valley breaks wire rope supplier

Example: Severe crown wire breaks on a 10-strand overhead crane wire rope. Crown breaks originate at the OUTSIDE of the rope at the contact point between rope and sheave/drum.

Remove the rope from service even if you find a SINGLE individual wire break which originates from inside of the rope. These so called VALLEY breaks have shown to be the cause for unexpected complete rope failures.

These 3 picture show what happens when you connect a left-lay rope to a right-lay rope, as done with this boom pendant extension. Both ropes are opening up to the point where the strands are nearly parallel to each other; they completely untwisted themselves and developed excessive wire breaks.

The result of such non-tensioning of the layers are looping of individual wires, completely crushed strands, total deterioration of a non-rotating rope due to gross neglect of inspection procedure.

NOTE: For a more indepth discussion on wire rope discard and inspection we suggest to attend our “Wire Rope” and “SlingMax® Rigger’s Mortis Seminar”. Call 1.800.457.9997 for details and dates.

Figure 43. A wire broken under a tensile load that exceeds its strength is recognized by the “cup and cone” configuration at the fracture point (a). The necking down of the wire at this point shows that failure occurred while the wire retained its ductility. Shear-tensile fracture (b) occurs in wire subjected to a combination of transverse and axial loads. Fatigue breaks are usually characterized by squared-off ends perpendicular to the wire either straight across or Z-shaped (c&d).

Like all industrial equipment, aircraft cables and wire ropes wear while in service, and will require replacement. Though the cycle life of each cable varies based on construction and application, factors such as load and pulley condition can actually reduce this lifespan by triggering wire breaks. Not all wire breaks look the same, and understanding these differences can help detect issues in your system before they damage additional cables, or put human lives in danger. Here is a quick guide to help you understand where wire breaks occur (crowns vs. valleys), and three common examples of wire breaks (tension, fatigue, and abrasion).

Wire breaks typically occur in two different locations on the outside of wire rope or aircraft cable. The first location is on the crowns of the strands, which are the highest points with the most surface area exposure. The second location is the valleys, or the spaces between the strands. Though crown breaks typically result from normal wear and tear, valley breaks are more suspicious and may indicate issues with the pulley system or wire rope itself.

Wires that have been worn to a knife-edge thinness are characteristic of abrasion breaks. Abrasion can occur from a number of different sources, but sheaves are the most common. Remember to check sheaves for signs of wear, damage, or deformity and replace as necessary.

If you notice one end of a broken wire is cupped, and the other end resembles a cone, your wire rope likely experienced a tension break. Tension breaks result from excessive loading, causing the wires to stretch beyond their limits until they snap. Once one wire break appears, others will continue to occur if the cable is not addressed.

Fatigue damage is usually represented by zig-zag breaks with square ends. Like abrasion breaks, fatigue breaks can be triggered by a broad range of factors, including incorrect pulley size and excessive vibration. Check for worn pulleys and slack in the system to prevent issues from exacerbating.

Once you have replaced your damaged pulleys, or removed sharp obstructions in your system, begin your quote for brand new wire rope at https://strandcore.com/contact/. Our wire rope craftsmen can help you select the ideal wire rope for your application, and oftentimes provide a better solution for your existing setup. Browse our selection ofwire rope and aircraft cableonline, and do not hesitate to contact our sales team at sales@sanlo.com if you have any questions.

All wire ropes will wear out eventually and gradually lose work capability throughout their service life. That"s why periodic inspections are critical. Applicable industry standards such as ASME B30.2 for overhead and gantry cranes or federal regulations such as OSHA refer to specific inspection criteria for varied applications.

You should thoroughly inspect all wire ropes at regular intervals. The longer it has been in service or, the more severe the service, the more thoroughly and frequently it should be inspected. Be sure to maintain records of each inspection.

Inspections should be carried out by a person who has learned through specialized training or practical experience of what to look for and who knows how to judge the importance of any abnormal conditions they may discover. It is the inspector"s responsibility to obtain and follow the proper inspection criteria for each application inspected.

Figure 1is what happens when a wire breaks under tensile load exceeding its strength. It"s typically recognized by the "cup and cone" appearance at the point of failure. The necking down of the wire at the point of failure to form the cup and cone indicates failure has occurred while the wire retained its ductility (the ability to change form without breaking).

Figure 2is a wire with a clear fatigue break. It is identified by the square end perpendicular to the wire. This break was produced by a torsion machine that"s used to measure the ductility. This break is similar to wire failures in the field caused by fatigue.

Figure 3 is a wire rope that has been subjected to repeated bending over sheaves under typical loads. This fatigue results in breaks in individual wires - these breaks are square and usually in the crown of the strands.

Figure 4 is an example of fatigue failure of a wire rope subjected to heavy loads over small sheaves. The breaks in the valleys of the strands are caused by "strand nicking." There may be crown breaks, too.

Figure 5 is a single strand removed from a wire rope subjected to "strand nicking." This condition is a result of adjacent strands rubbing against one another. While this is normal in a rope"s operation, the nicking can be accentuated by high loads, small sheaves or loss of core support. The ultimate result will be individual wire breaks in the valleys of the strands.

Reeving failures have been a leading cause of accidents in our trade. They were thirty years ago when Wilbert A Lucht wrote his article, “Sheave Design vs Wire Rope Life” (reprinted in the June issue ofWire Rope News, page 26), and are still today.

A Crane is a combination of two simple machines. One is a lever, and the other is a block and tackle. Both increase the machinal advantage of a crane’s lifting capability. However, the block and tackle (sheaves and wire rope, referred to as reeving) are “used-up” as the crane works.

The sheave differs from a “pulley” or roller importantly. Both change the direction of the rope and increase the mechanical advantage — pulling power. However, the sophisticated sheave does the same but also maintains the cross-section shape of the rope, critical to reducing wear, and the rope strength — if properly sized.

A Sheave gauge is being used to check the groove size by a crane inspector in Fig. 1. These gauges have the maximum size of the groove recommended for the rope that is installed on the crane.

An oversize or worn-out sheave acts just like a pulley, not preserving the rope’s shape, Fig. 2. Instead of the load being supported by at least three strands at the bottom of the groove, all the load is concentrated on one. With less support, increased pressure equals more significant sheave wear. There is another terrible consequence of improper groove support — premature wire breaks and internal wire wear. When the unsupported rope is bent over a sheave and loaded, the strands must adjust by sliding along each other. Sliding causes strand to strand nicking and “valley” wire breaks, a severe reduction in the rope’s life, Fig. 3.

The consequence of sheaves not correctly sized to the wire rope installed on them is accelerated wear and broken wires. How important is this to the crane owner depends on how many hours of operation per inspection interval. Some cranes aren’t used much, and owners aren’t too concerned with groove size, just so the grooves are “kind of” smooth — wrong. Current standards allow only one valley break, as shown in Fig.3.

The point is, to achieve a predictable rope life — the sheave must support about 150 degrees of the rope at the bottom of the groove, or the rope will flatten when loaded and be weaken — got that!

Plastic-infused rope was developed to provide better fatigue, abrasion and crushing resistance derived from the cushioning and dampening effect of the plastic. However great the benefits, the plastic becomes at the very least, an inconvenience when trying to inspect the wire rope. Because of the plastic coating, some operators choose to forego inspection and run the ropes to failure. Other operators may just visually inspect the plastic coating. Both practices are wrong and carry equally the potential for disaster.

AbrasionandCrushing.In inspecting plastic-infused ropes, the basic inspection guidelines still apply and should be followed. Abrasion and crushing damage still may occur, so it is imperative to inspect flanges, sheaves, bearings, rollers and fairleads. Look for unusual wear patterns in the plastic—a key indicator that damage to the wire rope is occurring.

WireBreaks.Wire breaks still will occur in a plastic-infused rope, but are sometimes extremely difficult to detect, though occasionally a broken wire will protrude through the plastic. Every effort must be made to determine the overall condition of the rope. The plastic covering the crown (surface) wires is generally applied in a thin coat and tends to wear quickly in areas which pass over sheaves and drums. As the rope runs at a slow speed, inspect the rope in these areas. As the rope and plastic open up, the inspector will be afforded a look at not only the surface area but also the interstrand contact points. If a valley break is detected, immediately pull the rope from service. Also inspect areas where the plastic has peeled, regardless of the location of the “window.” Remove as much plastic from these areas as possible to allow for efficient and effective inspection techniques. Remember, due to the nature of plastic-infused ropes, there is no way to clearly determine the number of valley breaks.

Corrosion.Plastic-infused ropes provide only improved corrosion resistance. Regardless of manufacturers’ claims, a plastic-infused rope can corrode, and rope failure due to corrosion is still possible. Moisture is sometimes trapped in the rope and, as with all machines the lubricant may become ineffective over time. The inspector must visually check for any signs of corrosion damage as evidenced by rope bleeding or rouging. In addition, the diameter must be measured frequently. If there is any damage to the core, it will be detected by a reduction in diameter. Also inspect the lay of the rope. As the plastic is thinner over the crown wires, a thorough inspector may be able to determine a lengthening of lay, also a sign of rope deterioration. Especially when trying to determine lengthening of lay, watch for and inspect areas where the plastic pulls away from the rope. While peeling in and of itself is not an indication of rope deterioration and is a factor of normal wear, peeling in areas where no abrasion exists may signify a problem.

Maintenance Records.Equally important in inspecting plastic-infused ropes is maintaining accurate service records. The service records of previous ropes will provide a guideline as to the expected life of the rope. However, they should not be used alone or only in conjunction with visual inspections due to the number of variables which exist, including installation, spooling and manufacturing practices. Maintenance records must be used in combination with both visual and physical inspection techniques to be truly of value in determining the remaining life of the rope.

Die drawn and swaged ropes fall into the compacted category. Compacting serves several purposes. By flattening the outer wires, metallic area increases allowing for a higher breaking strength as well as improved crushing and abrasion resistance. In addition, the compaction minimizes interstrand nicking and thereby improves fatigue resistance.

In the inspection of compacted rope designs, again it is imperative to follow the basic inspection guidelines and use both visual and actual measuring techniques to determine the remaining life of the rope. In fact, actual measuring techniques are very important when inspecting these ropes. While corrosion is relatively easy to visually determine, diameter reduction may not be due to the compacted rope’s appearance. Therefore, the inspector must regularly measure for diameter reduction and closely examine the rope for lay lengthening. Measurements must be recorded and the rope monitored for sudden variations.

By and large the most difficult retirement criteria to determine in compacted ropes are wire breaks. These breaks may not protrude from the rope due to the compaction and can be overlooked easily. Because of this, the inspector must slowly and carefully examine the rope, especially in those areas passing over drums and sheaves or in areas where problems existed in previous ropes.

A wire break may appear as nothing more than a crack in the wire, and again can be overlooked easily. If the inspector notes a “flaw” in a wire, it should be checked carefully. The inspector should carry some type of magnifying device to determine if a flaw is actually a break. If a break has occurred, thoroughly check the area for additional breaks, both on the crown and in the valleys. Remember, valley breaks in round strand ropes are difficult to determine; compaction only increases the difficulty. The inspector must be slow and methodical in inspecting compacted ropes; a quick check will reveal nothing.

Overall, perhaps the most important inspection technique is recognizing the limits of wire rope. While it’s true that compacted and plastic-infused ropes are more durable, neglect and abuse still will quickly end the rope’s life. There is no substitute for proper installation, handling and inspection techniques in combination with a preventative maintenance program.