The Netherlands: Dynamic Positioning Capability Forecast, Planning of Operations, Hours and Days Ahead
One of the extensions within OCTOPUS-Onboard is the Dynamic Positioning capability forecast function, DP for short. The OCTOPUS-DP functionality gives offshore vessels the possibility to make optimum use of a safe time window for their weather-sensitive operations. An important remark has to be made here.
The OCTOPUS-DP functionality can not be compared with already existing Dynamic Positioning Systems. Where traditional DP systems try to keep the vessels position during an offshore operation, OCTOPUS-DP takes it one step further. A forecast is given if the vessel is capable of maintaining her position and heading in changing environmental and weather conditions, hours and days ahead. In 2010 OCTOPUS-DP was installed on the Hoegh LNG vessels Suez Cape Ann and the Suez Neptune. Both vessels use OCTOPUS-DP to plan and document safe time windows for discharging LNG from the vessel to shore trough a turret mooring and transfer system designed by APL – Advanced Production Loading – of Norway.
How does it work?
Basically, the DP software calculates an onboard forecast of the mean and slowly varying forces acting on the vessel due to currents, wind and waves. The calculations are based on measured environmental conditions and on weather forecasts, which are an integrated part of OCTOPUS-Onboard. The first result is the forecast of the mean heading the vessel would obtain if weathervaning or drifting. The DP Capability software also calculates how the expected forces will influence the ship and if these forces would bring it out of position during an operation at sea for any available thruster configuration. OCTOPUS-DP uses the thruster properties as input. There is no direct link with the DP-system itself.
With the obtained information, it easy to judge for which DP thruster configuration the vessel is resistant against expected forces or that it is better to stop and start the operation at a different time. Safe heading sectors are given in Polar Plots. A safe time window is given in the OCTOPUS Weather Window. The window gives the crew a clear view on how these forces have a different impact on the ship at a change of heading. This way the crew gets a clear forecast if the operation can be executed in the hours and days ahead, and under which heading this can safely be done.
With DP capability the crew can easily see if it is sensible and efficient to start or go on with the operation at sea. Or is it better to start (again) at a different time? The benefits are clear:
• A clear and complete indication of the operational windows for weather-sensitive operations at sea
• Better and efficient preparation and execution of projects
• Less damages and stress to the vessel
• Optimal use of man and machine in a safe environment, leading to significant cost reductions.
Source: amarcon, January 4, 2011