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The term “rope grade” is regularly used in international standards to group wire ropes. While it may seem logical to assume that the higher the rope grade, the higher the tensile of the constituent wires and therefore the higher the corresponding breaking strength of the rope, this is not always true. Some wire rope manufacturers may offer different designs of rope with the same nominal diameter, construction and breaking strength for a rope, but specify different rope grades. This practice can confuse rope users, both when they are specifying/ describing wire ropes and when receiving wire ropes certified with different rope grades. This bulletin aims to provide background information to support the user when referring to rope grade as used in some selected international standards describing stranded wire ropesm +2% to +5% (28.56 mm to 29.12 mm).
Many stranded steel wire ropes are manufactured to standards compliant with the EN 12385 series. They include those used for general lifting applications within part 4 of this standard, EN 12385-4 “Steel wire ropes - Safety - Part 4: Stranded ropes for general lifting applications”. In this standard there are breaking strength tables for the different rope constructions and nominal diameters. The Minimum Breaking Force (MBF) for each rope diameter within these tables are specified in relationship to a rope grade, typically 1770, 1960, 2160. However, rope manufacturers also produce rope constructions offering increased breaking strength and performance which are used extensively, but their breaking strengths are not specifically given within these tables. The rope breaking strengths for those rope constructions, often referred to as high performance ropes, may be specified in the individual rope manufacturers catalogue. In these standards, rope grade (Rr) and wire tensile grade (R) are described:
Rope grade (Rr ): is a level of requirement of breaking force which is designated by a number (e.g. 1770, 1960, 2160) Extract: EN 12385-2 clause 3.10.11
Note: It does not imply that the actual tensile strength grades of the wires in the rope are necessarily of that grade.
Wire tensile grade (R): a level of requirement of tensile strength of a wire and its corresponding range. It is designated by the value according to the lower limit of tensile strength and is used when specifying wire and when determining the calculated minimum breaking force or calculated minimum aggregate breaking force, expressed in N/mm2. Extract: EN 12385-2 clause 3.1.10.
For those ropes where a rope grade is applicable, the tensile strength grades of the wires shall be subject to the limits given in the below. Extract: EN 12385-4 clause 5.2.1
Wire tensile strength grades excluding centre and filler
wires for given rope grades
Rope Grades
Wire tensile strength
grades (N/mm²)
Min
Max
1770
1570
1960
1960
1770
2160
2160
1960
2160
Wire:
wires before ropemaking, shall conform to EN 10264-2.Permitted tensile strength variations
Nominal dimension wire diameter:
d (mm)
Permitted plus tolerance over
the numerical value of tensile
strength grade MPa
(N/mm²)
0.2 ≤ d < 0.5
3900.5 ≤ d < 1.0
3501.0 ≤ d < 1.5
320 1.5≤ d < 2.0
290 2.0≤ d < 3.5
2603.5
≤ d < 8.0
250Range of wire tensile strength guides
Rope Grade
Wire Tensile Strength Guide
IPS (Improved Plow Steel)
Level 2 or 1570 to Level 4 or 1960EIPS (Extra Improved Plow Steel)
Level 3 or 1770 to Level 5 or 2160
EEIPS (Extra Extra Improved Plow Steel)
Level 4 or 1960 to Level 6 or 2160
1170 1570 or Level 2 to 1960 or Level 4 19601770 or Level 3 to 2160 or Level 5
2160 1960 or Level 4 to 2160 or Level 6wires before ropemaking, shall conform to EN 10264-2.Wire tensile strength grade - permitted variations: the tensile strength grades are specified in EN 10264 parts 2, 3 and 4. These values are the lower limits for tensile strength of each wire grade. The permitted upper limit for non-alloy steel wire for ropes for each grade shall not exceed the lower limits by a value greater than the values given in the table below. Extract: EN 10624-1 clause 5.2.1.Compliance with the rope grade requirements shall be through a visual verification of the inspection documents supplied with the wire in relation to the minimum breaking force value of the rope. Extract: EN 12385-4 clause 6.5.26 mm, Dyform 6xK36WS-IWRC, 1960 grade, galvanized(B), RHOL(sZ), MBF 560 kN rope grade 1960, which allows for wire tensile grades 1770 to 2160. Outer wire diameter 1.47 mm, which has a permitted tolerance of 320 N/mm2. Individual outer wires within this rope could have an actual tensile of between 1770 N/mm2 and 2450 N/mm2Therefore, this rope could be described and certified as a 1770, 1960 or 2160 grade provided the minimum breaking force value was achievedThe standard specification A1023 - Stranded Carbon Steel Wire Ropes for General Purposes is the most widely used rope standard in North America and is distributed by ASTM through governance of American National Standards Institute (ANSI). A1023 also specifies the rope grades in a similar way to the EN standard. For those ropes where a rope grade is applicable, the tensile strength grade of the wires shall be subjected to the limits in the table below. Extract: API 9A table 1Requirements for wire tensile strength are determined by either the wire level, as specified in ASTM Specification A1007, or by the tensile strength grade, as specified in ISO 2232. Extract: A1023, Section 3.13.2
A standard in frequent use in the oil and gas industries, is the American Petroleum Institute (API) specification 9A “Specification for steel wire ropes”, adopted the rationale
for rope grade specification from A1023. For those ropes where a rope grade is applicable, the tensile strength grade of the wires shall be subjected to the limits in the table below. Extract: API 9A table 1
Range of wire tensile strength guides
Rope Grade
Wire Tensile Strength Guide
IPS (Improved Plow Steel) Level 2 or 1570 to Level 4 or 1960 EIPS (Extra Improved Plow Steel) Level 3 or 1770 to Level 5 or 2160 EEIPS (Extra Extra Improved Plow Steel) Level 4 or 1960 to Level 6 or 2160 1170 1570 or Level 2 to 1960 or Level 4 1960 1770 or Level 3 to 2160 or Level 5 2160 1960 or Level 4 to 2160 or Level 6Permitted tensile strength variations
Nominal dimension wire diameter:
d (mm)
Permitted plus tolerance over
the numerical value of tensile
strength grade MPa(N/mm²)
The permitted variations in tensile strengths of non-alloyed steel wires shall not exceed the nominal values by an amount greater than given in the table below. Extract: API 9A table A. 1Note; In the case of alloy steel wires, the maximum values shall be no greater than the minimum value plus 15%For wire tensile strength grades, Levels 2, 3, 4 and 5 the maximum valued of tensile strength shall be no more than 207 N/mm2 (30,000 lbs/in2) greater than the minimum values.Further guidance is available at contact@bridon-bekaert.com Reference: TB.002 Ed.1 Sept 2021
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:
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.
There are four basic components that make up the design of a finished wire rope:
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.
The wires themselves can be coated but are most commonly available in a “bright” or uncoated finish.
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.
Strands made of larger diameter wires are more resistant to abrasion, while strands made of smaller diameter wires are more flexible.
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:
The following terms help to define the construction and properties of wire rope:
The total number of feet (cut to size) when wrapped around the spool and delivered.
This is the specified nominal diameter of the wire rope and can be specified in inches or millimeters.
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.
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).
Zinc coated (galvanized), zinc/aluminum alloy coated (mischmetal), stainless steel, or unfinished steel (“bright”).
The strength of wire rope is broken down into different grades, including:
The plow steel strength curve forms the basis for calculating the strength of most steel rope wires.
Wire rope cores are designated as:
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.
Based on what we’ve learned above, this wire rope description would provide the user with the following information:
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.
The table below shows some of the most common wire rope configurations arranged in specific classifications.
ClassificationOuter StrandsWires / Strand6 x763–146 x 19615–266 x 36627–496 x 61650–746 x 91675–1097 x 19715–267 x 36727–498 x 783–148 x 19815–268 x 36827–498 x 61850–74Besides 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:
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.
We can also manufacture assemblies with standard or custom end fittings. Special testing and tolerance requirements are also available.
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We can produce any assembly to fit your specifications precisely.
When ordering, many factors must be considered, including but not limited to:
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