NZ613875B2 - Apparatus and method for the dredging of sediments from the seabed - Google Patents

Abstract

dredging apparatus (1) is described for removing sediments from a bed (F) of an expanse of water (see S, figure 1). The apparatus comprises a suction apparatus (5). The suction apparatus (5) includes a submersible pump (18) and a suction head (9). The submersible pump includes a housing body (17), provided with an inlet mouth (19) and a discharge opening (20), and an impeller (21) rotatably supported in the body between the inlet mouth and the discharge opening, and rotatably driven by a respective driving device (see 22, figure 9). The suction head is associated with the inlet mouth of the housing body of the pump and is provided at the bottom with a suction opening (23). The suction opening of the head has a cross-sectional area dimensioned to achieve, in the working range of the pump, a suction speed capable of removing sediment. The dredging apparatus further comprises a separating device (8) and a recirculation system (10). The separating device (8) separates a slurry of water and sediments received from the suction apparatus (5) into a liquid phase and a solid phase. The liquid phase is then recirculated via the recirculation system (10) to an inner hollow space (34) in the suction head, which annularly surrounds the suction opening (23). The inner hollow space directs the recirculated liquid phase toward the suction opening in inside the suction head. The recirculation system (10) defines a closed hydraulic circuit of the fluid recirculating therein. A dredging method, utilising such an apparatus, is also disclosed. provided with an inlet mouth (19) and a discharge opening (20), and an impeller (21) rotatably supported in the body between the inlet mouth and the discharge opening, and rotatably driven by a respective driving device (see 22, figure 9). The suction head is associated with the inlet mouth of the housing body of the pump and is provided at the bottom with a suction opening (23). The suction opening of the head has a cross-sectional area dimensioned to achieve, in the working range of the pump, a suction speed capable of removing sediment. The dredging apparatus further comprises a separating device (8) and a recirculation system (10). The separating device (8) separates a slurry of water and sediments received from the suction apparatus (5) into a liquid phase and a solid phase. The liquid phase is then recirculated via the recirculation system (10) to an inner hollow space (34) in the suction head, which annularly surrounds the suction opening (23). The inner hollow space directs the recirculated liquid phase toward the suction opening in inside the suction head. The recirculation system (10) defines a closed hydraulic circuit of the fluid recirculating therein. A dredging method, utilising such an apparatus, is also disclosed.

Description

Replacement Specification — 10 August 2015 APPARATUS AND METHOD FOR THE DREDGING OF NTS FROM THE SEABED DESCRIPTION Field of the invention The present invention relates to the field of dredging systems for ng sediments from a bed of an expanse of water such as, for example, a sea bed, a river bed, a lake bed, a marsh bed, etc.

The present invention relates, more specifically, to a dredging apparatus for removing sediments from a bed of an e of water, as well as to a dredging method which may be carried out by means of the aforementioned apparatus.

Related art In the field of dredging of sediments from a sea bed, river bed or marsh bed, essentially three types of dredging apparatuses are known: dredging apparatuses making use of pumps (so—called sucking—dischargingpumps, screw pumps, vane pumps, diaphragm pumps), dredging apparatuses of the type with grab buckets and so-called bucket dredge apparatuses that use a plurality of cups or buckets moved by .

In ng apparatuses of the first type a pump is generally used the on of which is to supply energy to the water/sediment slurry sucked so as to push it into a discharge (or back flowing) conduit overcoming the losses due to friction and to the effects due to variations in slope.

In order to allow the removal of sediments that would otherwise be very limited, different types of agitating/disgregating devices are used that have the on of disgregate and suspending the sediments, creating a suspension that can be sucked by the pump.

Currently, essentially two types of agitating devices are used: a first of mechanical type and a second of the water jet type.

The first type of ing devices generally consists of a series of vanes with coatings made of a wear-resistant material, rotated by an extension of the drive shaft of the impeller of the pump or by means of auxiliary motors directly positioned close to the inlet mouth of the pump itself when it is necessary to operate at ularly low rotation speeds. ement Specification — 10 August 2015 The second type of agitating devices, on the other hand, uses a series of nozzles airanged close to the inlet mouth of the pump that direct pressurised water towards the water bed, ing a disgregating effect, ng the sediments into suspension and carrying out a pre-mixing thanks to the ence generated.

Dredging apparatuses of the so-called grab bucket type, on the other hand, comprise one or more buckets formed from two opposite centrally—hinged buckets, which rest on the bottom in an open position and which allow sediments to be withdrawn from the water bed.

The operating principle of these dredging tuses is the following: on the surface, the buckets are kept open with a hook, and are then lowered at a constant low speed.

The buckets are ed with holes that allow the air to come out during immersion.

Once the bottom is touched, the holding hook is disengaged and, while lifting, the buckets grip the sediment thanks to a lever linkage system. The amount of withdrawn material depends on the compactness of the bottom and on the size and weight of the buckets.

Dredging apparatuses of the so—called bucket dredge type, on the other hand, comprise a plurality of cups or buckets fixed to a chain that, sliding on a guide pivoted on the craft and suitably inclined to rest on the bottom, allow the sediments to be awn from the water bed.

Summary of the invention The Applicant has found that the aforementioned known dredging tuses which make use of pumps have a series of drawbacks for which an adequate solution has not yet been found.

A first drawback is essentially related to the fact that the agitating/disgregating devices that are used allow to operate with a content of solid material in the water/sediment mixture which does not normally exceed 20-25 volume % (normally equivalent to 40 — 45% by weight) and in any case with decreasing efficiency as the dredging depth increases.

The need to suspend the sediments implies in turn a low ency of the dredging apparatus, ie. the need to move very high flow rates of water to achieve the removal of the sediments, with undesired additional negative consequences in terms of size of the pump, of its driving motor, of the rge ducts, and therefore with inevitable negative uences in terms of time and cost of the dredging operations.

Replacement Specification a 10 August 2015 A second serious drawback is essentially d to the fact that the agitating/disgregating devicesthat are used generate a water turbidity which makes dredging apparatuses of the so-called sucking—discharging type unable to be used in dredging sites of the SCI type (Site of Community Importance), SNI type (Site of National ance) or in any case in areas where for nmental reasons it is not permitted to create any kind of water turbidity and/or any dispersion of polluting sediments in the water.

In the aforementioned areas, in fact, the absence of ity is one of the operating parameters that is lly imposed in order to avoid a possible imbalance of the environmental system (fauna and flora) with consequent environmental damage or to avoid the dispersion of sedimented polluting als which would be sed again by the disgregating action of the agitating/disgregating deviceswith totally harmful effects on the environment and on the health of flora and fauna.

More specifically, the dredging methods in SNI areas according to current standards must be such as to minimise the impact on the surrounding environment and achieve the following objectives: — to dredge safely and tely, minimising the amount of water present in the removed materials; - to make the amount of dispersed material proximal to zero or in any case minimal, 2O adopting closed systems where possible; and — to limit the turbidity and the dispersion of pollutants caused by the dredging operations.

It is evident, however, that these objectives cannot be achieved by any dredging apparatus provided with agitating/disgregating devices.

A third drawback is essentially d to the fact that the ical disgregating action d out by such known dredging apparatuses does not allow the latter to operate safely in the presence of cables, chains or other bulky debris: consequently, these apparatuses cannot be used in ports or rivers used for nautical activity or in areas where the presence of remnant explosive s may be possible without first performing a clearance sweep, which implies an additional penalisation in terms of time and cost of the dredging operations.

The Applicant has also found that although the dredging apparatuses of the grab bucket Replacement cation — 10 August 2015 type have city of operation that makes them suitable for carrying out dredging in SNI sites, these dredging apparatuses also have a series of drawbacks that still limit their performance. In particular, dredging apparatuses of the grab bucket type have: — a low positioning precision and a low capacity of awing the sediments; — a low ability to render proximal to zero or in any case minimal the amounts of material dispersed during the steps of loading and moving the withdrawn sediments ; — a low ability to limit the water turbidity during the operating steps, generating ascent turbulence; - a low production capacity; — a poor operating safety in the absence of a prior clearance sweep of t explosive devices; and — a poor or limited operability on water beds contaminated by the presence of n bodies (like chains, logs, ropes, anchors, or other bulky material).

The Applicant has thus perceived the possibility of at least lly overcoming the aforementioned drawbacks and, more specifically, the possibility of providing a dredging apparatus for removing nts from a bed of an expanse of water that can be used without any kind of limitations also in SCI or SNI sites or in any case in areas Where for environmental s it is not permitted to have any water turbidity, by intervening on the fluid—dynamic characteristics of the dredging operations, in particular 2O by creating an adequate depression upstream of the suction pump capable of determining the suction of an amount of liquid capable of carrying out an effective removal action of the sediments without any intervention of “active” disgregating devices of the mechanical or nozzle type.

In this specification unless the contrary is expressly stated, where a document, act or item of dge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date, publicly ble, known to the , part of common l knowledge; or known to be nt to an attempt to solve any problem with which this specification is concerned.

It is therefore an object of the present invention to provide an improved complete dredging apparatus and method for removing sediments from a water bed; that Replacement Specification — 10 August 2015 ameliorates some of the disadvantages and limitations of the known art or at least to e the public with a useful choice.

More specifically, according to a first aspect, the present invention relates to a dredging apparatus for removing sediments from a bed of an expanse of water, in absence of any t with the bed comprising a suction apparatus including: a) a submersible pump ing: a1) a housing body provided with an inlet mouth and with a discharge opening; a2) an impeller rotatably supported in said body between said inlet mouth and said discharge opening and rotatably driven by a respective driving device; b) a suction head associated to said inlet mouth of the housing body of the pump and provided at the bottom with a suction opening of the sediments; n the suction opening of the head has a value of the cross—section area dimensioned to e in the working range of the pump a suction speed capable of removing the sediments by means of a fluid dynamics removal action carried out by the water sucked into said head, n the dredging apparatus further comprises a separating device for separating a slurry of water and sediments discharged from the suction apparatus in a liquid phase and a solid phase ing the sediments and a recirculation system to the suction head of at least a part of the liquid phase separated by said separating device; wherein the n opening of the head has a cross-section area smaller than the m cross-section area of the suction head; wherein the suction head is provided with an inner hollow space defining an outer annular portion of said suction opening and in liquid communication with the recirculation system for feeding the liquid phase separated by the separating device towards the suction opening and inside said head; and wherein the recirculation system defines a closed hydraulic circuit of the fluid recirculating therein.

Preferably, according to the first aspect, the suction head comprises at least a first portion proximal to the n opening having a progressively increasing cross—section 3O area moving away from said g and a second portion distal with respect to the Replacement Specification w 10 August 2015 suction opening having a substantially constant cross—section area. ably, according to the first aspect, the suction head comprises at least a first portion proximal to the suction opening having a progressively sing cross—section area moving away from said opening and a second portion distal with t to the suction opening having a progressively decreasing cross—section area moving away from said first portion.

Preferably, wherein the suction head comprises a pair of portions proximal to the n opening having a progressively increasing cross—section area moving away from said opening and a different ation with respect to a longitudinal axis of the suction opening.

Preferably, the suction head further comprises an intermediate portion interposed between said first and second portion of the suction head.

Preferably, said intermediate portion has a substantially constant cross-section area.

Preferably, said intermediate portion comprises a lower n al to the suction opening and having a progressively increasing cross—section area moving away from said opening and an upper portion distal with respect to the suction opening and having a progressively decreasing cross—section area moving away from said lower portion.

Preferably, said first and/or second portion and/or intermediate portion of the suction head has a substantially frusto-conical shape.

Preferably, the suction head comprises a perforated partition supported in said head downstream of said suction opening.

Preferably, said perforated partition is supported in the n head at an intermediate portion interposed between said first and second portion of the suction head. ably, a plurality of flow deflecting elements is associated to the suction head close to said suction opening.

Preferably, said flow deflecting elements comprise a plurality of fins having a substantially rectilinear or curvilinear shape extending along a radial direction or along an inclined direction with respect to said radial ion.

Preferably, said first portion of the suction head is ed with a jacket forming a double wall wherein said inner hollow space is defined.

Replacement Specification — 10 August 2015 Preferably, the dredging apparatus further comprising a plurality of flow deflecting elements arranged in said hollow space close to said suction opening.

Preferably, according to the first aspect said flow deflecting elements comprise a plurality of fins having a substantially rectilinear or curvilinear shape extending along a radial direction or along an inclined direction with respect to said radial direction.

Preferably, ing to the first aspect comprising a first shut-off valve mounted on a rge duct ing downstream of said discharge opening of the housing body of the submersible pump.

Preferably, sing a second shut-off valve mounted on a recirculation duct of the liquid phase ted by the separating device to the suction opening of the suction head.

Preferably, according to the first aspect, further comprising a unit for chemically treating the liquid phase separated by said separating device.

In accordance with a second aspect thereof, the present invention relates to a dredging method for removing sediments from a bed of an e of water, in e of any contact with the bed, comprising: a) positioning, close to the bed, a suction apparatus including: a submersible pump including: — a housing body provided With an inlet mouth and with a discharge opening of the water; — an impeller rotatably supported in said body n said inlet mouth and said discharge opening and rotatably driven by a respective driving device; and a suction head ated to said inlet mouth of the housing body of the pump and provided at the bottom with a suction opening of the sediments provided with a longitudinal axis substantially vertically oriented in use; b) operating the submersible pump so as to achieve, in the working range of the pump a suction speed capable of removing the sediments by means of the fluid cs removal action carried out by the water sucked into said head. wherein the suction g of the head has a cross—section area smaller than the Replacement Specification — 10 August 2015 maximum cross—setion of the suction head, and wherein the method further comprises the steps of: — separating a slurry of water and sediments discharged by the submersible pump in a liquid phase and a solid phase including the sediments by means of a separating device; — recirculating at least a part of the liquid phase separated from said slurry s the suction opening of the suction head by means of a recirculation system and of an inner hollow space defining an outer r portion of the n opening, said inner hollow the liquid space being in liquid communication with the recirculation system for feeding phase ted by the separating device towards the suction opening and inside said head; and — keeping the fluid recirculating in the recirculation system (10) in a closed hydraulic circuit.

Preferably, according to the second aspect, wherein the suction speed is comprised between 0.3 and 30 m/s according to the particle size and cohesion characteristics of the sediments.

Preferably, according to the second aspect, further comprising the step of reducing the average speed of a water/sediment slurry sucked inside said suction head downstream said suction opening.

Preferably, the ng method further comprising the step of carrying out within said suction head a particle size separation of the nts incorporated in the water/sediment slurry sucked into said head.

Preferably, the dredging method wherein the liquid phase recirculated towards the suction opening has a speed equal to or lower than the suction speed. ably, the. dredging method wherein the liquid phase recirculated towards the suction opening has a speed sed between 0.2 and 15 m/s as a function of the n speed.

Preferably; according to the second aspect, wherein the ratio between the suction speed and a speed of the liquid phase is recirculated towards the suction opening is sed between 1 and 7.

Preferably, according to the second aspect, further comprising the step of imparting to Replacement Specification — 10 August 2015 the water sucked into said head a substantially rotary movement or a substantially radial movement with respect to said suction opening.

Preferably, according to the second aspect, further comprising the step of imparting to the recirculated liquid phase fed towards the n g a substantially rotary movement or a substantially radial movement with respect to said suction opening.

Preferably, according to the second aspect, further sing the step of eroding the sediments from the bed by channelling the water close to said opening outside of said head in a radial direction towards the suction opening.

Preferably, according to the second aspect, further comprising the step of chemically treating the liquid phase separated from the slurry of water and sediments.

Preferably, according to the second aspect, further comprising a stand-by step including a step of sealing a predetermined amount of the recirculated liquid phase separated from the slurry of water and sediments in a closed circuit.

In the following description and in the subsequent claims, the term “sediments”, will be used to indicate any type of solid or semi—solid substance deposited by gravity on the bed of an expanse of water, such as for e sand, , mud, slimes and debris.

In the following description and in the subsequent claims, the term “expanse of water”, should be interpreted in its widest sense including not only substantially confined water such as lakes, ports, watersheds, marshes, etc., but also open or unning water suchas seas and .

In the following ption and in the uent , the term rsible pump”, will be used to indicate a pump provided with an impeller and with a respective water— tight driving device, both ed in the expanse of water in which it is necessary to carry out the dredging operations, or in any case any pump capable of generating a depression inside the head such as of the type with a pulsed flow, for example peristaltic, a piston pump and a membrane pump,.

In the following description and in the subsequent claims, the term “impeller”, will be used to indicate any type of bladed wheel which allows to transform the energy supplied by the driving device of the pump into kinetic energy. Thus, for e, the impeller can be provided with a series of shaped blades radially arranged on a disc—shaped body (in which case, the pump is of the centrifugal type), or it can be provided with a series of blades radially extending from a hub (in which case, the pump is of the axial type), or Replacement Specification ~ 10 August 2015 it can be shaped like lobes or like a worm screw.

In the following description and in the subsequent c1aims,the tenn “driving device”, will be used to indicate any apparatus, such as for example a hydraulic or electric motor, or the impeller of the any kinematic motion transmission mechanism capable of ng pump at the desired speed.

In the following description and in the subsequent claims, the teim “working range of the pump”, will be used to indicate, for a pump of given size and power, the combination of flow rate and head Which allows the pump to carry out the dredging operations.

Within the framework of the present description and in the subsequent , the parameter “suction , is meant to be ed at the suction g of the suction head or immediately upstream thereof. This parameter should also be understood to refer both to the water as such and to a slurry of water and sediments as a function of the operating conditions of the dredging apparatus.

Within the framework of the present description and in the subsequent claims, the parameter “speed of the liquid phase recirculated towards the suction opening” is meant to be measured at the suction g of the suction head or immediately upstream thereof.

Within the framework of the present description and in the uent claims, all numbers expressing amounts, quantities, percentages, and so fOith, are to be understood as being ed in all instances by the term " except Where otherwise indicated.

Also, all ranges of numerical entities include all the possible combinations of the maximum and minimum numerical values and all the possible intermediate ranges therein, in addition to those specifically indicated hereinbelow.

In the following description and in the uent claims, finally, the terms “horizontal”, “vertical”, “upper”, “lower” and “lateral” will be used to indicate ric and structural elements of the dredging apparatus and of the components which constitute the same as oriented in the use condition thereof.

In accordance with the invention and thanks to the ce of: 3O — a submersible pump including an impeller and a respective driving device that can be both immersed in the expanse of water during the dredging operations, and Replacement Specification — 10 August 2015 — a suction head having a suction opening of the nts with a suitably dimensioned cross-section area, it is advantageously possible both to bring the suction head of the sediments as close as possible to the bed, and to greatly increase the suction speed in the working range of the pump Without having cavitation phenomena and at the same time ting a strong depression at the suction opening and immediately upstream thereof such as to draw from the outer perimeter of the suction opening of the head both water and sediments that are thus eroded - without any appreciable dispersion — by means of the effect of just the fluid dynamics removal action carried out by the water sucked in the head.

In other words and differently from the dredging apparatuses of the known so—called sucking—discharging type, the dredging apparatus of the invention lacks agitating/disgregating devices (be they of the mechanical type or using a water jet), or parts or devices having the function of disgregating and bringing in suspension the sediments thereby creating a suspension that can in some way disperse in water and be no longer sucked by the fluid dynamics removal action carried out by the water sucked in the head.

In sharp contrast, the dredging apparatus and method of the invention allow to effectively carry out the dredging operations in the e of any contact with the water bed by means of a fluid-dynamic suction/removal action of the sediments carried out by the water sucked by the suction head by means consequent to the depression generated both at the suction opening of the head and close to said suction opening, in particular beneath and around the same.

The dredging apparatus and method of the invention are therefore capable to overcome all the drawbacks of the known dredging apparatuses, both of the sucking—discharging type and of the grab bucket type or of the bucket dredge type, as well as of dredging methods carried out by means of the same.

In particular, the dredging apparatus and method of the ion allow to: - suck a water/sediment slurry having a high solid content, until a value equal to or greater than 40% by volume is reached and, therefore, to e a high dredging efficiency in terms of productivity; — cally reduce the nmental , allowing their use in SCI or SNI sites or in any case in areas where for nmental s water turbidity and/or dispersion of ing sediments in water is not admissible; Replacement Specification ~ 10 August 2015 _12_ — recover and, if needed, treat and/or exploit, the dredged solid als; — reduce the time and cost of interventions.

The present ion in at least one of the entioned aspects can have at least one of the preferred features which follow.

Dredging apparatus For the purposes of the invention, the suction opening of the suction head is preferably shaped such as to allow the passage of the desired suction flow rate in the working range of the pump at the aforementioned speed d to remove the sediments by means of the fluid dynamics removal action carried out by the water sucked in the head.

The suction opening of the head can thus be circular, elliptical, polygonal, or of another type according to the ng ions that are to be carried out.

Preferably, the n g of the suction head is circular or polygonal for obvious reasons of simplicity of construction.

Preferably, the minimum size (minimum diameter in the case of a circular suction opening) is 100 mm, s the maximum size (maximum diameter in the case of a circular suction opening) is 1500 mm. More preferably, the size (diameter in the case of a circular suction opening) of the suction opening is comprised between 200 mm and 1200 mm and, still more preferably, n 300 mm and 900 mm.

Preferably, the cross—section area of the suction opening is comprised between 0.008 and 1.76 m2. More preferably, the cross—section area of the suction opening is comprised between 0.03 and 1.13 m2 and, still more preferably, between 0.07 and 0.63 m2.

In this way, it is advantageously possible to impart optimal values to the size of the suction opening according to the physical and cohesion characteristics of the sediments to be drawn.

By ing Within the aforementioned preferred size values of the suction opening and as a function of the flow rate of the submersible pump (the value of which can be determined at the design stage), moreover, it is advantageously possible to generate a strong depression that determines the suction of a water/sediment slurry having a solid tration that may be very high.

In a preferred embodiment, the suction opening of the head has a cross—section area Replacement Specification — 10 August 2015 _13_ smaller than the maximum cross—section area of the suction head.

In this way, it is advantageously le to create, within the suction head, a calibrated section which generates a strong depression both at the suction opening of the head and close to said n opening with a consequent high suction speed of the water or of the water/sediment slurry.

Preferably and as will become clearer hereafter, the average suction speed, measured at the n opening of the suction head, can vary between 0.3 m/s and 30 m/s essentially as a function of the particle size and of the cohesion characteristics of the sediments.

More specifically, the e suction speed is a function of the following parameters: — particle size and cohesion characteristics of the al to be sucked; — degree of contamination by foreign bodies and size thereof; — suction depth; and — percentage of solids in the water/sediment slurry to be obtained.

Moreover, it is advantageously possible, thanks to the se of the section area downstream of the n opening, to achieve an adequate reduction in the average speed of the water/sediment slurry sucked into the head so as to allow an adequate slowing of the solid material (sediments but also broken stone, or debris of various kinds) sucked up.

Preferably, the average speed at the m cross—section area of the suction head is comprised between 0.1 m/s and 25 m/s.

As a consequence of such average suction speeds, the absolute pressure value at the inlet mouth of the g body of the pump is preferably kept at values not lower than 0.1 bar so as not to trigger red cavitation phenomena.

Clearly and as a function of the dredging depth, i.e. of the value of the liquid head which lies above the suction head and the pump associated thereto, it is possible to have a depression within the suction head and in particular at the inlet mouth of the housing body of the pump even with absolute pressure values greater than 1 bar for example when the dredging operations are carried out at depths higher than 10 m.

Replacement Specification » 10 August 2015 In this case, the liquid head further facilitates the dredging operations carried out by means of the apparatus and the method of the invention since the liquid head makes it possible, if wished, to increase the suction speed without significantly approaching the cavitation conditions of the pump.

For the purposes of the invention, the n head can have a variety of different shapes.

In a preferred embodiment and irrespective of the specific shape of the suction head, the latter comprises a perforated partition supported in the head downstream of the suction opening and adapted to hold solid material having a size exceeding the passing section of the holes made in the perforated partition.

Preferably, the perforated partition is mounted stationary within the suction head.

For the purposes of the invention, the shape, size, bution and number of holes can be selected by a man skilled in the art according to the le size characteristics of the sediments to be sucked so as to optimise the efficiency of the subsequent steps of separating and decontamination of the solid material sucked up.

Thus, for e, the shape of the holes made in the perforated ion can be circular, elliptical or polygonal according to the particle size characteristics of the sediments.

Preferably, the holes made in the perforated partition are uniformly distributed in the part of the partition exposed to the passage of the water/sediment slurry.

Preferably, the minimum size um diameter in the case of circular holes) of the holes is 15 mm, whereas the maximum size (maximum diameter in the case of ar holes) is 300 mm.

Preferably, the holes made in the perforated partition are circular and have a cross- section e area sed between 175 and 75000 mm . ageously, the positioning of the perforated partition within the suction head allows to , with respect to the known dredging apparatuses, not only a greater operating flexibility of the dredging apparatus since any large solid residues are no longer capable to interfere with the operation of the suction head, but also the possibility of separating the solid al having a size exceeding the passage section of the holes made in the perforated partition from the rest of the sediments, holding such material in Replacement Specification ~ 10 August 2015 the area of the head upstream of the perforated partition for subsequent recovery and removal.

In other words, the perforated partition advantageously carries out the function of a classifying partition which carries out a first particle size selection of the sediments sucked by the suction head.

The depression conditions generated Within the suction head during the dredging operations, moreover, advantageously allow to hold the coarse solid al separated by the perforated partition within the suction head during the dredging operations and thus allow to recover such material extracting it from the dredged area so as to suitably dispose of the same.

In particular, in the case of dredging in inated sites this characteristic allows the n head to carry out an energetic g of the sediments of dimensions exceeding the dimensions of the holes of the perforated partition, so as to remove all its ing impurities and allow the recover or disposal of the sediments at lower costs.

In the case in which a perforated partition is ted in the suction head, the preferred feature according to which the suction opening of the head has a smaller cross-section area than the m cross-section area of the suction head, allows to obtain the onal ant advantageous technical effects of: — limiting the mechanical stresses on the perforated partition; — limiting the wearing phenomena due to impacts on the perforated partition; — allowing a sufficient autonomy of operation between a cleaning operation of the area upstream of the perforated partition and the next one; and — carrying out a prior g of the sucked nts so as to optimise the subsequent steps of separation and/or decontamination.

In a preferred embodiment, the suction head can have a cylindrical shape and has a substantially constant cross—section area (thus equal to the maximum cross—section area of the head).

In a further preferred embodiment, the n head comprises at least a first portion proximal to the suction opening having a progressively increasing cross-section area moving away from said opening and a second n distal with respect to the suction opening having a substantially constant cross—section area.

Replacement Specification — 10 August 2015 —16— In this way, it is advantageously possible both to progressively slow down the speed of the water/sediment slurry sucked into the head, and to facilitate the emptying of the suction head from the debris held upstream of the perforated partition ly present in the head itself.

In this way, it is thus advantageously possible to optimise from the geometric and fluid— dynamic point of View the area of the suction head al to the suction opening (upstream of the ated partition, if present).

Preferably, the suction head comprises, in the aforementioned first n proximal to the suction g, a lower wall having an inclination with respect to a longitudinal axis of the suction opening comprised between 5° and 85° and, still more preferably, between 250 and 70°.

Within the framework of the present description and in the subsequent claims, the angular inclination values are meant to be measured in the ise direction starting from the longitudinal axis of the suction opening and considering the parts to the right of such an axis in the al use condition of the head.

It is evident that for reasons of symmetry, such angular inclination values are identical to those measured in the anti-clockwise direction starting from the longitudinal axis of the suction opening and considering the parts to the left of such an axis.

In a further preferred ment, the suction head comprises a first portion proximal to the suction opening having a ntially constant cross—section area and a second portion distal with respect to the suction g having a progressively decreasing cross-section area moving away from said first portion.

In this way, it is ageously possible to optimise from the ric and fluid— dynamic point of view the area of the suction head distal with t to the suction opening (downstream of the perforated partition, if present) in particular improving the fluid—dynamic efficiency of the head close to the inlet mouth of the body of the pump, optimising the operation of the latter.

In a further preferred embodiment, the suction head comprises at least a first portion proximal to the suction opening having a progressively increasing cross—section area moving away from said opening and a second portion distal with respect to the suction opening having a progressively decreasing cross—section area moving away from said first portion.

Replacement Specification H 10 August 2015 _17_ In this way, it is also advantageously possible to optimise from the geometric and fluid— dynamic point of View both the area of the suction head proximal to the suction opening, and the distal one with respect to such an opening (respectively upstream and downstream of the perforated partition, if present).

Preferably, the n head comprises, in the aforementioned second portion distal with respect to the suction opening, an upper wall having an inclination with respect to a longitudinal axis of the suction opening comprised between 95° and 175° and, still more preferably, between 120° and 150°.

In a preferred ment, the suction head comprises a pair of portions proximal to the suction opening having a progressively increasing cross-section area moving away from said opening and a different inclination with respect to the udinal axis of the suction opening.

More specifically, the suction head preferably comprises a first portion of its lower wall closer with respect to the suction opening having an inclination with respect to the udinal axis of the suction opening comprised between 0° and 85° and, still more preferably, between 5° and 70° and a second portion of its lower wall having an inclination with respect to such a longitudinal axis comprised between 5° and 80° and, still more preferably, between 25° and 65°.

In this way, it is advantageously possible to provide the suction head with an t which reduces its cross section and that, in the case of particularly cohesive sediments (e. g. compact clay), allows to obtain a suitably reduced cross—section area of the n opening so as to increase the suction speed and therefore the nt removal capacity by the head.

In a preferred embodiment, this reducing element can comprise a plurality of cut—outs formed at the peripheral edge of the suction g so as to avoid the triggering of possible cavitation phenomena in the case of ntal contact with the water bed.

In a further preferred embodiment, the suction head r comprises an intermediate n osed between said first and second portion of the suction head.

In a first preferred embodiment, this intermediate portion has a substantially constant cross—section area.

In a second preferred embodiment, the intermediate portion comprises a lower portion proximal to the suction opening and having a progressively increasing cross-section Replacement cation — 10 August 2015 —18— area moving away from said opening and an upper portion distal with respect to the suction opening and having a progressively decreasing cross—section area moving away from the lower portion.

In this case, the intermediate portion is preferably formed of two mutually adjacent end portions of the aforementioned first and second portion of the suction head and having a lower ation with respect to the longitudinal axis of the n opening with t to the remaining part of the first and of the second portion, respectively.

As a consequence of this, the intermediate portion thus has, in the lower part, a progressively increasing cross-section area moving away from the suction opening (even if to a lesser extent with respect to what occurs in the lower portion of the head due to the greater inclination of the first portion of the suction head) and, in the upper part, a progressively decreasing cross-section area moving away from the end portion of the first n of the suction head (even if to a lesser extent with respect to what occurs in the upper portion of the head due to the greater inclination of the second portion of the suction head).

Preferably, the lower portion of the intermediate portion rably consisting of the upper end of the first portion of the suction head) has an inclination with respect to the longitudinal axis of the suction opening comprised between 0° and 80° and, still more preferably, between 20° and 65°.

Preferably, the upper portion of the intermediate portion (preferably ting of the lower end of the second portion of the suction head) has an inclination with respect to the longitudinal axis of the suction opening comprised between 100° and 180° and, still more preferably, between 115° and 160°.

Within the framework of the preferred embodiment in which the suction head ses an intermediate portion interposed between the first and the second portion of the suction head, it is particularly able and advantageous that the aforementioned perforated partition, if present, is supported in the suction head at said intermediate portion of the suction head.

Thanks to the configuration of the ediate portion of the suction head and, particularly when the head has a double inclination, it is possible to achieve the following advantageous technical effects: — preventing the solid material having a size smaller than the passage section of the holes made in the perforated partition from being trapped between the lower wall of the Replacement Specification — 10 August 2015 head and the perforated partition and thus not passing beyond the latter; — preventing the solid material having a size greater than the passage section of the holes made in the perforated partition from being trapped between the lower wall of the head and the perforated partition thus making it difficult to carry out the operation of emptying the area of the head upstream of the perforated partition (the portion proximal to the suction opening); and - preventing solid material having a size smaller than the passage n of the holes made in the perforated partition from being trapped between the upper wall of the head and the perforated partition thus preventing it from being drawn by the pump.

Preferably, the aforementioned first and/or second portion and/or intermediate n of the suction head has a substantially frusto—conical shape so as to facilitate manufacturing operations thereof.

In an alternative preferred ment, the aforementioned first and/or second portion of the n head (including the optional end portion having a different inclination and/or the intermediate portion, if present) can consist of d walls comprising a plurality of planar ts suitably inclined with respect to the longitudinal axis of the suction opening and ted side—by—side.

For the purposes of the invention, the suction head can be integrally made as a single piece or, alternatively, it can consist of two or more structurally independent portions (for example a lower portion, an upper portion and optionally an intermediate n) removably associated to one another by means of conventional fixing means, such as , for example, a plurality of bolts ed in a flange or in suitable radially outer fins that are suitably ated.

In this case, it is advantageously possible to mount in a removable manner the perforated partition between the head portions and nt the suction head rated partition included) thus facilitating the cleaning and maintenance operations thereof.

In a further preferred embodiment, the portion of the suction head distal with respect to the suction opening can be provided with one or more inspection ports so as to be able to inspect the inner space of the suction head and verify the need for a possible ention to remove solid materials held by the perforated ion and/or to carry out maintenance or repair interventions.

Replacement Specification — 10 August 2015 In a further preferred embodiment, the dredging tus comprises a plurality of flow deflecting elements associated to the suction head close to said suction opening.

In this way, it is ageously possible to impart particular and advantageous orientations to the water flow sucked both upstream and ream of the suction opening of the head as a function of the inner and/or outer on, of the flow deflecting elements on the n head itself.

Thus, in a first preferred embodiment, the flow deflecting elements can be externally positioned on the suction head close to the suction opening: in this way, it is ageously possible to facilitate the erosion of the sediments by the water flow drawn towards the suction opening, according to a highly—directed radial or rotary movement of the centrifugal type, in particular when the sediments have a compact nature.

In a further preferred embodiment, the flow deflecting elements can be internally positioned in the suction head close to the suction opening: in this way, it is advantageously possible to impart to the sucked water/sediment slurry a —directed radial or rotary movement of the centrifugal type that facilitates its ing towards the inlet mouth of the pump.

Clearly, it is also possible to have both an inner and an outer configuration of the flow deflecting elements thereby achieving an advantageous combination of the aforementioned technical effects.

Within the framework of these preferred ments, the flow ing elements ably consist of a plurality of fins having a substantially rectilinear or curvilinear shape extending along a radial direction or along an inclined direction with respect to said radial direction.

In this way, it is advantageously possible to achieve the desired deflection effect of the liquid flow in a mechanically simple way, by imparting o a substantially rectilinear highly—directed motion or a substantially rotary motion of the centrifugal type.

In a preferred embodiment, the dredging apparatus further comprises a separating 3O device for separating the slurry of water and nts discharged from the suction apparatus into a liquid phase and a solid phase including the sediments.

For the purposes of the invention, any suitable solid—liquid separating device can be Replacement Specification — 10 August 2015 used, such as for example a centrifugal cyclone separator, a diaphragm filter, a Vibrating or ibrating screen or a on system.

In this way, it is advantageously possible both to recover the sediments for a subsequent treatment, storage or reuse thereof, and to have a water flow substantially free of sediments that can be recirculated to the suction head as will be illustrated hereinbelow.

Preferably, the separating device is on the surface and is installed on a hull of the dredging apparatus on which the ts for lling and positioning the suction head and the submersible pump are installed.

Within the framework of this preferred embodiment, the dredging apparatus preferably comprises a recirculation system to the suction head, in particular towards its suction opening, of at least a pat of the liquid phase separated by said ting device.

Preferably, the recirculation system is of the “passive” type, in other words it is not ed with any further apparatus, for example a pump, for pressurising and to actively recirculating the liquid phase towards the suction head, but it just comprises one or more ducts for ing the recirculated liquid phase to the suction head in palticular towards its suction opening.

In this preferred embodiment of the invention, the liquid phase is thus recirculated s the suction opening of the suction head in a “passive” manner; more specifically, the liquid phase is drawn towards the opening of the suction head thanks to the depression that is created at and close to such an opening by the submersible pump provided downstream of the suction head and which constitutes the sole liquid—moving member in the dredging apparatus.

In this way, it is advantageously possible to recirculate towards the suction g of the suction head at least a part of the liquid phase separated by the separating device, preferably all of the liquid phase separated except for the part that remains in the form of residual humidity in the sediments separated and/or d up, Without any additional driving element, but simply exploiting the action of the submersible pump which is in any case y provided to suck the sediments in the dredging apparatus.

Preferably, the recirculation system also defines an actual closed hydraulic circuit, 3O g with this term that the fluid recirculating in the circuit does not substantially come into contact with the environment outside the head.

The ulation fluid which continuously ulates in the aforementioned closed Replacement Specification — 10 August 2015 hydraulic circuit without substantial exchanges of matter with the outside nment advantageously carries out a diluting function of the water/sediment slurry sucked by the suction head adjusting its density (given by the concentration of solids) to values compatible with the correct operation of the circuit downstream of the submersible pump, thus optimising the efficiency of the overall system for sucking and discharging the slurry, as well as of the solid/liquid separating device that is fed with a slurry having density characteristics that are constant, controlled and adjustable as desired.

Preferably, the suction head is provided in this preferred embodiment with an inner hollow space defining an outer annular portion of said suction opening and in liquid communication with the recirculation system for feeding the liquid phase separated by the separating device towards the suction opening and inside the suction head. ably, the first portion bed above of the n head is provided with a jacket forming a a double wall (inner and outer) portion of the suction head n the entioned hollow space, which is thus located within the head, is defined.

In this preferred embodiment, therefore, such a jacket defines the outermost wall of the first portion of the n head (or of part of the same) as well as the outermost perimeter of the suction opening of the head.

In this preferred embodiment, therefore, the minimum size of the opening defined by the inner wall of the first portion of the n head (minimum diameter in the case of a circular opening) in the ce of the aforementioned hollow space is 70 mm, whereas the maximum size (maximum diameter in the case of a circular opening) is 1100 mm.

More preferably, the size of the opening defined by the inner wall of the first n of the suction head (diameter in the case of a circular opening) is comprised between 135 mm and 850 mm and, still more preferably, between 210 mm and 650 mm.

Preferably, the cross—section area of the opening defined by the inner wall of the first portion of the suction head is in this case comprised between 0.004 and 0.90 m2 so as to take into account the section of the hollow recirculation space. More preferably, the cross—section area of the opening defined by the inner wall of the first n of the suction head is comprised n 0.015 and 0.56 m2 and, still more preferably between 0.035 and 0.32 m2.

In this way, it is possible to carry out the suction of the sediments by optimising the percentage of solid in the sucked slurry and giving the ulation system the task of keeping the dredging system balanced and, consequently, to ensure a feeding continuity Replacement Specification ~ 10 August 2015 -23_ to the subsequent steps of separation and/or decontamination.

This additional red embodiment of the dredging apparatus allows to obtain a series of relevant advantageous cal effects, including: - increasing the erosion action of the nts and consequently the efficiency of the dredging operations thanks to the feeding of a predetermined flow rate of the liquid phase separated by the separating device towards the suction opening of the head according to a highly—directed flow; — effective confinement of the suction area of the sediments within the perimeter of the suction opening (in this case also including the hollow space defined within the suction head and defining an outer annular portion of the suction g) preventing the occurrence of any potential water turbidity phenomena; - possibility of keeping the sucked water in a substantially closed t, which circuit being possibly sealable at the end of the dredging operations, which is a particularly useful option in the case of polluted ons in which it is not possible or desirable to discharge the liquid phase ted on land or in the water; - possibility of using and recirculating a limited amount of recirculation water which amount the ulation system, preferably g a closed hydraulic circuit, “automatically” maintains at substantially constant values by withdrawing water from the surrounding environment, with s benefits in terms of installation and operating costs of the entire dredging system.

Within the frameworlk of this preferred embodiment, it is preferable and advantageous to e a plurality of flow deflecting elements in the entioned hollow space close to said suction opening.

Similarly to what has been outlined above, the flow deflecting elements preferably comprise a plurality of fins having a substantially rectilinear or curvilinear shape ing along a radial direction or along an ed direction with respect to said radial direction and they achieve the same advantageous technical effects of imparting also to the flow of liquid phase recirculated towards the suction opening a highly— directed substantially radial movement or a substantially rotary movement of the centrifugal type which increases the efficiency of the fluid—dynamic removal action of the sediments.

Moreover, the possibility of imparting a highly—directed movement to the flow of liquid Replacement Specification — 10 August 2015 phase recirculated towards the suction opening is extremely advantageous whenever polluted locations are dredged, since it allows to avoid any type of reintroduction into the environment of the polluting substances deposited on the sediments held by the perforated partition and it determines, Within the lower portion of the n head, an accurate cleaning and washing of the sediments held by the perforated partition substantially eliminating any possible pollution risk due to a sediments release from the head at the end of the dredging operations.

In this case, moreover, the flow ing elements advantageously constitute at the same time respective mechanical stiffening elements which contribute to strengthen the hollow space defined in the suction head.

In a further preferred embodiment, the dredging apparatus can comprise one or more suitable shut—off valves which may be operated in the start—up and/or stopping steps of the submersible pump and having the function of preventing an undesired back—flow of the slurry sucked by the suction head and of sealing the ve” recirculation system (as stated essentially consisting of one or more ducts) thus avoiding the escape from the recirculation system of the recirculated part of the liquid phase possibly containing polluting nces.

Preferably, the dredging apparatus comprises a first shut—off valve, for example a check valve of the swing type, mounted on a discharge duct of the slurry of water and sediments sucked by the suction head and extending downstream of the discharge opening of the housing body of the sible pump.

Preferably and in the red embodiment in which the dredging apparatus comprises the aforementioned recirculation , the first shut—off valve is mounted on a discharge duct extending between the discharge g of the housing body of the submersible pump and the separating device.

Preferably, the dredging tus also comprises a second shut—off valve, for example a throttle valve, mounted on a recirculation duct of the liquid phase separated by the separating device to the suction opening of the suction head.

The presence of these ff valves is extremely advantageous whenever polluted locations are dredged, since it allows to avoid any type of reintroduction into the environment of ants, be they present in the solid phase or in the liquid phase, in case of failure of the submersible pump or of other ts of the recirculation system or in case of ng of the dredging operations.

Replacement Specification _ 10 August 2015 Within the framework of the prefeired embodiment in which the aforementioned separating device is provided, the dredging apparatus preferably comprises a unit for chemically treating the liquid phase separated by the separating device.

In this way, it is advantageously possible to carry out an inertisation or neutralisation treatment of dissolved or suspended polluting substances present in the polluted sites, thus ng to carry out not only ng operations but also an actual decontamination of the site.

For the purposes of the invention, this al treatment unit comprises suitable devices (such as for example tanks for ting the dredged liquid phase and/or reactors for its treatment, ion exchange or active carbon columns, tanks for collecting and dosing suitable reactants, filters or apparatuses for solid-liquid tion, and so on) adapted to cairy out an incitisation and/or neutralisation treatment of any ing substances present in solution or sion in the liquid phase.

Preferably, the chemical treatment unit is located on the surface and is installed on the hull of the dredging apparatus on which the separating device and the control and positioning elements of the suction head and of the submersible pump are installed.

Dredging method In a preferred embodiment of the dredging method of the invention and as ed above, the n speed is comprised between 0.3 and 30 m/s as a function of the particle size and cohesion characteristics of the sediments and, more specifically, as a function of the particle size and cohesion characteristics of the material to be sucked; of the degree of contamination by foreign bodies and of the size thereof; of the suction depth and of the tage of solids in the water/sediment slurry that should be obtained.

Preferably, the suction speed is comprised between 1 and 25 m/s and, still more preferably, between 2 and 20 m/s as a function of the particle size and of the cohesion characteristics of the sediments.

Even more preferred values of the suction speed as a function of the particle size and of the characteristics of the nts are as follows: — silts (cohesion varying between 10 KPa and 0.5 MPa measured according to SPT (Standard Penetration Test» having an average rth paiticle size S 60 um: 0.4 — m/s; Replacement Specification — 10 August 2015 —26— — sands having an average rth particle size comprised between 60 um and 3 mm: 0.4 ~ 20 m/s; — gravels having an average Wentworth particle size comprised between 3 mm and 100 mm: 0.8 — 15 m/s; — 10 m/s. - s having an average Wentworth particle size 2 100 mm: 0.8 In a preferred embodiment, the ng method further comprises the step of reducing the average speed of the water/sediment slurry sucked inside the n head downstream of the suction opening.

Preferably, this speed reduction step is carried out by means of the aforementioned increase of the section area of the lower n of the suction head proximal to the suction opening and it allows an adequate slowing down of the sucked solid al ents but also broken stone or various kinds of debris) .

Preferably and as outlined above, the average speed of the slurry at the maximum cross— section area of the suction head is comprised between 0.1 m/s and 25 m/s.

In a preferred embodiment, the dredging method further comprises the step of carrying out a particle size tion, within the suction head, of the sediments incorporated in the water/sediment slurry sucked into said head.

Preferably and as outlined above, this step can be carried out by means of the perforated partition described above.

Advantageously and as outlined above, it is possible in this case to achieve, with t to known dredging apparatuses, not only a greater operating flexibility of the dredging method, since possible solid residues of large dimensions are no longer capable of interfering with the operation of the suction head, but also the possibility of separating solid material of large dimensions from the finer sediments, by carrying out a first particle size classification of the sediments and by holding such material in the area of the head upstream of the perforated partition for uent recovery and removal.

By carrying out also the aforementioned step of reducing the average speed of the water/sediment slurry downstream of the n opening, this preferred embodiment of the method of the invention allows to achieve the additional important advantageous 3O technical effects of: — ng the mechanical stresses on the perforated partition; Replacement Specification ~ 10 August 2015 — limiting the wearing ena due to impacts on the perforated partition; — allowing a ent autonomy of operation between a cleaning operation of the area upstream of the perforated partition and the next one; — carrying out a prior particle size tion of the sediments to be drawn so as to optimise the subsequent steps of separation and/or decontamination; and - carrying out, during the dredging operations, an accurate washing of the sediments held by the perforated partition.

In a red ment, the dredging method further comprises the step of separating a slurry of water and sediments discharged by the submersible pump in a liquid phase and a solid phase including the sediments.

In this way and as outlined above, it is advantageously possible both to r the sediments for their uent treatment, storage or reuse, and to have a flow of water substantially free of sediments that can be recirculated to the suction head.

Preferably and as ed above, this separation step can be cairied out by means of the ting device described above.

In this preferred embodiment, the method preferably comprises a step of recirculating a predetermined flow rate of the liquid phase towards the suction opening of the suction head.

In this way and as ed above, it is advantageously possible to achieve the following technical effects: — increasing the erosion action of the sediments and consequently the efficiency of the dredging operations thanks to the feeding of the liquid phase separated by the separating device towards the suction opening of the head; — effectively confining the suction area of the sediments blocking any possible water turbidity effect; — possibility of keeping the sucked water in a substantially closed circuit, which circuit being possibly sealable at the end of the dredging operations, which is a particularly useful option in the case of polluted locations in which it is not possible to discharge the separated liquid phase on land or in water.

.Preferably and as outlined above, these steps can be carried out by means of the Replacement Specification — 10 August 2015 —28— ulation system and of the inner hollow space located within the suction head described above.

Preferably, the recirculation step of the liquid phase is carried out by means of the aforementioned inner hollow space located within the suction head, which hollow space is advantageously e of directing a highly—directed liquid flow s the suction opening, thereby increasing the erosion action of the nts and more effectively confining the suction area of the sediments.

In a preferred embodiment of the dredging method, the liquid phase recirculated towards the suction opening has a speed equal to or lower than the suction speed.

In this way, it is advantageously possible to keep the desired sion conditions at the suction opening and ensure that the recirculated liquid phase is substantially confined in a closed hydraulic circuit substantially inside the perimeter of the aforementioned suction opening t any substantial disturbing action of the sediments and any undesired generation of turbulence which may bring the sediments in sion.

Preferably, the absolute re value at the suction opening is kept at values comprised between 0.1 and 0.9 bar, more preferably between 0.2 and 0.7 bar, by suitably adjusting the speed of the liquid phase ulated towards such an opening.

Moreover and if the speed of the liquid phase recirculated s the n opening is lower than the suction speed it is advantageously possible to achieve the additional technical effect of drawing a further flow of water from the areas around the suction opening of the head thus contributing to increase the peripheral erosion action of the sediments without substantial contact with the water bed, compensating at the same time any losses of the recirculated liquid phase.

In a preferred embodiment of the dredging method of the invention, the liquid phase recirculated s the suction opening has a speed comprised between 0.2 and 15 m/s as a function of the suction speed values given above.

More ably, the liquid phase recirculated towards the suction opening has a speed comprised between 0.5 and 10 m/s and, still more preferably, between 1 and 5 m/s as a function of to the preferred suction speed values given above.

In a preferred embodiment of the dredging method of the invention, the ratio between the suction speed of the water/sediment slurry and the speed of the liquid phase ement Specification — 10 August 2015 _29_ recirculated towards the suction opening is comprised between 1 and 7, more preferably between 1 and 5 and, still more preferably, between 1 and 2.

In further preferred embodiments, the dredging method further comprises one or more of the steps of: - imparting to the water sucked into the head a substantially rotary nt or a substantially radial movement with respect to the suction opening; — imparting on the recirculated liquid phase fed close to the suction opening a substantially rotary movement or a substantially radial movement with respect to the suction opening, - eroding the sediments from the bed by channelling the water present close to the suction opening outside the head in the radial direction towards the suction opening.

Preferably, these red steps can be carried out by means of the above described flow deflecting elements d inside (for example within the hollow space formed within the head) and/or outside of the suction head as illustrated earlier.

Advantageously and as outlined above, these steps allow to create a highly-directed flow of liquid towards the n g, thereby optimising the fluid-dynamics of the dredging operations, increasing their efficiency and reducing their times and costs.

In a red embodiment, the dredging method further comprises the step of chemically treating the liquid phase separated from the slurry of water and sediments.

Preferably, this step can be carried out by means of the aforementioned chemical treatment unit and it achieves the advantages outlined above in relation to the ption of such a unit.

In a preferred embodiment, the ng method r comprises a stand-by step including a step of sealing a predetermined amount of the ulated liquid phase separated from the slurry of water and sediments in a closed circuit.

Preferably, this step can be carried out by means of the aforementioned shut—off valves respectively mounted on the discharge duct of the slurry of water and sediments extending downstream of the discharge opening of the g body of the submersible pump and on the recirculation duct of the liquid phase separated by the separating device to the suction opening of the suction head.

Replacement Specification ~ 10 August 2015 _30_ Brief description of the figures Addtional features and advantages of the present invention will become more readily apparent from the ing detailed description of some preferred embodiments of a dredging apparatus according to the invention, made hereafter by way of explanation and not of limitation with reference to the attached drawings. In the drawings: — figure 1 is a schematic view of a preferred embodiment of a dredging apparatus according to the ion; — figure 2 is a schematic View showing some details of the dredging apparatus of figure 1 in an operative condition thereof; - figure 3 is a schematic axonometric View partially in cross section of the n tus of the dredging apparatus of figure 1; - figure 4 is a schematic axonometric View partially in cross section and in enlarged scale of some details of the suction apparatus of the dredging apparatus of figure 1 ; — figure 5 is a schematic axonometric view in enlarged scale and with some parts removed of some details of a suction apparatus of a further preferred embodiment of the dredging apparatus according to the invention; ~ figure 6 is a schematic axonometric view in ed scale and with some parts detached of some details of a suction tus of a further preferred embodiment of the dredging tus according to the invention; — figure 7 is a schematic axonometric View of a suction tus of a further preferred embodiment of the dredging apparatus ing to the invention; — figures 8—10 are as many schematic etric Views partially in cross section of respective suction apparatuses of further preferred embodiments of the ng apparatus according to the invention; — figures ll and 12 are as many tic axonometric Views partially in cross n and in enlarged scale of suction heads of respective suction apparatuses of further preferred embodiments of the dredging apparatus according to the invention; — figure 13 is a schematic view that illustrates some details of an alternative preferred embodiment of the suction apparatus of the dredging apparatus according to the 3O invention in an operating ion thereof.

Replacement cation — 10 August 2015 -3]- Detailed description of the currently preferred embodiments With reference to figures 1-5, a dredging apparatus according to a first preferred embodiment of the invention, for e a dredging apparatus of the so-called sucking—discharging type for ng sediments from a bed F of an expanse of water S like for example a sea bed, river bed, lake bed, marsh bed, etc, is lly indicated at The dredging apparatus 1 comprises a hull 2, preferably constituted by a plurality of modular bridge units (not illustrated in greater detail), tionally supporting a driving station 3, inside which a driving panel is positioned to drive all of the displacement operations of the hull and actual dredging operations by means of suitable driving devices, a power station 4 for operating a submerged suction apparatus 5 and a lifting frame 6 for moving the suction tus 5.

The power station 4 comprises in turn an endothermal engine (for example a diesel engine) and a hydraulic or electric l unit, not better shown in figure 1, to hydraulically or electrically operate the submerged suction apparatus 5 as will become clearer hereinafter.

The ng apparatus 1 also comprises one or more tanks of a suitable fuel of the endothermal engine and one or more devices for moving the hull 2, both of the conventional type and not shown.

The hull 2 also conventionally supports a work station 7 comprising: — a ting device 8 for the separation of a slurry of water and sediments coming from the suction apparatus 5, for example a ting device of the agm type (see figure 2), for separating a slurry of water and sediments discharged from the suction apparatus 5 in a liquid phase and a solid phase including the sediments; — a recirculation system 10 to a suction head 9 of the suction apparatus 5 of at least a part of the liquid phase separated by the ting device 8, comprising a tank 11 for collecting the liquid phase separated by the separating device 8 and at least one recirculation duct 12 to the suction head 9 of the separated liquid phase ; — a unit 13 for chemically treating the liquid phase separated by the separating device 8, for example including a tank 14 for neutralizing the pollutants in fluid communication with the tank 11 of the recirculation system 10 by means of a pair of ducts 15, 16 for feeding the liquid phase to the tank 14 and for returning the neutralized liquid phase to Replacement Specification ~ 10 August 2015 the tank 11.

The suction apparatus 5 includes, as better rated in figures 2—4: a) a submersible pump 18 including: — a housing body 17 provided with an inlet mouth 19 and with a discharge opening 20; — an impeller 21 rotatably supported in the body 17 between the inlet mouth 19 and the discharge opening 20 and rotatably driven by a respective driving device 22, in particular a motor operated by the control unit of the power station 4; and b) the aforementioned suction head 9, which is associated to the inlet mouth 19 of the g body 17 of the pump 18 and provided at the bottom with a suction opening 23 of the sediments.

In a way knownper se, the discharge opening 20 of the housing body 17 of the pump 18 is in fluid connnunication with the separating device 8 by means of a duct 24 (shown with a dashed line in figure 3) for sending the slurry of water and sediments discharged by the suction apparatus 5, said duct being connected to the body 17 by means of a flanged pipe fitting 25.

The suction opening 23 of the head 9 has a cross-section area dimensioned to achieve, in the working range of the pump 18, a suction speed capable of removing the sediments by means of the fluid dynamics l action carried out by the water sucked into the head 9.

In the preferred embodiment rated, the suction opening 23 of the head 9 has a cross-section area smaller than the maximum cross—section area of the suction head 9.

In this way, it is advantageously possible to create, in the suction head 9, a ated section that generates a strong depression and a consequent high suction speed of the water or of the water/sediment slurry.

Preferably, the average suction speed, measured at the suction g 23 of the head 9, varies between 0.3 m/s and 30 m/s essentially according to the particle size and on characteristics of the nts.

In the preferred ment illustrated, the suction head 9 comprises a first portion 9a proximal to the suction opening 23 having a progressively increasing cross—section area 3O moving away from the opening 23 and a second portion 9b distal with respect to the ement Specification — 10 August 2015 suction opening 23 having a progressively decreasing cross—section area moving away from the first portion 9a.

In the red embodiment illustrated, the suction head 9 comprises, inside the same, a perforated partition 26 supported in the head 9 ream of the suction opening 23 and adapted to hold solid material having a size exceeding the passage section of holes 27 made in the partition 26.

In the preferred embodiment illustrated, the holes 27 are uniformly distributed in the part of the partition 26 crossed by the liquid, they are preferably circular in shape and they preferably have a diameter comprised between 15 mm and 300 mm, so as to define a cross—section passage area preferably comprised n 175 and about 75000 mmZ.

Advantageously, by positioning the perforated partition 26 within the suction head 9 it possible to achieve the following advantages with respect to known dredging apparatuses: - greater operating flexibility of the dredging apparatus 1 since any solid residues of large size are no longer capable of interfering with the operation of the suction head, - ility of separating the solid material having a particle size exceeding the passage section of the holes 27 from the rest of the sediments, by holding such material during the dredging operations in the area of the head 9 upstream of the perforated partition 26 for subsequent recovery and removal thanks to the depression conditions generated Within the head 9.

Since the suction g 23 of the head 9 has a cross-section area smaller than the maximum cross—section area of the suction head 9, the following ant advantageous technical effects are also ed: — limiting the mechanical stresses on the perforated partition 26 g — ng the wearing phenomena due to impacts on the perforated partition 26; — allowing a sufficient my of operation between one cleaning operation of the area upstream of the perforated partition 26 and the next one; — carrying out a prior particle size classification of the sucked sediments so as to optimise the subsequent steps of separation and/or decontamination; and Replacement Specification — 10 August 2015 — washing the sediments held by the perforated partition 26, an operation that is particularly important in dredging operations of contaminated sites.

Thanks to the aforementioned geometric configuration of the portion 9a of the head 9, it is advantageously possible to progressively slow down the speed of the water/sediment slurry sucked into the head 9 and facilitate the ng of the suction head 9 from the debris held upstream of the perforated partition 26 present in the head 9.

In this way, it is thus advantageously possible to optimise from the geometric and fluid- c point of view the area of the suction head 9 proximal to the suction opening 23 upstream of the perforated partition 26.

Preferably, the suction head 9 comprises, in the aforementioned first portion 9a proximal to the n g 23, a lower wall 28 having an inclination with respect to a longitudinal axis X—X of the suction opening 23 comprised in the range of numerical values indicated above.

In this way, it is thus advantageously possible to optimise from the ric and fluid— dynamic point of view the area of the suction head 9 proximal to the suction opening 23 am of the perforated partition 26.

Preferably, the suction head 9 comprises, in the entioned second portion 9b distal with respect to the suction opening 23, an upper wall 29 having an inclination with respect to the longitudinal axis X-X of the suction opening 23 comprised in the range of numerical values indicated above.

Thanks to the aforementioned geometric ration of the portion 9b of the head 9, it is advantageously possible to se from the geometric and fluid-dynamic point of View the area of the suction head 9 distal with respect to the suction opening 23 downstream of the perforated partition 26 in particular improving the fluid—dynamic efficiency of the head 9 close to the inlet mouth 19 in the body 17 of the pump 18, y optimising the ion thereof.

In the preferred embodiment illustrated, the suction head 9 consists of two or more structurally independent portions, in this case consisting of the portion 9a proximal to the suction g 23 and of the second n 9b distal With respect to such an opening, removably associated to one another by means of a plurality of bolts (not shown) inserted in respective through holes 30a, 30b formed in respective radially outer fins 31a, 3 lb extending from a peripheral edge of the portions 9a and 9b.

Replacement Specification ~ 10 August 2015 _35_ Preferably, the suction head 9 further comprises an intermediate portion 9e comprising a lower portion proximal to the suction opening 23 and having a progressively increasing cross-section area moving away from said g and an upper portion distal with respect to the suction opening 23 and having a progressively decreasing cross—section area moving away from the lower portion (see figure 4).

In this case, the intermediate portion 96 is thus preferably formed of two mutually adjacent end portions of the portions 9a, 9b of the suction head 9 and having a lower inclination with respect to the udinal axis of the n opening 23 with respect to the remaining part of the first portion 9a and, respectively, of the second portion 9b.

Preferably, the lower portion of the intermediate portion 9e has an inclination with respect to the longitudinal axis of the suction opening comprised in the range of numerical values ted above. ably, the upper n of the intermediate portion 9e has an inclination with respect to the longitudinal axis of the suction g comprised in the range of numerical values indicated above.

In this preferred embodiment, the ated partition 26 is also provided With ponding radial fins 32 perforated so as to be able to be mounted between the portions 9a and 9b of the suction head 9 preferably at a transversal ane of the intermediate portion 9e of the head 9.

In this preferred configuration, it is advantageously possible to dismount the suction head 9 and the perforated partition 26, facilitating the cleaning and maintenance operations thereof.

Moreover, thanks to the configuration with a double inclination of the intermediate portion 9e of the suction head 9 it is possible to achieve the following advantageous technical effects: — preventing the solid material having a size smaller than the passage section of the holes 27 formed in the ated ion 26 from being trapped between the lower wall 28 of the head 9 and the partition 26 and thus not passing beyond the same; — preventing the solid material having a size greater than the passage section of the holes 3O 27 made in the partition 26 from being trapped between the lower wall 28 of the head 9 and the partition 26 thus making it difficult to carry out the operation of emptying the area of the head am of the partition 26 (the portion proximal to the suction Replacement Specification — 10 August 2015 —36- opening 23); and — preventing solid material having a size smaller than the e section of the holes 27 formed in the partition 26 from being trapped between the upper wall 29 of the head 9 and the partition 26 and not drawn by the pump 18.

In the red embodiment illustrated, the lower wall 28 of the portion 9a proximal to the suction opening 23 and the upper wall 29 of the second portion 9b distal with respect to such an opening (including the adjacent end portions forming the intermediate portion 9e of the head 9) are faceted and comprise a plurality of planar segments 9c, 9d inclined with respect to the longitudinal axis X—X of the suction opening and connected side-by-side.

In this case, there is ageously a fication of the manufacturing operations of the head 9 with a ion of the relative costs.

In this way a polygonal—shaped suction opening 23 is thus defined.

In the preferred embodiment illustrated, the suction head 9 is provided with an inner hollow space 34 defining an outer annular portion of the suction opening 23 and in liquid ication with the ulation system 10 for feeding the liquid phase separated by the separating device 8 towards the suction opening 23 and within the suction head 9.

Preferably, the first portion 9a of the suction head 9 is provided with a jacket 33 forming a portion 9a provided with an inner and outer double wall, wherein the aforementioned hollow space 34 is defined that is thus located within the suction head In this preferred embodiment, therefore, the jacket 33 defines the outermost wall of the lower part of the first portion 9a of the suction head as well as the outermost perimeter of the suction g 23 of the head 9.

In the preferred embodiment illustrated and depending on the structural teristics of the head 9, the n opening 23 is thus polygonal in shape, in particular with 9 sides and it circumscribes a circle having a diameter comprised between 100 mm and 1500 mm thus generating a cross-section area comprised between 0.008 and 1.76 m2.

Preferably, the cross—section area of the g defined by the inner wall 28 of the first portion 9a of the suction head 9 is in this case comprised between 0.004 and 0.90 m2 so Replacement Specification — 10 August 2015 as to take into account the section of the recirculation hollow space 34.

In this preferred embodiment, the dredging apparatus allows to achieve the following cal advantages: - increasing the erosion action of the sediments and therefore the efficiency of the dredging operations thanks to a highly—directed feeding of the liquid phase ted by the separating device 8 towards the suction opening 23 of the head 9 g — effectively confining the suction area of the sediments with a block of any ial water turbidity phenomena. — possibility of maintaining the sucked water in a ntially closed circuit, said circuit being ally sealable at the end of the dredging operations, which is a particularly useful option in the case of ed sites where it is not possible or desirable to discharge the liquid phase separated on land or in the sea.

In the red embodiment illustrated, the dredging apparatus comprises a plurality of flow deflecting elements associated to the suction head 9 close to the suction opening 23 (figure 5).

In this preferred embodiment, the aforementioned flow deflecting elements are positioned in the hollow space 34 close to the suction opening 23 and consist of a ponding plurality of ntially rectilinear fins 35 extending along an inclined direction with respect to the radial direction.

Thanks to the presence of these flow deflecting elements, the dredging apparatus 1 achieves the advantageous technical effect of imparting to the flow of liquid phase fed s the suction opening 23 a highly-directed substantially rotary movement of the centrifugal type which increases the efficiency of the fluid-dynamic removal action of the sediments.

With reference to the dredging apparatus 1 described above and to Figures 1—5, a dredging method for removing sediments from the bed F of the expanse of water S will now be described.

In a first step, the method provides for positioning the suction apparatus 5 including the submersible pump 18 described above close to the water bed F. 3O Thereafter, a ring step is carried out in which with the motor 22 of the pump 18 at start—up speed, the suction head 9 is brought close to the bed F by the lifting frame 6 up Replacement Specification ~ 10 August 2015 .38_ to a distance such that by actuating the submersible pump 18 the water drawn from the outside is forced to lap on the outer periphery of the lower portion 9a proximal to the suction opening 23 of the head 9 and then to discharge its c energy on the bed F, eroding the same.

The erosion of the water bed F therefore starts from the periphery of the n opening 23 and reaches the centre up to the longitudinal axis X—X by successive yielding.

As soon as the head 9 has penetrated the water bed, the submersible pump 18 is ed so as to achieve, in the working range of the pump, a suction speed capable of removing the sediments by means of the fluid cs removal action carried out by the water sucked into the head 9.

In this way, the ing apparatus enters into a —state operating condition in which the strong depression ted at the suction g 23 and in the areas immediately upstream thereof possesses a preferential direction axial to the head 9 and continues to draw water from the outside with a progressive erosion and l of the sediments.

At this point it is possible to distinguish two movements of the dredging front at any veitical movement of the head 9: - a front movement, which takes place in the same way as the triggering step; and - a peripheral movement, which takes place by virtue of the fact that the layers of material lying over the sucked layer close to the head 9 constitute unstable fronts and consequently slip downwards.

The Applicant observed that such a mechanism, once triggered, is capable of self- feeding making the dredging operations very efficient and free from any interruptions.

In an experimental test carried out according to this preferred embodiment of the dredging method of the invention, it was found that there was a suction speed comprised between 1.1 and 3.4 m/s with a particle size of the nts of 60-80 mm, whereas the suction flow rate was equal to about 2400 m3/h.

In this preferred embodiment, the dredging method also provides the step of reducing the average speed of the water/sediment slurry sucked into the suction head 9 downstream of the suction opening 23 carried out by means of the aforementioned increase of the cross—section area of the lower portion 9a of the suction head 9 proximal Replacement Specification — 10 August 2015 to the suction opening 23.

Advantageously, such a preferred step allows to adequately slowing down the sucked solid material (sediments but also broken stone, or various kinds of debris) .

In this preferred ment, the average speed of the slurry at the maximum cross— section area of the intermediate n 96 of the suction head 9 (where the perforated partition 26 is mounted) is comprised between 0.3 m/s and 0.9 m/s.

In this preferred embodiment, the dredging method also comprises the step of carrying out a particle size classification within the suction head 9 of the sediments incorporated in the water/sediment slurry sucked into said head 9. ably, this step is carried out by means of the perforated partition 26 described above.

Advantageously and as outlined above, it is possible in this case to achieve, with respect to known dredging apparatuses, not only a greater operating flexibility of the dredging , since any solid residues of large size are no longer capable of interfering with the operation of the suction head 9, but also the ility of separating solid material having a large particle size from the finer sediments, holding such material in the area of the head 9 upstream of the partition 26 for subsequent recovery and l.

In other words, thanks to the presence of the perforated partition 26 it is possible to achieve : - a selective withdrawal of the al according to its size; — a greater precision in achieving the desired dredging depths.

With respect to common ng heads, in fact, the dredging apparatus and method of the invention allow to withdraw the foreign bodies and all the material which does not them within the suction head pass through the partition 26 from a certain location, keep 9 and then deposit the same in a different area so as to be able to continue excavating the water bed F in the same location.

In common heads, on the contrary, the filter is oned e of the head and once it is saturated it is necessary to move the same with the consequence that the foreign bodies are ted and thus it is not possible to continue the dredging operations in the same location.

Replacement Specification H 10 August 2015 By carrying out also the aforementioned step of reducing the average speed of the water/sediment slurry downstream of the suction opening, this red embodiment of the method of the invention allows to achieve the additional ant advantageous technical effects of: - limiting the mechanical stresses on the perforated partition 26; — limiting the wearing phenomena due to impacts on the ated partition 26 ; ~ allowing a ent autonomy of operation n one cleaning operation of the area upstream of the partition 26 and the next one; and - carrying out a prior particle size classification of the sucked sediments so as to optimise the subsequent steps of separation and/or decontamination.

In this preferred embodiment, the dredging method also comprises the step of separating the slurry of water and nts discharged from the submersible pump 18 in a liquid phase and a solid phase including the sediments.

In this way and as outlined above, it is advantageously possible both to recover the sediments for their subsequent treatment, storage or reuse, and to have a flow of water substantially free of sediments that is at least partially recirculated to the suction head 9 by means of the duct 12 of the ulation system 10.

This separation step is in particular ably carried out by means of the ting device 8 described above. 2O Advantageously, the step of recirculating at least a part of the liquid phase separated from the slurry is carried out in a “passive” manner, thanks to the depression which is created at and close to the suction opening 23 by the submersible pump 18.

In this way, it is advantageously possible to recirculate at least a part of the liquid phase ted by the separating device 8 towards the suction opening 23 of the suction head 9 without any additional driving element, but simply by exploiting the action of the submersible pump 18 which is in any case already provided to suck the sediments in the ng apparatus 1.

In a preferred embodiment, the dredging method comprises the step of recirculating to the head 9 substantially all of the liquid phase separated from the , with the exception of the losses of the liquid which impregnates the separated solid phase, said losses being compensated by withdrawing water from the surrounding environment, and Replacement Specification — 10 August 2015 -41_ the step of feeding the recirculated liquid phase towards the suction opening 23.

In this way, the recirculated liquid phase has a speed substantially equal to the n speed for which reason it is advantageously le to ensure that the recirculated liquid phase is substantially confined in a closed hydraulic circuit without any substantial disturbing action of the sediments and without any red generation of turbulence capable of bringing the nts in sion. er and as outlined above, it is advantageously possible to achieve the following technical effects: — increasing the erosion action of the sediments and therefore the efficiency of the dredging operations thanks to the highly—directed feeding of the liquid phase separated by the separating device 8 towards the suction opening of the head 23; — effectively confining the suction area of the sediments with a block of any possible water turbidity phenomena; - possibility of keeping the sucked water within a substantially closed circuit.

These steps are in particular carried out by means of the duct 12 of the recirculation system 10 and by the hollow space 34 defined within the suction head 9.

In this preferred embodiment, the dredging method also comprises the steps of imparting to the recirculated liquid phase fed towards the suction opening 23 a highly- directed substantially rotary movement with respect to the suction opening 23 and of eroding the sediments from the water bed F by channelling the water t close to the suction g 23 outside of the head 9 in a tangential direction s the suction opening 23.

These preferred steps are carried out in this case by means of the flow deflecting elements (fins 35) described above oned within the hollow space 34 defined in the head 9.

Advantageously and as outlined above, these steps allow to optimise the fluid-dynamics of the dredging operations thereby increasing their efficiency and reducing the times and costs f.

In this preferred embodiment, the dredging method also comprises the step of 3O chemically ng the liquid phase separated from the slurry of water and sediments in the separating device 8.

Replacement Specification H 10 August 2015 This step is preferably d out by means of the chemical treatment unit 13 and it allows to achieve the ages outlined earlier.

With reference to figures 6—13 further preferred embodiments of the dredging apparatus 1 according to the invention will now be described.

In the ing ption and in such , the elements of the dredging tus which are structurally 0r functionally equivalent to those illustrated earlier with reference to figures 1—5 will be indicated with the same reference numerals and will not be described any fiirther.

In the embodiment of figure 6, a variant of the suction head 9 is illustrated in which the flow deflecting elements positioned in the hollow space 34 consist of substantially curvilinear fins 35 inclined with respect to the radial direction so as to impart to the ulated water flow a substantially rotary movement of the centripetal type which facilitates the water intake into the suction head 9 and effectively erodes the water bed F removing the sediments,.

In a further alternative preferred embodiment, not illustrated, the ntially curvilinear fins 35 can be oriented in the opposite direction with respect to the radial direction (in other words with the concavity to the left of the fins with reference to figure 6) so as to impart to the recirculated water flow a substantially rotary movement of the tangential type with respect to the suction opening 23, ing also in this case an effective erosion of the water bed F.

Figure 7 shows a variant of the suction apparatus 5 and of the n head 9 in the case in which the dredging apparatus 1 lacks the recirculation system 10 of the water to the head 9.

In this preferred embodiment, the suction head 9 comprises a plurality of flow deflecting elements, consisting of respective substantially rectilinear fins 35 extending along a ion inclined with respect to the radial direction, externally associated to the first portion 9a of the suction head 9 close to the suction opening 23.

Thanks to the presence of these ed fins 35, the dredging apparatus 1 es the advantageous technical effect of imparting to the liquid phase flow fed towards the 3O suction opening 23 a substantially rotary movement of the centrifugal type which increases the efficiency of the fluid—dynamic removal action of the sediments.

Consequently, the dredging method carried out by means of the aforementioned Replacement Specification — 10 August 2015 -43_ dredging apparatus 1 comprises the step of imparting to the water sucked into the head 9 a ntially rotary movement oriented towards the suction opening 23.

In this red embodiment, the second portion 9b of the suction head 9 distal with t to the n opening 23 is provided with a plurality of inspection ports 36 which advantageously allow to inspect the inner space of the suction head 9 and to verify the need for a le intervention to remove solid materials held by the perforated partition 26 and/or to carry out maintenance or repair interventions.

Clearly, the entioned inspection ports 36 can also be provided on the other embodiments of the invention.

Figure 8 illustrates a further preferred embodiment of the suction apparatus 5 and of the suction head 9 in the case in which the dredging apparatus 1 lacks the recirculation system 10 of the water to the head 9.

In this case, the suction head 9 is integrally formed as a single piece with the perforated partition 26, while the portions 9a and 9b of the suction head 9, respectively proximal and distal with respect to the suction opening 23, have a frustoconical shape, thereby ing the advantageous technical effects described above in relation to the presence of this specific ation of features.

Figure 9 illustrates a further preferred embodiment of the suction tus 5 and of the suction head 9 in the case in which the dredging apparatus 1 lacks the recirculation system 10 of the water to the head 9.

In this case, the n head 9 is integrally formed as a single piece with the perforated partition 26 and its intermediate portion 9e interposed between the portions 9a and 9b has a substantially constant cross-section area.

The ns 9a and 9b of the suction head 9, respectively proximal and distal with respect to the suction opening 23 have also in this case a frustoconical shape, thereby obtaining the advantageous technical effects described above in relation to the presence of this c feature.

In this case, the perforated partition 26 is supported in the suction head 9 at the intermediate portion 9e having a substantially constant cross section so as to achieve the advantageous technical effects illustrated above with reference to the embodiment of figures 1-5.

Replacement Specification — 10 August 2015 Figure 10 illustrates a further preferred embodiment of the suction tus 5 and of the suction head 9 in the case in which the dredging apparatus 1 lacks the recirculation system 10 of the water to the head 9.

In this case, the n head 9 is integrally formed as a single piece with the perforated partition 26 and ses a single cylinder—shaped portion having a substantially constant cross—section area.

In this case, the suction opening 23 is centrally formed in a bottom wall 37 of the head 9 and similarly to the other preferred embodiments illustrated, it has a smaller cross- section area than the maximum cross-section area of the suction head 9 (in this case equal to the area of its cross section that is constant).

Figure 11 illustrates a further preferred embodiment of the suction apparatus 5 and of the suction head 9 in the case in which the dredging apparatus 1 lacks the recirculation system 10 of the water to the head 9.

In this case and similarly to the preferred embodiment illustrated in figures 1-5, the portion 9a proximal to the suction opening 23 and the second portion 9b distal with t to such an opening are structurally independent and are removably associated to one another in an analogous manner by means of a plurality of bolts (not shown).

Also in this case, the perforated partition 26 is removably mounted between the portions 9a and 9b of the suction head 9 at the intermediate portion 9e and the walls of the head 9 are faceted and comprise a ity of planar segments inclined with respect to the longitudinal axis X—X of the n opening 23 and connected side—by-side to each other.

In this way, a nal suction opening 23 is thus defined also in this case.

In this case, the portion 9a proximal to the suction opening 23 differs from the previous ones in that it consists of a pair of portions 9a”, 9a” proximal to the suction opening 23 and having a progressively increasing section area moving away from said g and a different inclination with respect to the udinal axis X—X of the suction opening 23.

More specifically, a first portion 28a of the lower wall 28 closest to the suction opening 23 has an inclination with respect to the longitudinal axis X—X comprised between 0° and 85° and, still more preferably, n 5° and 70° and a second portion 28b of the lower wall 28 has an inclination with respect to such a longitudinal axis X-X comprised Replacement Specification ~ 10 August 2015 between 5° and 85° and, still more preferably, between 25° and 70°.

In this way, it is ageously possible to provide the suction head 9 with an element for reducing its cross section which, in the case of particularly cohesive sediments (e.g. compact clay), allows to achieve a cross—section area of the suction opening 23 that is adequately reduced so as to increase the suction speed and therefore the sediment removal capacity of the head 9.

In the embodiment of figure 12, the suction head 9 is entirely similar to the head of figure 11 with the difference that the reducing element — consisting of the portion 9a’ closest to the suction opening 23 — comprises a plurality of cut outs 38 formed at the peripheral edge of the suction opening 23 so as to avoid the triggering of possible cavitation ena in the case of accidental t with the bed F.

Finally, figure 13 illustrates a further preferred embodiment of the suction apparatus 5 and of the suction head 9 in the case in which the dredging apparatus 1 is ed with the recirculation system 10 of the water to the head 9 in a similar manner with respect to the us embodiment of figures l—5.

In this case, the dredging apparatus 1 comprises a first shut—off valve 40, for e a check valve of the swing type, mounted on the discharge duct 24 of the slurry of water and sediments sucked by the n head 9 and extending downstream of the discharge opening 20 of the housing body 17 of the submersible pump 18.

Preferably, the dredging apparatus 1 also comprises a second shut—off valve 41, for example a throttle valve, mounted on the recirculation duct 12 of the liquid phase separated by the separating device 8 to the suction opening 23 of the suction head 9.

The presence of the shut-off valves 40, 41 is extremely advantageous in the case in which polluted sites are dredged, since it allows to: of - g the recirculated water in a substantially closed circuit, ng any type oduction into the nment of pollutants present in the liquid phase, in case of failure of the submersible pump 18 or of other elements of the ulation system or when the dredging operations are stopped; and ~ preventing undesired back—flows of the slurry of water/sediments discharged by 3O impeller 21 of the submersible pump 18 in case of failure of the latter or when the dredging operations are stopped.

Replacement Specification H 10 August 2015 ~46- From what has been outlined above, it is thus clear that the dredging apparatus and method of the invention e s advantageous technical effects and, more cally: — possibility of carrying out the dredging operations Without any appreciable dispersion of the sediments which are eroded solely by means of the fluid dynamics removal action carried out by the water sucked into the head; - possibility of carrying out the dredging operations without contact with the water bed by means of a fluid-dynamic suction/removal action of the sediments carried out by the water sucked by the suction head by means of the depression which is generated close to, in particular beneath and around, the suction opening of the head; — possibility of sucking a water/sediment slurry having a high content of solids, up to a value equal to or greater than 40% by volume and, therefore, with the possibility of obtaining a high dredging ncy in terms of hourly tivity; - possibility of drastically reducing the environmental impact, so that the dredging apparatus and method may be used in SCI or SNI sites or in any case in areas where for environmental reasons it is not permitted to have any type of water turbidity and/or dispersion of polluting sediments in the water; - possibility of recovering and, if needed, ng and/or exploiting, the dredged solid materials; — possibility of reducing the times and costs of the entions.

Clearly, a man skilled in the art may introduce modifications and variants to the invention described hereinbefore in order to meet specific and contingent application requirements, ts and modifications which anyway fall within the scope of protection as defined in the attached claims.

Replacement Specification w 10 August 2015 _47_

Claims (30)

1. Dredging apparatus (1) for removing sediments from a bed (F) of an expanse of water (S) in absence of any contact with the bed (F), comprising a suction tus (5) including: a) a sible pump (18) including: a1) a housing body (17) provided with an inlet mouth (19) and with a discharge opening (20); a2) an impeller (21) rotatably supported in said body (17) between said inlet mouth (19) and said discharge opening (20) and rotatably driven by a respective driving device 10 (22); b) a suction head (9) associated to said inlet mouth (19) of the housing body (17) of the of the sediments; pump (18) and ed at the bottom with a suction opening (23) wherein the suction opening (23) of the head (9) has a value of the cross-section area ioned to achieve in the g range of the pump (18) a suction speed capable 15 of removing the sediments by means of a fluid dynamics removal action carried out by the water sucked into said head (9); wherein the dredging tus further comprises a separating device (8) for separating a slurry of water and sediments discharged from the suction apparatus (5) in a liquid phase and a solid phase including the sediments and a ulation system (10) to the 20 suction head (9) of at least a part of the liquid phase separated by said separating device (8); wherein the suction opening (23) of the head (9) has a cross—section area smaller than the maximum cross—section area of the suction head (9); n the suction head (9) is provided with an inner hollow space (34) defining an 25 outer annular portion of said suction opening (23) and in liquid communication with the recirculation system (10) for feeding the liquid phase separated by the separating device (8) towards the suction g (23) and inside said head (9); and wherein the recirculation system (10) defines a closed hydraulic circuit of the fluid recirculating therein. Replacement Specification — 10 August 2015 -48—

2. Dredging apparatus (1) according to claim 1, wherein the suction head (9) comprises at least a first portion (9a) proximal to the suction opening (23) having a progressively increasing cross-section area moving away from said opening (23) and a second portion distal with respect to the suction opening (23) having a substantially constant cross- section area.

3. Dredging tus (1) according to claim 1, n the suction head (9) comprises at least a first portion (9a) proximal to the suction opening (23) having a progressively increasing cross—section area moving away from said g (23) and a second portion (9b) distal with respect to the suction opening (23) having a progressively decreasing 10 cross-section area moving away from said first portion (9a).

4. Dredging apparatus (1) according to claim 2 or 3, wherein the suction head (9) comprises a pair of portions (9a’, 9a”) proximal to the suction opening (23) having a progressively increasing cross—section area moving away from said opening (23) and a different ation with respect to a longitudinal axis (X—X) of the suction opening 15 (23).

5. Dredging apparatus (1) according to claim 3 or 4, wherein the suction head (9) further comprises an intermediate n osed between said first (9a) and second (9b) portion of the suction head (9).

6. Dredging apparatus (1) according to claim 5, wherein said intermediate portion has a 20 substantially constant cross-section area.

7. Dredging apparatus (1) according to claim 5, wherein said intermediate n comprises a lower portion proximal to the suction opening and having a progressively increasing section area moving away from said opening and an upper portion distal with respect to the n opening and having a progressively decreasing cross— 25 section area moving away from said lower portion.

8. Dredging apparatus (1) according to any one of claims 2-7, n said first (921) and/or second (9b) portion and/or intermediate portion of the suction head (9) has a substantially frusto—conical shape.

9. Dredging apparatus (1) ing to any one of the preceding claims, wherein the 30 suction head (9) comprises a perforated partition (26) supported in said head (9) ream of said suction opening (23).

10. Dredging apparatus (1) ing to claim 9, wherein said perforated partition (26) Replacement Specification 4 10 August 2015 -49_ is supported in the suction head (9) at an intermediate portion interposed between said first (9a) and second (9b) portion of the suction head (9).

11. Dredging apparatus (1) ing to any one of the preceding claims, comprising a plurality of flow deflecting elements (35) associated to the suction head (9) close to said suction opening (23).

12. Dredging apparatus ( 1) according to claim 11, wherein said flow deflecting elements (35) se a plurality of fins having a substantially rectilinear or curvilinear shape extending along a radial direction or along an inclined direction with respect to said radial direction. 10

13. ng apparatus (1) according to claim 2 or 3, wherein said first portion (9a) of the suction head (9) is provided with a jacket (33) forming a double wall wherein said inner hollow space (34) is defined.

14. Dredging apparatus ( 1) according to claim 1 or 13, further comprising a ity of flow deflecting elements (35) arranged in said hollow space (34) close to said suction 15 opening (23).

15. Dredging apparatus ( 1) according to claim 14, wherein said flow deflecting elements (35) comprise a plurality of fins having a substantially inear or curvilinear shape extending along a radial direction or along an inclined ion with respect to said radial direction. 20

16. Dredging apparatus (1) according to claim 1, comprising a first shut—off valve (40) mounted on a discharge duct (24) extending downstream of said rge g (20) of the housing body (17) of the submersible pump (18).

17. Dredging apparatus (1) according to claim 1 or 13, comprising a second shut—off valve (42) mounted on a recirculation duct (12) of the liquid phase separated by the 25 separating device (8) to the suction opening (23) of the suction head (9).

18. Dredging apparatus (1) according to claim 1, r comprising a unit (13) for chemically ng the liquid phase separated by said separating device (8).

19. Dredging method for ng sediments from a bed (F) of an expanse (S) of water in absence of any contact with the bed (F), comprising: 30 a) positioning, close to the bed, a suction apparatus (5) including: Replacement Specification — 10 August 2015 a submersible pump (18) including: ~ a housing body (17) provided with an inlet mouth (19) and with a discharge opening (20) of the water; — an impeller (21) rotatably ted in said body (17) between said inlet mouth (19) and said discharge opening (20) and rotatably driven by a respective driving device (22); and a suction head (9) associated to said inlet mouth (19) of the housing body (17) of the pump (18) and provided at the bottom with a suction g (23) of the nts provided With a longitudinal axis substantially vertically oriented in use; 10 b) operating the submersible pump (18) so as to achieve, in the working range of the pump (18), a suction speed capable of removing the sediments by means of a fluid dynamics removal action carried out by the water sucked into said head (9); wherein the suction g (23) of the head (9) has a cross—section area smaller than the maximum cross-setion of the suction head (9), 15 and wherein the method further comprises the steps of: — separating a slurry of water and sediments discharged by the submersible pump (18) a liquid phase and a solid phasepincluding the sediments by means of a separating device (8); — recirculating at least a part of the liquid phase separated from said slurry towards the 20 suction opening (23) of the suction head (9) by means of a recirculation system (10) and of an inner hollow space (34) defining an outer annular n of the suction opening (23), said inner hollow space (34) being in liquid communication with the recirculation system (10) for feeding the liquid phase separated by the separating device (8) towards the n opening (23) and inside said head (9); and 25 ~ keeping the fluid recirculating in the recirculation system (10) in a closed hydraulic circuit.

20. Dredging method ing to claim 19, wherein the suction speed is sed between 0.3 and 30 m/s according to the particle size and cohesion characteristics of the sediments. 30

21. Dredging method according to claim 19, r comprising the step of reducing the Replacement Specification ~ 10 August 2015 -51_ average speed of a water/sediment slurry sucked inside said suction head (9) downstream of said suction opening (23).

22. Dredging method according to any one of claims 19—21, further comprising the step of carrying out within said suction head (9) a le size separation of the sediments incorporated in the water/sediment slurry sucked into said head (9).

23. Dredging method according to any one of claims 19-22, wherein the liquid phase recirculated towards the suction opening (23) has a speed equal to or lower than the suction speed.

24. Dredging method according to any one of claims 19—23, wherein the liquid phase 10 recirculated towards the n opening (23) has a speed comprised between 0.2 and 15 m/s as a function of the suction speed.

25. Dredging method ing to claim 19, wherein the ratio between the suction speed and a speed of the liquid phase recirculated s the suction opening (23) is comprised between 1 and 7. 15

26. Dredging method according to claim 19, further comprising the step of imparting to the water sucked into said head (9) a substantially rotary movement or a substantially radial movement with respect to said suction opening (23).

27. Dredging method according to claim 19, further comprising the step of imparting to the recirculated liquid phase fed towards the suction opening (23) a substantially rotary 20 movement or a substantially radial movement with t to said suction opening (23).

28. ng method ing to claim 19, r comprising the step of eroding the sediments from the bed by lling the water close to said g (23) outside of said head (9) in a radial direction towards the suction opening (23).

29. Dredging method according to claim 19, r comprising the step of chemically 25 treating the liquid phase separated from the slurry of water and sediments.

30. Dredging method according to claim 19, further comprising a stand-by step including a step of sealing a predetermined amount of the recirculated liquid phase separated from the slurry of water and sediments in a closed circuit.