1991 Fiscal Year Final Research Report Summary
Studies on the Safety and Control of the Deep Ocean Mining System
| Project/Area Number |
02452225
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
資源開発工学
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| Research Institution | Akita University |
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Principal Investigator |
ASO Kazuo Akita Univ., Mining College, Professor, 鉱山学部, 教授 (30006639)
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| Co-Investigator(Kenkyū-buntansha) |
KAN Katsushige Akita Univ., Mining College, Res. Assistant, 鉱山学部, 助手 (40006672)
DOKI Hitoshi Akita Univ., Mining College, Associate Prof., 鉱山学部, 助教授 (80134055)
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| Project Period (FY) |
1990 – 1991
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| Keywords | Deep ocean mining system / Pipe-string / Longitudinal vibration / Buffer / Pump-module / Optimum shape / Vibration absorber / Optimum condition for design |
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| Research Abstract |
For mining mineral resources from deep sea bottoms, a pipe string is needed to connect the mining ship on the sea surface with the collector or miner on the sea floor. Furthermore, in the pump lift system of ore, the string must be equipped with one or more pump modules for pumping the mineral resources up to the ship and with the buffer which regulates the density of ore-fluid mixture in the pipe string and plays a role of the weight to stabilize the mechanical behavior of the string. The pipe string in this system is apt to vibrate longitudinally and laterally due to the ship motions. Hence, these vibrations of the string must be controlled for the safe operation of the above mentioned mining system.
In the fiscal year of 1990, the method evaluating fluid forces acting on the pump-modules and, the buffer was established, and the fluid forces acting on various shapes of the pump-modules as well as buffer were determined by this method. Then, the longitudinal and lateral vibrations of the pipe-string were analyzed, and the former was found to be more destructive than the latter as far as the strength of the pipe-string was concerned.
In the fiscal year of 1991, the shape-effects of the pump-modules and buffer on the longitudinal vibration of the pipe-string were examined, and the pump-modules or buffer causing higher drag force proved to be more effective in order to reduce the longitudinal vibration. Thus, the buffer with the optimum shape for this purpose could reduce the resonance amplitude of the vibration of the pipe-string by about 40%. Next, vibration absorbers were attached to the pump-modules as well as the buffer for the same purpose. Then, i t was found that the absorber attached to the buffer could reduce the resonance amplitude of the pipe-string by 50-63% and the maximum axial stress produced in the pipe-string by 18-40%. Moreover, the optimum condition for designing the vibration absorber was determined.
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