Monday, December 17, 2018
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Navy salvaging sunken tug

De Mist salvageThe Navy’s going it alone and will salvage the sunken tug De Mist using own resources.

The decommissioned tug sank last Saturday in the Still Water Basin of Simon’s Town Harbour. She settled on her port side at a depth between eight and to 10 metres, with her bow deepest.

“This was not ideal as divers could not attach lifting bags to both sides of the tug. Bags were attached to one side only, which caused her to roll and she is presently at an angle of 30 degrees to starboard,” said Commander Greyling van den Berg adding this was fortunate because divers can now work on both sides of the sunken vessel.

The next phase of salvage work saw divers close all vents and watertight hatches to make the tug as watertight as possible.

“From here the plan is to use two large hoses to simultaneously pump water out and air into the hull. Divers will also attach lifting bags, sufficient to give 50 tons of lift, to the vessel. This will make De Mist positively buoyant causing her to rise.

“The tug sank about 50m from the synchrolift. This platform is designed to be lowered into the water, where a ship sails onto the lift and is raised using winches.

“Tug De Mist only needs to be raised off the seabed to clear the synchrolift platform,” Van den Berg said.

The entire operation to date – and through to completion – has and will be done using SA Navy equipment with no extra or special equipment having to be acquired.

“Navy divers, Naval Engineering Section and Armscor Dockyard worked tirelessly to solve numerous mathematical, physical and engineering problems to lift the tug safely. This operation is an ideal training opportunity providing invaluable practical salvage experience for the SA Navy. The salvage operation is proceeding slowly with all Navy divers given opportunities to work salvage, even less experienced divers so they can gain experience,” he said.

The pollution aspect is also receiving the same attention to detail with a floating barrier put up to contain minimal oil spill from the sunken vessel.

The salvage operation has allowed more oil out of De Mist and a second barrier was positioned to ensure no oil escapes the Still Water and into the Harbour Outer Basin. Some oil has been recovered from the water. Its origin is probably the vessel’s bilge. The tug only had enough diesel aboard to start its generators, as most fuel was removed when she was decommissioned.

Van den Berg is cautiously optimistic the Navy team will have De Mist out of the water and on the synchrolift in the next few days.

 

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