Exploration • Drilling • Field Services
Increase rope life span with plastified steel cores
Kurt Schmidsberger explains how plastification of a lubricated steel core increases the service life of ropes.
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lastified lubricated steel cores generally increase the life span of offshore crane ropes. Tat is the reason why the product portfolios of all major manufacturers of high-performance steel wire ropes also
feature ropes that incorporate this technology. Steel wire rope specialist Teufelberger has already been using plastic-covered steel cores for several years. Plastification has a positive impact on a rope’s life span in two different ways. Firstly, the compact plastic cover acts like a cushion between the rope’s inner portion and its outer strands. Secondly, this technology effectively blocks the ingress of water into the core.
Cushioning properties When the rope is tensioned, all strands will be stretched accordingly. As the helix of the outer strands gets longer, their diameter decreases. Hence, the rope’s inner portion is subjected to lateral compression. Tis is where the Plastfill core comes in. It causes punctiform pressures to be distributed across larger areas and, in this way, eases the contact pressure per unit area exerted on the wire. Tis reduces stress concentration and, as a result, enhances the rope’s service life. In use, ropes are not only tensioned but also exposed, on a daily basis, to repeated bending stresses while running over sheaves or subjected to high lateral pressures in multilayer spooling. In this connection, Plastfill cores offer another
advantage: when running over sheaves, there is relative movement of the wires and strands. Internal wear frequently results in fretting corrosion that shortens the rope’s service life accordingly. Lubricating the steel core and surrounding it with a compact plastic cover in order to keep the lubrication intact helps to reduce fretting corrosion in the rope’s inner portion. Furthermore, by embedding the outer strands in the plastic cover, it is possible to position the strands accurately, which in turn ensures the consistent spacing of the strands in a vault-like configuration.
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Tis optimised construction features the stabilised strand structure ensured by the Plastfill core. It helps distribute the pressure evenly onto all strands and,
Tis is of particular importance for multilayer spooling where ropes are exposed to high lateral pressures.
Fig. 1. Schematic view of the lateral compression.
Fig 2. A cross-section of EVOLUTION Q 8 rope
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