In order to reduce the longitudinal vibration of the pipe string in the deep ocean mining system, a vibration absorber, which was composed of a mass, springs and dampers, was attached to the pump module as well as the buffer. Then, the effect of the absorber on the vibration was analyzed theoretically. The results indicate that the abovementioned absorber attached to the buffer could almost reduce the resonance amplitudes of the buffer and pump module to almost 40% values and that larger mass of the absorber more reduces those amplitudes within the range where the mass ratio of absorber's to buffer's is small, although the effective range of the absorber is more limited. There are the optimum values for the spring constant of the absorber and the above mentioned mass ratio to reduce the vibration of the pipe string. Furthermore, the absorber attached to the buffer causes much greater effect on the vibration of the pipe string than that attached to the pump module.
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 the 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.
