wire rope failure modes for sale

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 ropes are complex machines with a great many moving parts. They require attention, skilled operators, careful maintenance, inspection and lubrication.

In spite of their vital importance, wire ropes are frequently treated as and considered low-tech commodities. Failures are frequently accepted as “inevitable.”

With the appropriate inspections, wire rope failures can be predicted, and expenses and losses reduced. Consider that the price tag of rope failures can easily be in the seven or even eight digit range, and the cost of an inspection is marginal.

Much more dependable than visual inspections, magnetic rope testing (MRT) is a reliable non-destructive evaluation/examination (NDE) procedure used for the in-service inspection of wire ropes. NDE methods allow the detection and evaluation of external as well as internal rope deterioration. This allows the inspection of a rope’s entire cross-section to the core. MRT drastically increases wire rope safety. At the same time, it promises significant annual savings.

Ropes usually degrade internally with no visible indications. Internal deterioration modes include inter-strand nicking that will eventually develop into clusters of internal broken wires and corrosion including corrosion pitting.

External deterioration includes winding-on-drum damage. Urgently needed, suitable inspection equipment and procedures are now available – especially for the quantitative characterization of internal rope deterioration.

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.

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.

A competent person must begin a visual inspection prior to each shift the equipment is used, which must be completed before or during that shift. The inspection must consist of observation of wire ropes (running and standing) that are likely to be in use during the shift for apparent deficiencies, including those listed in paragraph (a)(2) of this section. Untwisting (opening) of wire rope or booming down is not required as part of this inspection.

Significant distortion of the wire rope structure such as kinking, crushing, unstranding, birdcaging, signs of core failure or steel core protrusion between the outer strands.

In running wire ropes: Six randomly distributed broken wires in one rope lay or three broken wires in one strand in one rope lay, where a rope lay is the length along the rope in which one strand makes a complete revolution around the rope.

In rotation resistant ropes: Two randomly distributed broken wires in six rope diameters or four randomly distributed broken wires in 30 rope diameters.

In pendants or standing wire ropes: More than two broken wires in one rope lay located in rope beyond end connections and/or more than one broken wire in a rope lay located at an end connection.

If a deficiency in Category I (see paragraph (a)(2)(i) of this section) is identified, an immediate determination must be made by the competent person as to whether the deficiency constitutes a safety hazard. If the deficiency is determined to constitute a safety hazard, operations involving use of the wire rope in question must be prohibited until:

If the deficiency is localized, the problem is corrected by severing the wire rope in two; the undamaged portion may continue to be used. Joining lengths of wire rope by splicing is prohibited. If a rope is shortened under this paragraph, the employer must ensure that the drum will still have two wraps of wire when the load and/or boom is in its lowest position.

If the deficiency (other than power line contact) is localized, the problem is corrected by severing the wire rope in two; the undamaged portion may continue to be used. Joining lengths of wire rope by splicing is prohibited. Repair of wire rope that contacted an energized power line is also prohibited. If a rope is shortened under this paragraph, the employer must ensure that the drum will still have two wraps of wire when the load and/or boom is in its lowest position.

Where a wire rope is required to be removed from service under this section, either the equipment (as a whole) or the hoist with that wire rope must be tagged-out, in accordance with § 1926.1417(f)(1), until the wire rope is repaired or replaced.

If a deficiency in Category II (see paragraph (a)(2)(ii) of this section) is identified, operations involving use of the wire rope in question must be prohibited until:

The employer complies with the wire rope manufacturer"s established criterion for removal from service or a different criterion that the wire rope manufacturer has approved in writing for that specific wire rope (see § 1926.1417),

If the deficiency is localized, the problem is corrected by severing the wire rope in two; the undamaged portion may continue to be used. Joining lengths of wire rope by splicing is prohibited. If a rope is shortened under this paragraph, the employer must ensure that the drum will still have two wraps of wire when the load and/or boom is in its lowest position.

Wire ropes on equipment must not be used until an inspection under this paragraph demonstrates that no corrective action under paragraph (a)(4) of this section is required.

At least every 12 months, wire ropes in use on equipment must be inspected by a qualified person in accordance with paragraph (a) of this section (shift inspection).

In the event an inspection under paragraph (c)(2) of this section is not feasible due to existing set-up and configuration of the equipment (such as where an assist crane is needed) or due to site conditions (such as a dense urban setting), such inspections must be conducted as soon as it becomes feasible, but no longer than an additional 6 months for running ropes and, for standing ropes, at the time of disassembly.

The inspection must be complete and thorough, covering the surface of the entire length of the wire ropes, with particular attention given to all of the following:

If the deficiency is localized, the problem is corrected by severing the wire rope in two; the undamaged portion may continue to be used. Joining lengths of wire rope by splicing is prohibited. If a rope is shortened under this paragraph, the employer must ensure that the drum will still have two wraps of wire when the load and/or boom is in its lowest position.

(1) A competent person must begin a visual inspection prior to each shift the equipment is used, which must be completed before or during that shift. The inspection must consist of observation of wire ropes (running and standing) that are likely to be in use during the shift for apparent deficiencies, including those listed in paragraph (a)(2) of this section. Untwisting (opening) of wire rope or booming down is not required as part of this inspection.

(A) Significant distortion of the wire rope structure such as kinking, crushing, unstranding, birdcaging, signs of core failure or steel core protrusion between the outer strands.

(1) In running wire ropes: Six randomly distributed broken wires in one rope lay or three broken wires in one strand in one rope lay, where a rope lay is the length along the rope in which one strand makes a complete revolution around the rope.

(2) In rotation resistant ropes: Two randomly distributed broken wires in six rope diameters or four randomly distributed broken wires in 30 rope diameters.

(3) In pendants or standing wire ropes: More than two broken wires in one rope lay located in rope beyond end connections and/or more than one broken wire in a rope lay located at an end connection.

(i) If a deficiency in Category I (see paragraph (a)(2)(i) of this section) is identified, an immediate determination must be made by the competent person as to whether the deficiency constitutes a safety hazard. If the deficiency is determined to constitute a safety hazard, operations involving use of the wire rope in question must be prohibited until:

(B) If the deficiency is localized, the problem is corrected by severing the wire rope in two; the undamaged portion may continue to be used. Joining lengths of wire rope by splicing is prohibited. If a rope is shortened under this paragraph, the employer must ensure that the drum will still have two wraps of wire when the load and/or boom is in its lowest position.

(ii) If a deficiency in Category II (see paragraph (a)(2)(ii) of this section) is identified, operations involving use of the wire rope in question must be prohibited until:

(A) The employer complies with the wire rope manufacturer"s established criterion for removal from service or a different criterion that the wire rope manufacturer has approved in writing for that specific wire rope (see § 1926.1417),

(C) If the deficiency is localized, the problem is corrected by severing the wire rope in two; the undamaged portion may continue to be used. Joining lengths of wire rope by splicing is prohibited. If a rope is shortened under this paragraph, the employer must ensure that the drum will still have two wraps of wire when the load and/or boom is in its lowest position.

(B) If the deficiency (other than power line contact) is localized, the problem is corrected by severing the wire rope in two; the undamaged portion may continue to be used. Joining lengths of wire rope by splicing is prohibited. Repair of wire rope that contacted an energized power line is also prohibited. If a rope is shortened under this paragraph, the employer must ensure that the drum will still have two wraps of wire when the load and/or boom is in its lowest position.

(iv) Where a wire rope is required to be removed from service under this section, either the equipment (as a whole) or the hoist with that wire rope must be tagged-out, in accordance with § 1926.1417(f)(1), until the wire rope is repaired or replaced.

(3) Wire ropes on equipment must not be used until an inspection under this paragraph demonstrates that no corrective action under paragraph (a)(4) of this section is required.

(1) At least every 12 months, wire ropes in use on equipment must be inspected by a qualified person in accordance with paragraph (a) of this section (shift inspection).

(ii) The inspection must be complete and thorough, covering the surface of the entire length of the wire ropes, with particular attention given to all of the following:

(iii) Exception: In the event an inspection under paragraph (c)(2) of this section is not feasible due to existing set-up and configuration of the equipment (such as where an assist crane is needed) or due to site conditions (such as a dense urban setting), such inspections must be conducted as soon as it becomes feasible, but no longer than an additional 6 months for running ropes and, for standing ropes, at the time of disassembly.

(B) If the deficiency is localized, the problem is corrected by severing the wire rope in two; the undamaged portion may continue to be used. Joining lengths of wire rope by splicing is prohibited. If a rope is shortened under this paragraph, the employer must ensure that the drum will still have two wraps of wire when the load and/or boom is in its lowest position.

Wire rope is a key part of numerous applications for construction, aerospace, and the marine industry. However, you severely reduce cable service life by causing damage to your wire products and could jeopardize your whole operation or cause injury. Two of the most common types of wire rope damage are kinking and bird caging. Continue reading to learn about these damage types and how to prevent them from occurring in your applications.

A kink appears is the place where a wire rope where the rope has been bent past what it can take. It is caused by applying a bending force beyond a wire rope"s tolerable level of flexibility. The problem most commonly occurs when the wires in the wire rope are all closed in the same direction. Kinking is often caused by the improper handling and uncoiling of wire rope products. If kinking occurs, your wire rope product can be severely damaged, and failure becomes inevitable.

While kinking can be a serious problem, it can be easily avoided. One way to prevent kinking is by using lifting hooks with swivels. A swivel helps prevent kinking as it takes the pressure off wire rope. Kinking can also be prevented by using correct uncoiling techniques. By properly handling your wire rope products, you will avoid kinking and have a wire rope product that lasts for many years! If your current wire rope is kinked, it is best to replace the item as soon as possible.

Bird caging happens when a wire rope experiences stress and then frays or pulls apart, resembling the appearance of a birdcage. The problem most commonly occurs where the wires in the wire rope are closed in different directions. Bird caging is often caused by improper installation or having too much slack in the wire ropes. Bird caging can also result from a sudden release of tension or forced through a light sheave.

One way to prevent bird caging is to use the right size and strength of sheaves and pulleys with your wire rope. By proper installation and preparation of your wire rope application, you can also reduce the possibility of bird caging. A third way to prevent bird caging is to make sure there is torsional balance in your wire rope. If your current wire rope has occurred any form of bird caging, you should replace the item.

Now that you understand how to prevent kinking and bird caging, you can expect to get the highest level of performance from your wire rope products. If you are searching for a replacement wire rope, choose Loos and Company! Our products are domestically manufactured to the highest of standards and offer extreme strength and durability. You can find out more about our wire products here. Alternatively, if you have any questions, our team is happy to help! Reach out to us by email at sales@loosco.com or by phone at (860) 928-7981.