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How Do I Choose a Wire Rope?

How Do I Choose a Wire Rope?

Monday, August 1, 2021
Posted in: Wire Rope

What Is Wire Rope?

Wire rope is the term assigned to diameters greater than  ⅜”, although most engineers refer to wire rope as anything ¼” or greater. By comparison, mechanical cable refers to product that is smaller than ⅜” and, as a matter of fact, Sava manufactures what is known as ultrafine cable and it is as small as .004”. For context, miniature or, as mentioned, ultrafine cable that is .004” in diameter is comparable to the thickness of a sheet of paper.

Wire rope (and mechanical cable) is made when a group of stranded metal extrusions are twisted in a helical manner, around a center wire, or another internal helix. Wire rope is typically named for its strand construction, such as a 19x19 wire rope, which consists of 361 individual filaments or wires. An important distinction to make however, is that this same 19x19 wire rope, becomes miniature or ultrafine mechanical cable once it is made in diameters less than ⅜”.

How Many Types of Wire Rope Are There?

The Brooklyn Bridge is suspended using four, 15.75” wire ropes made from galvanized steel. That’s some huge wire rope. Alternatively, Sava produces ⅜” wire rope used in retractable lighting systems for nighttime road work areas. Said plainly, there are limitless wire rope use cases to pour over. 

However, as versatile as wire rope is, there are as many ways to define it. Wire rope can be distinguished from mechanical cable by size, as already covered, but there are also other characteristics that are useful to examine as well.

Wire rope can be coated in Teflon® (FEP), or other extruded materials such as nylon (PA), vinyl (PVC) or polyurethane (PU). This protective coating ensures the wire rope is not exposed to particulates and other undesirable environmental contaminants. Furthermore, wire rope can be made from a vast array of alloys, such as stainless steel, galvanized steel, tungsten and others.

The material used to produce wire rope depends entirely on what needs to be accomplished. 

For example, the Brooklyn Bridge required galvanized steel due to its strong resistance to oxidation. Tungsten, used prolifically in surgical robotics, by comparison, is characteristically malleable, and thus allows for the mechanical cable to turn around tight, miniature pulleys with ease. So one’s choice of wire rope material depends entirely on what needs to be achieved.

How Strong Must Wire Rope Be?

Wire rope strength is a critical factor in determining the product’s efficacy. Factors that can affect the strength of mechanical cables include:

  • Construction & Diameter: The size and structure of wire rope can affect its strength in different applications. For example, mechanical cables, with more space or air between the strands, allow greater compression, which works well in a pulley system, but may lack the pull strength needed to hang a heavy load.
  • Cable Lay: Lay refers to the way wires and strands are twisted, including its direction and lay length, which can inform strength and overall lifecycle.

What Material Characteristics Are Needed?

The material with which wire rope is made will determine much of its performance, including such characteristics as:

  • Malleability — It is important to know if your project requires wire rope that is rigid or flexible. Stainless steel wire rope is extremely strong, but tends to resist bends. Thus, if the application calls for the wire rope to complete tight radii, without the urge to spring back to its original shape, tungsten cable may be the alternative.
  • Cutting & Resistance —  Lifecycle can be shortened by both the presence of corrosion and how the wire rope is terminated. Because of tungsten cable’s meteorological properties, for instance, the cable filaments want to fall away from one another if cut mechanically. It is therefore necessary to electrocut tungsten cable to ensure a small amount of molten material is applied to the cut, simultaneously, to ensure the filaments stay bonded at the ends. Wire rope exposed to seawater, or rain water, is produced with different alloys. Stainless steel does a better job tolerating salt water than a galvanized cable alternative.

Numerous industries take advantage of the strength, flexibility and versatility of wire rope, including:

  • Military — Multiple applications, including in the crew compartments and turrets of tanks.
  • Medical — While much of the medical industry's demand for wire rope has shifted to smaller diameter cables, wire rope is still a vital component in some life sciences applications.
  • Industrial/Manufacturing — Larger diameter pulleys and steel wire rope are common in industrial and manufacturing environments.
  • Robotics — Including exoskeletons, logistics robots and military applications.

The engineers at Sava can help you decide what wire rope material satisfies your environmental requirements.   

Will My Budget Accommodate It?

Realistically, budget constraints may affect the material selection. For example, tungsten mechanical cable will generally be more expensive than stainless steel wire rope. And while tungsten is superior in many ways to stainless steel, when all variables are identical, the application may be well served by a more modestly priced stainless wire rope. It is quite common to arrive at a cost-effective wire rope or mechanical cable material that suits application requirements, but does so without undermining the product’s ability to compete in fierce markets. It is therefore critical that product designers collaborate with Sava’s engineers on material type.

At Sava, we have manufactured and supplied wire rope, precision miniature and ultrafine cables and assemblies to satisfied customers across dozens of industries for over 50 years. Contact us today to take advantage of our expertise in selecting wire rope and related products.

 

August 1, 2021
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