Saving the big ships24 August 2012
If Emma Mærsk, the world’s biggest container vessel collided with a rock and sunk, salvors using traditional cranes would be in over their heads. To prepare for bigger lifts they’re designing new devices.
Rich Habib's salvage firm Titan has been contracted to salvage the ultra-large 45,000t cruise ship Costa Concordia grounded off the coast of Italy.
He says, "If you ask the insurance companies, who are our primary clients, the lifts and jobs are getting more expensive and bigger because ships are bigger than they used to be."
The problem: Big ships
Needing to salvage larger ships, and facing globalization and cost issues, Salvors have designed pullers, big winches and other underwater devices to increase the efficiency of salvage over the years.
Mammoet, innovator of its own crane band of land cranes, is one firm using its engineering smarts to remove wrecks offshore and on coastlines.
It also designs and builds ancillary salvage equipment such as protective casings to go around the ship for environmental containment. Commercial Manager of Mammoet Salvage, Timon van der Vlies, says capacities grow as lifts get more demanding.
"If you see the development of the size of container vessel, it's huge: the 'triple E' Class container vessels have a capacity of 18,000 TEU with LOA of 400m and a Breath of 59m. If something were to happen with one those vessels a serious problem for owner, insurer and salvor arises.
"The biggest concern of the insurance companies is, if something were to happen with the biggest container vessels, is assistance available? Additional and specialized equipment will be required to deal with extraordinary situations."
The new generation of container vessels will require a different approach from salvors as a traditional approach will be insufficient, he says.
Many of today's heaviest salvage lifts couldn't be done a decade ago: now giant offshore 3,000t-7,000t sheerleg vessels such as Scaldis' Rambiz are used for salvage and construction.
Thanks to the sturdy A-frame design, allowing work to be done quickly and regardless of weather, sheerlegs are used for handling heavy ship pieces during salvage.
Regional salvors GPS Marine in the UK has a fleet of 400t and 450t sheerlegs, often using four in tandem to salvage vessels up to 3,000t.
Numbering under fifty in the world, large sheerleg vessels are in high demand for modular concrete construction and heavy cargo lifts at riversides and shipyards, and are often hard to get ahold of.
Managing director Gary Spencer says, "The geography of the available sheerlegs is always an aspect of salvage work or wreck removal."
While the large sheerleg crane for the main hull lift is being mobilized, more readily available, cheaper crane barges with land crawlers can do the lighter work of installing wire and removing small debris, cargo, and oil.
Spencer, says, "Installation of wires under the wreck is normally quite a time-consuming and unpredictable process. You're relying on the conditions of the seabed, tidal and weather conditions to allow divers to work in conjunction with the surface equipment to underrun or fix wires to the wrecks this work can take days and sometimes weeks to get the lifting wires installed on the wreck."
"Crawler cranes do not react well to the shock loading and side jib loading caused by wave action, but for grab work and lighter work, they're fine."
When this is done, a heavily built sheerleg, designed to withstand the dynamic loading of waves acting on the vessel, arrives to the site to do the heavy lift of the hull.
Spencer says, "When the sheerlegs arrive on site they connect their lifting hooks to the wires which are installed on the sunken or stricken vessel. As per the designed salvage plan, the vessel will then be lifted slowly to the surface and held by the sheerleg at the surface, just breaking the water.
With major international salvage firms globalizing, and the increasing size of the lifts, companies with smaller equipment are becoming subcontractors and pushing their fleets for support work.
GPS Marine adds to its business by using its fleet as support for larger salvors. It works in Europe and may soon begin working in Africa.
To handle bigger load capacities, GPS Marine is considering increasing the 400t lifting capacity of the GPS Atlas to 475t , by installing an extra hook, for a total of three in the main A-frame.
Spencer says the three hook configuration, while adding heft to the sheerlegs, could also counteract overbalancing in one hook.
Pullers and TPCs pick up the pace
These days international companies are improving proprietary systems that can in some cases get to the scene of a wreck faster than a sheerleg, and lift heavier ship parts.
Titan is known for being a forerunner in the development of tandem use of its own chain pullers, up to 40 at once, for lifting up to 12,000t.
Rich Habib is Managing Director of Titan Salvage. He explains that engineering lifts for chain pullers means less time is spent on coordinating with sheerleg suppliers.
"I think that whenever we can we try to use our pullers because we own them. If you have a wreck somewhere in the world, you have to find where the nearest sheerleg in the world, and they're harder to move," says Habib.
Realizing the advantages of pullers, Titan recomposed its fleet. "Later in the eighties, we sold our tugs and cranes and changed the model to become a company that had top notch crews and could fly away, because we could always find barges and cranes to rent everywhere in the world. e tried to use our brains instead."
Titan designed its own linear hydraulic chain puller, which is today the 300t Titan puller. The firm owns a fleet of forty.
It built its puller fleet because tandem puller lifts can achieve much heavier lifts than a sheerleg alone can handle, Habib explains. "We chain them together. We just did a job where we had forty pullers together so we can bring to bear about 12,000t of force."
Winches are used alongside pullers to increase capacity, Habib says. "Last year we bought 12 500t winches. That's another 5,000-6,000t, so we have 18,000t in total. We have done some of salvage's largest pulls and lifts: Up to 6,000t for pulls and 3,000t for lifts. Nowadays, there are 7,000t cranes that can do that, but several years ago there weren't."
Another major salvor, Mammoet Salvage, draws on its fleets of crane barges, sheerlegs, and proprietary
equipment at its three international bases.
In 1997, Mammoet innovated the first of its own multi-thousand ton movers, the 2000t Platform TwinRing ringer crane, with a platform that rests on a ring for slewing.
Increasing the mobility of giant cranes, Mammoet created Platform Twinring; containerized (PTC) versions of ringer cranes up to 3,200t, with components that fit in standard shipping containers.
While PTCs are not very common in the salvage industry, they are particularly convenient for speedy heavylift salvage whether by land or by sea.
Van der Vlies explains, "There are two options with a PTC depending of the situation of the wreck. If the wreck is near close to land, we place the PTC on land nearby and cut the wreck in pieces. We discharge those pieces with the PTC crane on a barge or on shore.
"The seaside option is to put the PTC on a big barge and use it as a sheerleg or crane barge."
PTCs also offer the advantage of being modular, so they can be built up to increase reach across the width of a large cargo vessel. "The problem with big container vessels could be the reach of the crane because the width is huge and you need that reach to remove the containers," says Van der Vlies.
Lifting from the deepest depths
Apart from heavy lift, a challenge salvors face is salvaging deeper than 150m, where divers cannot easily go attach the ropes for lifting, so they are looking beyond cranes to do it.
A Deep Water Recovery System (DWRS), developed by Mammoet using underwater excavators, is intended for this. "We try to develop and engineer special tools for each kind of project," says Van der Vlies.
Remote controlled excavators used at 140m depth, put onto a seabed, remove the cargo from the ship, placing it into a basket which is then lifted onto a barge, Van der Vlies says:
"For cargo removal we empty the ship. We often design and build special equipment and tools for such a project depending of depth and situation. We designed and built once a special vacuum grip to remove aluminum blocks from a cargohold from a ship on a depth of 130m."
"For a big environmental protection removal job in Canada at a depth of 360m, we designed a special environmental protecting case around a fuel truck."
Mammoet is already using its engineering experience to design a tool which may be able to handle lifts for new generation 16,000 TEU cargo vessels. "At the moment we have been working with some insurance companies to develop special equipment to remove the containers in case of an extraordinary situation, because the contents are valuable, and the insurance value of the containers is huge. You are talking about a few €100m for container vessels of this size," says Van der Vlies.
Mammoet estimates that designing and making the heavy lift salvage tool for the job will require large investments. The financing opportunities for such an undertaking may not become available until insurance companies need to call on companies to handle a 16,000 TEU shipwreck.
Van der Vlies says, "It is matter of time until something happens with this kind of new generation container vessel, and we can't say whether the ship will be laying in deep or shallow water, or if it will be on fire, or if it will collide with another vessel. No two situations are the same in salvage world."
Looking to expand not heft but depth, a firm in the UK called Deep Tek is poised with the patented winch technology to literally take salvage where it has never been before: 5,000m underwater.
Wire rope winches for deepwater lifting bottom out at about 3,000m water depth where the heavy weight of the rope makes lifting impossible.
While fibre ropes are light enough to use with winches, the problem of rope deformation has traditionally made this kind of rope equally impractical.
Deep Tek's patented spooling pattern counters the problem, and will increase applications for fibre rope winches.
Moya Crawford, Deep Tek's Managing Director, plans on developing the salvage market for its winches in 2013 by launching a rental fleet to demonstrate the smaller end of their potential.
Small versions of the winches will be able to lift 30t at depths as low as 5000m.
Deep Tek also told Cranes Today that development is underway for its heavylifting winch range, which will specifically address heavy lift of 750t down to 2250m underwater.