Abstract
A comparative study of lifting lines for subsea equipment decommissioning was conducted to evaluate the applicability of fiber ropes. Generally, conventional steel wire ropes are used for subsea equipment decommissioning operations, but there are some disadvantages in using steel wires as the lifting lines at deepwater depth. To overcome the disadvantages, fiber ropes are proposed for using as lifting lines. The comparative methods to evaluate the performance of both lifting lines include three sections of calculations, payload capacity, and horizontal offset due to current, critical length of lifting line. Moreover, dynamic analysis using Orcaflex was performed to compare the dynamic forces occurring in the lifting lines during subsea equipment decommissioning. The results showed that the fiber ropes had advantages in payload capacity, critical length of lifting line and lower dynamic forces occurred compared to the steel wire ropes at deepwater depth.
Highlights
Many subsea fields are currently in operation, and an increasing number of subsea equipment such as a tree, manifold, and pipeline have or will reach their end of the service life in the near future, which may consider being decommissioned
A new installation method has been proposed in the field of subsea installations, which is fiber ropes can be used as lifting line for ultra-deepwater installation, and can be substituted for the conventional steel wire rope [2], and in two-fall system using fiber ropes [3]
The main objective of this study is to do the comparative study of two lifting lines, steel wire ropes and fiber ropes to evaluate the applicability of fiber ropes during subsea equipment decommissioning
Summary
Many subsea fields are currently in operation, and an increasing number of subsea equipment such as a tree, manifold, and pipeline have or will reach their end of the service life in the near future, which may consider being decommissioned. Conventional steel wire ropes have been typically used as lifting lines to install, operate, and decommission the subsea equipment. The steel wire ropes have some disadvantages such as a heavy self-weight, and resonance problem that may occur more frequently at deepwater depth. To overcome these drawbacks, a new installation method has been proposed in the field of subsea installations, which is fiber ropes can be used as lifting line for ultra-deepwater installation, and can be substituted for the conventional steel wire rope [2], and in two-fall system using fiber ropes [3].
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