Dynamic Positioning Optimization using quick release hooks
For several years, our customer McDermott have been using our custom designed quick release mooring hooks on their pipelaying vessels.
McDermott owns several pipelaying vessels. These vessels are all fitted with a Dynamic Positioning System (DP) to hold their exact location during operation. This location is critical for pipelaying, as the pipes need to be installed in one exact position on the seabed. During one of McDermott's projects with their Lay Vessel North Ocean 105, they experienced heavy weather conditions. The DP had to run on full capacity but it was almost impossible to hold location. Quitting was not an option, so they had to use tugboats to assist them. This worked out, but the external pulling force from the tugboats to hold the vessel's position created several alarms in the DP system. The added force by the tugboats couldn’t easily be handled by the DP software, as this “external force” did not match the measured values on the DP.
The onboard engineers came up with a solution to solve this for the future. This solution entails registering the pull of the tugboats and integrating these values into the DP. The DP software can then calculate its position and required operation by using the loads in the lines to the tugboats. The best way to measure the load on a line is to use a quick release mooring hook, fitted with a load cell. This hook can be used to release the line in case of emergencies as well.
In 2019 we were asked to design a special hook foundation, with the intention of fitting six quick release mooring units at different locations on the deck of the vessel. This vessel is used for specialist and heavy towing operations. The quick release hooks themselves are fitted with load cells to measure the exact load on the lines, and using our MoorControl software these loads are displayed on the PC at the bridge of the vessel. The load monitoring system is integrated to the Dynamic Position Optimization (DPO) system, where the load data is used to optimize operations and increase safety. In addition to the load monitoring system, they can release the hooks remotely in case of emergencies, by using our electric release system.
McDermott are so pleased with the capabilities of this system that they have ordered a new unit to be installed on Lay Vessel 108. This vessel will be deployed in support of the Ichthys LNG Project, located about 220 km offshore in Western Australia. This particular hook will have an impressive 200t SWL.