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Nantong Fasten Metals Products Co., LTD is located in the coastal open city—Nantong which is in the lower area of the Yangtze River. We are a professional corporation which produces a variety of standards and types of galvanized steel wire rope, ungalvanized steel wire rope, steel-wire, stranded wire and spring steel wire. Our products mainly exported to Southeast Asia, the United States, Europe, the Middle East, Africa and other countries.

Wire rope is technically defined as multi-wire strands laid geometrically around a core while also used more generally as a term to classify multiple product families including aircraft cable, coated aircraft cable, general purpose wire rope, strand, rotation resistant wire rope, compacted/swaged wire rope, and cable laid wire rope.

Aircraft cable does not fit the definition of wire rope in the strictest sense as it does not have an independent core, but rather a strand core, in which the center is one of the strands that is laid with the outside strand layers. Aircraft cable is available in diameters 3/8" or less with breaking strengths similar to that of equal diameter independent wire rope core (IWRC) and is available in stainless steel and galvanized steel.

Wire rope can be galvanized via three processes. Listed from least corrosion-resistant to the most corrosion-resistant, they are electro-galvanizing, hot-dip galvanizing, and drawn-galvanizing. In addition to being the most corrosion-resistant types of galvanized wire rope, drawn-galvanized has another added benefit which is a breaking strength that is the same as bright wire rope does. Electro-galvanized and hot-dip galvanized wire rope have breaking strengths that are approximately 10% lower.

Wire rope is specified by the number of strands in the rope, the number of wires in each strand, and a description of the core’s material of construction. For example, the notation “6x7 FC” means that the rope has six strands with seven wires in each strand and a fiber core. Commonly used core designations include FC (fiber core), independent wire rope core (IWRC), wire strand core (WSC), and poly core (PC).

There are two elements to wire rope lubrication, the core, and outer strands. IWRC wire rope always has a lubricated core (unless specially ordered as otherwise). Bright wire rope always has lubricated outer strands.  Galvanized wire rope can be manufactured in either dry finish or lubricated with respect to the outer strands.  Typically stainless steel wire rope is manufactured with a lubricated IWRC and dry finish outer strands.

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Industrial wire ropes are designed for extreme resilience and strength. They can withstand thousands of pounds of pressure and be used on all types of applications. However, issues with the wire rope installation process can significantly decrease its longevity and even its capacity and durability.

When wire ropes are not used properly, it can create an unsafe environment. The rope can snap, even if the load it’s supporting is below its maximum load limit. In anoted by the IMCA (International Marine Contractors Association), a wire rope sling rope broke due to improper installation. A crew member was seriously injured after the sling disconnected and hit the worker.

Many of these common accidents are easily avoidable through correct wire rope installation. Here are five of the most common mistakes made and how to prevent them on your worksite.

Determining the diameter of the wire rope is an essential step of the installation process. Installers are required to double-check that the correct diameter rope is being used, as this impacts the rope’s breaking strength and load limit.

Wire ropes are measured with a parallel-jawed caliper (also called a machinist’s caliper). This is placed over the wire rope to measure the diameter – but if the rope is inserted at the wrong angle, you will get an inaccurate result.

The strands of a wire rope must be flush against the measuring portion of the caliper. If a raised strand is at the top, the measurement will have a smaller dimension, which could affect breaking strength calculations.

Wire ropes are reeled onto these spools for easy handling and shipments, as it prevents the rope from getting tangled or crushed. But unreeling the wire rope incorrectly can cause severe damage, such as snagged wires, twists, kinks, or unraveled strands.

A common mistake that is often made is to unreel the wire rope by laying the spool vertically on its axis. The wire rope has to be yanked off of the spool, which increases the likelihood of it getting kinked or twisted. The wire rope should also not touch the ground as it is unreeled, as this could damage the wires as well.

Instead, the reeled wire rope should be placed on a shaft that allows the spool to turn 360°. It also should require two people, one to slowly pull the rope off of the spool in a straight line and another to regulate the speed by controlling the turn rate.

Occasionally ais added during wire rope installation to create a load-bearing eye or to connect two cables together. These small but mighty pieces only diminish a wire rope’s strength by around 10%, if they are added correctly.

These little issues can cause the wire rope to slip out of the clip. It is very important to follow the directions and use the right number of clips with the correct spacing in-between, depending on the rope’s diameter and approximate load weight.

Sometimes a damaged wire rope can be repaired through a method called seizing. First, the rope is cut at a straight angle, then a wire is tightly wound around this end to prevent the strands from unraveling.

Two methods can be used to securely seize a wire rope. First, it can be placed at a right angle between the starting and ending point of the seizing. The wire is then wrapped around this angled piece to hold it in place, and the ends are twisted together to secure it. Another option is to wrap the seizing wire around and twist the two end pieces together, creating a tourniquet type of attachment.

The type of end preparations recommended depends on several factors. This includes the diameter of the rope and the number of wires and strands. In some cases, double seizing and fuse welding is required for additional securement. Failing to follow these instructions could result in the core or strands of the wire rope to slip and unravel.

Although wire ropes are usually damaged due to improper use, they can get ruined during storage as well. Failing to follow through with routine maintenance and storage recommendations could cause the wire rope to rust, unravel, or kink. Further, keeping your wire rope on the ground, in wet areas, or directly in hot sunlight can cause it to break down faster.

the right way can improve their long-term performance and use. This includes following all instructions during wire rope installation, as well as storage and upkeep. Wire ropes should be cleaned before going into storage and may need lubricant from time to time to protect the wires from drying out.

Wire ropes are intended to be a strong, reliable piece of industrial hardware. There is no reason to compromise its durability due to simple installation mistakes. By avoiding these common mishaps, you can ensure a far safer work environment and also extend the use of your wire ropes.

Another tip is to start by purchasing top-quality hardware from a trusted wire rope supplier. Elite Sales is proud to carry a vast selection of wire rope sizes, styles, and finishes that are made to fit many applications.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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This checklist covers regulations issued by the U.S. Department of Labor, Occupational Safety and Health Administration (OSHA) under the general industry standards 29 CFR 1910.184 and the construction standards 1926.251. It applies to slings used with other equipment to move material by lifting or hoisting. The regulations cited apply only to private employers and their employees, unless adopted by a State agency and applied to other groups such as public employees. A yes answer to a question indicates that this portion of the inspection complies with the OSHA or U.S. Environmental Protection Agency (EPA) standard, or with a nonregulatory recommendation. Definitions of terms in bold type are provided at the end of the checklist.

Do alloy steel chain slings have permanently affixed durable identification stating the size, grade, rated capacity, and reach? [29 CFR 1910.184(e)(1) and 1926.251(b)(1)]

Do hooks, rings, oblong links, pear-shaped links, welded or mechanical coupling links, or other attachments have rated capacities at least equal to that of the alloy steel chain with which they are used? [29 CFR 1910.184(e)(2)(i) and 1926.251(b)(2)]

Have new, repaired, or reconditioned alloy steel chain slings been proof tested by the manufacturer, and is a certificate of proof tested available? [29 CFR 1910.184(e)(4) and (e)(7)(i)]

Are maximum working loads reduced in accordance with the manufacturer’s recommendations if the chain or sling is exposed to temperatures above 600ºF? [29 CFR 1910(e)(6)]

Are slings removed from service if their hooks are cracked or are opened more than 15 percent of the normal throat opening (measured at the narrowest point)? [29 CFR 1910.184(e)(9)(ii)]

Are fiber core wire rope slings permanently removed from service if they are exposed to temperatures above 200ºF? [29 CFR 1910.184(f)(3) and 1926.251(c)(14)]

Are recommendations of the sling manufacturer followed when non fiber core wire rope slings are used at temperatures above 400ºF or below -60ºF? [29 CFR 1910.184(f)(3) and 1926.251(c)(14)]

Are all welded end attachments proof tested by the manufacturer or equivalent entity at twice their rated capacity before their initial use, and is a certificate of the proof test available? [29 CFR 1910.184(f)(4)(ii) and 1926.251(c)(15)(ii)]

Hooks that have been opened more than 15 percent of the normal throat opening (measured at the narrowest point), or hooks twisted more than 10 degrees from the plane of the unbent hook

Does each metal mesh sling have a permanently affixed durable marking that states the rated capacity for vertical basket hitch and choker hitch loading? [29 CFR 1910.184(g)(1)]

Are all new and repaired metal mesh slings and handles proof tested by the manufacturer or other competent person at a minimum of one and a half times their rated capacity? Is a certificate of proof test available? [29 CFR 1910.184(g)(5)]

Once repaired, are metal mesh slings marked or tagged, or are written records maintained to indicate the date and nature of the repair and the person or organization that performed the repairs? [29 CFR 1910.184(g)(8)(ii)]

Cleat: a ladder crosspiece of rectangular cross section placed on edge. A person steps on a cleat while ascending or descending a ladder. [29 CFR 1926.1050(b)]

Extension trestle ladder: a self-supporting portable ladder, adjustable in length, consisting of a trestle ladder base and a vertically adjustable extension section, with a suitable means for locking the ladders together.

Step stool (ladder type): a self-supporting, foldable, portable ladder, nonadjustable in length, 32 inches or less in overall size, with flat steps and without a pail shelf, designed to be climbed on the ladder top cap as well as all steps. The side rails may continue above the top cap.

Wire rope and cable are each considered a “machine”. The configuration and method of manufacture combined with the proper selection of material when designed for a specific purpose enables a wire rope or cable to transmit forces, motion and energy in some predetermined manner and to some desired end.

Two or more wires concentrically laid around a center wire is called a strand. It may consist of one or more layers. Typically, the number of wires in a strand is 7, 19 or 37. A group of strands laid around a core would be called a cable or wire rope. In terms of product designation, 7 strands with 19 wires in each strand would be a 7×19 cable: 7 strands with 7 wires in each strand would be a 7×7 cable.

Materials Different applications for wire rope present varying demands for strength, abrasion and corrosion resistance. In order to meet these requirements, wire rope is produced in a number of different materials.

Stainless Steel This is used where corrosion is a prime factor and the cost increase warrants its use. The 18% chromium, 8% nickel alloy known as type 302 is the most common grade accepted due to both corrosion resistance and high strength. Other types frequently used in wire rope are 304, 305, 316 and 321, each having its specific advantage over the other. Type 305 is used where non-magnetic properties are required, however, there is a slight loss of strength.

Galvanized Carbon Steel This is used where strength is a prime factor and corrosion resistance is not great enough to require the use of stainless steel. The lower cost is usually a consideration in the selection of galvanized carbon steel. Wires used in these wire ropes are individually coated with a layer of zinc which offers a good measure of protection from corrosive elements.

Cable Construction The greater the number of wires in a strand or cable of a given diameter, the more flexibility it has. A 1×7 or a 1×19 strand, having 7 and 19 wires respectively, is used principally as a fixed member, as a straight linkage, or where flexing is minimal.

Cables designed with 3×7, 7×7 and 7×19 construction provide for increasing degrees of flexibility but decreased abrasion resistance. These designs would be incorporated where continuous flexing is a requirement.

Selecting Wire Rope When selecting a wire rope to give the best service, there are four requirements which should be given consideration. A proper choice is made by correctly estimating the relative importance of these requirements and selecting a rope which has the qualities best suited to withstand the effects of continued use. The rope should possess:Strength sufficient to take care of the maximum load that may be applied, with a proper safety factor.

Strength Wire rope in service is subjected to several kinds of stresses. The stresses most frequently encountered are direct tension, stress due to acceleration, stress due to sudden or shock loads, stress due to bending, and stress resulting from several forces acting at one time. For the most part, these stresses can be converted into terms of simple tension, and a rope of approximately the correct strength can be chosen. As the strength of a wire rope is determined by its, size, grade and construction, these three factors should be considered.

Safety Factors The safety factor is the ratio of the strength of the rope to the working load. A wire rope with a strength of 10,000 pounds and a total working load of 2,000 pounds would be operating with a safety factor of five.

It is not possible to set safety factors for the various types of wire rope using equipment, as this factor can vary with conditions on individual units of equipment.

The proper safety factor depends not only on the loads applied, but also on the speed of operation, shock load applied, the type of fittings used for securing the rope ends, the acceleration and deceleration, the length of rope, the number, size and location of sheaves and drums, the factors causing abrasion and corrosion and the facilities for inspection.

Fatigue Fatigue failure of the wires in a wire rope is the result of the propagation of small cracks under repeated applications of bending loads. It occurs when ropes operate over comparatively small sheaves or drums. The repeated bending of the individual wires, as the rope bends when passing over the sheaves or drums, and the straightening of the individual wires, as the rope leaves the sheaves or drums, causing fatigue. The effect of fatigue on wires is illustrated by bending a wire repeatedly back and forth until it breaks.

The best means of preventing early fatigue of wire ropes is to use sheaves and drums of adequate size. To increase the resistance to fatigue, a rope of more flexible construction should be used, as increased flexibility is secured through the use of smaller wires.

Abrasive Wear The ability of a wire rope to withstand abrasion is determined by the size, the carbon and manganese content, the heat treatment of the outer wires and the construction of the rope. The larger outer wires of the less flexible constructions are better able to withstand abrasion than the finer outer wires of the more flexible ropes. The higher carbon and manganese content and the heat treatment used in producing wire for the stronger ropes, make the higher grade ropes better able to withstand abrasive wear than the lower grade ropes.

Effects of Bending All wire ropes, except stationary ropes used as guys or supports, are subjected to bending around sheaves or drums. The service obtained from wire ropes is, to a large extent, dependent upon the proper choice and location of the sheaves and drums about which it operates.

A wire rope may be considered a machine in which the individual elements (wires and strands) slide upon each other when the rope is bent. Therefore, as a prerequisite to the satisfactory operation of wire rope over sheaves and drums, the rope must be properly lubricated.

Loss of strength due to bending is caused by the inability of the individual strands and wires to adjust themselves to their changed position when the rope is bent. Tests made by the National Institute of Standards and Technology show that the rope strength decreases in a marked degree as the sheave diameter grows smaller with respect to the diameter of the rope. The loss of strength due to bending wire ropes over the sheaves found in common use will not exceed 6% and will usually be about 4%.

The bending of a wire rope is accompanied by readjustment in the positions of the strands and wires and results in actual bending of the wires. Repetitive flexing of the wires develops bending loads which, even though well within the elastic limit of the wires, set up points of stress concentration.

The fatigue effect of bending appears in the form of small cracks in the wires at these over-stressed foci. These cracks propagate under repeated stress cycles, until the remaining sound metal is inadequate to withstand the bending load. This results in broken wires showing no apparent contraction of cross section.

Experience has established the fact that from the service view-point, a very definite relationship exists between the size of the individual outer wires of a wire rope and the size of the sheave or drum about which it operates. Sheaves and drums smaller than 200 times the diameter of the outer wires will cause permanent set in a heavily loaded rope. Good practice requires the use of sheaves and drums with diameters 800 times the diameter of the outer wires in the rope for heavily loaded fast-moving ropes.

It is impossible to give a definite minimum size of sheave or drum about which a wire rope will operate with satisfactory results, because of the other factors affecting the useful life of the rope. If the loads are light or the speed slow, smaller sheaves and drums can be used without causing early fatigue of the wires than if the loads are heavy or the speed is fast. Reverse bends, where a rope is bent in one direction and then in the opposite direction, cause excessive fatigue and should be avoided whenever possible. When a reverse bend is necessary larger sheaves are required than would be the case if the rope were bent in one direction only.

Stretch of Wire Rope The stretch of a wire rope under load is the result of two components: the structural stretch and the elastic stretch. Structural stretch of wire rope is caused by the lengthening of the rope lay, compression of the core and adjustment of the wires and strands to the load placed upon the wire rope. The elastic stretch is caused by elongation of the wires.

The structural stretch varies with the size of core, the lengths of lays and the construction of the rope. This stretch also varies with the loads imposed and the amount of bending to which the rope is subjected. For estimating this stretch the value of one-half percent, or .005 times the length of the rope under load, gives an approximate figure. If loads are light, one-quarter percent or .0025 times the rope length may be used. With heavy loads, this stretch may approach one percent, or .01 times the rope length.

The elastic stretch of a wire rope is directly proportional to the load and the length of rope under load, and inversely proportional to the metallic area and modulus of elasticity. This applies only to loads that do not exceed the elastic limit of a wire rope. The elastic limit of stainless steel wire rope is approximately 60% of its breaking strength and for galvanized ropes it is approximately 50%.

Preformed Wire Ropes Preformed ropes differ from the standard, or non-preformed ropes, in that the individual wires in the strands and the strands in the rope are preformed, or pre-shaped to their proper shape before they are assembled in the finished rope.

This, in turn, results in preformed wire ropes having the following characteristics:They can be cut without the seizings necessary to retain the rope structure of non-preformed ropes.

They are substantially free from liveliness and twisting tendencies. This makes installation and handling easier, and lessens the likelihood of damage to the rope from kinking or fouling. Preforming permits the more general use of Lang lay and wire core constructions.

Removal of internal stresses increase resistance to fatigue from bending. This results in increased service where ability to withstand bending is the important requirement. It also permits the use of ropes with larger outer wires, when increased wear resistance is desired.

Outer wires will wear thinner before breaking, and broken wire ends will not protrude from the rope to injure worker’s hands, to nick and distort adjacent wires, or to wear sheaves and drums. Because of the fact that broken wire ends do not porcupine, they are not as noticeable as they are in non-preformed ropes. This necessitates the use of greater care when inspecting worn preformed ropes, to determine their true condition.