Ropes with Dyneema played a key role in the largest and most complex maritime salvage operation ever carried out by Titan Salvage and Micoperi on the rocks of the Italian island of Giglio
DSM Dyneema has been supplying ultrahigh molecular weight polyethylene (UHMWPE) fiber, branded as Dyneema for ropes used in tug[ds_preview] and salvage operations for 15 years. Ropes made with Dyneema have been used to pull stricken ships stranded in shallow waters, as well as oil platforms damaged in hurricanes, to safety all around the world. The »Costa Concordia« project’s objective to retrieve in one piece, such a massive vessel (117,000t) with minimal damage to the delicate marine environment, was probably the company’s most critical salvage project to date.
According to Kedar Sule, Global Marketing Manager at DSM Dyneema, the »Costa Concordia« salvage operation is the biggest salvage operation carried out by anybody, anywhere. »Never before has a ship of this size been salvaged in one piece. Normally wrecks are cut up and the pieces are then removed, but that was not an option in this case due to the location and its environmental sensitivity.«
Steel wire rope remains the most commonly used product in salvage operations, followed by polyester rope. High modulus polyethylene (HMPE), accounts for a small portion of the market, but its importance in critical and environmentally critical operations is being increasingly recognized. For the »Costa Concordia« salvage operation, Titan Salvage and Micoperi ruled out the use of steel because of the high risk of damage it would cause to the sea floor, and to reduce the total weight of the parbuckling system.
Titan-Micoperi realized 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. The »Costa Concordia« went aground in an area of great natural beauty where the underwater ecosystem is very precious. So it was imperative that any further damage to the ecosystem be kept to a minimum. For this reason, it was decided 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. Nick Sloane, the salvage master for the project, estimates that installation of the ropes, including pulling into position and connections at each end, saved around two weeks compared to if steel ropes had been used.
During the installation process, the ropes with Dyneema did 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. »With this solution, the rope cores are kept safer, as is the local ecosystem,« says Sule. The covers for the »Costa Concordia« project contain a reflective additive so that they can easily be seen by divers working with torches in the dark.
OTS is increasingly being seen as the »go to« choice for tug ropes, not least because of its high performance protective jackets. For the »Costa Concordia« project, core and jacket are made in two different grades of Dyneema, each ideal for the specific application. Vebjørn Løviknes, Sales and Marketing Manager at OTS, says the OTS Protective Jacket »is probably the best synthetic protective cover for HMPE ropes in the market today.«
There were 22 Dextron 12-Plus ropes holding the »Costa Concordia«, all have the same diameter, but each has a different length, of between 40 and 55m. »Most of the work for DSM Dyneema was in the run-up to the production of the ropes,« says Sule. »None of us had been involved before in an operation of this scale, and we only had one chance to get it right. But we have substantial technical expertise to back up our product, and we made it all available to OTS and to Titan-Micoperi. With this support, OTS was able to determine the construction, length and size of ropes needed and OTS was able to manufacture exact lengths of the ropes with great precision.«
There was no room for any slack in the ropes to be taken up. Furthermore, 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.
Creep is a phenomenon that occurs very slowly, but in the »Costa Concordia« salvage operation creep was going to be measurable over the several months that the ropes were holding the ship in place, and so it needed to be calculated in advance. Creep is a well-known phenomenon, yet it is complex to predict, since it depends on multiple parameters. DSM Dyneema has developed a sophisticated model that can accurately predict this irreversible elongation over the period of the salvage operation. The company is unique among HMPE fiber suppliers in being able to offer this type of support.
Marc Eijssen, Senior Application Manager, Offshore & Industrial, 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.
»We are used to dealing with major projects« says Eijssen. »We have a lot of experience in marine applications. Many salvage companies work with Dyneema, and they provide us with important feedback. But each case has its own requirements. We rely on our years of experience and technical expertise and strong partnerships to provide the right solution in each specific case.« OTS needed to produce ropes with a breaking load of 1100 tonnes. »When the parbuckling operation was carried out in September 2013, the vessel had been stuck on the rocks for 20 months, during which time its structure could have seriously deteriorated. Each line had to fully contribute to avoid any chance of other lines being overloaded.«
Safeguarding the sub-sea environment was crucial to the total salvage operation. Eijssen: »Titan-Micoperi had originally considered constructing the holdback system using steel rope, despite its weight and handling disadvantages. Following discussions with OTS at a salvage conference, they became convinced that ropes with a patented protective cover to protect the load-bearing core were the way to go.« And DSM Dyneema was ready and willing to provide full support for the project.
Sloane has worked with ropes made with Dyneema for over ten years. »I find it an ideal component«, he says. »The choice of the ropes with Dyneema, along with the OTS abrasive resistant outer protection coat, has resulted in a system that met our needs exactly. The performance allowed us to carry out the operation without having to worry about a failure of the holdback system, and focus on the offshore side of the parbuckling components which required continual monitoring and adjustments.«
