What Do You Know About Wire Rope?

Rigging 101: Wire Rope Slings

In the industry, slings are essential tools that help you complete projects safely and efficiently. Most people know how manufacturers make slings, but few understand the details behind their strength and construction. At LGH, we ensure only the safest and most reliable equipment reaches our customers’ job sites.

I’d like to pass along some insight into what makes these slings, from their construction to the maintenance and inspections that keeps them safe but, at the same time, don’t want to make your eyes bleed. That said, today, we’ll cover wire rope and we’ll cover the other sling types in future installments.

So we all know that strands of wire twisted around a core cable give wire rope its strength, right? You may ask what else is there to know about their construction beyond that. Well, frankly, a lot.

Composition

Our rental fleet has sizes of wire rope ranging from 3/4” up to 4” in diameter for single part slings and 2-1/2″ to 11″ diameter in our 9-part braided slings, but there are larger varieties available for purchase. Each wire rope sling consists of several strands twisted in a helix around a central strand, often made from the same material as the outer strands. A wire rope strand typically consists of 19 to 36 wires, but it can have up to 109 wires, all twisted around a core wire or strand, depending on the wire rope’s configuration.

Typical 6×19 construction features 6 complete strands of wire twisted around a center core strand.

Knowing the composition of the sling you’re using gives an understanding of what the rope will be able to do or, in some cases, how it will act. Various configurations exist to combat crushing, allow for greater flexibility or reduce the chances of rotation among other things. Ensuring you’ve got the correct wire for the project can be the difference between a successful job or causing damage or complete failure. As a general rule of thumb, improving one aspect will tend to reduce another. For example, a wire rope made up of smaller diameter wires provides increased flexibility, but doesn’t offer great abrasion resistance, whereas a wire rope of larger wires increases abrasion resistance while remaining more rigid.

Different Classes

The 6×19 class, the most common wire rope configuration, consists of six outer strands with 15-26 wires each, twisted around a center core with the same number of wires. This configuration offers excellent abrasion and crushing resistance but sacrifices some flexibility. It’s available in sizes from 3/4″ to 1-1/8” outer diameter. The 6×36 class, used for thicker diameters, features six outer strands of 27-49 wires, offering more flexibility and maintaining crushing resistance, but with reduced abrasion resistance compared to the 6×19 class. LGH offers 6×19 and 6×36 wire ropes ranging from 1-1/4” to 4” in outer diameter, with SWL from 5.6 to 130 tons, as well as 9-part braided slings with SWL from 59 to 485 tons.

Side-by-side comparison shows the difference between Lang and regular lay wire rope.

Different Classifications

Next, consider the lay of the wires within the strands and how the strands are laid around the core. There are two main classifications of wire rope lay seen with alternating directions within each. These classifications are Regular Lay and Lang Lay.

Regular lay wire ropes have strands twisted in opposite directions, making the wires appear parallel to the rope’s axis. It is more flexible, crush-resistant, and easier to splice, but lasts shorter than Lang lay rope. It also tends to spool on a drum more easily and is naturally more rotation resistant.

Lang Lay wire ropes twist both the strand wires and strands in the same direction, making the wires run diagonally. Lang lay rope offers increased abrasion resistance for a longer lifespan, but sacrifices flexibility.

Both regular and Lang lay can be spun clockwise (right lay) or counterclockwise (left lay). The starting point and spooling direction of your winch drum will determine which direction is appropriate for your project.

Production

During production, wire rope is heavily lubricated, allowing the lubricant to penetrate the entire rope and core. This reduces friction between wires and enhances the rope’s lifespan. Maintaining proper lubrication with both penetrating and coating lubricants is essential for preserving the wire rope’s lifespan and structure. Penetrating lubricants use petroleum solvent to coat each strand’s core, evaporating after reaching it and leaving the lubricant behind. Coating lubricants seal the cable from moisture and reduce wear and corrosion.

In 2011, the Discovery series How It’s Made?, dedicated an episode to wire rope and crane cable production. They provided a quick, insightful look at their composition in just five minutes. You can find that video here.

 

 

 

For more information or to rent wire rope slings and accompanying equipment, reach out to Lifting Gear Hire at www.rentlgh.ca or call us at 800-878-7305.