wire rope failure modes manufacturer

Due to the wide variety of service conditions for wire ropes, they are susceptible to many types of inadequacies and failures. It is important for consumers to frequently inspect wire ropes for signs of wear and fatigue. Wire ropes will inevitably fail if not used according to manufacturing limitations or when routine inspections for fatigue and wear are not properly performed. Eventually, all wire ropes are removed from service when they meet established discard criteria.

In 1998, a crane load line broke while lifting the south topside module of the Petronius platform, dropping the module into the Gulf of Mexico. The cost was estimated to be around 116 million US dollars. Since 1999 more than 60 people have been killed as a result of wire ropes breaking and more than 65 associated injuries.

Not many people appreciate that there are literally thousands of wire rope designs, most of which can be put into a specific category. According to BS ISO 4309 2010 there are currently more than 25 categories of crane wire rope, each with differing characteristics and also different discard criteria. Deterioration can be measured, counted or calculated and the wire rope eventually taken out of service based on sophisticated discard criteria published in chosen standards, codes of practice or users handbooks.

Unfortunately there is no simple answer to either of these questions. All wire ropes will eventually break due to corrosion, wear or fatigue even if they are maintained and used properly. Unpredictable wire rope failures will inevitably occur, quite often when you least expect it if the discard criteria is ignored, or those using the equipment are ignorant of it.

James Dawes of Topeka, Illinois, was killed in 2008 after being struck by the boom of a Link-Belt crane; the accident was caused by the boom hoist wire rope breaking. The crane rope had been inspected, but a report said that the inspector failed to reject the rope showing a high number of visible wire breaks. Premature or unexpected wire rope failures can also be attributed to poor manufacture, incorrect handling and storage, poor installation technique, poor selection or fitting of its termination, infrequent or inadequate inspection and poor maintenance. Of course there is always the possibility that mechanical damage can occur and this is usually attributed to human error.

It is necessary, particularly during offshore operations that frequent inspections are carried out over the whole length of the working part of all steel wire ropes. The frequency of inspections should be based on the severity of use and risk assessment and particular attention should be paid to the critical areas of the wire rope; areas that are frequently running over sheaves, compensating sheaves and the rope termination to name a few.

If a wire rope has not been subjected to an abnormal environmental condition such as excessive heat, chemical attack or any corrosive solution and it has not been the victim of any form of mechanical damage, then trained operatives and inspectors can reasonably predict the length of time the steel wire rope is likely to last. That prediction, of course, will be dependent on the knowledge and experience of those making it coupled with known facts about the rope, its current condition and the application it is running on. The Inspector should be aware of the previous rope’s history, capacities of loads and the reeving systems employed together with the frequency of use etc.

Various standards and codes of practice have been written by recognized bodies and institutes based on the experience of experts or representatives of corporate organizations who have a vested interest. These standards do offer guidance on when a wire rope should be removed from service based on wear, abrasion and fatigue amongst others things, but none of these standards have any legal status except when they are called up by contract. Indeed they can all be supported or overturned in a court of law by an expert.

The users handbook, or more importantly the safe use instructions do have legal status. In many parts of the world these days, suppliers of cranes or any machinery for that matter, issue safe use instructions with new equipment. Modern applications employ modern wire rope and, in some cases, sheaves and pulleys that are made with materials other than steel. Original equipment manufacturers of such applications may impose discard criteria for the wire rope that is stricter than those in chosen standards. By law the user must follow manufacturers’ instructions.

Wire ropes will deteriorate much more quickly if they go dry and are allowed to remain in that condition. Tests have proven that a dry rope will lose up to 60 % of its expected life if it is not re-lubricated. There are differing schools of thought as to how wire rope should be lubricated. Some believe that a thin lubricant should be applied using a paintbrush. It is thought that this method allows the lubricant to penetrate. Experience has proven however, that thin penetrative lubricants will easily drain away or fly off in hot climates.

Another school of thought, and the one I stand on, is that grease should be pressure lubricated into the rope. This method, if applied properly, will ensure that the grease penetrates the rope pushing out the old lubricant with it and any possible corrosive agents such as salt water and sand. Any lubricant that is used must be compatible with the type that was applied previously and it is a good idea to consider the environment as well.

In any event, wire ropes usually announce that they are about to break. A series of individual wire breaks can be heard. These are likely to go on over several seconds and continuing for up to ten minutes before ultimate failure. Therefore, if operatives understand the warning signals, expensive incidents could be avoided.

Figure 2 shows two pieces of the same rope, the bottom portion quite clearly shows a progression of wire breaks. The operator was able to put the load down before disaster struck. The root cause of this fault was core deterioration brought about by internal corrosion.

To answer the other question on accountability, the list is extensive. Usually the first suspect is the wire rope manufacturer and that may be where the problem lies, but very often that is not the case. What if you were supplied the wrong rope for the application? Maybe you ordered the wrong rope or your buyer bought it from a cheap unapproved manufacturing source.

Perhaps your supplier is responsible, maybe he provided you with a rope that was produced to the wrong specifications. Would you know the difference? Perhaps you were sold a rope that had been stored in the suppliers or manufactures stock for a number of years and, whilst it was there, it hadn’t been properly maintained. Maybe the rope had been badly handled or installed incorrectly. The list of possibilities is endless.

In 1999 a ropeway in the French Alps snapped causing 21 deaths. In 2003, a ropeway wire rope snapped and 7 people died and a further 42 were injured. In 2007 a crane wire rope snapped at New Delhi’s metro, the entire structure tumbled down crushing workers underneath, six people were killed and 13 more were injured. In 2009 26 people were killed and 5 people were injured when a rope failed in a mine and a further 6 people were injured when a lift rope broke inside London’s Tower Bridge.

If you find yourself in the unfortunate situation after the unthinkable premature failure of a wire rope, then you might like to know that there are independent analytical services capable of determining probable cause. One of these is Doncaster Analytical Services Ltd (DAS), they have an independent metallurgical laboratory providing factual analysis and testing of wire rope for any reason (contact Mr Shui Lee, Technical Director, Tel +44(0)1302 556063, email: shui.lee@doncasteranalyticalservices. com).

You do not need a wire rope to fail in order to learn. Careful analysis of discarded ropes can also give you valuable information about your application, the way it operates, and the rope you have been using.

Based on this information, a trained, skilled and experienced inspector will be able to advise on a better crane or wire rope design, or to an improvement in maintenance procedures and safety.

Wire rope is often referred to as a "machine" because when bends the individual slide relative to each other. For this reason wire ropes on running rigging require lubrication. Proper lubrication retards wear and corrosion. A wire rope can have hundreds of separate wires in its cross section. Each wire was made separately at what was possibly a different day. For this reason it is unlikely that a "local" weak area can exist due to a manufacturing error. This characteristic of wire ropes also allows an un-fractured adjacent section to be tested to estimate the pre-fracture strength of a wire rope. Wire ropes fracture because they are loaded in excess of their strength, but their strength can be reduced due to such things as wear, corrosion, or local damage. It is possible for a system to create a load which is greatly in excess of that which was originally intended.

Unfortunately, many phone calls into ITI Field Services begins this way, “We have had an incident with a wire rope and we believe the rope failed. How do we determine the cause of failure?”

Fortunately, the calls come in because wire rope users want to determine cause of failure in an effort to improve their crane, rigging and lifting activities.

A wire rope distributor received a hoist rope and sockets from a rubber-tired gantry. The rope and sockets were returned by the customer who believed the rope and sockets failed. The distributor hired ITI Field Services to conduct an analysis on the rope and sockets to determine the cause of the failure and to produce written documentation.

Based on the findings of the examination, fatigue-type breaks in the wires indicated that the wire rope lost significant strength due to vibration. There was no indication that the rope was overloaded. The poured sockets showed no evidence of abnormalities in the pouring method, wire zinc bonding length or the materials used in the speltering process. The conclusion of the inspection is that rope failed due to fatigue.

Wire rope examination is just one of the many services that is offered by ITI Field Services. ITI has some of the most highly-regarded subject-matter experts in the crane and rigging industry with experience in performance evaluations, litigation, accident investigations, manual development and critical lift planning reviews.

Hoisting loads with a wire rope is a simple operation. Hook it up; lift it. Turns out, it’s more complicated than it appears. The details of setting up, inspecting, and maintaining lifts with wire ropes are not complicated, but are critical. A lift that goes awry is dangerous. A bad lift puts workers at risk. In this article, we discuss the causes of wire rope failure and how to avoid them.

Abrasion breaks are caused by external factors such as coming into contact with improperly grooved sheaves and drums. Or just hitting against some object during operation. Worn, broken wire ends is the result of an abrasion break. Common causes of abrasion breaks include:

Core slippage or protrusion is caused by shock load or improper installation of the wire rope. Excessive torque can cause core slippage that forces the outer strands to shorten. The core will then protrude from the rope. Wire ropes designed to be rotation-resistant should be handled carefully so as not to disturb its lay length.

Corrosion breaks cause pitting on the individual wires that comprise the rope. This type of damage is caused by poor lubrication. However, corrosion breaks are also caused by the wire rope coming into contact with corrosive chemicals, such as acid.

There are many ways the strands of a rope can be crushed or flattened. Improper installation is a common cause. To avoid crushing, you’ll want the first layer of the wire rope to be very tight. You’ll also need to properly break-in a new wire rope. Other causes of crushing include cross winding, using a rope of the wrong diameter, or one that it too long.

Cracks to individual wires are caused by fatigue breaks. Fatigue breaks happen because the wire rope is being bent over the sheave over and over again. In time, the constant rubbing of the wire rope against the sheave or drum causes these breaks. Sheaves that are too small will accelerate fatigue breaks because they require more bending. Worn bearings and misaligned sheaves can also cause fatigue. A certain number of broken wires is acceptable. The worker responsible for equipment inspection prior to use should know the American Society of Mechanical Engineers (ASME) standard for wire ropes. The ASME standard determines whether the wire rope must be replaced. (https://www.asme.org/)

Selecting the right wire rope for the job is critical. There is never a perfect rope. For example, you will need to make a tradeoff between fatigue resistance and abrasion resistance. There are several aspects to wire rope design to consider, including:

In general, the proper wire rope will have a strength rating high enough to handle the load. (Strength is rated in tons.) It can handle the stress of repeated bending as it passes over sheaves or around drums. How you attach the rope in preparation for the lift matters and should only be handled by properly trained workers.

The wire rope (and all the equipment involved in a lift) should be fully inspected prior to the lift. The worker performing the inspection should be well-versed in the types of damage that can cause a wire rope to fail. Using a checklist is highly recommended. This will ensure that the inspection is complete. Worker and supervisor signoff will increase accountability. Of course, the wire rope must be maintained according to the manufacturer’s instructions.

How a wire rope is stored, the weather conditions in which it is used, and how they are cleaned all affect its useful life. The Occupational Safety and Health Administration (OSHA) provides these recommendations: (Source: https://www.osha.gov/dsg/guidance/slings/wire.html)

Preventing wire rope failures starts with selecting the right one for the job. When in doubt, talk with your local equipment dealer. Be prepared to discuss your specific job requirements. A thorough inspection of the wire rope prior to using it is critical. Finally, properly store your wire rope. The selection, inspection, and care of wire rope is key to job safety.

Wire ropes with diamond beads used in machines for cutting blocks of stone are subjected to fatigue, contact fatigue, corrosion and corrosion-fatigue loads in an aggressive environment.

As shown in Figure 1 1-3, multi-wire machines for cutting blocks of stone are made of two structural main components: the supporting structure, fixed with flanged bolts to the ground, (1 in Figure 1), and a vertical moving part 4 (Figure 1). Several wire ropes with diamond beads are put in motion by a driven drum (2 and 7 in Figure 1). The tensioning mechanical system (9 in Figure 1) allows to apply a tension to the wire ropes with diamond beads while the machine is cutting the stone blocks. Several pulleys guide the wire ropes; up to 80 wire ropes can be used and mounted in parallel on the structural component 4 and on several pulleys. the motorized drum is the component 3 in Figure 1 and a three-phase asynchronous electric motor is mounted on the machine and puts the drum and the wires in motion. Wire ropes with diamond beads are the cutting tools of the machine and the designer must take care of such components when mounted on the machine. It is well known that the structural behavior of steel wire ropes, composed of several strands, is complex and multiaxial stresses, along with contact fretting stresses, must be managed. Working conditions of the wire ropes have to be strictly controlled and checked periodically.

Notwithstanding there are many literature references on the study of the damage of wire ropes, few research references can be found in the literature, as far as the author knows, that would allow to understand their structural behavior in terms of damage or failure analyses 4-11. In 4 Authors report a study on the diamond wire cutting of concrete materials. Wire cutting with diamond technique was used in the United States until the early 1980s and allowed to cut reinforced concrete structures, regardless of thickness and reinforcement content. In 5 an innovative and optimized design of automatic adjustment system for beaded rope of new diamond wire sawing machine is reported, while in 6 the mechanics of sawing granite with diamond wire is considered. Research on cutting performance optimization of diamond wire saw is deepened in 7. In these papers the structural design of the wire rope with diamond beads is introduced and the mechanical structure and control of the adjusting device of the diamond wire saw are described. Working parameters are transmitted via wireless signals to achieve remote control. Mechanics of cutting procedure is deepened and mechanical simulation and optimization models of the wires with diamond beads are proposed. Many references are available on the study of wire ropes without diamond beads 8-11; such references allow to understand the mechanisms of failure in case of absence of the beads: unfortunately, the Author pf this paper found that the structural fatigue and corrosion-contact-fatigue behavior of the wire rope is highly influenced by the presence of the diamond beads.

This paper contains the results of the observation of surface damage of wires used in multi-wire machines for cutting blocks of stone and the optical analysis of beads for 2.35 mm cables. The cables are used as a support for pearls equipped with diamond inserts for cutting stones (beads) (Figure 2).

The samples were taken from wire ropes having 2,35 mm diameter. The wire rope is composed of 7 strands wires, one of which is located at the centre of the wire rope (“soul”). Each strand contains 7 single wires having 0.3 mm wires diameter (Figure 5).

Significant sections of the beaded wire as shown in Figure 4 were investigated. Section X.1 was not considered but we focused on the evaluation of the centering of the cable in the beads. The sections were obtained using a metallographic cutting machine.

The wire ropes with beads were also observed by unwinding the strands and the core both by opening the individual strands and by releasing the individual wires before proceeding with the observation. Figure 5 shows two examples of preparation of a stranded cable and single strands and wires.

Figure 6 shows two examples of the cracked surfaces of the wires. Those cracks greatly affect the fatigue resistance of the whole wire rope with beads.

To evaluate the effect of the environment on the wire rope, tests were carried out with penetrating liquids (blue ink). Liquids were poured onto the flexed sample to simulate operational behavior. Figure 8 shows the penetrating liquids experimental test.

Contact between the wire rope and the beads was observed (Figure 9). Beads and the wire rope are made of different materials and this might cause corrosion of the wires in the rope, along with contact fatigue damage.

The wire ropes studied in this work are designed with low fatigue resistance safety factors (2-3). Previous analyses helped in reaching some useful conclusions 3-10.

Detachment of brass or zinc coatings which, being thin, are unable to adhere to the wire at the cracks. Causes can also be found in the straightening operation and incorrect handling of the ropes.

Observations and analysis of the damaged wire ropes allowed to highlight that the beads have no continuous side surface and at the discontinuity the finish is very poor. Moreover the insertion of the diamond chips is not uniform. The insertion of the splinters causes localized lifting of the material. This could cause premature detachment of some of them. Wire ropes are mechanical components that work in a complex stress state with contact loads, wear, corrosion and fatigue resistance problems. The presence of the diamond beads is a further stress concentration, with corrosion and contact wear fatigue problems if the beads come into contact with the wire rope during assembly or in working condition.

The advice is to product wire ropes with beads in which the centering of the cable with respect to the bead is carefully controlled. No contact between rope and bead should occur. According to the results and observations this is the most important advice for producer of the ropes with diamond beads.

This paper reports the failure analysis of the damage mechanisms of wire ropes with diamond beads mounted in machines for cutting stones. Wire ropes with diamond bead are cutting tools subjected to fatigue, corrosion-contact-fatigue stresses. Cracks and defects are present in the strands of the wire ropes, generated during the production process: these cracks are further sources of stress concentrations. The observation at the microscope, and the penetrating liquids analyses, highlighted that the most important advice to give to the producer of the wire ropes with diamond beads is to product components in which the centering of the cable with respect to the bead is carefully controlled.

Pedrini, G., Baragetti, S., 2016, “Multi-wire machine for cutting blocks of stone and wire tensioning device”, International Patent n° WO 2016/071936A1.

Bangju Wei et al, 2020, “Innovative and optimized design of automatic adjustment system for beaded rope of new diamond wire sawing machine”IOP Conf. Ser.: Mater. Sci. Eng. 892 012078.

Janusz Stefan Konstanty, 2021,”The mechanics of sawing granite with diamond wire”, The International Journal of Advanced Manufacturing Technology (2021) 116:2591–2597.

Liu S., Sun Y.Send mail to Sun Y., Jiang X., Kang Y., 2022, “A new MFL imaging and quantitative nondestructive evaluation method in wire rope defect detection”, Mechanical Systems and Signal Processing, vol. 163.

Peng, Y., Wang, G., Zhu, Z., Jiang, F., Chen, G., 2021, “Effect of low temperature on tribological characteristics and wear mechanism of wire rope”, Tribology International, vol. 164.

Wang et Ali, 2021, “Tribological properties and residual strength of wire rope with different strands during the interlayer-transition stage”, vol. 480-481, Wear.

Bassir Y., et Ali, 2021, “Comparative study of the service life of a central core and a helical strand constituting the same rope”, vol. 247, Engineering Structures.

Wire ropes are largely used in marine environment or for rigging purposes. They receive considerable loads and thus suffer a great deal of mechanical damage throughout their service life. Moreover, research has shown that the major cause of wire rope failure is excessive deterioration and corrosion, lack of maintenance and inspection, and wrong usage resulting in early discarding, reduced safety and replacement cost increase.

Sometimes damage can be easily detected, while in other cases fractured wires may occur on the inside. Hence, wire ropes should be inspected and maintained by the right person (competent person assigned by the company), to assure they’re in perfect condition. Regular inspectionsensure high rope performance, long service lifetime , safety of personnel and equipment, and reduced operating costs.

All ropes (synthetic, high modulus and wire ropes) should be inspected before and after an operation. This guideline ensures maximum safety for both a ship’s personnel and equipment. Even though it’s difficult to determine the exact service life span of ropes, there is a way to have a more precise estimation about their efficient lifecycle. Calculating the exact time ropes have been in use (e.g mooring time, mooring conditions, weather and tidal conditions) is the answer. All in all, rope inspections should occur at least once a year.

Inspecting wire ropes in particular, comes with great responsibility. Inspection results should be recorded, and any defects noticed have to be reported and addressed properly. Some defects can be repaired, while in some cases replacing a wire rope is inevitable.

Periodical inspections ofvessel deck equipment is also crucial for maintaining the good condition of wire ropes. The condition of the drum, chocks, bitts, rollers, sheaves, cable clamps and other end fittings, affect the rope’s performance, threads and cords. Make sure to mark these parts during your overall inspection.

In order to help marine officers and staff conduct successful wire rope inspections – and keep an up-to-date record of them – we have created an inspection solution that helps in maintaining and monitoring a ship’s ropes and deck equipment.

When calculating mass using F = Minimum Breaking Force, according to the wire rope’s diameter, you can determine the Minimum Breaking Massand therefore the wire’s max strength. When calculating mass using F = Safe Load according to the wire rope’s diameter, you can determine the Safe Load Mass,which is the advised load for this rope diameter.

The strands of a wire rope absorb the majority of the tensile force applied on the rope. Their design and manufacturing standards affect the level of fatigue resistance and resistance to abrasion. An easy way to understand which rope design is suitable for each purpose, is the wire rope classification.

Wire ropes are classified according to the number of strands in each construction and the number of wires in each strand. For example, a classification of 6X19 means that a wire rope of this type always has six strands, but its wires could be 15-26 per strand. This is because 19 is not the exact number of wires, but the classification of a wire number range.

Visual inspections are a common and fast way to assess wire rope condition. Both the standard and rotation resistant wire rope inspectionprocesscomply with the same four steps of examination. A ship’s crew can perform them as follows:

Steel wire rope distortion is obvious in most cases and can easily be identified by the inspector or the ship‘s crew. It usually occurs if load is suddenly applied or abruptly released (shock loading), or even if swift torque is forcefully induced.

Although not all of these deformations make the rope absolutely dangerous to use, they all may cause ropes to wear unevenly in time. This means inspections should take place more often, and distorted ropes should be handled with caution.

The rag and visual inspection is a good method for regular inspection intervals. The inspector pulls a rag along the rope trying to find broken wire cords. If the rug gets snagged by the rope, the inspector has to stop and assess the wire rope’s condition. Extreme caution should be exercised during the visual inspection, and under no circumstances should this method be the only one used to inspect wire ropes.

Tip: When you encounter a protruding wire end, bend it back and forth manually, until it separates from the wire. This will protect neighboring wires from wearing out.

Diameter reduction is a critical factor in steel wire rope wear and if not properly taken care of, it can result in rope breakage. Excessive abrasion, loss of core mass, corrosion or inner wire failure are all factors that contribute to diameter reduction.

To get an accurate measurement of the rope’s diameter, measure the rope at three different points at least 5 feet apart. Take the average of these three measurements to determine the true diameter.

Any measurements showing a reduction of ⅓ or more, indicate that a replacement should follow without delay. A diameter reduction of less than 1/3 still requires attention, and the inspector or the ship’s crew should be on guard in the next scheduled wire rope inspection.

Failure from abrasion or corrosion is a result of deficient deck equipment inspection or insufficient wire rope lubrication respectively. Internal corrosive damage is more difficult to identify than any other types of degradation. In most cases, the damage has progressed more than the external signs suggest.

Wire rope storage plays a significant role in the rope’s operation life.Wire rope corrosion and pitting can be avoided if ropes are safely stored in a clean, cool, dry and well-ventilated place. Steel wire ropes should not by any means rest on the floor, and should be protected from water, dust or any chemical fumes. Long term storage requires periodic greasing, turning the reel upside down for preventing grease dripping and possibly re-winding to another reel with larger inner tube diameter.

Wire ropes should be maintained with periodical lubrication. In order to prevent internal corrosion, a pressure lubricator is suggested to be used. In this case, a small amount of grease is used to lubricate the rope internally, while the deck stays grease-clean. Pressure lubricators clean the rope before they grease it so that the new grease enters a clean rope. The type of grease used is very important for maximum protection and greasing efficiency.

Steel wire ropes exposed to dirt, grime and other contaminants, have to be cleaned with a wire brush and petroleum (unless a pressure lubricator is used). Optimal cleaning of wire ropes can extend their service life and guarantee safe operations.

The reeling process is of high importance for the longevity of wire ropes. To protect them from being damaged, it is important that the surface of the drum is clean, smooth and dry. Improper reeling may cause wire-rope strands to spread or get flattened, when in contact with one another, as successive layers are being spooled and upper layers apply pressure on the lower ones.

Katradis S.A. offers a wide range of top quality wire ropes for shipping (mooring and hoisting operations), fishing and construction purposes. Our wire ropes have greater resistance to fatigue, and they distribute tension force equally among the rope strands. They are less likely to kink, providing higher staff safety and assuring operation success.