An underwater mining system using flexible riser concept was demonstrated for operations in the Indian seas at 410 metres water depth in 2000 for short duration. Based on the tests, enhancements were done on the mining system for long term operations in areas pertaining to distribution of buoyancy packs, sealing and heat dissipation arrangements. The mother ship was also equipped with Launch and Recovery System and Dynamic Positioning System. The modified system was tested for long term maneuverability and pumping operations at 451 m depth in 2006. The paper discusses the enhancements carried on the mining system and the mother vessel and the results from the sea tests.
India has been allotted a mining site in the Central Indian Ocean Basin (CIOB) by the International Sea-bed Authority and is keen on developing technologies to mine manganese nodules. Deep sea mining of manganese nodules from soft ocean floor at 5000 to 6000 metres depth is a major technological challenge. India has been working on developing this complex technology in a phase wise manner. To minimize development costs and associated risks, initial efforts are focused on realization and qualification of machinery for long term operations in shallow waters, followed by further development of machinery for deep waters. An initial study was done on the various deep sea mining concepts and the flexible riser concept (Grebe, 1997) was chosen for development. An underwater mining system was developed for operations and the flexible riser concept was validated in the Indian seas at 410 metres water depth in 2000. (Deepak et al, 2001) jointly by National Institute of Ocean Technology (NIOT) and Institut für Konstruktion (IKS) of University of Siegen, Germany. The modified system was tested for long term operations at 451 m depth off Goa coast during March 2006.