2012-02-20 - ABB distributed control systems are installed in several of the huge storm barriers that protect the low-lying Netherlands from tidal surges and flooding. Among them is the Maeslant Barrier, which protects Rotterdam – Europe’s busiest port and the country’s second largest city – from the potentially devastating effects of high floodwater.
By ABB Communications
The Maeslant storm surge barrier is one of the largest moving structures on Earth.
It is part of a huge series of dams, sluices, locks, levees, dikes and barriers that protect the Netherlands from flooding from the North Sea. Collectively known as the Delta Works or North Sea Protection Works, the barriers are an engineering marvel that the American Society of Civil Engineers has named one of the 'Seven Wonders of the Modern World.'
The Maeslant Barrier is longer than the Eiffel Tower and weighs about four times as much. It is the only storm surge barrier in the world with such large moveable parts.
Spanning the New Waterway (Nieuwe Waterweg), a canal that connects the river Rhine to the North Sea, the Maeslant Barrier acts as a final line of defence for Rotterdam against high levels of incoming seawater.
ABB supplied the original automation system that controls this critical piece of national infrastruture in 1997 and modernized the system in 2005. ABB is currently evolving and enhancing the control system again in time for the next storm season in the winter of 2012-13.
The Maeslant storm barrier in normal 'open' mode on the left, and in 'closed' storm mode on the right.
Images courtesy of Rijkswaterstaat.
The barrier consists of two huge hollow doors, each 240 meters in length and comprising 15 floodable compartments. Under normal conditions the doors are fully opened to allow ships to sail to and from Rotterdam. However, if the water level rises by 3 meters above the designated norm, the doors are closed and flooded with water. This causes them to slowly sink.
The entire process takes about 90 minutes. When the doors are closed, the water level on the North Sea side is higher than on the canal side. The pressure against the barrier is equal to 350 meganewtons, a tremendous force that would instantly capsize a large ship.
The Netherlands is a geographically low-lying country with 25 percent of its land area below sea level and 50 percent less than one meter above sea level.
The ABB control system is essential to the operation of the barrier. It consists of two identical subsystems, one for each door, which are interconnected to form a single system.
In the event of barrier activation, the ABB control system receives the command to close from a central decision computer system. The command is issued if a number of parameters - such as current and predicted water levels, flow rates, wind speed and wind direction – combine to become crictical.
An important task of the ABB control system is to execute the door-closing process and keep both doors level and aligned on the channel bottom by letting water in and out of the 30 compartments. All the operating equipment, such as pumps, valves, motor control centers and control systems are located in the doors.
Both the ABB hardware and software are highly redundant to ensure the highest level of reliability. The present upgrade evolves the existing Advant-based system to System 800xA and includes an 800xA Simulator. The simulator enables the customer – Rijkswaterstaat, the Dutch public works and water management agency - to perform operator training, dry runs and software changes all year round, even during the 6-month winter storm season.
The Maeslant Barrier was opened in 1997. Although it is activated once a year for testing purposes, the barrier has only been closed once in response to a tidal surge in 2007.
ABB has supplied the control systems for several storm barriers in the Netherlands, including the longest of them all, the nine-kilometer-long Oosterschelde (above). ABB has also supplied several Dutch semi-government agencies with control systems that ensure that the water levels behind many of the country’s dikes are kept at the right level. Some of the land protected by the dikes is several meters below sea level.