(3)Numerical analysis of an over-boarding operation for a subsea template
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Lin Lia,∗, Adham M. Amera, Xinying Zhub
a Department of Mechanical and Structural Engineering and Materials Science, University of Stavanger, Norway
b Ocean Installer AS, Stavanger, Norway
Received 16 May 2020; received in revised form 7 August 2020; accepted 7 August 2020
Available online 12 August 2020
Abstract
Subsea templates are normally transported to the installation site on the deck of a crane vessel. After being lifted off from the deck, the
template is 1) over-boarded from the initial location to the target position by the side of the vessel; 2) lowered through the splash zone; 3)
further lowered down to the seabed and 4) finally positioned and landed. All the mentioned phases should be evaluated. Usually, the splash
zone crossing phase is taken as the critical phase and analyzed to define the installation weather criterion. The over-boarding phase has not
been the focus of analysis due to a large involvement of human actions and little involvement of hydrodynamic effects. During offshore
operations, the offshore manager may decide to decrease the defined installation weather criterion if the risk of the personnel safety on deck
during over-boarding phase is considered high. Thus, it is of great need to quantify the operational criterion for such operation. The objective
of this paper is to perform numerical analyses and define the allowable sea states for a safe over-boarding operation. The numerical analyses
using time-domain simulations have been performed in various sea states. Tugger lines have been modelled to control the motions of the
template during the operation. The pendulum motions of the subsea template are considered as the critical responses for the assessment of
the allowable sea states.
© 2020 Shanghai Jiaotong University. Published by Elsevier B.V.
This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)
Keywords: Over-boarding; Subsea template installation; Tugger lines; Allowable sea states; Pendulum motion.