Mooring Line Systems for Tanker Vessels – Current Standards in Analysis and Design Compared to Real Life Data

Design and analysis of moorings of tanker vessels have traditionally been approached from two sides: from the vessel side, regulated by classification societies and with proposed guidelines from OCIMF, and from the land side, regulated by local codes and standards. As an example, ASCE COPRI recently published ASCE Manuals and Reports on Engineering Practice No. 129 – Mooring of Ships to Piers and Wharves, which gives guidelines to determine the forces that will be transferred to the supporting structures at the berth. In addition, PIANC has also published recommendations for design of marine oil terminals that outlines design guidelines for mooring systems.

With the installation of mooring hooks with tension monitoring capabilities at new terminals there is now a lot of available data that can be compared with and possibly verify the design methodologies currently in use. Many factors that are difficult to account for in an analysis due to sheer volume of possible scenarios have the possibility to be captured in the tension data from the mooring hooks. Some of these factors are pre-tension of mooring lines, actual line tending procedures on the moored vessels, and deviations from assumed design conditions in environmental and other loading cases on the moored vessel.

An overview of the available data will be given, and cases exhibiting high line loads or vessel movements will be selected for a more detailed study, including metocean data, vessel loading conditions, as well as possible passing vessel effects. The actual data will be compared to results from analyses of the selected cases. In addition, metocean data for these cases will be compared to the mooring design conditions for the location in question.

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