ABSTRACT:

The Continuous Line Bucket (CLB) is a mechanical system using an endless loop of rope suspended from " a surface platform to reach the seabed and to which dredge buckets are attached at regular intervals. The Turning CLB is a recent important innovation; by steering the vessel in a circular track, trailing the empty buckets over the stern and bringing UP the loaded buckets amidships from within the arc of the ship" s track a good separation of lines has been achieved. Improvements to the CLB components which have been tested recently include: horizontal traction wheels and ball rollers used in combination to decrease the number of traction wheels by half; new bucket guides and dumping device to automate discharge of the loaded buckets without removing them from the line: and small model test for bucket guides was done. double braided polyester/nylon rope adopted to increase the life of the rope; and various bucket configurations including a piano wire mesh bucket designed by the French Group IFREMER. Filling efficiencies of over 60% were recorded for the buckets. The CLB system was evaluated for nodule deposits in 5.000 mwater depth. for three sizes of ship (15.000 t. 30,000 t and 60,000 t), and three production rates (500tld. 1.000tld and 2.000t/d). Rope sizes selected for the evaluation were 110 mm for 500 t/d. 150 mm for 1.000 t/d and 210 mm for 2, 000 t/d. Two 8 ton ball rollers and 6 traction wheels for the traction device were estimated to cost about 6 million dollars for the case of 1.000 t/d. Rope and buckets were costed as consumables. With a rope life of 1-1.5 years. unit production cost was estimated at $109/t for 500 t/d. $76. 7/t for 1.000 t/d. and $ 54. lit for 2.000 t/d in 1994 study.

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