Tug De Mist finally salvaged

2018-12-18 06:01
Tug De Mist is out of the water.

Tug De Mist is out of the water.

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After several days and nights of ingenuity, tenacity and sheer hard work by those involved, the SA Navy succeeded in bringing Tug De Mist out of the water in the early hours of Thursday 6 December. Tug De Mist sank on Saturday 10 November in the still-water basin of Simon’s Town Harbour, settling on her port side at a relatively shallow depth of 10m.

Commander Greyling van den Berg says after the Naval Engineering Department and Navy divers conducted a comprehensive assessment, operations commenced to bring her out of the water using a limited array of lifting bags and submersible pumps. “The salvage entailed raising the tug off the seabed and towing her to the Synchrolift facility about 50m away; however shallow water salvages are known to be extremely difficult (because of the lack of air expansion and buoyancy at this depth),” he says.

Van den Berg says the main challenge experienced over the last few weeks was trying to make the 39-year-old tug airtight (and thus buoyant). “The divers used underwater welding equipment to seal off holes in order to pump her full of air, but as soon as leaks were sealed, other leaks bubbled to the surface. The personnel of the Armscor Dockyard were however constantly on hand to provide bungs and other mechanisms for leak stopping and shoring.”

On Wednesday 28 November, the Navy divers concentrated all lifting efforts on the aft of the tug, managing to raise her and bring her 2m away from the quay, with her keel resting on the bedrock. The same was achieved on the forward side. The mooring lighter (built by dockyard apprentices more than 100 years ago) was used as mechanism to create further lift. Because of her age, the mooring lighter does not have a generator and cannot operate her capstan. In order to mitigate this, the winch of Tug Umalusi was used to create this lift through the mooring lighter’s fair leads. The docking plate under the tug kept on getting stuck in the sand during the lifting process, adding to complications. Throughout the lifting process, divers continued sealing off leaks and filling fuel, freshwater and ballast tanks with air.

On Monday 3 December, the naval riggers in conjunction with the naval harbour master, devised a way of using “snatch blocks” to create further buoyancy. The aim was to raise the tug high enough to clear the platform of the Synchrolift. This was achieved on Wednesday 5 December at approximately 15:00. The prevailing airlocks in the tug created balance issues, however, which were finally overcome at around midnight on 5 December. Floating, but still listing slightly, she was finally pulled to the Synchrolift.

‘’The salvage operation and obstacles overcome are an amazing display of teamwork and resourcefulness by the dedicated team of professionals who worked tirelessly to solve numerous mathematical, physical and engineering problems. This exercise also provided invaluable practical salvage experience for the Navy divers, at no cost to the organisation. A floating barrier was also put in place to contain the oil spill within the still-water basin, with a second barrier between the still-water basin and outer basin,” says Van den Berg.


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