The lifting pipe system has been developed as one of the subsystems of the manganese nodule mining system supported by NEDO (New Energy Development Organization) directed by the Agency of Industrial Science and Technology the Ministry of International Trade and Industry of Japan. The lifting pipe system consists of a pipe string with its functions as nodule transfer channel as well as a means of towing a collector on the seabed floor. The pipe string is subjected to static axial stresses due to dead weight, as well as the fluctuating axial and bending pipe stresses will be produced due to the motion of a mining ship. During connection of the next new pipe to the already connected pipe string, the top pipe is held by a special device in order to ensure the connection of the new one. During this operation, the top part of the pipe string is deformed due to the ship motion and high stresses will be yielded. This paper discusses how to decrease these high stresses, using a simplified calculation method for bending stresses due to the ship motion.
The lifting pipe for the Manganese Nodule Mining System is an important subsystem in organizing a mining system, because, it has the following roles: transfer channel for the manganese nodule slurry, installation of pumps or air inlet nozzles and means to pull a tow-sled collector both during deployment and at seabed floor. This time we analyzed the bending strength from the view point of handing and deployment as a series of structural strength analysis. We previously studied the strength during the handling and deployment by the nonlinear FEM (Ishikawa, et al. 1990) but this time we analyze it using a program which treats it as a linear beam theory.