The pursuit of better wire rope performance
- Mar 2
- 3 min read
The invention of wire ropes nearly 200 years ago had a major impact on the world of lifting. Prior to that for thousands of years fibre ropes were used.
In mining, running ropes were typically made from materials such as jute, manila and hemp. In some mines iron chain was also used but had the serious feature of unexpected failure (the weakest link concept) and miners were very reluctant to use it. Ropes made from fibre did not last long and were relatively weak. As mining depths increased the weight of the fibre rope became a factor as the weight of the rope was added to the load being lifted.
It is reported that in 1834, a German mining engineer, Wilhelm Albert, developed the first stranded wire rope to be used as a running rope. The construction was three strands with each strand having four wires made from soft iron wire and it coiled easily around a sheave. A wire rope of the same diameter as a fibre rope would typically be 6 times stronger than the fibre rope. The wire rope had significant advantages and quickly replaced fibre ropes in mining and other industries. Since then there have been numerous technical developments in wire rope technology, improving efficiency and longevity.
Some of the main developments were:
Early Developments. Equal Lay, Seale, Warrington.
Briefly, unequal or cross lay strands (wires all the same diameter) had the disadvantage of wires in successive layers developing wire indentations at crossovers in the strand.
The introduction of equal lay, or Seale lay, where there are the same number of wires in each strand layer, and the wires in each layer of the strand lie in the grooves formed by the inner layers, resulted in a significant increase in service life, due to reduction of compressive stress of the wires and elimination of the wire indentation at crossovers.
Filler strand development. By inserting small diameter wires (filler wires) in the interstices of a strand, the breaking strength and stability of the strand was increased. Another development, Warrington, has two different size wires in the outer strand. Thos allows for improved “steel fill”, more flexibility, better fatigue performance and higher strength for the same rope diameter.
A combination of Warrington and Seale construction has the benefit of both and is common. A good example is 6X36(14/7-7/7/1. Triangle Strand Rope and Haggie
In 1921, 105 years ago, a company called Haggie Son and Love set up a wire rope manufacturing facility in the Jupiter Mine premises in Johannesburg. Within a few months they started manufacturing triangle strand winding ropes for the mining industry.
This is a high speed application and the slightly curved shape of the triangle strand not only provided a higher breaking load than the same diameter round strand rope, but also created more support of the wires going through the headgear sheave, resulting in less pressure on the individual wires, more wear resistance and longer rope life.
Haggie subsequently developed non spin ropes for special mine winding applications.
High-Performance Ropes
The development of Compact Strand Wire Ropes has made a huge impact on wire rope performance. Once conventional strands are produced, they are then passed through dies, compacting the wires in the strand. The compacted strands are then laid up to form the rope. Because of the compaction, the compact strand rope has a higher breaking force than a standard wire rope of the same diameter. Another important feature of the compaction is that because the wires are deformed the contact area and support between wires is enhanced, and fatigue is significantly reduced. In addition, compared with conventional strands, there is more surface area of the wires in contact with the sheave, resulting in better wear resistance.
Another significant technical innovation is the impregnation of a plastic layer between the steel core and the outer strands. This plastic layer provides a separation of steel-upon steel, greatly reducing the wear and damage of the core. It also assists with locking in the lubricant and preventing the ingress of water, avoiding corrosion.
In recent times there have been a variety of high-performance ropes introduced, using combinations of multiple strand layers, compacted strands , plastic impregnation, plus higher tensile steel, many with spectacular results.
Be aware that detection of broken wires in service is more difficult with many high performance ropes. Magnetic Rope Testing is highly recommended.
LEEASA,
+27 (0) 83 650 7471,
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