Analysis of coupled hull - Cold water pipe mooring for offshore desalination plant

The design of a 0.25 Million Litres per Day (MLD) low pressure desalination plant in 150m water depth using a Tension Leg Counterweight Platform (TLCP) consisting of a 10m diameter hull, 1m diameter cold water pipe with counterweight and vertical taut mooring has been carried out. A 1:50 scale model of the TLCP is tested in the 30m × 30m ×3m wave basin in Department of Ocean Engineering, IIT Madras. The tensions in mooring lines are measured using load cells. The coupled analysis of the TLCP is studied using the Nonlinear Analysis of Offshore Structures (NAOS) program developed at IIT MADRAS. The measured tension response of mooring line compare well with numerical results. The Surge, Heave, Pitch and Tension response amplitude operators for the TLCP obtained from numerical study are observed to be within the permissible limits for the operational wave condition whereas the TLCP performs satisfactorily for the survival wave condition. The numerical and model studies are carried out for regular waves. The effect of counterweight and pretension on platform motions is studied in this paper. Copyright ©2007 by ASME.