ROPES Ӏ SECTOR REPORT
RopED ToGETHER
Steel ropes are the default for lifting applications. Are we about to see a step-change? Julian Champkin reports.
Ropes have been made of steel wire ever since 1831 when a mining engineer by the name of Wilhelm Albert, in the Harz Mountains in Germany, twisted four wires into a strand then twisted three of his strands around each other to make the first wire rope. Until then lifting ropes had been made of natural fibre such as hemp; or when those were inadequate – as they frequently were – chains were used instead. Chains at the time were brittle and inclined to snap suddenly, even when not overloaded. It was that same Wilhelm Albert who discovered the cause of this: he built a test rig which subjected chains to repeated small loadings and discovered a phenomenon he called metal fatigue. The lifting industry clearly owes him a lot, and it is not remotely unfair that the wire ropes that he replaced his mining chains with were for many years called ‘Albert ropes’. They were clearly so much better that they gained almost immediate acceptance in the ever-deeper mining enterprises that were springing up worldwide. Today they are almost universal in the lifting industry. Good as they are wire ropes
are not perfect. They are heavy. They are vulnerable to corrosion and strand breakages – including
52 CRANES TODAY Verlinde’s
Eurobloc VF3 is designed for synthetic rope
in the inside strands which visual inspection cannot see. Incorrect matching of groove
width to rope diameter can lead to ‘birdcaging’ in which the rope appears to unravel; and they need lubrication, which is time consuming and labour intensive and, particularly in marine environments, potentially polluting. Now we have ropes of synthetic
fibres. The big advantage of synthetics is their low weight. It lies somewhere between one-fifth and one-tenth of that of steel. On a long lift – as in deep-shaft mining, and sub-sea operations – the self-weight of steel rope can become a major issue. Weight is
also important in handling. A single rigger can carry a fibre sling on his shoulder; the same fitting in wire rope would need a fork-lift or crane. And fibre is much less
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