Analysis of Deep Sea Umbilical in Steep Wave Configuration

Abstract

Deep sea mining is mineral retrieval process that takes place on the ocean floor wherein global industries are actively exploring and experimenting of different techniques in this relatively new concept of mining for extracting it economically from depths of 5000–5500 m below the ocean’s surface. National Institute of Ocean Technology (NIOT), India has been working on a mining concept for ∼6000 m water depth where a crawler based mining machine collects, crushes and pumps nodules to the mother ship using a positive displacement pump through a flexible riser (umbilical) system. The umbilical also serve as the weight supporting member for the miner and pump. In this paper, static and dynamic analysis of the umbilical system in steep wave configuration and the miner is carried out using ORCAFLEX for launching and touchdown conditions. Three different materials are considered and the best suitable material for umbilical is selected as the first step based on the tension. Then umbilical with Single Miner System is analyzed for the launching and touchdown conditions. Based on the analysis the optimum number and spacing of buoyancy tanks that will keep the stresses within the allowable limits in the umbilical cable are recommended.