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China, Wanshan Archipelago, Salvage of the Trans Summer
||Empty cargo holds of sunk freighter
||DOP® 200 dredge pump
On August 14th 2013 the 190 meter long, 56.824 dwt bulk freighter Trans Summer sank off the coast of the Wanshan Archipelago. The Trans Summer was at anchor with its cargo of nickel ore at an anchorage 45 miles southwest of Hong Kong when it became overwhelmed by 15 meter waves and 90 kph winds caused by Typhoon Utor. The bulk freighter had suffered some water ingress in the hold causing the cargo to liquefy and shift and the vessel capsized and sank. The 21 crew were able to send out a distress call before abandoning ship. Some of the crew was able to reach the life rafts while others jumped into the water as the vessel listed 30 degrees. Authorities dispatched two helicopters to the scene which were able to save all 21 men, leaving the ship behind. The Trans Summer was headed to China from Indonesia before it sank.
Guangzhou Salvage Bureau was awarded the challenging salvage job of this vessel. The Bureau dispatched the 900t Revolving Construction Barge “Nan Tian Long” for the project. As the Trans Summer sank in open seas, wind and wave action are a major concern. The ship lies immobile on its side in 22m deep water, with the side of the hull rising 5 meters above the water line. The 100m long Nan Tian Long is sufficiently large to be unaffected by external factors. However, wave surges create dangerous torrents and vortex’ in the cargo hold itself.
The Salvage Bureau needed a reliable cutter dredger pump that is easy to set up, performs well in a corrosive saline environment, can handle a 30m discharge height to clear the full 22m deep cargo holds, with enough power remaining to transport the mixture a few hundred meters to the dumping site.
Guangzhou Salvage operates two units of the DOP® 200, one powered by the hydraulics of an excavator, the other unit powered by diesel powered power pack. The dredge pumps have a capacity of 800m3/h and are fixed to an extended boom of an excavator to reach deep into the cargo holds through incisions in the hull. The ore is a mixture of fine clay-like particles and larger rock-like particles which when in contact with water start to cake and become hardened clay. Now that the cargo has been submerged for over 6 months a cutter dredger is essential. The dredge pumpes are equipped with a hardened rotating cutter (cast steel 30Mn5) to loosen up the mineral ore. The client has added a high pressure water jetting system to further agitate the mixture and increase the dredging output. The cargo mixture is pumped over a distance of 100m to a collection point. This set-up, along with the compact design of the pump, allows for maximum control of the movement of the DOP® 200 and ensures neither the pump nor the ship’s hull is damaged by contact.