Barge-mounted cranes came to the rescue off the New Zealand coast
Contributed by Auckland Cranes
Barge-mounted cranes are often seen working diligently to deliver jetty and wharf projects and in the construction of bridges. What most of us never get to witness is these unsung heroes doing their thing at sea. Barge-mounted cranes are often the solution in the event of a ship wreckage or grounding. Project Rena is a great example of where barge-mounted cranes were deployed to recover cargo which otherwise would have been lost at sea.
On 5 October 2011, near the Astrolabe Reef, the cargo ship Rena ran aground near Tauranga, New Zealand. The Rena, a 236-metre container ship, was carrying 1,368 containers and 1,733 tonnes of heavy fuel oil when she hit the reef. By 13 October the ship was listing by 20 degrees and 88 of her containers had fallen into the sea. Due to increased pressure to her hull, Rena was expected to split in two at any time. The salvors’ first priority was to pump the oil off the Rena but bad weather hampered efforts and more than 350 tonnes of oil spilled into the ocean.
Auckland Waikato Cranes was engaged by Svitzer Salver to recover containers from the precariously poised ship. Auckland Waikato Cranes deployed a Kobelco 7150 and one Liebherr LR1280 crane (supplied by Smith Crane & Construction). The P&B Sea-Tow barge was deployed from Australia to carry the two cranes.
The Port of Tauranga provided the assembly area for the crawler cranes and a berth to walk the cranes onto Sea-Tow 60. Once the cranes were secured to the barge it was towed to site and moored at the stern of the Rena where the containers were lifted off the ship and onto the tug Go Canopus.
This project was a mammoth team effort lasting almost two years with crews working 7 days a week right through Christmas and Easter. The barge-mounted cranes not only removed freight from the Rena and the ocean, but supported demolition works including cutting up the wreck and removing parts.
Dealing with a listing ship and tumbling cargo
The location of the Rena on the Astrolabe reef made this a very challenging project. The wreck was on a 22-degree list when the salvage operation commenced, making standing and walking difficult. Getting access to the containers from a man cage was impossible because of the pitching and rolling of the barge caused by the ocean swell. Riggers had to be lowered onto the containers with a helicopter.
Due to the list of the ship and the lean of the containers, the crew had to identify the sequence in which the containers could be safely removed. Prior to lifting each container, additional lashings were applied to the neighbouring containers to prevent them from falling. This painstaking process had to be repeated for each container.
Working in rough seas
Rough seas made it impossible to place a container in an exact location on the shuttle barge without two or three crew members controlling the container tag lines. A highly competent dogman was required to predict the movements of the load and the barge, and to time the lowering of the hook to suit.
Health and safety risks for the project team included wind, sunburn, dehydration, fatigue and physical strain. As well as managing the risks to personnel, Auckland Waikato Cranes implemented numerous safety measures for the cranes themselves prior to deploying the machines to sea. Foul weather boom rests were installed for when the cranes were out of service as well as stools to prop the counterweights on. These measures reduced the wear and tear caused by the constant swaying motion of the barge. Tugger hoists were fitted to stop the pendulum effect of the hook (swinging the load out of radius or away from the crane) caused by the ocean swell as it passed under the barge.
All in all, this was an extremely challenging project but it is a great illustration of how barge-mounted cranes can be a very valuable and flexible solution for a salvage mission.
Numerous parties and contractors were involved in the salvage project. It took until 2014 for the wreck to salvaged, along with approximately 77% of the initial containers.