope systems cost one-tenth as much and had lower friction losses than line shafts. Because of these advantages, wire rope systems were used to transmit power for a distance of a few miles or kilometers.

Steel wires for wire ropes are normally made of non-alloy carbon steel with a carbon content of 0.4 to 0.95%. The very high strength of the rope wires enables wire ropes to support large tensile forces and to run over sheaves with relatively small diameters.

In the mostly used parallel lay strands, the lay length of all the wire layers is equal and the wires of any two superimposed layers are parallel, resulting in linear contact. The wire of the outer layer is supported by two wires of the inner layer. These wires are neighbors along the whole length of the strand. Parallel lay strands are made in one operation. The endurance of wire ropes with this kind of strand is always much greater than of those (seldom used) with cross lay strands. Parallel lay strands with two wire layers have the construction Filler, Seale or Warrington.

In principle, spiral ropes are round strands as they have an assembly of layers of wires laid helically over a centre with at least one layer of wires being laid in the opposite direction to that of the outer layer. Spiral ropes can be dimensioned in such a way that they are non-rotating which means that under tension the rope torque is nearly zero. The open spiral rope consists only of round wires. The half-locked coil rope and the full-locked coil rope always have a centre made of round wires. The locked coil ropes have one or more outer layers of profile wires. They have the advantage that their construction prevents the penetration of dirt and water to a greater extent and it also protects them from loss of lubricant. In addition, they have one further very important advantage as the ends of a broken outer wire cannot leave the rope if it has the proper dimensions.

Stranded ropes are an assembly of several strands laid helically in one or more layers around a core. This core can be one of three types. The first is a fiber core, made up of synthetic material or natural fibers like sisal. Synthetic fibers are stronger and more uniform but cannot absorb much lubricant. Natural fibers can absorb up to 15% of their weight in lubricant and so protect the inner wires much better from corrosion than synthetic fibers do. Fiber cores are the most flexible and elastic, but have the downside of getting crushed easily. The second type, wire strand core, is made up of one additional strand of wire, and is typically used for suspension. The third type is independent wire rope core (IWRC), which is the most durable in all types of environments.ordinary lay rope if the lay direction of the wires in the outer strands is in the opposite direction to the lay of the outer strands themselves. If both the wires in the outer strands and the outer strands themselves have the same lay direction, the rope is called a lang lay rope (from Dutch langslag contrary to kruisslag,Regular lay means the individual wires were wrapped around the centers in one direction and the strands were wrapped around the core in the opposite direction.

Multi-strand ropes are all more or less resistant to rotation and have at least two layers of strands laid helically around a centre. The direction of the outer strands is opposite to that of the underlying strand layers. Ropes with three strand layers can be nearly non-rotating. Ropes with two strand layers are mostly only low-rotating.

Stationary ropes, stay ropes (spiral ropes, mostly full-locked) have to carry tensile forces and are therefore mainly loaded by static and fluctuating tensile stresses. Ropes used for suspension are often called cables.

Track ropes (full locked ropes) have to act as rails for the rollers of cabins or other loads in aerial ropeways and cable cranes. In contrast to running ropes, track ropes do not take on the curvature of the rollers. Under the roller force, a so-called free bending radius of the rope occurs. This radius increases (and the bending stresses decrease) with the tensile force and decreases with the roller force.

Wire rope slings (stranded ropes) are used to harness various kinds of goods. These slings are stressed by the tensile forces but first of all by bending stresses when bent over the more or less sharp edges of the goods.

Technical regulations apply to the design of rope drives for cranes, elevators, rope ways and mining installations. Factors that are considered in design include:

Donandt force (yielding tensile force for a given bending diameter ratio D/d) - strict limit. The nominal rope tensile force S must be smaller than the Donandt force SD1.

The wire ropes are stressed by fluctuating forces, by wear, by corrosion and in seldom cases by extreme forces. The rope life is finite and the safety is only ensured by inspection for the detection of wire breaks on a reference rope length, of cross-section loss, as well as other failures so that the wire rope can be replaced before a dangerous situation occurs. Installations should be designed to facilitate the inspection of the wire ropes.

Lifting installations for passenger transportation require that a combination of several methods should be used to prevent a car from plunging downwards. Elevators must have redundant bearing ropes and a safety gear. Ropeways and mine hoistings must be permanently supervised by a responsible manager and the rope must be inspected by a magnetic method capable of detecting inner wire breaks.

The end of a wire rope tends to fray readily, and cannot be easily connected to plant and equipment. There are different ways of securing the ends of wire ropes to prevent fraying. The common and useful type of end fitting for a wire rope is to turn the end back to form a loop. The loose end is then fixed back on the wire rope. Termination efficiencies vary from about 70% for a Flemish eye alone; to nearly 90% for a Flemish eye and splice; to 100% for potted ends and swagings.

When the wire rope is terminated with a loop, there is a risk that it will bend too tightly, especially when the loop is connected to a device that concentrates the load on a relatively small area. A thimble can be installed inside the loop to preserve the natural shape of the loop, and protect the cable from pinching and abrading on the inside of the loop. The use of thimbles in loops is industry best practice. The thimble prevents the load from coming into direct contact with the wires.

A wire rope clip, sometimes called a clamp, is used to fix the loose end of the loop back to the wire rope. It usually consists of a U-bolt, a forged saddle, and two nuts. The two layers of wire rope are placed in the U-bolt. The saddle is then fitted to the bolt over the ropes (the saddle includes two holes to fit to the U-bolt). The nuts secure the arrangement in place. Two or more clips are usually used to terminate a wire rope depending on the diameter. As many as eight may be needed for a 2 in (50.8 mm) diameter rope.

The mnemonic "never saddle a dead horse" means that when installing clips, the saddle portion of the assembly is placed on the load-bearing or "live" side, not on the non-load-bearing or "dead" side of the cable. This is to protect the live or stress-bearing end of the rope against crushing and abuse. The flat bearing seat and extended prongs of the body are designed to protect the rope and are always placed against the live end.

The ends of individual strands of this eye splice used aboard a cargo ship are served with natural fiber cord after splicing to help protect seamens" hands when handling.

An eye splice may be used to terminate the loose end of a wire rope when forming a loop. The strands of the end of a wire rope are unwound a certain distance, then bent around so that the end of the unwrapped length forms an eye. The unwrapped strands are then plaited back into the wire rope, forming the loop, or an eye, called an eye splice.

A Flemish eye, or Dutch Splice, involves unwrapping three strands (the strands need to be next to each other, not alternates) of the wire and keeping them off to one side. The remaining strands are bent around, until the end of the wire meets the "V" where the unwrapping finished, to form the eye. The strands kept to one side are now re-wrapped by wrapping from the end of the wire back to the "V" of the eye. These strands are effectively rewrapped along the wire in the opposite direction to their original lay. When this type of rope splice is used specifically on wire rope, it is called a "Molly Hogan", and, by some, a "Dutch" eye instead of a "Flemish" eye.

Swaging is a method of wire rope termination that refers to the installation technique. The purpose of swaging wire rope fittings is to connect two wire rope ends together, or to otherwise terminate one end of wire rope to something else. A mechanical or hydraulic swager is used to compress and deform the fitting, creating a permanent connection. Threaded studs, ferrules, sockets, and sleeves are examples of different swaged terminations.

A wedge socket termination is useful when the fitting needs to be replaced frequently. For example, if the end of a wire rope is in a high-wear region, the rope may be periodically trimmed, requiring the termination hardware to be removed and reapplied. An example of this is on the ends of the drag ropes on a dragline. The end loop of the wire rope enters a tapered opening in the socket, wrapped around a separate component called the wedge. The arrangement is knocked in place, and load gradually eased onto the rope. As the load increases on the wire rope, the wedge become more secure, gripping the rope tighter.

Poured sockets are used to make a high strength, permanent termination; they are created by inserting the wire rope into the narrow end of a conical cavity which is oriented in-line with the intended direction of strain. The individual wires are splayed out inside the cone or "capel", and the cone is then filled with molten lead-antimony-tin (Pb80Sb15Sn5) solder or "white metal capping",zincpolyester resin compound.

Koetsier,Teun; Ceccarelli, Marc (2012). Explorations in the History of Machines and Mechanisms. Springer Publishing. p. 388. ISBN 9789400741324. Archived from the original on 31 March 2017. Retrieved 9 April 2014.

Donald Sayenga. "Modern History of Wire Rope". History of the Atlantic Cable & Submarine Telegraphy (atlantic-cable.com). Archived from the original on 3 February 2014. Retrieved 9 April 2014.

Some of our calculators and applications let you save application data to your local computer. These applications will - due to browser restrictions - send data between your browser and our server. We don"t save this data.

Wire breakshowsone end of broken wire coned, the other cupped. Necking down of the broken ends is typical of this type of break.Where tension breaks are found, the rope has been subjected to overloading, either for its original strength (new rope) or for its remaining strength in the case of a used rope. Tension breaks frequently are caused by the sudden application of a load to a slack rope, thereby setting up incalculable impact stresses.

Wire break shows broken ends worn to a knife-edge thinness.Abrasive wear obviously is concentrated at points where the rope contacts an abrasive medium, such as the grooves of sheaves and drums, or other objects with which the rope comes into contact. Unwarranted abrasive wear indicates improperly grooved sheaves and drums, incorrect fleet angle, or other localized abrasive conditions.

Wire breaksareusually transverse orsquareshowinggranularstructure.Oftenthese breaks will develop a shattered orjagged fracture, depending on the type ofoperation.Where fatigue breaks occur, the rope has been bent repeatedly around too small a radius. Whipping, vibration, slapping and torsional stresses also will cause fatigue. Fatigue breaks are accelerated by abrasion and nicking.

Easily noted by the wire"s pitted surface, wire breaks usually show evidence of tension, abrasion and/or fatigue.Corrosion usually indicates improper lubrication. The extent of the damage to the interior of the rope is extremely difficult to determine; consequently, corrosion is one of the most dangerous causes of rope deterioration.

Wirewill be pinched down and cut atbroken ends, or will show evidence of ashear-like cut.This condition is evidence of mechanical abuse caused by agents outside the installation, or by something abnormal on the installation itself, such as a broken flange.

Wire ropes are widely employed components in diverse areas, such as in industrial production, tourist cable cars, mining, metallurgy, shipbuilding, and elevators. Wire rope is a heavily loaded component, and long-term continuous operation eventually result in corrosion, wear, broken wires, loose wires, and fatigue, which decrease the loading strength of the rope, and can cause accidents, resulting in property damage and injury [1]. The traditional damage detection method is artificial visual inspection, which is a low efficiency, time-consuming, and unreliable method [1]. The development of a fast, non-destructive, and automatic detection technology is therefore necessary.

Wire rope defects include three main types: the loss of metallic area (LMA), local faults (FLs), and structural faults (SFs). The main non-destructive testing (NDT) methods employed for wire rope inspection include electromagnetic detection, ultrasonic guided wave (UGW) evaluation, radiation testing, eddy current inspection, and optical detection [1]. However, designing a precise detection device that can quantitatively determine the characteristics of defects, such as the number of broken wires, remains problematic, particularly when operating in severe environments [2].

The UGW method has been shown to provide a detection speed that is faster than other methods, but the method demonstrates a low anti-interference ability and suffers from strong background noise [3,4,5,6,7]. Treyssède and Laguerre’s [3] applied the transmission characteristics of UGW for wire rope testing. The researchers developed a semi-analytical finite element method, and calculated the optimal excitation and receiving sites. This approach provided a wave dispersion curve for spiral steel rope. Vanniamparambil [4] proposed a novel detection method that combined three technologies: UGW, acoustic emission techniques, and digital image processing. Xu [7] evaluated the detection precision of the UGW method for wire rope defects obtained at different frequencies, showing that wire ropes at higher frequencies had longer recovery lengths for their elastic waves. Raisuitis [5] investigated the propagation of UGWs along composite multi-wire ropes with various types of acoustic contacts between neighboring wires and the plastic core. Tse and Rostami [6] investigated the efficiency of employing the magnetostriction of ferromagnetic materials in conjunction with the UGW method for wire rope defect inspection, and the location and severity of defects were approximately identified and characterized using the short-time Fourier transform and wavelet analysis. Other detection methods, such as radiation testing [8] and eddy current inspection [9], have not been applied to wire rope inspection to a large extent.

Electromagnetic detection methods are commonly employed for the NDT of wire rope [2]. The basic principle behind wire rope electromagnetic detection is illustrated in Figure 1. The lower permeability of the air leads to magnetic field leakage (MFL) from the rope defect, and the strength of the MFL can be obtained from an appropriately designed magnetic detection device. In terms of the type of excitation source employed, electromagnetic detection can be divided according to the use of a coil [10,11] or a permanent magnet [12,13,14,15,16,17] for generating a magnetic field. Modified main-flux equipment has been developed for wire rope inspection, which induced changes in the electromagnetic field strength owing to the leakage field derived from defects in various large-diameter wire ropes [10]. Other researchers [11] employed a pair of saddle coils for the magnetization of a steel track rope, and this system was applied to detect small, inner flaws in the rope. Permanent magnets have been employed in a saddle structure to saturate wire rope in a uniform magnetic field [14,15,16,17]. Wang et al. [12] investigated the effect of excitation distance and the lift-off distance between the sensors and the wire rope surface on the detection precision. The researchers accordingly modified the magnetic circuit of the detector to restrain the impact of fluctuations in the sensor lift-off distance. Xu et al. [18] developed a magnetic excitation model. Based on this model, the researchers established design criteria for the size of the excitation structure, proposed a theoretical framework for the excitation structure size based on numerical analysis, and adjusted the theoretical design using finite element analysis (FEA).

Obtaining a precise MFL signal is the most important aspect for the accurate electromagnetic NDT of wire rope. For MFL signal acquisition, a commonly employed in-service NDT method utilizes an induction coil [10,17], Hall effect sensor [14,18,19,20,21], giant magnetoresistive (GMR) sensor [11,22], and tunnel magnetoresistive (TMR) sensor [23]. Jomdecha and Prateepasen [10] modified a conventional induction coil into a coil array that densely covered the wire rope to acquire the MFL signal. Wang and Tian [14] utilized FEA to address the problems associated with the weak MFL signals derived from small defects, and they investigated the gathered magnetism of the magnetization rope. They designed a detector with an annular pole polymagnet on one side using Hall elements as inductors. This detection system was able to capture weak MFL signals within the strong magnetic field. Xu and Wang [18] developed an online modular-detector NDT system using a Hall effect sensor that successfully detected inner broken wires. The researchers also presented three filtering algorithms. Detectors based on Hall effect sensor arrays have been widely applied for NDT under strong magnetic field conditions [19,20,21]. Cao [19] created an image from the defect data which was obtained by Hall sensors array, and applied digital image processing to extract and detect defect characteristics. Zhang et al. [20] employed signal processing to suppress the effect of lift-off distance, and applied statistical processing to distinguish different types of defects and to obtain binary image data describing the spatial extent of defects. Zhang et al. [21] applied a space filter to suppress the texture of strand waves after obtaining MFL gray-level images of wire rope defects, and the image spectrum texture was extracted as the characteristic vector used for recognition. GMR sensors have been employed for MFL signal acquisition because of their high sensitivity, high precision, and small size. GMR sensors were placed into a sensor array and densely distributed on the wire rope surface in a manner similar to that employed in a Hall effect sensor application [11]. Zhang and Tan [22] utilized the high sensitivity of a GMR sensor to develop a detection technique based on remanence magnetization, which combined the benefits of a simple structure and high detection speed with high precision. Wu et al. [23] demonstrated that TMR sensors can be applied to detect small discontinuities on a wire rope surface.

MFL signals contain a variety of distinct noise signals, which makes the development of an efficient de-noising algorithm challenging work. Currently, a number of noise reduction algorithms are commonly employed, including wavelet analysis de-noising, low-pass filter, notch filter [21], adaptive filter [20], morphological filter [24], and a de-noising algorithm based on compressed sensing (CS) [22]. Zhang et al. [20] applied digital image processing to develop a space filter for smoothing the defects in an MFL signal image. Zhang et al. [21] proposed a baseline estimation algorithm to suppress the effect of undulations in the lift-off distance and an adaptive notch filtering algorithm to filter the strand wave for increasing the signal-to-noise ratio. Zhang and Tan [22] utilized wavelet multi-resolution analysis to eliminate the baseline of the signal. Their work was based on the CS wavelet de-noising algorithm, and they calculated the best sparse transform expression to completely filter out the noise. Tian et al. combined the wavelet transform and the morphological transform to create a morphological filter algorithm that suppressed the interference associated with the baseline drift in the wire rope signal. Artificial neural networks have been widely applied to realize the quantitative detection of wire rope defects. These networks operate much like back propagation (BP) neural networks employed by a number of researchers [20,21,22]. However, BP neural networks suffer from some limitations and shortcomings, such as poor generalization and slow convergence.

Devices based-on the x-ray method are generally bulky, heavy, and suffer from high maintenance costs, and furthermore, it is difficult to accurately locate defect positions with the UGW detection method, which suffers from external disturbances and limited detection length. The eddy current inspection method is difficult to apply in practice for producing coils on-site, and the system is difficult to manage. However, conventional electromagnetic NDT typically utilizes a large, heavy excitation device as well. Moreover, extracting defect information from the induction coil is difficult, and, in addition, the sensitivity of Hall effect sensors is low. Conventional digital filter algorithms cannot adequately suppress the noise in the MFL signal. This limited ability to reduce noise makes it difficult to separate the defect signal and the strand wave under low signal-to-noise ratio conditions while processing the signal.

To overcome the disadvantages of existing detection devices, we developed a prototype device based on the RMF of a wire rope. This inspection method utilizes GMR sensors for excitation signal acquisition. After magnetizing the wire rope with permanent magnets, the GMR sensor array was utilized to obtain the RMF strength of the rope surface. This detection system is non-contact and non-invasive which prolongs the service life of test equipment. A novel filter algorithm based on the Hilbert-Huang transform (HHT) and compressed sensing wavelet filtering (CSWF) was developed to suppress the various system noises. The HHT was employed to remove the DC component of the signal and balance the sensor channels. CSWF was employed to suppress high-frequency noises and strand waves. Then, we applied digital image processing to create a binary image using a filter based on corrosion and expansion. Subsequently, defects were located and segmented within the gray-level image. Because an 18 GMR sensor array was employed, the resulting gray-level image included only 18 pixels in its circumference. Three spline interpolations were performed to improve the circumferential resolution of the gray-level image. Thirteen image characteristics comprising 6 image textures and seven invariant moments were extracted as defect feature vectors. A radial basis function (RBF) neural network, which is a fast-learning classification network that provides a global optimum, was adopted to quantitatively detect the number of broken wires in the rope. Experimental results demonstrate that, when the absolute limiting error for the detected number of broken wires is 2, the recognition rate is as high as 93.75% with an average recognition error of 0.7813 wires.

EN12385-2 Steel wire ropes – Safety – Definitions, designation and classification provides a detailed explanation of all the terms and abbreviations used when describing a wire rope and its components. Below are a few of the most common abbreviations;

Steel wire ropes are specified in terms of a Nominal Rope Diameter and when produced have a manufacturing diameter tolerance, this tolerance can vary depending upon customer requirements and specifications and is often dictated by the diameter of grooving within sheaves and drums in which the wire rope will be expected to operate. If no diameter tolerance is specified, the general diameter tolerance is, Nominal Diameter +0% to +5% as specified within various International Rope Standards (EN12385-4, API-9A, ISO 2408). However, please note other diameter tolerances may be applied to ‘small’ diameter ropes and ropes used for specific applications/industries e.g. Mining, Aerials, Elevators, etc.

When designing any rope operated equipment, designers should consider the relevant National and/or International Standards which refer to acceptable sheave and drum diameters based upon the application, industry, etc. The diameter of sheaves and drums together with the tension, are normally associated with overall service life of the rope and in ‘simple terms’ the larger the diameter the longer the service life, although consideration should also be given to the anticipated modes of rope deterioration which will also significantly affect the service life. Typically, the diameter of sheaves and drums for crane applications are 16 to 28 times the nominal rope diameter.

Wire ropes are generally subjected to a visual examination and specifically for crane ropes these is an International Standard ISO 4309 “Cranes – Wire ropes – Care and maintenance, inspection and discard” which provides guidance on the inspection of wire ropes and provide the discard criteria. The document also includes information on the Magnetic testing of roper in service / Non-Destructive Examination and how this can assist the competent person in combination with his visual examination, determine the overall condition of the rope. All wire ropes should be inspected on a routine basis by a competent person to ensure that they remain is a good condition whilst in service and removed from service before they become dangerous. However, this standard is used for offering guidance for ropes operating in other systems where no specific discard criteria are given for that application, industry or country in which the rope is operating.

Please note, wire ropes can cause death and/or serious injury if not correctly handles, operated and maintained to good condition and care should always be taken when work with or close to wire ropes.

A new rope can easily be damaged if the pulley wheel groove is too tight, this will in effect pinch the rope probably causing a wave (spiral) deformity in your new rope.

If left unchecked in a steel pulley, parallel, linear fatigue wire breaks will be found where the contact pressures have become too high, due to a pinch affect.

The Lang’s construction, due to the wires running across the axis of the rope is the same direction as the strand, provides a greater length of wire on the exterior surface of the rope and hence since there is an increased surface area there is an increased area of steel to wear away before a broken wire occurs, therefore offering greater wear resistance. Therefore, applications where the rope is operating over larger number of support rollers and/or sheaves, the Lang’s lay rope may be of benefit.

The direction of the wires within the Lang’s lay construction also reduces the level of mechanical damage and rope interference, which takes place between adjacent wraps of rope within the crossover zones during multi-layer spooling of wire rope.

It is important to state that, single layer strand and parallel laid, rope constructions, manufactured in Lang’s lay, MUST NOT be used with one end free to rotate. Since the wires and the strands as twisted in the same direction, if the rope is free to rotate the wires and the strands will untwist tighter and seriously affect the integrity and breaking strength of the rope.

Wire ropes may be considered as machines, each with approximately 200 to 300 individual wires, which move independently to each over whenever ropes operate around sheaves or spool on or off winch drums, therefore ensuring ropes are lubricated internally will minimise the level of friction between the individual wires and optimise the ropes bend fatigue performance. Lubricant internally and externally will protect the ropes from corrosion and this applies equally to both un-galvanised/bright ropes and galvanised rope. Although the zinc on the surface of the individual wires of a galvanised rope will protect the wires from corrosion, once the zinc has sacrificed itself (oxidised) to protect the steel, the wires are then susceptible to corrosion. The longer the zinc can be protected by the lubricant the longer the zinc remains to offer protection to the steel. However there are applications where internal or external lubricant on the rope may not be advisable, anywhere the lubricant could drop off the rope and contaminate products (paper, food, etc.) in the vicinity of the rope or where the lubricant on the exterior of the rope may be contaminated with debris in the atmosphere (grit, sand, etc.). In this application, it must be accepted that ‘dry’ ropes will have a significantly reduced service life.

Ropes may be lubricated in-service with either oil or grease, both products offering slightly different benefits. Oils may be applied from a portable spray unit and although the ropes may require being re-lubricated more frequently, since it is relatively easy and cleaning to apply, operators are more likely to re-lubricate the ropes in service. The thin oil may penetrate the rope and surface coat the exterior of the rope with a thin film of lubricant, which also allows for relatively easy routine visual inspection of the rope. Alternatively, rope may be lubricated with a soft bearing type grease; the grease may be applied using a suitable pressure greasing system (Masto, Viper, etc.) to ensure uniform coating of grease along the total length of the rope passing through the greasing system, although the level and colour of grease may make visual inspection difficult. It is important that any oil or grease used to lubricate ropes in service is compatible with the lubricant applied to the rope during manufacturing and Bridon-Bekaert offer a range of wire rope lubricants specially formulated to be suitable for most environments and operations, including ECO VGP 2013 compliant (Bio-degradable, Non-toxic & Non-accumulative) products.

For ropes operating above ambient temperature consideration must be given to the effects the operating temperature may have on the wire rope. For guidance, unless otherwise stated, the maximum operating temperatures are provided in the International Standards e.g. EN 12385-3. However searches of these standards by Bridon-Bekaert indicate that the quoted temperatures within the standards have remained constant for a significant period of time, having been developed when rope constructions and usage centred around common 6-stranded rope constructions. With the introduction of more complex rope constructions incorporating higher tensile grade wires, synthetic lubricants and polymers, Bridon-Bekaert’s experiences indicate that reconsideration of the maximum operating temperatures is required. For high performance ropes incorporating synthetic lubricants and polymers Bridon-Bekaert recommend a maximum operating temperature of 100 degrees C. Excessive bleed out of lubricant from the rope may occur depending upon the rope operating temperature and the type/composition of the lubricant and frequent re-lubrication may be required.

Certain applications (Heave compensation systems, etc.) can generate high operating temperatures and for these and any application or where ropes are stored above ambient temperature, Bridon-Bekaert would be please to discuss this subject further.

Also due the smoothness of the circumference of these rope designs, they reduce wear at the cross over contact points as the rope wraps over itself as it is wound onto the drum.

An Ordinary lay rope is where the individual wires in the outer strands are spun / twisted together in the opposite direction to the direction the outer strands are twisted around the core, which results in the individual wires running along the axis of the rope. A Lang’s lay rope is where the individual wires in the outer stands are twisted in the same direction as the outer strands are twisted around the core, which results in the individual wires running across the rope in the same direction as the strands.

It is important to state that a left hand lay rope and a right hand lay rope MUST never be joined together unless the jointing mechanism is prevented from rotating, otherwise the rope will be allowed to un-twist together, which may have a significant effect on the integrity of the ropes, and could result in failure of the rope. There are two particular situations/arrangements where a left hand and/or right hand rope combination may be considered beneficial;

To prevent rotation of load – Twin rope operating systems (Overhead hoists, Grabbing systems, Container handling cranes, etc.) are generally designed to utilise one left hand rope and one right hand lay rope. When lifting a load both ropes will be subjected to an axial load and will try to un-twist, but since the ropes have been spun in different directions during manufacture one rope will trying to un-twist in one direction whilst the other rope will try to un-twist in the opposite direction, the two ropes therefore acting against each other to prevent/minimise rotation of the load.

When spooling a rope – Tension is generally applied to ropes whilst they are being spooled on to a winch drum and this tension will try to rotate / untwist the rope and therefore it is preferable to have the rope rotating up against the previous wrap of rope to minimise ‘gapping’ between the adjacent wrap of rope particularly on the bottom layer. Therefore, to achieve this, depending if the rope is anchored on the left or right hand side of the drum or the rope is being spooled under-wound or over-wound will determine if, a left or right hand lay rope should be utilised.

Rotation Resistant ropes are normally used to lift or suspend a load without the load rotating (example, hoist ropes used on Offshore, Mobile and Tower cranes, etc.) and are constructed by spinning the inner part of the rope in one direction and the outer part of the rope in the opposite direction. When an axial load is then applied to the rope the inner part will try to untwist in one direction and the outer part will try to untwist in the opposite direction, with the two parts of the rope reacting against each other. Rotation Resistant ropes are normally of a multi-strand construction and constructed of 2-layers of strands with the inner layer spun in the opposite direction to the outer layer and of 3-layers of strands with the inner two layers spun in the opposite direction to the outer layer. Three and four stranded rope constructions may also be considered as rotation resistant, but having only three or four strands, the ropes do not exhibit such a smooth exterior profile and may prove to be more difficult to spool, particularly when multi-layer spooled.

Wire rope does not have a defined shelf-live, provided the rope has been stored and maintained to ensure that the rope has not been allowed to deteriorate. To ensure that ropes remain in good condition, it is considered good practice to ensure the ropes are stored off the ground in a well-ventilated environment, protected from the sun, rain, sand/grit/dirt, chemicals or any other forms of contamination. Depending upon the environment the lubricant on the rope will tend to migrate to the bottom of the reel and dry out during storage. It is therefore good practice to rotate reels to prevent the lubricant migrating out of the rope on to the floor and to re-lubricate the ropes during storage by simple spraying a thin oil on to the surface of the rope to prevent the steel wires from corroding and/or zinc coating on the wires from oxidising (white rust). Whilst wire ropes are in storage they should be routinely inspected to ensure they have not been accidentally damaged, that all identification and certification remains in place and that the ropes remain fit for use. Rope being taken from storage on a ‘first in – first out’ basis, to minimise the length of time in storage.