nominal strength of wire rope supplier

*These limits have been adopted by the Wire Rope Technical Board (WRTB). In the case of certain special purpose ropes, such as aircraft cables and elevator ropes, each has specific requirements. If a question should arise regarding compliance with oversize tolerances, the rope may be measured under tension of not less than 10% nor more than 20% of the nominal strength.

The calculated breaking strength of a steel wire rope is defined as the metallic cross section of a steel wire rope (the sum of the individual cross sections of all the wires making up the rope) multiplied by the nominal tensile strength of the steel wire rope. The minimum breaking strength of the steel wire rope is the calculated breaking strength of the rope multiplied by the spin factor.

The actual breaking strength of a steel wire rope is the breaking strength of the rope as determined in a pull test. A new steel wire rope must achieve an actual breaking strength equal to or higher than the minimum breaking strength. The breaking strength of a steel wire rope can be increased by increasing the metallic area of the rope (e.g. by using strands with higher fill factors, by compacting the strands or by swaging the rope), by increasing the tensile strengths of the individual wires or by increasing the spin factor of the rope. This can also be achieved by improving the contact conditions between the rope elements by using a plastic infill.

The bending fatigue resistance of steel wire ropes is defined as the number of bending cycles a rope can achieve in a bending fatigue test under defined parameters (e.g. running over sheaves with a defined diameter and a predetermined line pull corresponding to the MBL of the steel wire rope). The bending fatigue resistance of the steel wire rope increases with increasing D/d ratio (= sheave diameter (D): nominal rope diameter (d)) and by reducing the line pull. The bending fatigue resistance of a steel wire rope can be increased by increasing the contact area between the steel wire rope and the sheave and by increasing the contact conditions between the rope elements, by adding a plastic layer between the IWRC and the outer strands. Due to the larger contact area between the ropes and the sheaves and due to the increased flexibility, 8- strand ropes are more resistant to bending fatigue than 6- strand ropes of a similar design.

The flexibility of a steel wire rope typically increases with increasing a number of strands and wires in the rope. The flexibility is also influenced by the lay lengths of the strands, of the rope core and the rope as well as by the gaps between wires and strands. If a rope is not flexible enough, it will have to be forced to bend around a sheave of a given diameter, which will reduce the bending fatigue life of the rope. It will also be forced to bend around a drum of a given diameter. Spooling problems might be a consequence.

When running over a sheave a rope has to be converted from a straight condition into a bent condition at the point when the rope runs onto the sheave and has to be converted again from the bent into the straight condition when it runs off the sheave. Also the bearing has to be turned. In doing so, the friction forces in the rope as well as the friction forces in the bearing have to be overcome. This leads to a change of the rope force. One describes the relationship of the rope force on both sides of the sheave as the efficiency factor and accepts that this numerical value also takes into account the friction losses of the bearing. When measuring the efficiency factor of a rope the loss of the line pull while the rope is running over the sheave is measured. An efficiency factor of 0,98, or alternatively a strength loss of 2%, is generally assumed for wire ropes.

Galvanized wire rope is categorized by number of strands in its construction. We supply most of them but we concentrate on the two major categories of galvanized (and ungalvanized or bright) wire rope. These “classes” are referred to as 6x19 and 6x36. Within each category of galvanized wire rope there are different “constructions” illustrated in the tables below.

Wire rope, galvanized and ungalvanized is used for many kinds of projects and applications. No matter the application galvanized wire rope must be used properly to insure the safest working conditions. All of our galvanized wire rope is manufactured to meet or exceed Federal Specification RRW-410 and is mill certified.

All of these general purpose wire ropes are available in full reels, custom cut sizes or as part of a custom made wire rope sling. Contact us today for more information.

Galvanized wire rope also comes in different strength categories (IPS and EIPS) and different cores (FC or fiber core and IWRC or independent wire rope core). Relevant data for each is listed in the table below.

To assure you of the highest quality product and engineering, American Rigger’s Supply represents WireCo WorldGroup products. Wire rope design, manufacture and use are highly specialized fields and that is why we rely on their unsurpassed technical support.

All wire ropes feature design characteristic tradeoffs. For example, when you increase fatigue resistance by selecting a rope with more wires, the rope will have less abrasion resistance because of its greater number of smaller outside wires.

Wire rope strength is generally measured in U.S. tons (2,000 lbs.). In published material, wire rope strength is shown as “nominal strength. Nominal strength refers to calculated strength figures that have been accepted by the wire rope industry. The nominal strength applies to new, unused rope. A rope should never operate at or near the nominal strength.

Fatigue resistanceFatigue resistance involves metal fatigue of the wires that make up the rope. To have high resistance, wires must be capable of bending repeatedly under stress, for example, a rope passing over a sheave. Increased fatigue resistance is achieved in a rope design by using a larger number of wires. It involves both the basic metallurgy and the diameters of wires.

Crushing resistanceCrushing is the effect of external pressure on a rope, which damages it by distorting the cross-section shape of the rope, its strands or core - or all three. Crushing resistance therefore is a rope’s ability to withstand or resist external forces and is term generally used to express comparison between ropes.

Resistance to metal loss and deformationMetal loss refers to the actual wearing away of metal from the outer wires of a rope, and metal deformation is the changing of the shape of the outer wires of the rope. In general, resistance to metal loss by abrasion (usually called “abrasion resistance”) refers to a rope’s ability to withstand metal being worn away along its exterior. The most common form of metal deformation is generally called “peening”. Outside wires of a peened rope appear to have been hammered along their exposed surface. Peening usually occurs on drums, caused by rope-to-rope contact during spooling of the rope on the drum. It can also occur on sheaves.

The word “stability” is most often used to describe handling and working characteristics of a rope. It is not a precise term since the idea is expressed to some degree as a matter of opinion. For example, a rope is called stable when it spools smoothly on and off a drum or doesn’t tangle when a multi-part reeving system is relaxed.

Some rope constructions are by nature more bendable than others. Small ropes are more bendable than large ones. As a general rule, ropes of many wires are more bendable than ropes made with fewer, larger wires.

Reserve strengthReserve strength of a rope is the percentage of its catalog strength which is represented by its inner wires. This recognizes that outer wires should be the first to be damaged or worn away. Usually, the more wires there are in each strand of rope, the greater will be its reserve strength. Reserve strength is especially important in selecting a rope for use where consequences of rope failure are great

Wire ropes are essential for safety purposes on construction sites and industrial workplaces. They are used to secure and transport extremely heavy pieces of equipment – so they must be strong enough to withstand substantial loads. This is why the wire rope safety factor is crucial.

You may have heard that it is always recommended to use wire ropes or slings with a higher breaking strength than the actual load. For instance, say that you need to move 50,000 lbs. with an overhead crane. You should generally use equipment with a working load limit that is rated for weight at least five times higher – or 250,000 lbs. in this case.

This recommendation is all thanks to the wire rope safety factor. This calculation is designed to help you determine important numbers, such as the minimum breaking strength and the working load limit of a wire rope.

The safety factor is a measurement of how strong of a force a wire rope can withstand before it breaks. It is commonly stated as a ratio, such as 5:1. This means that the wire rope can hold five times their Safe Work Load (SWL) before it will break.

So, if a 5:1 wire rope’s SWL is 10,000 lbs., the safety factor is 50,000 lbs. However, you would never want to place a load near 50,000 lbs. for wire rope safety reasons.

The safety factor rating of a wire rope is the calculation of the Minimum Break Strength (MBS) or the Minimum Breaking Load (MBL) compared to the highest absolute maximum load limit. It is crucial to use a wire rope with a high ratio to account for factors that could influence the weight of the load.

The Safe Working Load (SWL) is a measurement that is required by law to be clearly marked on all lifting devices – including hoists, lifting machines, and tackles. However, this is not visibly listed on wire ropes, so it is important to understand what this term means and how to calculate it.

The safe working load will change depending on the diameter of the wire rope and its weight per foot. Of course, the smaller the wire rope is, the lower its SWL will be. The SWL also changes depending on the safety factor ratio.

The margin of safety for wire ropes accounts for any unexpected extra loads to ensure the utmost safety for everyone involved. Every year there aredue to overhead crane accidents. Many of these deaths occur when a heavy load is dropped because the weight load limit was not properly calculated and the wire rope broke or slipped.

The margin of safety is a hazard control calculation that essentially accounts for worst-case scenarios. For instance, what if a strong gust of wind were to blow while a crane was lifting a load? Or what if the brakes slipped and the load dropped several feet unexpectedly? This is certainly a wire rope safety factor that must be considered.

Themargin of safety(also referred to as the factor of safety) measures the ultimate load or stress divided by theallowablestress. This helps to account for the applied tensile forces and stress thatcouldbe applied to the rope, causing it to inch closer to the breaking strength limit.

A proof test must be conducted on a wire rope or any other piece of rigging equipment before it is used for the first time.that a sample of a wire rope must be tested to ensure that it can safely hold one-fifth of the breaking load limit. The proof test ensures that the wire rope is not defective and can withstand the minimum weight load limit.

First, the wire rope and other lifting accessories (such as hooks or slings) are set up as needed for the particular task. Then weight or force is slowly added until it reaches the maximum allowable working load limit.

Some wire rope distributors will conduct proof loading tests before you purchase them. Be sure to investigate the criteria of these tests before purchasing, as some testing factors may need to be changed depending on your requirements.

When purchasing wire ropes for overhead lifting or other heavy-duty applications, understanding the safety dynamics and limits is critical. These terms can get confusing, but all of thesefactors serve an important purpose.

Our company has served as a wire rope distributor and industrial hardware supplier for many years. We know all there is to know about safety factors. We will help you find the exact wire ropes that will meet your requirements, no matter what project you have in mind.

Wire rope is a complex mechanical device that has many moving parts all working in tandem to help support and move an object or load. In the lifting and rigging industries, wire rope is attached to a crane or hoist and fitted with swivels, shackles or hooks to attach to a load and move it in a controlled matter. It can also be used to lift and lower elevators, or as a means of support for suspension bridges or towers.

Wire rope is a preferred lifting device for many reasons. Its unique design consists of multiple steel wires that form individual strands laid in a helical pattern around a core. This structure provides strength, flexibility, and the ability to handle bending stresses. Different configurations of the material, wire, and strand structure will provide different benefits for the specific lifting application, including:Strength

However, selecting the proper wire rope for your lifting application requires some careful thought. Our goal is to help you understand the components of a wire rope, the construction of wire rope, and the different types of wire rope and what they might be used for. This will allow you to select the best performing and longest-lasting wire rope for the job at hand.

From childhood, many of us have been conditioned to think of a machine as some device with gears, shafts, belts, cams, and assorted whirring parts. Yet, by the rules of physics, an ordinary pry bar is a simple machine, even though it has only one part.

A wire rope is, in reality, a very complicated machine. A typical 6 x 25 rope has 150 wires in its outer strands, all of which move independently and together in a very complicated pattern around the core as the rope bends. Clearances between wires and strands are balanced when a rope is designed so that proper bearing clearances will exist to permit internal movement and adjustment of wires and strands when the rope has to bend. These clearances will vary as bending occurs, but are of the same range as the clearances found in automobile engine bearings.

Understanding and accepting the “machine idea” gives a rope user a greater respect for rope, and enables them to obtain better performance and longer useful life from rope applications. Anyone who uses a rope can use it more efficiently and effectively when they fully understand the machine concept.

Wires are the smallest component of wire rope and they make up the individual strands in the rope. Wires can be made from a variety of metal materials including steel, iron, stainless steel, monel, and bronze. The wires can be manufactured in a variety of grades that relate to the strength, resistance to wear, fatigue resistance, corrosion resistance, and curve of the wire rope.

Strands of wire rope consist of two or more wires arranged and twisted in a specific arrangement. The individual strands are then laid in a helical pattern around the core of the rope.

The core of a wire rope runs through the center of the rope and supports the strands and helps to maintain their relative position under loading and bending stresses. Cores can be made from a number of different materials including natural or synthetic fibers and steel.

Lubrication is applied during the manufacturing process and penetrates all the way to the core. Wire rope lubrication has two primary benefits:Reduces friction as the individual wires and strands move over each other

The number of layers of wires, the number of wires per layer, and the size of the wires per layer all affect the strand pattern type. Wire rope can be constructed using one of the following patterns, or can be constructed using two or more of the patterns below.Single Layer – The most common example is a 7 wire strand with a single-wire center and six wires of the same diameter around it.

Filler Wire – Two layers of uniform-size wire around a center with the inner layer having half the number of wires as the outer layer. Small filler wires, equal to the number in the inner layer, are laid in valleys of the inner wire.

Seale – Two layers of wires around a center with the same number of wires in each layer. All wires in each layer are the same diameter. The large outer wires rest in the valleys between the smaller inner wires.

Warrington – Two layers of wires around a center with one diameter of wire in the inner layer, and two diameters of wire alternating large and small in the outer later. The larger outer-layer wires rest in the valleys, and the smaller ones on the crowns of the inner layer.

On a preformed wire rope, the strands and wires are formed during the manufacturing process to the helical shape that they will take in a finished wire rope.

Preformed rope can be advantageous in certain applications where it needs to spool more uniformly on a drum, needs greater flexibility, or requires more fatigue-resistance when bending.

Direction and type of lay refer to the way the wires are laid to form a strand (either right or left) and how the strands are laid around the core (regular lay, lang lay, or alternate lay).Regular Lay – The wires line up with the axis of the rope. The direction of the wire lay in the strand is opposite to the direction of the strand lay. Regular lay ropes are more resistant to crushing forces, are more naturally rotation-resistant, and also spool better in a drum than lang lay ropes.

Lang Lay– The wires form an angle with the axis of the rope. The wire lay and strand lay around the core in the same direction. Lang Lay ropes have a greater fatigue-resistance and are more resistant to abrasion.

A fiber core can be made of natural or synthetic polypropylene fibers. Fiber cores offer greater elasticity than a steel core but are more susceptible to crushing and not recommended for high heat environments.

A steel core can be an independent wire rope or an individual strand. Steel cores are best suited for applications where a fiber core may not provide adequate support, or in an operating environment where temperatures could exceed 180° F.

The classifications of wire rope provide the total number of strands, as well as a nominal or exact number of wires in each strand. These are general classifications and may or may not reflect the actual construction of the strands. However, all wire ropes of the same size and wire grade in each classification will have the SAME strength and weight ratings and usually the same pricing.

Besides the general classifications of wire rope, there are other types of wire rope that are special construction and designed for special lifting applications.

Some types of wire rope, especially lang lay wire rope, are more susceptible to rotation when under load. Rotation resistant wire rope is designed to resist twisting, spinning, or rotating and can be used in a single line or multi-part system.

Special care must be taken when handling, unreeling, and installing rotation resistant wire rope. Improper handling or spooling can introduce twist into the rope which can cause uncontrolled rotation.

Compacted strand wire rope is manufactured using strands that have been compacted, reducing the outer diameter of the entire strand, by means of passing through a die or rollers. This process occurs prior to closing of the rope.

This process flattens the surface of the outer wires in the strand, but also increases the density of the strand. This results in a smoother outer surface and increases the strength compared to comparable round wire rope (comparing same diameter and classification), while also helping to extend the surface life due to increased wear resistance.

A swaged wire rope differs from a compacted strand wire rope, in that a swaged wire rope’s diameter is compacted, or reduced, by a rotary swager machine after the wire rope has been closed. A swaged wire rope can be manufactured using round or compacted strands.

The advantages of a swaged wire rope are that they are more resistant to wear, have better crushing resistance, and high strength compared to a round strand wire rope of equal diameter and classification. However, a swaged wire rope may have less bending fatigue resistance.

A plastic coating can be applied to the exterior surface of a wire rope to provide protection against abrasion, wear, and other environmental factors that may cause corrosion. However, because you can’t see the individual strands and wires underneath the plastic coating, they can be difficult to inspect.

Plastic filled wire ropes are impregnated with a matrix of plastic where the internal spaces between the strands and wires are filled. Plastic filling helps to improve bending fatigue by reducing the wear internally and externally. Plastic filled wire ropes are used for demanding lifting applications.

This type of wire rope uses an Independent Wire Rope Core (IWRC) that is either filled with plastic or coated in plastic to reduce internal wear and increase bending fatigue life.

Remember, wire rope is a complex piece of mechanical machinery. There are a number of different specifications and properties that can affect the performance and service life of wire rope. Consider the following when specifying the best type of wire rope for your lifting application:Strength

When you select a piece of rope that is resistant to one property, you will most likely have a trade-off that affects another property. For example, a fiber core rope will be more flexible, but may have less crushing resistance. A rope with larger diameter wires will be more abrasion resistant, but will offer less fatigue resistance.

At Mazzella Companies, we offer all different kinds of wire rope from all of the leading manufacturers. We sell the highest-quality domestic and non-domestic rigging products because product quality and operating safety go hand-in-hand. We have one of the largest and most complete inventories of both domestic and non-domestic rigging and lifting products to suit your lifting needs.

If you’re looking for a standard or custom specified wire rope for your lifting project, contact a Lifting Specialist at a Mazzella Companies location near you.

We stock well over 2,000,000 feet of wire rope in our various locations … ready for immediate delivery! We provide wire rope assemblies, and manufacture bridge cables, crane cables, steel mill cables, and thousands of OEM assemblies.

In addition, there is the special class (designated class, Class C) category: 195 kgf/mm2 (1910 N/mm2) grade or higher. These are products that were developed jointly by a manufacturer of construction machinery or elevators and a rope manufacturer. In general the ordinary sale of these products is prohibited by an agreement between the manufacturers at the time of development. Many TADANO products use special class (designated class, Class C) wire ropes.

The standard Wire Rope for the Steel fabricating industry is 6 x 19 EIP/IWRC. In short this means the wire rope is made up of 6 independent wires. Each of these 6 wires has 19 individual strands.

The illustration below shows the configuration of standard Wire Rope in Classification 6 x 19 IWRC / EIP. IWRC refers to the inner core strand, which is independent of the 6 outer strands.