ABSTRACT:

Underwater sand mining system consisting of a crawler that can mine and pump sand slurry from 500 metre water depth through a flexible hose to the mother ship has been designed and developed as the first step towards development of technology for deep sea mining. The crawler is designed to work on a soft sea bed and has a special track belt with involute teeth to compact the bed during motion. The crawler has a manipulator arm with a cutter to sweep the seabed and mine sand and a positive displacement pump to deliver the sand slurry to the mother ship through a flexible hose. A cone tester and vane tester are provided to perform soil testing in-situ. The main drives of the crawler an: hydraulically operated. The crawler has transducers for measurement of velocity, drum speed, heading, sand concentration etc. and has a closed loop control for speed, heading and slip. An umbilical cable with an outer steel armour carries the weight of the crawler during launching and retrieval. The cable has copper conductors and optical fibres for power and data transmission respectively. The crawler has he en designed for a pressure rating of 600 bar. The system has been tested for locomotion, pumping etc. on land and was soak tested in the sea and water pumped using the slurry pump.

INTRODUCTION

A joint collaborative programme involving National Institute of Ocean Technology, (NIOT) India and Institut für Konstruktion (IKS) of University of Siegen, Germany was initiated to develop a deep sea mining system with a crawler and a flexible riser system. The existing deep sea mining concepts are based on the deep sea tests carried out by various consortia in the seventies (Chung, Whitney and Loden 1980; Brink and Chung, 1981; Chung, 1996).

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