A 50 year old floating dock located at a shipyard in Munkebo by the Odense fjord in Denmark was set to be demolished and sold for scraps earlier this year. Unfortunately it broke during the process, and sunk to the bottom of the sea.
A shipping company named J.A. Rederiet was brought in to salvage the dock. They contacted Søren Lindstrøm Andersen, a leading expert in Denmark on diamond wire cutting and a long time freelance consultant for Husqvarna Construction Products. Could he help them with getting this dock, measuring 100x32 metres and weighing about 3500 metric tons, up again?
“They had heard about a project I worked on where we equipped a small submarine with a wire saw to cut down wind turbine towers at sea. I drew up a sketch for how I thought the dock best could be cut into liftable sections, and they said let’s go with it”, says Søren Lindstrøm Andersen.
Cut in sections
CS 2512, PP 455 E and Cobra C 1000 wire
For the project, Søren Lindstrøm Andersen used two Husqvarna CS 2512 wire saws, two hydraulic power packs PP 455 E and a total of 520 metres of Cobra C 1000 diamond wire.
“The ideal solution would have been to make the cuts starting from the bottom going upwards, but there was no way to get the wire under the dry-dock, so we had to start by cutting from the top going down”, says Søren Lindstrøm Andersen.
To accomplish this, they created an ingenious rig using a 40 meter long over water causeway as base. They attached a number of gauge wheels both on the rig and – with the help of divers – on the sea bottom 14 metres below surface that the wire would run on.
The floating dock was cut into 18 sections, with each cut taking between two to five days to accomplish.
“We had to go slowly, there was a lot of scrap in the construction and loose objects we couldn’t always
see from our position, that threatened to damage or break the wire”, says Søren Lindstrøm Andersen.
520 metres of Cobra C 1000 diamond wire was used
After a cut was complete, J.A. Rederiet lifted the sections, each weighing up to 180 tons, using a floating crane. Kim Alfastsen at J.A. Rederiet says that this was the largest construction his firm has salvaged from the sea bottom.
“It was a very special and in some ways challenging project, due to the massive size of the dry-dock. Of course there are always a few road bumps, but in the grand scheme of things, everything went according to plan”, says Kim Alfastsen.
He has nothing but praise for Husqvarna’s role in the project.
“The equipment has worked great, it’s been very reliable”, he says.
The project started in April and the last section was lifted from the sea during the first days of June. Søren Lindstrøm Andersen says that although he’s been in this business for almost 30 years, he has never heard of a project as big as this.
“Not when it comes to how large the cuts were, no. This was an extreme project”, he says.
Looking back, would he do something different?
“Well, here we used the two CS 2512 wire saws one at a time, but next time a project of this size comes along, I think I’ll alter the set up so that the saws work simultaneously. That way we should be able to cut even faster”, he concludes.