Experimental investigation of an external turret-moored FPSO system by VALM arrangement

Abstract

This article deals mainly with an experimental study on a typical external turret-moored floating, production, storage and offloading (FPSO) system by a vertical anchor leg mooring (VALM) arrangement in order to investigate the effect of parameters influencing the mooring and hawser line forces and motion response for different loading conditions with different hawser lengths. A 1:100 scale model of 140,000 DWT turret-moored FPSO system was tested for three loading conditions (i.e. 40% DWT, 70% DWT and 100% DWT) with three hawser lengths (i.e. 15%, 20% and 25% of the length of the FPSO model). The tests were conducted in a 2-m wide wave flume at the Department of Ocean Engineering, Indian Institute of Technology Madras, Chennai. The model tests were carried out under regular waves for the wave frequencies ranging from 0.55 to 1.25 Hz in steps of 0.04 Hz at a water depth of 1 m for head sea condition. The motion response was measured using rotary-type potentiometers, and mooring forces were measured using specially fabricated ring-type load cells. The test results of the mooring forces and motion response are analysed and presented with discussion.