Keeping Venice afloat

High accuracy pressure transmitters from Keller are helping to keep Venice afloat through their integration into the foundations of the city's flood prevention system

The idea thatVenice might sink into the sea has been circulating in the media for many years now.Around one hundred years ago, the city was 25 centimetres higher out of the water than it is today.When its industries moved to the mainland in the 1960s and began to grow and expand rapidly, there was a great need for fresh water, and Venice therefore decided to pump groundwater out from under the Venetian Lagoon.That's when the city began to sink.

The problem was actually identified in the I 960s, and Venice then began restricting the volume of water that was pumped out - but this could not stop the process entirely.The situation was exacerbated when the channels in the lagoon were expanded to accommodate ships travelling to Mestre.Tourism also increased and the water connection from the city to the Adriatic Sea was widened.The huge amount of water thus introduced carries sediment away and out of the lagoon, and this phenomenon is being reinforced by the effects of global warming.

Over the years, various proposals were presented to deal with the problem, but there were also corruption scandals and protests by the local population. Finally, the parties involved agreed to launch a project known as M.O.S.E. (Modulo Sperimentale Elettromeccanico - "Electromechanical Experimental Module").

This flood prevention project uses moveable flood gates installed at the four entrances to the Venetian Lagoon.The idea is to protect the historic centre ofVenice from floods that are becoming ever more frequent.The concept is not completely new, as similar flood barriers have also been built in London (Thames Barrier) and Rotterdam (Maeslant Barrier).

When a flood alert is issued, the four entrances to the lagoon are closed off using floating barriers.The flood prevention system consists of a total of 78 movable elements. The technology used here is tried and tested, as it is been employed for quite some time at the gates of large ship docks. MO.S.E. is a lot bigger, however, and its gates are also
networked with one another and equipped with intelligent control and monitoring systems. Data from throughout the system is sent to a control centre. Information on weather conditions and sea currents is also analysed and used as a basis for decisions on when to close the flood gates.

Secured by giant hinges set in concrete, the steel gates are 20 metres wide, five metres thick and up to 30 metres high.When there is a danger of flooding, air is pumped into the gates, which causes them to rise up to form a protective barrier against the Adriatic Sea and block off the lagoon like a floodwall.When the water is at a normal level, the gates lie retracted beneath it.

Extremely precise data is needed to control and monitor the gates. In order to monitor the structure of the caissons, geotechnical specialists at Agisco s.rl. therefore installed
digital (bus) profilometers in the concrete elements.The prof lometers work with highly accurate KELLER X series transmitters with IP-68 protection.This solution guarantees impressively high precision - down to onetenth of a millimetre over a length of several kilometres.

The pressure transmitter's extremely high accuracy of 0.01 %FS is available as an option; the standard precision of the X series (33X, 35X and 36X) is 0.05%FS.This high degree of measurement precision is achieved by combining a stable, floating, built-in piezoresistive transducer with an XEMICS microprocessor with an integrated I 6-bit A/D converterThe latter uses mathematical compensation to eliminate the temperature dependencies and non-linearity of the sensor. The transducer registers even the tiniest pressure fluctuations, In order to ensure that this high sensitivity is effectively exploited, the measuring element must be well shielded from disruptive external influences. For example, the floating installation setup completely decouples the transducer from mechanical tension in the outer housing.

KELLER is a member of the LoRa Alliance
The long range wide area network "LoRaTM" connects objects via radio and offers safe, bidirectional communication within the Internet of Things. LoRaWAN is based on the open industry standard LoRa and has been set out by the non-profit organisation LoRa Alliance, of which KELLER AG fur Druckmesstechnik is a member. This technology offers high coverage and a low level of energy consumption, which is especially suited to battery-operated applications.

For more information, please contact:-

Keller (UK) Ltd.
Tel: +44(0) 845 643 2855 Fax: +44(0) 845 643 2866

June 2019

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