Costruzioni Navali started building motor ships for excavating and inert transportation at the beginning of sixties. First units, equipped with diggers, were extracting gravel from Po and Ticino rivers beds. As time went on, the massive request led to the construction of bigger and modern concept boats, equipped with dredging pump and cargo hold. Today the loading and unloading operations are steered by a PLC panel which energizes pumps, clutch, valves and other components, according to the selected working program. In addition to facilitate the tasks of the operator, the system protects the ship machinery from damage caused by a wrong use; for example, it is impossible to insert the clutch of the dredging pump if the diesel engine is not at a low engine speed or to operate the hydraulic gates if the lubricating - washing system does not have the correct pressure.
Costruzioni Navali built hopper dredgers with capacity up to 1600 m3, authorized to navigate on international coasts.
The hopper dredgers (used in internal waters or limited floors) are generally equipped with hydraulic propulsion groups which can adjust the propeller’s position according to the draft of the ship; no ballast is to be used and the dredger is kept perfectly in horizontal position. As a rough indication, a dredger with capacity of 500 mc has only 80 cm draft when empty and 2.4 meters at full load.
A special attention is reserved to the sieve system design; it has to treat dredged material without slowing down the unload operations which take approximately 40 minutes for 600 mc of sand (with 14/12” pump).
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