The design approaches taken and alternatives considered in concept selection and design features associated with the construction of a proof-of concept test system for mining deep seabed manganese nodules at 16,000 foot abyssal depths are presented. Summary results of operational testing undertaken during a two-year test period are presented with principal conclusions derived there from. General information on two other pilot mining tests is included. In addition, considerations associated with the extension of results of the test system to a commercial system are addressed.
The development of systems to mine the deep ocean manganese nodule resource have come a long way since the early 1970' s when serious commercial interest in the exploitation of this unique resource began. By the end of 1978 and early 1979 pilot testing of the principal hydraulic pumping systems had been successfully accomplished on 1/4–1/5 commercial scale, and the industry was poised to move-ahead with the final engineering and development of the commercial sized prototype systems. Adverse-metals market conditions and the realities of risk-reward ratios have postponed the start of private commercial development; although national programs associated with the desire to obtain independent sources of strategic and critical metals, regardless of return on investment, are presently in progress.
A multitude of mining systems were conceived during the initial R&D phase (1968–74). After over fifteen years of R&D and pilot mining testing, the requirement to produce very large quantities of material (1-½to 3 million tons per year) day in and day out, year in and year out, with the necessary efficiency and reliability has resulted in a zeroing-in on continuous hydraulic pumping techniques as the most viable ones to satisfy system economics.
During the years 1977 through 1979 three pilot mining tests were undertaken. These tests involved three international consortia, Ocean Mining Associates (OMA), Ocean Management Incorporated (OMI), and Ocean Minerals Company (OMCO). OMA's test ship was the R/V DEEPSEA MINER II; OMI's the SEDCO 445 and OMCO's the GLOMAR EXPLORER.
The OMA DEEPSEA MINER II tests spanned a two year period 1977-1978 and included four major sea test campaigns. The tests were conducted at a test site within the OMA license exploration area which is located about 1100 nautical miles southwest of San Diego, California. Figure 1 shows the location of the test site as well as boundaries of the OMA, OMI and OMCO license areas which have been issued by the U. S. government pursuant to the Deep Seabed Hard Minerals Resources Act.
Figure 2 is a schematic drawing of the R/V DEEPSEA MINER II, proof-of concept, pilot mining test system. Collection of the nodules is accomplished by a dredge head towed by the mining ship via a dredge pipe string which moves over the ocean floor at low speed gathering and concentrating ore.
