Rope science: wire, strand, rope, lay direction, elongation, material

The lay direction indicates the direction in which the outer wires (outer strands) of the strand (cable) are laid around the center wire (core strand).

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Strand in S-lay – left hand lay direction of wires.

Strands in Z-lay (lright hand ay direction of wires).

Steel cables with right hand ordinary lay (sZ).

Steel cables with left hand ordinary lay (zS).

Steel cable with right hand langs lay (zZ).

Steel cable with left hand langs lay (sS).

“S-lay” means: the outer wires (outer strands) are laid in left direction around the center wire (core strand).

“Z-lay” means: the outer wires (outer strands) are laid in right direction around the center wire (core strand).

Furthermore, a distinction is made between ordinary/regular lay and langs in the stranding (see figure). As standard, Carl Stahl Technocables delivers the steel cables in right hand ordinary lay (sZ).

For example, in the case of cable systems that run over pulleys, we recommend using coated cables in order to achieve a high bending cycle and a long service life. With higher bending cycles a longer service life could be achieved.

Carl Stahl Technocables uses polyamide as the standard coating material. Polyamide is an optimum cable coating, distinguished by its high wear resistance and high bending cycle capability. A further advantage of the coated cables:  The coating protects the rope from dirt.

We recommend PA12 if the cable runs over a pulley or if flexibility is the main priority. This is our standard coating material.

Furthermore, the coating keeps the manufacturing lubricant within the rope. This film of oil functions as a lubricant between the individual wires and strands, thereby reducing wear on the cable.

Are high temperatures or good sliding properties required of your steel wire rope? Then we use special materials for coating of the steel wire rope. For example, we recommend FEP/PTFE for temperatures of between -190°C and + 205° C.

We can also offer PA6.

Depending on the application, the appropriate coating material is used. Don’t you know which wire rope coating is the right for your rope application? - We're glad to help you finding the right material. Contact us directly

Two different kinds of elongation can be distinguished:

1. Constructional elongation
After the manufacturing process of the ropes and strands, small gaps remain between each wire within the strand and between each strand in the rope. When the rope is tensioned, the wires and the strand move closer to each other, and reach their optimum position. A result of this process is, that the rope elongates to a certain extent. This constructional elongation is not the same in every rope construction. It depends on lay, lay length, rope construction and other factors.

2. Material elongation
This elongation concerns the material that the single wires are made of. It occurs, when the wire is tensioned. The material elongation is proportional to the applied load. Under normal circumstances the rope will almost regain its original length as soon as the load is removed.

We can recommend suitable steel cables for your purposes.

The diverse properties and possibilities of wire ropes and strands are attracting more and more attention when it comes to implementing mechanical applications flexibly and safely. The result is high-quality solutions for a wide range of applications, in a wide variety of industries. The possible applications of wire ropes are almost endless. Wire ropes with larger diameters up to 8.00 mm are used in mechanical engineering or in the sun protection sector. Fine wire ropes with smaller diameters from 0.09 mm are used in the medical, furniture or lighting industries, among others. Optical aspects also often play a role.

The selection of the right wire rope for the respective application is of great importance. This is done according to various criteria, which are selected on the basis of the respective area of application. Properties and conditions such as tensile strength, environment, corrosion resistance, form, function, surface and structure are taken into account.

Standard wire ropes and strands are made of galvanized steel, or stainless steel. Stainless steel ropes, for example, offer very high corrosion protection, are solid and have a very long service life. Wire ropes made of galvanized wire, are in many cases the most economical option and offer sufficient corrosion protection for various applications.

Carl Stahl Technocables GmbH is your competent partner from the initial consultation, through the development of technical specifications, to the manufacture of assembled ropes, Bowden cables, wire ropes and strands. We supply our products to a wide variety of industries and markets worldwide.

Ropes made of stainless steel are rustproof. They score high on durability due to low abrasion, are solid and have low ductility. Stainless steel ropes offer high tensile strength for mechanical applications and are temperature resistant.

Stainless steel is a corrosion-resistant alloy of iron, chromium-nickel and other elements, containing not less than 10.5% chromium, and its specific ratios vary depending on the alloy. The higher the chromium content in stainless steel, the higher the corrosion resistance. There are different types of stainless steel cables. We mainly use AISI 316 / 1. or AISI 304 / 1.. The most common stainless steel is 1.. We also offer other stainless steels on request.

1. is a stainless austenitic chromium-nickel-molybdenum steel. Special properties are e.g. good corrosion resistance.
1. is the standard material for austenitic chromium-nickel steels. It is characterized above all by its good workability and also has a high corrosion resistance. AISI 304 / 1., for example, has about 10 percent more tensile strength than equivalent materials.

Although the differences between stainless steel specifications are small, they affect their effectiveness in various applications. For example, the additional molybdenum content in 316 stainless steel helps make it even more corrosion resistant than 304.

AISI 304 / 1. is widely used in medical applications due to its strength, malleability, precision in manufacturing and reliability. In addition, it is recyclable, heat resistant.

Stainless steel wire rope is the right choice for applications where the rope needs to be protected from corrosion. Applications that are likely to be used outdoors, underwater or in an area where the wire rope would be exposed to the elements. In particular, it is highly resistant to corrosion by acids and bases.

strands / wire ropes made of stainless steel

In the case of steel cables made of galvanized steel, the steel has undergone a galvanizing process called hot-dip galvanizing or HDP. HDP is the process of immersing the steel in molten zinc, which forms a coated zinc layer around the steel that protects the material from corrosion. While it is not as corrosion resistant as stainless steel cable, it is sufficient for an outdoor application in some cases.

The low cost-to-benefit ratio of galvanized steel wire rope makes this the preferred material for many mechanical applications intended for indoor use such as hanging heavy signage or suspending, lifting or balancing large objects.

strands / wire ropes made of galvanized steel

The diameter of the deflection pulley / guide pulley is decisive for the service life of the rope that is deflected or guided by the pulley. A deflection pulley that is too small can considerably shorten the service life of the rope. The rope construction is also very important for the service life. The more wires the rope has with the same diameter, the more flexible it is, which can lead to an increase in service life. In order to achieve a long service life with extremely small deflection pulleys / guide pulleys, the design and quality of the deflection pulley (shape and material) and the selection of a suitable rope are crucial. The rope material also has a decisive influence on the service life of the rope. The service life of tungsten ropes can be up to 5 times longer than that of stainless steel ropes (material 1./AISI316).

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When using a small / miniature pulley, the bending stress can be extremely high. As a result, the service life of the wire rope suffers or even the pull-off force of the ready-to-install assembly is insufficient. To enable the use of the smallest miniature pulleys, it is necessary to select a rope with high bending fatigue strength. This rope has a long service life despite high bending stress on a pulley.

To achieve the longest service life in your application, our highly flexible tungsten wire ropes are best suited.

Pulleys / guide pulleys

Properties of tungsten ropes

Did you know wire ropes were used as far back as the s for mining hoist applications? Nowadays, we can use steel ropes for many different applications such as lifting and hoisting in elevators and cranes, and for mechanical power transmission. US Cargo Control's wire rope slings are an excellent choice for heavy-duty jobs as their fabrication offers excellent abrasion resistance and heat resistance for extreme conditions.

Although these slings are beneficial for the lifting and rigging industry, there are a few specifications to know before purchasing them. Continue reading what is wire rope, what are important specifications to look for, and how it's different from cable rope.

What is Wire Rope?

These slings carry different properties that can determine their performance. Wire rope is constructed where a strand consists 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. Once the wires are formed, they all come together to create greater strength and flexibility.

These slings work well for lifting, hoisting, towing, or anchoring loads. They're manufactured in a variety of configurations, with 6x19 and 6x36 being the most common. When you see 6x19 or 6x36 from our website, these numbers represent the number of wires making up the strand and the number of strands wrapped around the core.

For example, a 6x19 indicates that there are 19 wires making up a strand, and 6 strands wrapping around the core. To learn more about our 6x19 wire ropes, look into our bestselling 1/2" Galvanized Wire Rope EIPS IWRC, 1/2" Stainless Steel Wire Rope IWRC T304, and 1/2" Bright Wire Rope EIPS FC.

The configurations will offer different benefits for certain applications. In general, a smaller number of large outer wires offers better wear and corrosion resistance, while a larger number of small wires provides a better level of flexibility and fatigue resistance. Continue reading to learn which wire rope fits your job.

Terms that Define Construction and Properties of Wire Rope

Before immediately purchasing a wire sling, there are 8 properties that you should know about:

1. Different Types of Wire Rope Slings
2. Length
3. Size
4. Direction and Type of Lay
5. Finish of Wires
6. Grade of Rope
7. Type of Core
8. Construction

1. Different Types of Wire Rope Slings

There are different versions of wire rope slings, ranging from single leg to 4 legs, as well as braided wire rope and domestic wire rope slings (manufactured in the U.S. with Crosby® hardware). When looking at the types of slings we offer at US Cargo Control, be sure to consider how much versatility and capability you need.

For example, a braided wire rope has increased flexibility and friction to grip loads over a regular wire rope. Adding an additional leg to the sling can add additional versatility and strength.

2. Length

This is the total number of feet that are cut to size when wrapped around.

3. Size

This is the measurement of the rope's diameter and can be displayed in inches or millimeters. The industry standard is to measure the rope at its widest point.

These sizes commonly display different strand patterns where the number of layers, wires per layer, and size of the wires per layer all affect the strand pattern. Wire rope can be constructed using one of the following patterns below or using two or more patterns.

• Single Layer - a common example is a 7 wire strand. This has a single-wire center with six wires of the same diameter around it.
• Filler Wire - this has two layers of uniform-size wire around a center with the inner layer having half the number of wires as the outer layer.
• Seale - has 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.
• Warrington - this construction has two layers of wires around a center with one diamter of wire in the inner layer, and two diameteres of wire alternating large and small in the outer layer.
• Combination - when a strand is formed in a single operation using two or more of the above constructions, it's referred as a "combined pattern."

4. Direction and Type of Lay

The type of lay refers to the way the wires are laid to form a strand. They're how the strands are laid around the core which can be regular lay, long lay, or alternate lay.

Regular Lay

The wires line up with the axis of the rope. This is where the wires are twisting in one direction, and the strands in the opposite direction create the rope. Regular lay is less likely to untwist and less likely to crush.

Lang Lay

This is the opposite of regular lay where the wires form an angle with the axis of the rope. The wires and strands spiral in the same direction and run at a diagonal to the centerline of the rope. Lang lay is more flexible and resistant to abrasion than regular lay wire ropes. The only con is this type of lay will be more likely to twist and crush than the regular lay.

Alternate Lay

Sometimes known as reverse lay, this type of lay consists of alternating regular lay and long lay strands. This unites the best features of both types, and it's using relatively large outer wires to provide an increase of abrasion resistance.

5. Finish of Wires

This refers to the protective coating that's applied to the wire rope. There are three types of finishes which are galvanized (zinc-coated), stainless steel, and bright (unfinished steel).

Note that the galvanized material will provide extra corrosion resistance, and stainless steel is highly resistant to corrosion.

6. Grade of Rope

The grade of the rope means the grade of steel being used. The plow steel strength calculates the strengths of most steel wire ropes. Some classifications include Improved Plow Steel (IPS), Extra Improved Plow Steel (EIPS), Extra Extra Improved Plow Steel (EEIPS), Galvanized Improved Plowed Steel (GIPS), and Drawn Galvanized Imrpoved Plow Steel (DGEIP).

EIPS is 15% stronger than IPS, and EEIPS is 10% stronger than EIPS. Along with that, GIPS and DGEIP wires can add corrosion resistance to your application, but DGEIP wires have a higher break load than GIPS.

7. Type of Core

The type of core is what makes up the center of the wire rope. There are three types of core: Fiber Core (FC), Independent Wire Rope Core (IWRC), and Wire Strand Core (WSC).

A fiber core can be made of synthetic polypropylene fibers. The fiber cores offer greater elasticity than a steel core, but are more susceptible to crushing. This isn't recommended for high heat environments.

A steel core can either be an independent wire rope or individual strand. The steel cores can provide adequate support, or in an operating environment where temperatures can exceed very high heat.

8. Construction

Wire rope is composed of individual wires combined to form strands that twist around the core. The construction is indicated by a number such as 6x19 or 7x19. The first number is the number of strands, while the second number is the number of wires that make up each strand.

What's the Difference between Wire Rope and Cable Rope?

Wire and cable ropes are terms that are often interchangeable but do have one varying difference. Wire rope refers to the diameters that are larger than 3/8 inch. Sizes smaller than this are classified as cable rope or even cords. Regardless of the size difference, cable and wire rope are still classified as a "machine." Even a group of strands laid around a core would still be called a cable or wire rope.

Tackle the Toughest Lifting Jobs with High-Quality Rigging Hardware

We know the importance of quality when it comes to lifting supplies. We carry a variety of rigging hardware, as well as lifting beams and spreader bars that are designed to lift heavy loads safely and efficiently. If you're interested in other lifting slings, check the other types of slings we carry like nylon slings and chain slings.

Need a custom lifting sling? We can do that. We’ll work with you and customize a lifting sling to meet your specific needs.

Read more information about wire rope slings below!

How to Safely Apply Wire Rope Clips to Wire Rope Assemblies

How to Use Wire Rope Clips

What is Sling Protection, What are the Different Types of Slings, & How to Protect Them

Want more information on zinc coated steel wire strand? Feel free to contact us.

Contact our sales team at US Cargo Control today at 866-444-. Our team of product experts is here to answer any questions about rigging hardware, lifting slings, and more.