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What is a Steel Wire Ropes - explanations and technical terms

Structure of a Steel Wire Ropes

In order to define a steel wire rope, the following parameters must be specified: Cable diameter, Cable construction, Core type, Material grade, Lay direction.

The Steel Wire Ropes components

Wire (Steel Wire)
The wire is the most basic component of the Steel Wire Ropes and is the main raw material used to produce steel wire ropes.

Strand:
A strand is the result oftwisting steel wires in one or more layers around a central wire (core).

Steel Wire Ropes:
A Steel Wire Ropes consists of one or more layers of strands twisted around the Steel Wire Ropes core. Single-layer Steel Wire Ropes are Steel Wire Ropes with only one layer of strands around the core, usually 6 or 8 strands. Multi-layer Steel Wire Ropes are Steel Wire Ropes with more than one layer of strands, these are non-twisting Steel Wire Ropes.

Steel Wire Ropes Core (Heart):
The Steel Wire Ropes core can be made of a fibrous material or steel wires. There are also types of cables without a core at all.

Steel Wire Ropes Diameter

The nominal diameter of the Steel Wire Ropes is the diameter of the circle that encloses the Steel Wire Ropes section.
The actual diameter is defined as the average of 4 measurements taken at two points spaced one meter apart. At each point, two measurements are taken in perpendicular planes.
Measurement is done using a caliper. It should be ensured that the diameter of the enclosingcircle is being measured.
We typically use special calipers with wide jaws that cover 2-3 wires simultaneously.
The actual diameter of the Steel Wire Ropes should fall within the allowable tolerances according to the standard

Fiber Steel Wire Ropes

Synthetic Fibers: Typically, the core is made of synthetic fibers, primarily polypropylene. The raw material consists of yarns woven from fibrillated film polypropylene threads. These ropes are used as the core based on specifications derived from extensive testing and relevant regulatory requirements.

Natural Fibers:
Another material used for making the fiber core is sisal fibers. These are natural fibers extracted from the agave plant. Sisal fiber cores are commonly used in elevator Steel Wire Ropes. Another type of natural fiber permitted by the standards is Manila, but its usage is less common. Other types of natural fibers that were previously accepted for use but are now prohibited by current standards include cotton, jute, flax, and others. Synthetic fibers have several advantages over natural fibers. They are stronger, non-degradable, less sensitive to chemicals, and their production process can be controlled more effectively to achieve high precision and uniformity.

Lubricants

Wire ropes are “machines” consisting of metal parts (strands) that touch each other and move relative to each other during operation. Like any other machine, wire ropes also require lubrication. The purpose of lubricants in wire ropes is to provide protection against corrosion and to reduce internal friction and wear.

All wire ropes supplied by Messilot Steel Wire Ropes are lubricated during strand stranding so that all wire strands are coated with lubricant. In wire ropes with a fiber core, the core is also impregnated with a suitable amount of lubricant.

Braiding

One of the key characteristics by which a Steel Wire Rope is defined is its lay direction. Here it is important to distinguish between the lay direction of the strands within the Steel Wire Rope and the lay direction of the Steel Wire Ropes within the Steel Wire Rope  itself. A Steel Wire Rope is called right-lay or has a right lay when the lay direction of the strands in the Steel Wire Rope is to the right, and it is called left-lay when the lay direction of the strands in the Steel Wire Rope is to the left.

Two main types are differentiated:

Regular Lay: In a Steel Wire Rope  with regular lay, the direction of the strand lay is opposite to the direction of the Steel Wire Rope  lay. When looking at such a Steel Wire Rope, one can see that the outer strands are laid along the length of the cable. The lay directions of the Steel Wire Rope can be left or right. Steel Wire Ropes with regular lay are marked with the letter pair sZ for right-lay Steel Wire Ropes and zS for left-lay Steel Wire Ropes.

Lang’s Lay (Lay to the Left): In such a Steel Wire Rope, the lay direction of the strands in the Steel Wire Rope is the same as the lay direction of the Steel Wire Rope , and it can be seen that the outer strands are laid across the width of the Steel Wire Rope . This lay pattern is named after the English engineer who developed it, LANG. Again, the Steel Wire Rope can be right-lay or left-lay. These Steel Wire Ropes are marked with the letter pair zZ for right-lay Steel Wire Ropes and sS for left-lay Steel Wire Ropes.

When the Steel Wire Rope is under load, it tends to rotate (twist) in its lay direction and to unwind. In a Steel Wire Rope with Lang’s lay, this tendency is stronger than in a Steel Wire Rope with regular lay. In a Steel Wire Rope  with regular lay, the opposing lay direction of the strands and the cables somewhat counteract each other.

In contrast, a Steel Wire Rope with Lang’s lay is more resistant to wear when passing over sheaves because a longer section of the strands is in contact with the sheave, so the load is distributed over a larger area, resulting in lower pressure and therefore less wear.

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Core

Steel Wire Ropes core

The core can be manufactured in several ways:

  • Fiber core made of natural or synthetic fibers.
  • Stranded steel core.
  • Steel Wire Ropes steel core.
  • Parallel steel core.

It provides the Steel Wire Rope with flexibility, which is why it is preferred. When the load is very high, it is preferable to use a Steel Wire Rope  with a steel core that is more resistant to crushing and pressure. The steel core increases the breaking strength of the Steel Wire Rope but also makes the Steel Wire Rope less flexible. Steel Wire Ropes with steel cores are also used in hot conditions. For Steel Wire Ropes with a fiber core, the maximum working temperature is about 100°C, for Steel Wire Ropes with a steel core it is up to 150°C.

Natural or Synthetic Fiber Core (NFC or SFC):

As already explained in the section on raw materials, natural fiber core (sisal) is commonly used to create elevator Steel Wire Ropes. For other Steel Wire Ropes, polypropylene fibers are commonly used, where for cables thinner than 8mm the core consists of a single twisted wire or a twisted strand of wires, and for thicker Steel Wire Ropes the core consists of several fiber strands twisted from wires.

Wire Strand Core (WSC):

The core of the Steel Wire Rope is a strand, usually in a structure similar to the other strands of the Steel Wire Rope. Used mainly in relatively thin Steel Wire Ropes and in multi-layer Steel Wire Ropes (non-twisting).

Independent Wire Rope Core (IWRC):

This is a core that is actually similar to a Steel Wire Rope, it is made up of strands and a core and is manufactured in a separate process.

Parallel Wire Rope Core (PWRC):

This core is also made up of twisted strands and a core, but it is not manufactured in a separate process from the Steel Wire Rope but during the closing of the Steel Wire Rope. The lay step of the Steel Wire Rope strands and the core strands is equal, hence its name.

Steel Wire Ropes with such a core have a larger metal cross-sectional area than Steel Wire Ropes of the same diameter with an IWRC core, therefore the minimum breaking strength is also higher. In addition, because the contact between the Steel Wire Rope strands and the core strands is along a line and not at single points, the compressive forces between the strands are significantly lower. This translates to better fatigue resistance.

A parallel steel core (PWRC) improves the Steel Wire Rope’s fatigue resistance compared to a Steel Wire Rope steel core (IWRC), but Steel Wire Ropes with such a core have a stronger tendency to twist under load.

A larger machine is required to produce Steel Wire Ropes with such a core, so the range of Steel Wire Rope diameters that can be produced is usually narrower than for cables with a Steel Wire Rope steel core.

Pre-forming

In a pre-formed Steel Wire Rope, during the Steel Wire Rope braiding process, the strands are shaped into their helical form within the Steel Wire Rope. This shaping process nearly eliminates the tendency of the strands in the Steel Wire Rope to open up and reduces the elastic stresses in the strands composing the Steel Wire Rope. This process provides several advantages:

  • Increased Steel Wire Rope  lifespan – reducing internal stresses in the strands improves their fatigue resistance.
  • Prevention of fraying of broken strands – in every Steel Wire Rope, strands break during operation. In a Steel Wire Rope that is not pre-formed, these broken strands fray outwards, damaging neighboring strands and potentially causing injuries when handling the Steel Wire Ropes.
  • Elimination of the Steel Wire Rope’s tendency to open up when cut. When a non-pre-formed Steel Wire Rope is cut, it opens up and disintegrates into a “bird’s nest” type of structure. To prevent this, the Steel Wire Rope end needs to be tied with iron wire several times. With a pre-formed Steel Wire Rope , there is no such tendency, and when cut, it remains intact. However, it is still necessary to secure the Steel Wire Rope end to prevent unraveling due to blows or vibrations. For thin Steel Wire Ropes, adhesive tape can be wrapped instead of tying with wire.

Except for a few special structures and Steel Wire Ropes for specific uses, all Steel Wire Ropes manufactured by Messilot are pre-formed.

Information Required When Ordering Wire Ropes

  • Nominal diameter.
  • Steel Wire Rope structure.
  • Core type.
  • Nominal strength of the strands.
  • Coating: {Black | Regular galvanization (drawn) | Thick hot galvanization | PVC | Other.}
  • Lay direction: {Right | Left}, {Regular | Lang’s}.
  • Preforming: Preformed | Non-preformed.
  • Lubrication type.
  • Steel Wire Rope length and required number of units.
  • Required packaging format.
  • Steel Wire Rope application.
  • If required, end fittings details, type, and size.

Storage, Transportation, Installation, and Maintenance of Wire Ropes

Storage:
It is preferable to store Steel Wire Ropes indoors. If storing them outside is unavoidable, they should be covered to protect them from rain and dust. Avoid placing Steel Wire Rope drums or packages directly on the floor; it is always better to elevate them slightly to keep them away from moisture.

Transportation:
Exercise caution to prevent damage to the Steel Wire Rope during transportation from protruding objects, metal edges, etc. When rolling a drum, ensure there are no protruding objects in the way that could cause damage to the Steel Wire Rope. Avoid rolling the Steel Wire Rope on sand or dirt, as these particles can adhere to the lubricant coating the Steel Wire Rope, leading to increased wear during operation.

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אחסון נכון

Installation:
When transferring the Steel Wire Rope from the drum or package to the facility where it is intended to be used, it is important to do so correctly. Improper installation can lead to the ingress of foreign objects into the Steel Wire Rope, the creation of “eyes,” and irreversible damage already during the installation process. If an “eye” is formed, do not attempt to open it by unwinding in the opposite direction. Instead, release the Steel Wire Rope end and rotate it until all the twists are removed and the loop is opened.