Designing An Ocean Mining Collector System

ABSTRACT Simplicity of form and function, flexibility, ruggedness, and redundancy are four important characteristics of a manganese nodule mining collector. Since the collector is the least accessible element of any ocean mining system, it's reliability will tend to dominate the overall reliability, and, therefore, the economics of the total mining system. A design philosophy and development program is proposed which maximizes the influence of the above characteristics on the reliability of the collector system. Although the design and test philosophies described in this paper were developed for ocean mining collectors, they are general in nature and are applicable to subsea systems outside the ocean mining industry. INTRODUCTION The collector is probably the most critical component of a manganese nodule mining system and its reliability affects the efficiency of the entire mining operation. The recovery, repair, and redeployment of a collector which has failed, at a nominal working depth of 5200 meters, may take more than seven days. The daily operating costs of the mining system dictates that collector reliability be maximized. Insuring maximum reliability of the mining system requires a development program that directs its efforts towards maintaining simplicity, flexibility, ruggedness and redundancy in the design and operation of the collector and its support systems. The authors of this paper were responsible for the collector development program of the multinational Ocean Management, Inc. consortium which recently completed the first successful deep ocean mining tests in the Pacific. Based on their experience and knowledge of the mining environment, one approach for the development of an ocean mining collector system is proposed. This approach maximizes reliability by stressing the application of the four design characteristics throughout all phases of the program, from the conceptual evaluation to the final tests and operation of a commercial collector system. COLLECTOR CONCEPTS The collector system designs used during a commercial scale mining operation will have emerged from a series of design, test, and evaluation cycles that started initially with the collector concepts. The concepts will progress from the simple to the more complex as governed by the operational requirements of the system, but must be restrained in complexity by the need to maintain high reliability. Two of the primary objectives in any collector project are: first, to develop and prove the concept, and second, to insure its feasibility for use in a commercial scale system. Small scale model tests are often sufficient to prove that a concept is feasible. However, they are not generally adequate to insure compatibility with a commercial scale system. The increase in collection width required for commercial operations may have practical limitations due to the concept's power requirements or by limitations of the design principles on which the concept is based. It is essential, therefore, that the development program include an iterative approach to relatively large scale testing phases that are more representative of commercial scale systems.