Page 28 - Navigator 2021

‘The idea was born to conduct own research into the roll period
of deep-draught tankers and
bulk carriers in relation to tidal window’
Getting to the bottom!
EVERY SHIP THAT SAILS CONTINUOUSLY MOVES BACK AND FORTH SOMEWHAT FROM PORT TO STARBOARD. IN PRINCIPLE, THIS SO-CALLED ROLLING IMPACTS THE SHIP’S DRAUGHT AND THUS ITS ABILITY TO SAFELY ENTER A PORT. OUT OF PERSO- NAL INTEREST, REGISTERED PILOT JUAN BLANKENBURGH HAS CONDUCTED IN-DEPTH RESEARCH INTO THE ROLLING PERIODS OF THE LARGEST TANKERS AND BULK CARRIERS THAT CALL AT THE PORT OF ROTTERDAM. HIS NEWLY PROPOSED ESTIMATION FORMULA MAKES IT POSSIBLE TO MORE ACCURATELY CALCU- LATE TIDAL WINDOWS FOR SAFE PORT ACCESS.
A tidal window enables a large ship to safely access a port within the given circumstances, thus avoiding the risk of seabed disturbance.
In the Netherlands, these tidal windows are issued by the Hydro- Meteorological Centre of Rijkswaterstaat, which has been using the program Protide (Probabilistic Tidal window Determination) for its calculations since 2011. The ports of Rotterdam, Amsterdam and Eemshaven rely on Protide with great regularity. In Rotterdam, it is used for about a quarter of all ships that navigate the Eurogeul. This fairway starts about 31 nautical miles off the port entrance and has a minimum depth of 23 metres (LAT). Blankenburgh: “The use of Protide is standard practice for ships with a draught over 20 metres. If the swell height exceeds 70 centimetres, all ships with a draught of 17.40 metres or more will receive a tidal window via Protide.”
RESEARCH INTO ROLL PERIODS
Blankenburgh is one of approximately 60 pilots in the Rotterdam- Rijnmond region who are authorised to pilot vessels through the Eurogeul access channel. He also worked as an instructor for many years, training colleagues to guide ships through this fairway. It explains his interest in Protide and his participation in the Protide Users Group on behalf of the Rotterdam pilots until 2018. Combined with a natural aptitude for mathematics, the idea was thus born to conduct own research into the roll period of deep-draught tankers and bulk carriers in relation to tidal windows. The length of a roll period is crucial information. The more and faster a ship rolls from port to starboard, the greater the risk of seabed disturbance. Rolling increases the vessel’s draught.
Blankenburgh: “Much of the data for calculating the tidal windows comes directly from Rijkswaterstaat's meteorological sensors. Numerous variables in terms of exact water level, wave spectrum, etc. are taken into account in that respect. However, the necessary input provided by the ship itself for a tidal window is considered hard data. Of course, that is not the case. A ship does not know the actual extent
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