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Pumping system of dry dock in Venice Arsenale (Italy)
REVAMPING OF THE PUMPING SYSTEM FOR EMPTYING THE “MEDIUM” DRY DOCK OF THE ARSENALE OF VENICE BY SUBSTITUTION OF THE EXISTING VERTICAL PUMPS AND PIPELINES AND STRUCTURAL AND ARCHITECTONICAL RESTORATION OF THE PUMPING HOUSE
Project: New pumping system for emptying the “Medium” dry dock of the Arsenale of Venice
Location: Venice, Italy
Client: Venezia Nuova Consortium for Ministry of Public Works - Water Board - Venice
Cost of total Works: € 1,422,501
Services: Preliminary and Detailed Design
The northern area of Venice Arsenal is a key site for the management and maintenance activities for the MO.S.E. (flood protection) system of Venice lagoon. The area is currently used for ship maintenance and docking operations and is provided with two dry docks (“medium” and “large” dry dock) suitable for the unloading operations of the barriers. The structures in the northern area of the Venice Arsenal, including the medium dry dock and the pumping system for emptying it, have an architectural and artistic value since they were built in the 19th century. The emptying system of the “medium” dry dock was based on two vertical pumps with a flow discharge of 2,500 m3/h each: by a system of steel pipelines (s =700 mm), the pumps took the water from the bottom of the dry dock (-9,00 m, measured on the mean sea level) to the Lagoon. The pumps and the connected pipes and valves system, installed in the earlier of the 20th century, had many problems like corrosion, leakages and mechanics frictions that involved a sensible reduction of the pumped flow and hence longer times for emptying operations. In order to reduce this time and improve the reliability of the system for the medium-long term period, the old pumps and the pipeline system were removed and new vertical pumps with a 5,300 m3/h each flow discharge, were installed. The pumping system was also provided with a small auxiliary pump (350m3/h) and a vacuum priming pump. Since the pumps had a dry installation, to prevent the surging of cavitations at the impellers when the water level is lower than the impellers (low values of the available NPSH), inverters were provided to control the electric motors revolutions. With this configuration the dry dock could be emptied in less than 3 hours. The bottom of the sump was -4,5 m below the mean sea level and the walls presented much seepage; to restore the integrity of the walls and ensure their sealing and prevent corrosion of the flanges of the new pumps, the installation of bentonite panels and concrete cast counterwalls was provided. In addition to the restoration of the pumping station, the project also included the installation of a supplementary pump (140 l/s with a head of 21,00 m) within a well in connection with the dock, placed at -11,00 m below mean sea level. This pump not only ensured the completion of the emptying of the dry dock, but also through pressure pipeline (350 m long, DN 315 mm) could send the process water to the treatment plant planned for the area.