APPLICATION REPORT | OFFSHORE AND SUBSEA LIFTING
Q Parkburn’s capstan for synthetic fibres, here installed on a crane.
R Modulift’s disassembled beam for Safe Lifting BV is not small
require a 250t SWL wire-rope crane to lift the same payload. There is, though, a drawback: synthetic
is more elastic than steel. A synthetic rope stretches under a load, so when in a lifting operation it is wound, under tension, onto a drum winch, it is in a stretched state. Storing a stretched rope at high tension is inadvisable; the contained energy can be dangerous, the winding is uneven, and frictional heat is created as the rope relaxes. Scottish company Parkburn Precision Handling Systems, based in Hamilton, has developed a solution specifically to address this problem. Its patented Deep Water Capstan de-tensions the synthetic rope as it winds it in. It consists of two separate drums that intersect: each drum
S Fred.Olsen’s Brave Tern as she will be outfitted
has 16 “fingers” which interleave with those of the other drum to provide the rope- bearing surface. The drums are offset to each other around the rotational centreline to create a natural helix and a slightly elliptical cable path through the machine. This results in a unique tensioning/de- tensioning profile that spreads the work evenly through the rope as it passes through the machine. After it emerges from the Deep Water Capstan the rope can be stored at low tension. Each drum has its own motor and gearbox, supplied by Dana SAC. The device can be used on cranes also: a 150t variant of Parkburn’s Deep Water Capstan lies at the heart of MacGregor’s FibreTrac 1500 marine crane. Another offshore trend is the increasing
size and weight of lifts. Topsides for rigs are standardly now constructed as ever- larger modules to be transported and lifted
into place rather than being constructed offshore. An essential component of such lifts is the spreader beam, and specialists Modulift have just constructed their largest- ever beam. It can lift a staggering 2,000t and has a 33m span. The feat of below-the- hook engineering was delivered for offshore work to the Dutch company Safe Lifting Europe. It is not the first record-breaking beam it has supplied for Safe Lifting. An earlier beam for the same client, of 1,500t at 20m span, was at the time also a record- breaker for Modulift. “We are working in a market that is showing unlimited potential in terms of capacity,” says Jacques Vroegop, technical director, Safe Lifting Europe. “We could be talking about much
heavier lifts becoming commonplace. At the moment we are working with cranes offering up to 1,000t capacity but we are in a very dynamic sector.”
www.hoistmagazine.com | May 2021 | 33
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