wire rope failure analysis 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.

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.

TTI Testing offers a full range of consultancy, research, development and forensic analysis in fields related to the design, inspection, operation, testing, appraisal and discard of tension elements. We have internationally recognised expertise in wire and fibre ropes, chains, electromechanical cables, hoses and related interface components in the onshore, industrial and offshore markets and can also offer a full range of additional industrial mechanical testing.

In addition to fundamental research and experimental work, TTI Testing also offers services related to condition assessment and failure analysis of wire and fibre ropes and chains.

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 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).

The study was conducted by means of microscopic analysis, X-ray microtomography and tests with penetrating liquids. For the first, two Leica stereoscopic microscopes (MZ 75 with magnification up to 50x and microscope with magnification up to 40x) with digital camera (Canon Powershot S50 and Canon EOS 1100D) and an Opto-De monofocal optical microscope with magnifications were used up to 400x with Motic 2300 USB 2.0 acquisition camera. A new stereoscopic optical microscope mod. ZENITH SZM-4500 Trinocular Zoom 7x-45x with additional lens 2x mod, ST-087 2x for 14x-90x magnification and a variable double LED illuminator mod. ZENITH CL-31 with double jointed self-standing arm. The images were taken with a USB micro-camera Mod. OPTIKAM B-3 complete with optics. The effectiveness of the protective plastic coating was evaluated by pouring liquids (blue ink) on the cable.

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, pulleys, counterweights, and connecting systems are used for auto tensioning of contact wires of electric railways. A wire rope in one such auto tensioning system suffered premature failure. Failure investigation revealed fatigue cracks initiating at nonmetallic inclusions near the surface of individual wire strands in the rope. The inclusions were identified as Al-Ca-Ti silicates in a large number of stringers, and some oxide and nitride inclusions were also found. The wire used in the rope did not conform to the composition specified for AISI 316 grade steel, nor did it satisfy the minimum tensile strength requirements. Failure...

But on one particular day in early May of 2009, it wasn’t a boom reaching toward the big Texas sky that was causing people to stop and stare; it was one that was lying in a heap just beside the water, lattice sections bent and lacings twisted into mess of mangled steel and frayed wire rope. “I got the call to investigate the cause of loss on a Manitowoc 888 that was being used to drive underwater pilings at a dock in Port Isabel,” says JR Bristow, of Bristow Truck and Equipment Specialists, an organization based in Ridgewood, NJ that provides failure analysis and appraisals, among other things, for heavy equipment. “The operator was hoisting the boom when it just sort of gave out and crashed to the ground. No one was hurt, but the boom was in bad shape. The initial reserve was set at $500,000.”

Though a half million dollars wasn’t a total loss – the crane was valued at $1.5 million – it was a pretty hefty price to pay for something that, as it turned out, could have been avoided. On lattice-type cranes, booms are raised and lowered using boom hoist wire rope, and when that wire rope shows surface wear or corrosion, or worse, has broken wires within the rope strand, it can fail. It’s usually just a matter of time.

The subsequent investigation that followed revealed that the wire rope used to hoist the boom of the Model 888 had been in an out-of-service condition for quite some time, due to lack of proper lubrication.

“An examination of the failed boom hoist wire rope revealed that the wire rope had gone without the proper lubrication, which was the responsibility of the insured per the attached lease agreement,” Bristow remembers. “I also noted significant broken wires within the rope strands at an average of six to 12 per strand lay. Clearly, if the insured had performed a daily inspection of the boom hoist wire rope as required, that incident would not have happened.”

The broken strand condition that Bristow observed was caused by load cycles that occurred during boom up and boom down functions that were part of the daily operation of the crane. Simultaneous compression and expansion of the wire rope usually occurs as it travels over the hoist sheaves, and that causes the gradual deterioration of the strand wires.

Like many other segments of the crane and rigging industry, the nuances of wire rope are complicated and varied. Considerable time, money and resources have been invested in new technology, new inspection suggestions and new manufacturers. And rightly so. As was the case in Bristow’s example earlier, there’s quite a bit at stake in terms of both human capital and equipment cost.

Python High Performance wire rope, a wire rope manufacturer that has produced a number of resources to assist people in understanding and ultimately purchasing wire rope, clarifies the structure of wire rope on its website www.pythonrope.com.

Python’s site explains that a typical wire rope can contain hundreds of individual wires. These wires are fabricated and formed to operate at close bearing tolerances to one another. When a wire rope bends, each of its many wires slides and adjusts in the bend to accommodate the difference in length between the inside and the outside bend. The sharper the bend, the greater the movement, and the greater capacity for stress on the wire rope.

While manufacturers of wire rope are many and varied, each of the wire ropes they produce have three basic components:The wires, which form the strands and collectively provide the rope strength

According to Python’s site, the greatest differences in wire ropes are found in the number of strands, the construction of strands, the size of the core and the lay direction of the strand versus the core. But what does that mean for the layperson? What should he or she look for when purchasing wire rope?

Tony Fastuca, vice president Python America & High Performance Products, says that most people buy rope based on four ideal standards. “Abrasion resistance, fatigue resistance, flexibility and strength. Those four typical standards often weigh into a purchase decision: he says. “A buyer sometimes has to give a little in one area to get a bit more in another, but a lot of buyers are looking for a good balance of those four standards.”

Whereas other products usually come with an expected lifespan, wire ropes don’t really have an average operational life. “There are records that exist of wire ropes getting two to three years of use, sometimes longer,” says Fastuca. ”But it’s about the level of wear on the rope, not the length of time it’s been in service.”

Just as the crane itself needs to undergo frequent and period inspections, the wire rope does, too. Fastuca talks of the so called “A,B,Cs” of wire rope abuse – abrasion, bending, crushing.

The principle goal of a wire rope inspection is to find potential problems before they manifest into incidents or serious accidents. Inspections should be performed slowly and methodically, with a keen eye for corrosion or broken wires or sections of rope that look questionable. Because the reality of wire rope is that it will fail if it becomes worn out, overloaded, damaged, misused or improperly maintained. It can lead to huge headaches for companies that try to take shortcuts or don’t properly maintain it – a risk that just isn’t worth taking.

Present work describes the failure analysis of AISI 304 stainless steel lanyard wire rope which has failed during application in humid atmosphere. The wire rope has 7´19 construction which means that it consists of seven strands and each strand having 19 wires twisted in a helical fashion. The microstructures and properties of failed wire rope have been investigated and compared with unused wire rope. Both the periphery and fracture surface of the wire rope display the presence of corrosion debris enriched with O and Cl. The fracture surfaces of the failed and unused wire ropes display intergranular and dimples, respectively. The lanyard wire rope has been exposed in corrosive atmosphere and failed in intergranular mode due to enrichment of O and Cl along the grain boundaries.

Following a tragic accident during a routine drill procedure, a National Accident Investigation body approached consultancy experts from The Test House (TTH), to carry out a confidential failure investigation into the cause of the failure. During the drill, a life boat was being recovered and hoisted when the forward fall wire parted, causing the life boat to swivel on the aft hook. The hook failed and the boat plummeted 20 metres, rotating as it fell, and eventually hitting the water upside down. One crew member was thrown out from the lifeboat as it entered the water, and two crew members managed to escape from the upturned lifeboat by their own efforts. The remaining five crew members were subsequently removed by local divers and were declared deceased at the scene.

Assured by TTH’s reputation and integrity, and its long history of mechanical testing expertise, the marine company was confident that the investigation would uncover the exact cause of the failure. TTH holds UKAS accreditation in the fields of NDT, mechanical testing, metallurgical testing and corrosion testing.

Initially TTH completed a thorough, comprehensive and multi-disciplinary report that covered receipt inspection of the failed wire rope, a visual examination at the parted site, a scanning electron microscope (SEM) examination, metallographic examination, hardness testing and break load testing. The TTH provides a range of preparation techniques for metallurgical examination of metals, alloys, backed up by comprehensive photographic and digital imaging capabilities.

The failure investigation found that the strength of the rope had been below the original certified value. There were clear areas of poor condition, showing open lay, internal rusting and wire breaks. There had been an apparent failure to maintain a suitably protective level of lubricant at the sheave location when the rope was left under tension to stow the lifeboat. There was also an apparent failure to monitor the ropes deteriorating condition consistently using a regular and effective inspection procedure.

Having completed the failure analysis, TTH were then able to work with the client to identify effective safety and maintenance procedures for future use, to minimise all risks to the company and its crew. The National Accident Investigation Body’s, Marine Safety Investigation Unit (MSIU) issued a ‘Safety Alert’ which concluded the cause of the failure. The MSIU findings including The Test House investigation report and safety alert can be found at: