ABSTRACT

The Agency of Industrial Science and Technology [AIST]. the Ministry of International Trade and Industry Japan [MITI]. started the Large-Scale Project entitled "The Research and Development Project of Manganese Nodule Mining System" in 1981. The mining system of this project consists of many subsystems. Many activities on the research and development of each subsystem have already been performed. One of the most important structural elements is the pipe strings with its function given by the nodule transfer channel and a means of towing the collector on the sea bed. The pipe strings are subjected severe static axial stresses due to the dead weight. In addition to this fact, the fluctuating axial and bending stresses are produced in the pipes due to the motion of the mining ship. Under these circumstances, the strength design of the pipe string should be carefully performed. This paper presents the design considerations of the lifting pipes such as the evaluation of hydrodynamic load, the procedure to predict the behavior of the pipe strings, fatigue and buckling strength, nondestructive inspection and other important aspects.

INTRODUCTION

The mining system in the project is a hydraulic mining system in which nodules are collected by a towed collector on the sea bed and transported in a slurry of seawater and nodules through the lifting pipes onto the mining ship. The mining system consists of many subsystems such as the mining ship, the lifting procedure, the lifting pipe, the machinery and pipe handling, the collector and the measurement and control Subsystems. The many activities on the research and development of each subsystem have been performed under the management of "The Technology Research Association of Manganese Nodule Mining System (TRAM)" promoted by the AIST, MITI and supported by the "New Energy and Industrial Technology Development Organization (NEDO)" (Wakabayashi. 1986. Kajitam. 1988. Oyama. 1990).

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