Stacks of experience

18 June 2012

Both pontoons stacked with a total of 18 barge hulls ready for Mammoet to begin unloading

Both pontoons stacked with a total of 18 barge hulls ready for Mammoet to begin unloading

Unloading stacks of barges, some 135 metres long and weighing as much as 1,460 tonnes, was a challenge for Mammoet where a wide range of in-house capabilities were brought to bear. "This project is an excellent opportunity to show how Mammoet can offer the client a complete solution. By providing a combination of maritime, terminal, heavy lifting, engineering and project management services for a fixed price, we took care of the job," says Sander Splinter, Mammoet Europe managing director, who explained the job to Alex Dahm.

The job started in China with a load of 18 steel hulls (known as a casco) for inland waterway vessels and two pontoons. The barge hulls, weighing from 400 tonnes to more than 1,400 tonnes, were built prior to an insolvency. A Dutch shipyard bought them all ex-China and had them shipped to the Netherlands.

A semi-submersible heavy lift vessel, the Blue Marlin from Dockwise, picked up the entire load in China and sailed to Rotterdam. Mammoet was contracted by client Veka, a Dutch ship and yacht builder, to move and offload the hulls from the two pontoons. Project manager was Jaap van de Riet. The two triple stacks were floated off from the Dockwise vessel in a deep canal and then moved, using Mammoet Maritime tugs, to the company's yard in Schiedam. In addition to its own quay, Mammoet used its own pontoons as floating storage.

The cascos, without their deck house superstructure, were stacked four high with the deck houses loaded together on the top. Some are already sold and will go straight off to shipyards to be fitted out for customers with engines, instrumentation, and so on while others will be stored.

When the unloading started at the end of March one of the two pontoons was sold in the Netherlands.

While Mammoet's rail mounted PHB crane on the quay has a capacity of 250 tonnes and was used in the project, its capacity is nothing like enough to lift the barges. For that a pair of 1,350 tonne capacity Liebherr LR 11350 crawler cranes were brought in and set up on heavy duty steel matting at the quayside of the Mammoet European headquarters in Schiedam near Rotterdam.

Lifting together

The cranes lifted in tandem and, according to the size of the vessel being unloaded next, one crane was tracked along the quay prior to lifts to accommodate the different load lengths, which ranged from 72 to 135 m. Both cranes were set up in SDB2 superlift configuration with 72 m of main boom. Both had 300 tonnes of counterweight while one had 500 tonnes of superlift ballast and the other 400 tonnes, both set at 30 metres radius.

Other equipment used included a Kobelco crawler crane, a 100 tonne capacity all terrain crane and two Mammoet Maritime pushboats or tugs.

The morning of 5 April saw the lift of one of the heaviest vessels, Barge 1, at 1,460 tonnes. It was in the stack closest to the quayside and was lifted at a radius of 20 m where the crane with 500 tonnes of superlift counterweight took 892 tonnes of the load (97.6% of its capacity) and the other 704 tonnes (85.2% of capacity), each including a 39 tonne hook block and around 30 tonnes of rigging.

Each crane was attached to the load from its double hook with eight lifting lugs via long adjustable steel slings. The slings on the 16 attachment points had to be adjusted to prevent peak loads. "We did a lot of engineering to get the right rigging," Splinter explains, "Some things were a little different on the vessels from the drawings but we were able to make the necessary adjustments in the rigging."

Mammoet only had one crane available so the other was cross-hired from Roll-Lift. Following completion of testing in March the new machine was taken directly from the Liebherr factory in Germany. "The equipment we need for our projects will preferably be our own, but it must be economical as well. In this case we could only deliver one of our own machines because the other ones are busy in other parts of the world. Our network enables us to find the most economic solution to support our project needs. By managing our subcontractors we make sure that we deliver Mammoet quality to our clients," Splinter explains.

Other capabilities

As well as heavy lifting capability a lot of ballasting was also required. The lowest pontoon, the floating one, on top of which the barge hulls were stacked had to be compensated so it remained stable and level as the loads are lifted off. With the pontoon ballasted the sequence was to move it out of the way so that the cranes could lower the suspended load into the water for it to be floated away, ready for the return of the loaded pontoon and for the process of unloading another barge to begin again.

"What we achieved is that we brought together a lot of our wide range of capabilities and expertise to complete the job. We have the terminal, we have the marine division and the knowledge to shift the barges, we have the heavy lift capability and we did all the engineering ourselves," Splinter explains.

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