Dyneema ropes fundamental for ‘Concordia’ parbuckling

The Titan-Micoperi salvage partnership realised early on that any ropes required for the creation of the holdback system, to hold the wreck in place and then help bring it upright, would rub along the sea floor. It was imperative that any further damage to the ecosystem, beyond that caused by the ship itself running aground, be kept to a minimum. For this reason, the decision was made to go for a rope system that is not only extremely strong, but also very light and easy to handle. As Dyneema has neutral buoyancy in water, the ropes are easy to pull through the water by divers.

During the installation process, the ropes with Dyneema did indeed not drag along the seabed as steel ropes would have done. Nevertheless, since they are in constant contact along much of their length with the hull of the ship, they need surface protection, which is why Dextron 12 Plus ropes with patented protective jackets from leading Norwegian rope maker Offshore and Trawl Supply (OTS) were chosen. The covers for the Costa Concordia project also contained a reflective additive so that they could easily be seen by divers working in the dark.

In all, there were 22 Dextron 12 Plus ropes holding the Costa Concordia, two running from each of the 11 towers mounted on the sea floor along the starboard (shore-side) side of the ship and connecting to chains that ran under the hull and which were attached to the far (port) side. All the ropes had the same diameter, but each had a different length, of between 40 and 55 meters.

Since the ropes were to be loaded for a prolonged period of time, creep had to be considered. Among the various types of HMPE fiber on the market today, Dyneema has been demonstrated to creep the least, and by a significant factor.

Marc Eijssen, Senior Application Manager, Offshore & Industrial at DSM Dyneema, says the company carried out a series of creep evaluations using its in-house model to predict creep under a variety of load and temperature scenarios. Based on these models, Titan-Micoperi and OTS were able to calculate the exact length needed for each rope. As is clear to see, the model proved accurate, and the parbuckling operation went exactly according to plan.

By Jake Frith