Title of Invention	A WATER JET DREDGING DEVICE
Abstract	A dredging device with water jets, which includes a dredge head consisting an enclosed agitation chamber with a series of rotatable nozzles and circumferential wall opening, connected with water distributor. A pump mounted on barge supplies pressurized water through a feed line to the circular water distributor of the dredge head from where water is distributed to nozzles and to the circumferential opening. Water jets emanating from a set of nozzles dislodge solid material on seabed and agitate solids with water, creating solid water suspension in the agitation chamber of the dredge head. Peripheral jets emanating from the circumferential opening assists dredge head to sink in to the waterbeds. A vertical submersible slurry pump mounted on the dredge head transports solid-water suspension to transporting barge/ship. This dredging device can operate in any water depth without effecting surrounding sub sea ecosystem. This device may safely be utilized for mining of rich minerals deposited on the seabed and for usual dredging of sea / river docks.

Title of Invention

A WATER JET DREDGING DEVICE

Abstract

A dredging device with water jets, which includes a dredge head consisting an enclosed agitation chamber with a series of rotatable nozzles and circumferential wall opening, connected with water distributor. A pump mounted on barge supplies pressurized water through a feed line to the circular water distributor of the dredge head from where water is distributed to nozzles and to the circumferential opening. Water jets emanating from a set of nozzles dislodge solid material on seabed and agitate solids with water, creating solid water suspension in the agitation chamber of the dredge head. Peripheral jets emanating from the circumferential opening assists dredge head to sink in to the waterbeds. A vertical submersible slurry pump mounted on the dredge head transports solid-water suspension to transporting barge/ship. This dredging device can operate in any water depth without effecting surrounding sub sea ecosystem. This device may safely be utilized for mining of rich minerals deposited on the seabed and for usual dredging of sea / river docks.

Full Text	This invention relates to a water jet dredging device. The present invention particularly relates to a dredging device with water jets which includes a dredge head consisting an enclosed chamber with a series of rotatable nozzles capable of directing pressurized water jets on to the under water seabed. The dredging device of the present invention may safely be utilized for mining of rich minerals deposited on the seabed and for usual dredging of sea / river docks, ports to keep sufficient water depth for ease of ships, barges and other water borne vehicles to move freely. Reference may be made to the U.S. Patent No. 4,352,251, entitled Hand Operated Suction Dredge Head And Hydraulic Submersible Pump Assembly, wherein operator has to control the dredge head standing on waterbed beneath the water surface. The dredge head mainly consist of a tubular suction nozzle, lower end of which open to water bed, upper end admits water in to it with provision of regulating the flow rate by a manually operated butterfly vale, thereby changing the density of the solid water suspension. Solid water suspension in the dredge head is pumped out by a submersible pump through a conduit to the above water. A jet digger may also be incorporated to the dredge for better performance. The drawbacks of this system are: (i) operator has to work beneath the water surface and to be always provided oxygen from a source via compressor on the barge, (ii) It also involves costly hydraulic drive for the submersible pump, iii) Another problem present in this system, that dredge intake diameter, three to eight inches and it digs in to a smaller area. Reference may also be made to U.S. Patent No. 5,970,635 entitled "Jet Agitation Dredging System", wherein cutting of water bed taken place inside a pressurized enclosed agitation chamber, front side of which is open to take water bed material. Agitation of solids with water takes place by pressurized water jets in the chamber, solid- water suspension flow through the riser conduit by a water jet directed in the flow direction. Drawbacks of the system are : i) while the system may be effective shallow waterbed dredging but it may encounter the problem raising the dredge material from deep bed by the water jet. ii) the agitation chamber sinks in to the waterbed by its own weight which may not be very effective in case of hard compact water bed. Reference may be made to U.S. Patent No. 5,603,171 entitled "Process and Apparatus for Suctioning off the Solid Material from Waterbeds", wherein water is pumped to under water suction basket. The water flow in the suction basket is divided into motive water flow and pressure water flow. The pressure water flow is directed through a set of nozzles and water jets impinge on the waterbed, dislodge the solids and agitate with water to form solid water suspension. The motive flow is directed through the suction tube to accelerate solid-water suspension in suction tube of the suction pump, mounted on the ship, which pumps solid-water mixture to hopper on the ship. The drawbacks of the systems are : i) Deep sea/river bed mining using this technology may encounter a difficulty of suctioning the solid water mixture to a great height though the flow is accelerated in the suction tube by motive flow, ii) The suction basket sinks in to the waterbed by its own weight which may not be very effective in case of hard compact water bed. The above and other prior art devices has certain shortcomings in dredging the under waterbeds. Some devices require a diver with oxygen mask to operate the dredge head standing on the waterbeds while dredging. Most of the dredging devices sink in to the waterbed by its own weigh, which is not very effective. The prior dredging devices with water jets are always associated with de-merits of discharging the solid water suspension from the water bed to a low/medium height hence they are not suitable for deep seabed dredging. These dredging devices also lack control on the jets parameters e.g. jet velocity, jet direction and the distance between nozzle tips & waterbeds i.e., on the dredge output. These devices also generated enormous disturbance to marine life while dredging. The prior art details reveal the presence of jet agitation dredging without the means of regulating jet velocity and jet direction i.e., the control on the dredge output. The main object of the present invention is to provide a water jet dredging device, which obviates the drawbacks of hitherto known prior art as detailed herein above. Another object of the present invention is to provide a dredging device for which dredge depth is independent of the suction head of the dredging pump. Still another object of the present invention is to control solid concentration in the dredge output by regulating the jet pressure/velocity by operating a bypass flow control valve. Yet another object of the present invention is to provide a water jet dredging device wherein the distance between nozzle tips to soil bed can be varied to enable achieve maximum dredging of the waterbed. Still yet another object of the present invention is to provide a water jet dredging device wherein the direction of the water jets can be varied to establish an optimum jet direction, which results in maximum effect in dredging the waterbed and agitating solid water suspension. A further object of the present invention is to enable dredging in an enclosed space, which does not disturb the surrounding sub-sea ecosystem with a view to minimized sea pollution and disturbance to marine lives. A still further object of the present invention is to free the dredging device from the up down motion of seawater due to tidal wave. Another object of the present invention is to provide a dredging device which will be always seated on the waterbed due to its self-weight. The present invention provides a water jet dredging device, which includes a dredge head consisting an enclosed agitation chamber with a series of rotatable nozzles and circumferential wall opening, connected with water distributor. A pump mounted on barge supplies pressurized water through a feed line to the circular water distributor of the dredge head from where water is distributed to nozzles and to the circumferential opening. Water jets emanating from a set of nozzles dislodge solid material on seabed and agitate solids with water, creating solid water suspension in the agitation chamber of the dredge head. Peripheral jets emanating from the circumferential opening assists dredge head to sink in to the waterbeds. A vertical submersible slurry pump mounted on the dredge head transports solid-water suspension to transporting barge/ship. Solid concentration in solid-water suspension can be varied and maximized for a set operating condition by adjusting water jet velocity, nozzle orientation and distance between nozzle tip to under water seabed. This dredging device operated in the under water without effecting surrounding sub sea ecosystem. The device can operate in any water depth; submersible slurry pump to be selected accordingly. It is free from the effect of sea wave and it doesn't move up and down effecting dredging operation. The present invention relates to an improved dredging device having rotatable water jets which is most useful for seabed mining as well as riverbed mining and for usual dredging of sea / river docks. In an enclosed chamber high-pressurized water jets emanating from a series of nozzles are directed to impinge on the underwater soil bed. Water jets start to scour, tear and penetrate the underwater soil bed and agitate loosed sands with water in the chamber to form sands-water suspension. A submersible slurry pump mounted on the water box discharge the slurry to a dredge hopper on the barge/ ship. The jet direction & velocity and the distance between nozzle tip to soil bed can be varied to maximize the dredge output. The present invention is illustrated in figures 1- to 6 of the drawings accompanying this specification. Figure 1 represents the water jet dredging device of the present invention, wherein the dredging device with water jets being operated from barges. Figure 2 represents the perspective view of the dredge head of the water jet dredging device of the present invention. Figure 3 represents the sectional front view of the dredge head of the water jet dredging device of the present invention. Figure 4 represents the bottom view of the dredge head of the water jet dredging device of the present invention. Figure 5 represents the perspective view of a single nozzle with revolving joint of the water jet dredging device of the present invention. Figure 6 represents the sectional view of a single nozzle with revolving joint of the water jet dredging device of the present invention. Figure 1 illustrates the water jet dredging device (1) of the present invention, which includes a dredge head (2) and to which pressurized water feed line (3) is attached. The horizontal centrifugal pump (6) mounted on the anchored barge (7) sucks water from sea through the suction line (8) and delivers pressurized water to the discharge pipe (5) and subsequently to feed line (3) of the dredge head (2). Water supply to the dredge head (2) is controlled by regulating the flow control valve (10) in the bypass pipeline (9). Pressurized water emanates from a series of nozzles attached to the dredge head (2) and impinges on the waterbed and a solids-water suspension is formed in agitation chamber of dredge head (2). A vertical submersible slurry pump (11) is mounted on the dredge head (2) to discharge the solids-water suspension to the discharge line (4) and subsequently to the anchored barge (12). The dredge head (2) with vertical submersible slurry pump (11) and hoses are suspended from a lift boom (13) and wire ropes (14) via a swell compensator (15) to the underwater seabed. Ultrasonic slurry density meter (16) mounted on slurry discharge line (4) to measure the percentage of solid particles in solid-water suspension. Suction line (8), feed line (3), discharge line (4) are steel braided hoses capable to withstand tensile stress while puling the dredge head (2) by a lift boom (13) and wire ropes (14). Figure 2 represents perspective view of the dredge head (2) with a cut out on the peripheral wall (17) to show the nozzles (18). Figure 3 and Figure 4 are respectively cross sectional front view and plan view of the dredge head (2) looking from waterbed. Pressurized water from centrifugal pump (6) is supplied to the dredge head water distributor (19) through steel braided hose (3) and the inlet pipe (20). Distributor (19) feeds pressurized water to a series of nozzles (18) and to the peripheral opening (21) between two concentric circular walls (17). Water jets emanating from nozzles (18) scour, tear waterbed and agitate loose solids with water resulting formation of solids-water slurry in the agitation chamber (22) of the dredge head (2). The Vertical submersible slurry pump (11) mounted on the dredge head (2) sucks in the solids-water suspension from the agitation chamber (22) via discharge port (23) and delivers through a discharge hose (4) to the barge (12). The peripheral jets emanating from peripheral opening (21) cut the waterbed along the periphery of the dredge head (2) as a result it assists the dredge head (2) to sink into the waterbed. Figure 5 and Figure 6 are respectively the perspective view and cross sectional view of a nozzle (18), nozzle pipe (24) along with revolving joint connection (25) with the water distributor (19). The nozzle (18) can be rotated adjusting the revolving joint (25) to set the water jets direction as desired to maximize the dredge output. Water jet velocity can also be adjusted by regulating the by pass flow control valve (10). Accordingly the present invention provides a water jet dredging device which comprises: a dredging device with water jets (1) consisting of a dredge head (2) provided with a series of nozzles (18) connected through nozzle pipes (24) to a water distributor (19) which is connected to a pressurized water feed line (3, 20); characterized in that each of the said nozzle pipes (24) being provided with revolving joints (25) and the said series of rotatable nozzle assemblies (18, 24, 25) being enclosed in an agitation chamber (22) in the said dredge head (2) formed by two concentric circular walls (17) having a peripheral opening (21) between them connected to the said water distributor (19), the said dredge head (2) having a discharge port (23) at the top being connected to a vertical submersible pump (11) having a slurry discharge line (4). In an embodiment of the present invention, the pressurized water feed line (3, 20) is connected through discharge pipe (5) of an anchored barge (7) mounted horizontal centrifugal pump (6) having suction line (8). In another embodiment of the present invention, the discharge pipe (5) of the horizontal centrifugal pump (6) being provided with by-pass piping (9) having flow regulating by-pass valve (10). In yet another embodiment of the present invention, the series of rotatable nozzle assemblies (18, 24, 25) are spatially distributed in the said agitation chamber (22) in the said dredge head (2). In still another embodiment of the present invention, the dredge head (2) with vertical submersible slurry pump (11) and hoses are suspended from barge (7) mounted lift boom (13) and wire ropes (14) via a swell compensator (15) to the underwater seabed. In still yet another embodiment of the present invention, the vertical submersible pump (11) is mounted on the dredge head (2) and is capable of sucking solid-water suspension from the discharge port (23) and delivering to a barge (12) through the slurry discharge line (4) provided with an ultrasonic slurry density meter (16). In a further embodiment of the present invention, the dredge output is of the order of 17 to 19 % (volume of solids / volume of solids and water) at water jet velocity in the range of 14 to 15 m/s. In a yet further embodiment of the present invention, the dredge output is of the order of 20 to 21 % (volume of solids / volume of solids and water) at standoff distance between 40 to 50 mm keeping water jet velocity in the range of 14 to 15 m/s. In a still further embodiment of the present invention, the dredge output is of the order of 22 to 24 % at water jet velocity in the range of 14 to15 m/s with nozzle angle in the range of 30° to 45° with horizontal plane and standoff distance in the range of 40 to 50 mm. The steps to be followed for carrying out dredging with the water jet dredging device of the present invention are: First step : Mount the horizontal centrifugal pump (6) on the barge (7) and to connect the dredge head (2) with flexible hose (3) to the discharge pipe (5) of the pump (6). Second step: Mount the vertical submersible slurry pump (11) on the dredge head (2) and to connect discharge flexible hose (4) with pump for discharging slurry to the barge (12). Ultrasonic slurry density meter (16) is mounted on discharge line (4). Third step: Suspend the dredge head (2) with all mountings on it from a lift boom (13) mounted on the barge (7) to the water bed. Fourth step: Start the horizontal centrifugal pump (6) to supply pressurized water to the dredge head distributor (19) which will distribute water to the peripheral opening (21) and to the series of rotatable nozzles (18). Dredging and formation of the solid-water suspension takes place by the water jets in the agitation chamber (22). Fifth step: Start the vertical submersible slurry pump (11) mounted on the dredge head (2) for discharging dredged solid-water suspension from agitation chamber (22) to the barge (12) through the flexible hose (4). Sixth step: Dredge output may be maximized with the variation of angle of attack of water jets by controlling revolving joint (25) and by controlling flow to the dredge head (2) i.e., varying water jet velocity by regulating the bypass control valve (10) and by varying the distance between nozzle (18) tip and the water bed. Dredge output i.e., solid concentration is displayed by the ultrasonic density meter (16). The dredging device with water jets of the present invention which constitutes a dredge head to which pressurised water is supplied through water feed line by a horizontal centrifugal pump mounted on the equipment barge. Pressurized water is collected in the water distributor. A series of nozzles with revolving joint and suitable piping is connected to the water distributor. The rotatable nozzles are enclosed in the dredge head by two concentric circular walls having a peripheral gap between them which is also connected with the water distributor. Pressurised water is directed from the water distributor to the series of rotatable nozzles and the peripheral opening. Water jets emerging from the nozzle cuts the under water seabed / riverbed and agitates the dredged solids with water to form solid water suspension in the agitation chamber. Peripheral jets helps the dredge head sink in to the waterbed. Due to jet pressure in the agitation chamber solid water suspension is directed toward the discharge port of the dredge head. A vertical submersible slurry pump is mounted on the dredge head sucks the solid-water suspension and discharges to a hopper barge through suitable discharge piping. Dredge output is controlled by regulating the water supply to distributor i.e. water jet velocity, varying jet direction by the adjusting revolving joints and varying distance between nozzle tip and the waterbed. The novelty of the present invention lies in the dredging device having facility for varying water jet velocity, water jet direction and variation of distance between nozzle tip and water bed and being capable of both deep-sea bed mining as well as shallow seabed mining and for normal dredging work with water jets with minimal/nil disturbance on surrounding sub sea ecosystem. The features present in the water jet dredging device of the present invention but not present in the hitherto known prior art are: 1. The water jets emerging from a series of nozzles connected with the water distributor. 2. The revolving joints with the nozzle piping, which is utilised to vary the angle between centrelines of the nozzles and vertical axes i.e., the water jet direction. Dredge output can be maximised by varying water jets direction. 3. Inclusion of a bypass flow control valve in the pressurised water supply line of the dredge head. By regulating the by-pass flow control valve water flow in the pressurised water supply line to the dredge head is varied. Consequently, the velocity of the water jets emerging from the nozzles is varied which helps to maximise the dredge output. Performance of the pressurised water supply pump is not disturbed, as the flow to the dredge head is control by regulating the by-pass flow control valve. 4. The peripheral jets, which emerge from the gap between two concentric circular walls, assist the dredge head to sink in to the waterbed as the dredging progresses. 5. Inclusion of a vertical submersible pump which discharge the solid- water suspension from the agitation chamber of the dredge head to the hopper barge through suitable discharge piping. The novelty of the present invention has been achieved by the non-obvious inventive steps of unique constructional features, such as: 1. Nozzles with revolving joints which helps changing the direction of water jets; the bypass flow control valve in the pressurized water supply line which enables to regulate velocity of water jets. 2. Peripheral opening between the two concentric walls of the dredge head. 3. All the nozzles being in an enclosed agitation chamber. 4. Discharge of the solid-water suspension by a submersible pump through a slurry discharge line having an ultrasonic slurry density meter, which ultimately helps in deciding the distance between nozzle tips and water bed, water jet direction and velocity. The new results achieved due to the non-obvious inventive steps are: 1. Dredge output is varied with variation of intensity of water jet velocity emanating of nozzles. We got the maximum dredge output 17 to 19 % (volume of solids /Volume of solids and water) at water jet velocity of 14 to 15m/s. 2. Dredge output is also varied by changing standoff distance (between nozzle tips and soil bed surface), We found out in our test that solid concentration is maximized to 20 to 21 % (volume of solids /Volume of solids and water) at standoff distance between 40 to 50 mm keeping water jet velocity of 14 to 15 m/s. 3. It has been observed that water jet velocity of 14 to 15 m/s with nozzle angle 30° to 45° with the horizontal plane and keeping the standoff distance of 40 to 50 mm gives the optimum dredge output of 22 to 24 %. The following examples are given by way of illustration of the present invention in actual practice and should not be construed to limit the scope of the present invention. Example -1 Several experiments to check the dependency of dredge output on the intensity of water jet velocity emanating from the nozzles were carried out. The results obtained at water jet velocity of 14 to 15 m/s for maximum dredge output was 17 to 19 % (volume of solids /Volume of solids and water). Example - 2 Several experiments were carried out to check the dependency of dredge output on the standoff distance (between nozzle tips and soil bed surface), and the cohesive strength of the underwater soil bed. Increasing the standoff distance, depth of cut decreases but width of the cut increases because of diffusion of the immersed water jets and vice versa. The results obtained at standoff distance between 40 to 50 mm keeping water jet velocity of 14 to 15 m/s was found to be 20 to 21 % (volume of solids /Volume of solids and water). Example - 3 Several experiments were carried out to check the dependency of dredge output direction on change of water jet velocity in dredge head by adjusting the revolving joint attached with the nozzle. The results obtained for dredge output was 22 to 24 % at water jet velocity of 14 to 15 m/s with nozzle angle 30° to 45° with the horizontal plane and keeping the standoff distance of 40 to 50 mm. The main advantages of the present invention are: 1. The dredge head is effective for deep water depth as well as shallow water depth sea bed dredging and may safely be utilized for mining of rich minerals deposited on the seabed and for usual dredging of sea / river docks. 2. The dredge output can be easily controlled by varying the water jet velocity, jet direction and the distance between nozzle tip and water bed. 3. The dredge head utilizes high-pressure water jets to cut the sea bed and therefore the possibility of the damage of the dredge head while cutting the seabed is minimized. 4. The dredging is carried out in an enclosed space of the dredge head and it does not disturb the surrounding sub-sea ecosystem with a view to minimized sea pollution and disturbance to marine life. 5. It is free from the effect of sea wave and it doesn't move up and down effecting dredging operation. We claim: 1. A water jet dredging device which comprises: a dredging device with water jets (1) consisting of a dredge head (2) provided with a series of nozzles (18) connected through nozzle pipes (24) to a water distributor (19) which is connected to a pressurized water feed line (3, 20); characterized in that each of the said nozzle pipes (24) being provided with revolving joints (25) and the said series of rotatable nozzle assemblies (18, 24, 25) being enclosed in an agitation chamber (22) in the said dredge head (2) formed by two concentric circular walls (17) having a peripheral opening (21) between them connected to the said water distributor (19), the said dredge head (2) having a discharge port (23) at the top being connected to a vertical submersible pump (11) having a slurry discharge line (4). 2. A water jet dredging device as claimed in claim 1, wherein the pressurized water feed line (3, 20) is connected through discharge pipe (5) of an anchored barge (7) mounted horizontal centrifugal pump (6) having suction line (8). 3. A water jet dredging device as claimed in claim 1-2, wherein the discharge pipe (5) of the horizontal centrifugal pump (6) being provided with by-pass piping (9) having flow regulating by-pass valve (10). 4. A water jet dredging device as claimed in claim 1-3, wherein the series of rotatable nozzle assemblies (18, 24, 25) are spatially distributed in the said agitation chamber (22) in the said dredge head (2). 5. A water jet dredging device as claimed in claim 1-4, wherein the dredge head (2) with vertical submersible slurry pump (11) and hoses are suspended from barge (7) mounted lift boom (13) and wire ropes (14) via a swell compensator (15) to the underwater seabed. 6. A water jet dredging device as claimed in claim 1-5, wherein the vertical submersible pump (11) is mounted on the dredge head (2) and is capable of sucking solid-water suspension from the discharge port (23) and delivering to a barge (12) through the slurry discharge line (4) provided with an ultrasonic slurry density meter (16). 7. A water jet dredging device as claimed in claim 1-6, wherein the dredge output is of the order of 17 to 19 % (volume of solids / volume of solids and water) at water jet velocity in the range of 14 to 15 m/s. 8. A water jet dredging device as claimed in claim 1-7, wherein the dredge output is of the order of 20 to 21 % (volume of solids / volume of solids and water) at standoff distance between 40 to 50 mm keeping water jet velocity in the range of 14 to 15 m/s. 9. A water jet dredging device as claimed in claim 1-8, wherein the dredge output is of the order of 22 to 24 % at water jet velocity in the range of 14 to15 m/s with nozzle angle in the range of 30° to 45° with horizontal plane and standoff distance in the range of 40 to 50 mm. 10. A water jet dredging device substantially as herein described with reference to the examples and drawings accompanying this specification.

Full Text

This invention relates to a water jet dredging device. The present invention particularly relates to a dredging device with water jets which includes a dredge head consisting an enclosed chamber with a series of rotatable nozzles capable of directing pressurized water jets on to the under water seabed.
The dredging device of the present invention may safely be utilized for mining of rich minerals deposited on the seabed and for usual dredging of sea / river docks, ports to keep sufficient water depth for ease of ships, barges and other water borne vehicles to move freely.
Reference may be made to the U.S. Patent No. 4,352,251, entitled Hand Operated Suction Dredge Head And Hydraulic Submersible Pump Assembly, wherein operator has to control the dredge head standing on waterbed beneath the water surface. The dredge head mainly consist of a tubular suction nozzle, lower end of which open to water bed, upper end admits water in to it with provision of regulating the flow rate by a manually operated butterfly vale, thereby changing the density of the solid water suspension. Solid water suspension in the dredge head is pumped out by a submersible pump through a conduit to the above water. A jet digger may also be incorporated to the dredge for better performance. The drawbacks of this system are: (i) operator has to work beneath the water surface and to be always provided oxygen from a source via compressor on the barge, (ii) It also involves costly hydraulic drive for the submersible pump, iii) Another problem present in this system, that dredge intake diameter, three to eight inches and it digs in to a smaller area.
Reference may also be made to U.S. Patent No. 5,970,635 entitled "Jet Agitation Dredging System", wherein cutting of water bed taken place inside a pressurized enclosed agitation chamber, front side of which is open to take water bed material. Agitation of solids with water takes place by pressurized water jets in the chamber, solid- water suspension flow through the riser conduit by a water jet directed in the flow direction. Drawbacks of the system are : i) while the system may be effective shallow waterbed dredging but it may encounter the problem raising the dredge material from deep bed by the water jet. ii) the agitation chamber sinks in to the waterbed by its own weight which may not be very effective in case of hard compact water bed.
Reference may be made to U.S. Patent No. 5,603,171 entitled "Process and Apparatus for Suctioning off the Solid Material from Waterbeds", wherein water is pumped to under water suction basket. The water flow in the suction basket is divided into motive water flow and pressure water flow. The pressure water flow is directed through a set of nozzles and water jets impinge on the waterbed, dislodge the solids and agitate with water to form solid water suspension. The motive flow is directed through the suction tube to accelerate solid-water suspension in suction tube of the suction pump, mounted on the ship, which pumps solid-water mixture to hopper on the ship. The drawbacks of the systems are : i) Deep sea/river bed mining using this technology may encounter a difficulty of suctioning the solid water mixture to a great height though the flow is accelerated in the suction tube by motive flow, ii) The suction basket sinks in to the waterbed by its own weight which may not be very effective in case of hard compact water bed.
The above and other prior art devices has certain shortcomings in dredging the under waterbeds. Some devices require a diver with oxygen mask to operate the dredge head standing on the waterbeds while dredging. Most of the dredging devices sink in to the waterbed by its own weigh, which is not very effective. The prior dredging devices with water jets are always associated with de-merits of discharging the solid water suspension from the water bed to a low/medium height hence they are not suitable for deep seabed dredging. These dredging devices also lack control on the jets parameters e.g. jet velocity, jet direction and the distance between nozzle tips & waterbeds i.e., on the dredge output. These devices also generated enormous disturbance to marine life while dredging.
The prior art details reveal the presence of jet agitation dredging without the means of regulating jet velocity and jet direction i.e., the control on the dredge output.
The main object of the present invention is to provide a water jet dredging device, which obviates the drawbacks of hitherto known prior art as detailed herein above.
Another object of the present invention is to provide a dredging device for which dredge depth is independent of the suction head of the dredging pump.
Still another object of the present invention is to control solid concentration in the dredge output by regulating the jet pressure/velocity by operating a bypass flow control valve.
Yet another object of the present invention is to provide a water jet dredging device wherein the distance between nozzle tips to soil bed can be varied to enable achieve maximum dredging of the waterbed.
Still yet another object of the present invention is to provide a water jet dredging device wherein the direction of the water jets can be varied to establish an optimum jet direction, which results in maximum effect in dredging the waterbed and agitating solid water suspension.
A further object of the present invention is to enable dredging in an enclosed space, which does not disturb the surrounding sub-sea ecosystem with a view to minimized sea pollution and disturbance to marine lives.
A still further object of the present invention is to free the dredging device from the up down motion of seawater due to tidal wave.
Another object of the present invention is to provide a dredging device which will be always seated on the waterbed due to its self-weight.
The present invention provides a water jet dredging device, which includes a dredge head consisting an enclosed agitation chamber with a series of rotatable nozzles and circumferential wall opening, connected with water distributor. A pump mounted on barge supplies pressurized water through a feed line to the circular water distributor of the dredge head from where water is distributed to nozzles and to the circumferential opening. Water jets emanating from a set of nozzles dislodge solid material on seabed and agitate solids with water, creating solid water suspension in the agitation chamber of the dredge head. Peripheral jets emanating from the
circumferential opening assists dredge head to sink in to the waterbeds. A vertical submersible slurry pump mounted on the dredge head transports solid-water suspension to transporting barge/ship. Solid concentration in solid-water suspension can be varied and maximized for a set operating condition by adjusting water jet velocity, nozzle orientation and distance between nozzle tip to under water seabed. This dredging device operated in the under water without effecting surrounding sub sea ecosystem. The device can operate in any water depth; submersible slurry pump to be selected accordingly. It is free from the effect of sea wave and it doesn't move up and down effecting dredging operation.
The present invention relates to an improved dredging device having rotatable water jets which is most useful for seabed mining as well as riverbed mining and for usual dredging of sea / river docks. In an enclosed chamber high-pressurized water jets emanating from a series of nozzles are directed to impinge on the underwater soil bed. Water jets start to scour, tear and penetrate the underwater soil bed and agitate loosed sands with water in the chamber to form sands-water suspension. A submersible slurry pump mounted on the water box discharge the slurry to a dredge hopper on the barge/ ship. The jet direction & velocity and the distance between nozzle tip to soil bed can be varied to maximize the dredge output.
The present invention is illustrated in figures 1- to 6 of the drawings accompanying this specification.
Figure 1 represents the water jet dredging device of the present invention, wherein the dredging device with water jets being operated from barges.

Figure 2 represents the perspective view of the dredge head of the water jet dredging device of the present invention.
Figure 3 represents the sectional front view of the dredge head of the water jet dredging device of the present invention.
Figure 4 represents the bottom view of the dredge head of the water jet dredging device of the present invention.
Figure 5 represents the perspective view of a single nozzle with revolving joint of the water jet dredging device of the present invention.
Figure 6 represents the sectional view of a single nozzle with revolving joint of the water jet dredging device of the present invention.
Figure 1 illustrates the water jet dredging device (1) of the present invention, which includes a dredge head (2) and to which pressurized water feed line (3) is attached. The horizontal centrifugal pump (6) mounted on the anchored barge (7) sucks water from sea through the suction line (8) and delivers pressurized water to the discharge pipe (5) and subsequently to feed line (3) of the dredge head (2). Water supply to the dredge head (2) is controlled by regulating the flow control valve (10) in the bypass pipeline (9). Pressurized water emanates from a series of nozzles attached to the dredge head (2) and impinges on the waterbed and a solids-water suspension is formed in agitation chamber of dredge head (2). A vertical submersible slurry pump (11) is mounted on the dredge head (2) to discharge the solids-water suspension to the discharge line (4) and subsequently to the anchored barge (12). The dredge head (2) with vertical submersible slurry pump (11) and
hoses are suspended from a lift boom (13) and wire ropes (14) via a swell compensator (15) to the underwater seabed. Ultrasonic slurry density meter (16) mounted on slurry discharge line (4) to measure the percentage of solid particles in solid-water suspension. Suction line (8), feed line (3), discharge line (4) are steel braided hoses capable to withstand tensile stress while puling the dredge head (2) by a lift boom (13) and wire ropes (14).
Figure 2 represents perspective view of the dredge head (2) with a cut out on the peripheral wall (17) to show the nozzles (18).
Figure 3 and Figure 4 are respectively cross sectional front view and plan view of the dredge head (2) looking from waterbed. Pressurized water from centrifugal pump (6) is supplied to the dredge head water distributor (19) through steel braided hose (3) and the inlet pipe (20). Distributor (19) feeds pressurized water to a series of nozzles (18) and to the peripheral opening (21) between two concentric circular walls (17). Water jets emanating from nozzles (18) scour, tear waterbed and agitate loose solids with water resulting formation of solids-water slurry in the agitation chamber (22) of the dredge head (2). The Vertical submersible slurry pump (11) mounted on the dredge head (2) sucks in the solids-water suspension from the agitation chamber (22) via discharge port (23) and delivers through a discharge hose (4) to the barge (12). The peripheral jets emanating from peripheral opening (21) cut the waterbed along the periphery of the dredge head (2) as a result it assists the dredge head (2) to sink into the waterbed.
Figure 5 and Figure 6 are respectively the perspective view and cross sectional view of a nozzle (18), nozzle pipe (24) along with revolving joint connection (25) with the water distributor (19). The nozzle (18) can be
rotated adjusting the revolving joint (25) to set the water jets direction as desired to maximize the dredge output. Water jet velocity can also be adjusted by regulating the by pass flow control valve (10).
Accordingly the present invention provides a water jet dredging device which comprises: a dredging device with water jets (1) consisting of a dredge head (2) provided with a series of nozzles (18) connected through nozzle pipes (24) to a water distributor (19) which is connected to a pressurized water feed line (3, 20); characterized in that each of the said nozzle pipes (24) being provided with revolving joints (25) and the said series of rotatable nozzle assemblies (18, 24, 25) being enclosed in an agitation chamber (22) in the said dredge head (2) formed by two concentric circular walls (17) having a peripheral opening (21) between them connected to the said water distributor (19), the said dredge head (2) having a discharge port (23) at the top being connected to a vertical submersible pump (11) having a slurry discharge line (4).
In an embodiment of the present invention, the pressurized water feed line (3, 20) is connected through discharge pipe (5) of an anchored barge (7) mounted horizontal centrifugal pump (6) having suction line (8).
In another embodiment of the present invention, the discharge pipe (5) of the horizontal centrifugal pump (6) being provided with by-pass piping (9) having flow regulating by-pass valve (10).
In yet another embodiment of the present invention, the series of rotatable nozzle assemblies (18, 24, 25) are spatially distributed in the said agitation chamber (22) in the said dredge head (2).
In still another embodiment of the present invention, the dredge head (2) with vertical submersible slurry pump (11) and hoses are suspended from barge (7) mounted lift boom (13) and wire ropes (14) via a swell compensator (15) to the underwater seabed.
In still yet another embodiment of the present invention, the vertical submersible pump (11) is mounted on the dredge head (2) and is capable of sucking solid-water suspension from the discharge port (23) and delivering to a barge (12) through the slurry discharge line (4) provided with an ultrasonic slurry density meter (16).
In a further embodiment of the present invention, the dredge output is of the order of 17 to 19 % (volume of solids / volume of solids and water) at water jet velocity in the range of 14 to 15 m/s.
In a yet further embodiment of the present invention, the dredge output is of the order of 20 to 21 % (volume of solids / volume of solids and water) at standoff distance between 40 to 50 mm keeping water jet velocity in the range of 14 to 15 m/s.
In a still further embodiment of the present invention, the dredge output is of the order of 22 to 24 % at water jet velocity in the range of 14 to15 m/s with nozzle angle in the range of 30° to 45° with horizontal plane and standoff distance in the range of 40 to 50 mm.
The steps to be followed for carrying out dredging with the water jet dredging device of the present invention are:
First step : Mount the horizontal centrifugal pump (6) on the barge (7) and to
connect the dredge head (2) with flexible hose (3) to the discharge pipe (5) of
the pump (6).
Second step: Mount the vertical submersible slurry pump (11) on the dredge
head (2) and to connect discharge flexible hose (4) with pump for discharging
slurry to the barge (12). Ultrasonic slurry density meter (16) is mounted on
discharge line (4).
Third step: Suspend the dredge head (2) with all mountings on it from a lift
boom (13) mounted on the barge (7) to the water bed.
Fourth step: Start the horizontal centrifugal pump (6) to supply pressurized
water to the dredge head distributor (19) which will distribute water to the
peripheral opening (21) and to the series of rotatable nozzles (18). Dredging
and formation of the solid-water suspension takes place by the water jets in
the agitation chamber (22).
Fifth step: Start the vertical submersible slurry pump (11) mounted on the
dredge head (2) for discharging dredged solid-water suspension from
agitation chamber (22) to the barge (12) through the flexible hose (4).
Sixth step: Dredge output may be maximized with the variation of angle of
attack of water jets by controlling revolving joint (25) and by controlling flow
to the dredge head (2) i.e., varying water jet velocity by regulating the bypass
control valve (10) and by varying the distance between nozzle (18) tip and
the water bed. Dredge output i.e., solid concentration is displayed by the
ultrasonic density meter (16).
The dredging device with water jets of the present invention which constitutes a dredge head to which pressurised water is supplied through water feed line by a horizontal centrifugal pump mounted on the equipment barge. Pressurized water is collected in the water distributor. A series of
nozzles with revolving joint and suitable piping is connected to the water distributor. The rotatable nozzles are enclosed in the dredge head by two concentric circular walls having a peripheral gap between them which is also connected with the water distributor. Pressurised water is directed from the water distributor to the series of rotatable nozzles and the peripheral opening. Water jets emerging from the nozzle cuts the under water seabed / riverbed and agitates the dredged solids with water to form solid water suspension in the agitation chamber. Peripheral jets helps the dredge head sink in to the waterbed. Due to jet pressure in the agitation chamber solid water suspension is directed toward the discharge port of the dredge head. A vertical submersible slurry pump is mounted on the dredge head sucks the solid-water suspension and discharges to a hopper barge through suitable discharge piping. Dredge output is controlled by regulating the water supply to distributor i.e. water jet velocity, varying jet direction by the adjusting revolving joints and varying distance between nozzle tip and the waterbed.
The novelty of the present invention lies in the dredging device having facility for varying water jet velocity, water jet direction and variation of distance between nozzle tip and water bed and being capable of both deep-sea bed mining as well as shallow seabed mining and for normal dredging work with water jets with minimal/nil disturbance on surrounding sub sea ecosystem.
The features present in the water jet dredging device of the present invention but not present in the hitherto known prior art are:
1. The water jets emerging from a series of nozzles connected with the
water distributor.
2. The revolving joints with the nozzle piping, which is utilised to vary the
angle between centrelines of the nozzles and vertical axes i.e., the
water jet direction. Dredge output can be maximised by varying water jets direction.
3. Inclusion of a bypass flow control valve in the pressurised water
supply line of the dredge head. By regulating the by-pass flow control
valve water flow in the pressurised water supply line to the dredge
head is varied. Consequently, the velocity of the water jets emerging
from the nozzles is varied which helps to maximise the dredge output.
Performance of the pressurised water supply pump is not disturbed,
as the flow to the dredge head is control by regulating the by-pass
flow control valve.
4. The peripheral jets, which emerge from the gap between two
concentric circular walls, assist the dredge head to sink in to the
waterbed as the dredging progresses.
5. Inclusion of a vertical submersible pump which discharge the solid-
water suspension from the agitation chamber of the dredge head to
the hopper barge through suitable discharge piping.
The novelty of the present invention has been achieved by the non-obvious inventive steps of unique constructional features, such as:
1. Nozzles with revolving joints which helps changing the direction of
water jets; the bypass flow control valve in the pressurized water
supply line which enables to regulate velocity of water jets.
2. Peripheral opening between the two concentric walls of the dredge
head.
3. All the nozzles being in an enclosed agitation chamber.
4. Discharge of the solid-water suspension by a submersible pump
through a slurry discharge line having an ultrasonic slurry density
meter, which ultimately helps in deciding the distance between nozzle tips and water bed, water jet direction and velocity.
The new results achieved due to the non-obvious inventive steps are:
1. Dredge output is varied with variation of intensity of water jet velocity
emanating of nozzles. We got the maximum dredge output 17 to 19 %
(volume of solids /Volume of solids and water) at water jet velocity of
14 to 15m/s.
2. Dredge output is also varied by changing standoff distance (between
nozzle tips and soil bed surface), We found out in our test that solid
concentration is maximized to 20 to 21 % (volume of solids /Volume of
solids and water) at standoff distance between 40 to 50 mm keeping
water jet velocity of 14 to 15 m/s.
3. It has been observed that water jet velocity of 14 to 15 m/s with
nozzle angle 30° to 45° with the horizontal plane and keeping the
standoff distance of 40 to 50 mm gives the optimum dredge output of
22 to 24 %.
The following examples are given by way of illustration of the present invention in actual practice and should not be construed to limit the scope of the present invention.
Example -1
Several experiments to check the dependency of dredge output on the intensity of water jet velocity emanating from the nozzles were carried out.
The results obtained at water jet velocity of 14 to 15 m/s for maximum dredge output was 17 to 19 % (volume of solids /Volume of solids and water).
Example - 2
Several experiments were carried out to check the dependency of dredge output on the standoff distance (between nozzle tips and soil bed surface), and the cohesive strength of the underwater soil bed. Increasing the standoff distance, depth of cut decreases but width of the cut increases because of diffusion of the immersed water jets and vice versa. The results obtained at standoff distance between 40 to 50 mm keeping water jet velocity of 14 to 15 m/s was found to be 20 to 21 % (volume of solids /Volume of solids and water).
Example - 3
Several experiments were carried out to check the dependency of dredge output direction on change of water jet velocity in dredge head by adjusting the revolving joint attached with the nozzle. The results obtained for dredge output was 22 to 24 % at water jet velocity of 14 to 15 m/s with nozzle angle 30° to 45° with the horizontal plane and keeping the standoff distance of 40 to 50 mm.
The main advantages of the present invention are:
1. The dredge head is effective for deep water depth as well as shallow water depth sea bed dredging and may safely be utilized for mining of
rich minerals deposited on the seabed and for usual dredging of sea / river docks.
2. The dredge output can be easily controlled by varying the water jet
velocity, jet direction and the distance between nozzle tip and water
bed.
3. The dredge head utilizes high-pressure water jets to cut the sea bed
and therefore the possibility of the damage of the dredge head while
cutting the seabed is minimized.
4. The dredging is carried out in an enclosed space of the dredge head
and it does not disturb the surrounding sub-sea ecosystem with a view
to minimized sea pollution and disturbance to marine life.
5. It is free from the effect of sea wave and it doesn't move up and down
effecting dredging operation.

We claim:
1. A water jet dredging device which comprises: a dredging device with water
jets (1) consisting of a dredge head (2) provided with a series of nozzles (18)
connected through nozzle pipes (24) to a water distributor (19) which is
connected to a pressurized water feed line (3, 20); characterized in that each
of the said nozzle pipes (24) being provided with revolving joints (25) and the
said series of rotatable nozzle assemblies (18, 24, 25) being enclosed in an
agitation chamber (22) in the said dredge head (2) formed by two concentric
circular walls (17) having a peripheral opening (21) between them connected
to the said water distributor (19), the said dredge head (2) having a discharge
port (23) at the top being connected to a vertical submersible pump (11)
having a slurry discharge line (4).
2. A water jet dredging device as claimed in claim 1, wherein the pressurized
water feed line (3, 20) is connected through discharge pipe (5) of an
anchored barge (7) mounted horizontal centrifugal pump (6) having suction
line (8).
3. A water jet dredging device as claimed in claim 1-2, wherein the discharge
pipe (5) of the horizontal centrifugal pump (6) being provided with by-pass
piping (9) having flow regulating by-pass valve (10).
4. A water jet dredging device as claimed in claim 1-3, wherein the series of
rotatable nozzle assemblies (18, 24, 25) are spatially distributed in the said
agitation chamber (22) in the said dredge head (2).
5. A water jet dredging device as claimed in claim 1-4, wherein the dredge
head (2) with vertical submersible slurry pump (11) and hoses are
suspended from barge (7) mounted lift boom (13) and wire ropes (14) via a
swell compensator (15) to the underwater seabed.
6. A water jet dredging device as claimed in claim 1-5, wherein the vertical
submersible pump (11) is mounted on the dredge head (2) and is capable of
sucking solid-water suspension from the discharge port (23) and delivering to
a barge (12) through the slurry discharge line (4) provided with an ultrasonic
slurry density meter (16).
7. A water jet dredging device as claimed in claim 1-6, wherein the dredge
output is of the order of 17 to 19 % (volume of solids / volume of solids and
water) at water jet velocity in the range of 14 to 15 m/s.
8. A water jet dredging device as claimed in claim 1-7, wherein the dredge
output is of the order of 20 to 21 % (volume of solids / volume of solids and
water) at standoff distance between 40 to 50 mm keeping water jet velocity in
the range of 14 to 15 m/s.
9. A water jet dredging device as claimed in claim 1-8, wherein the dredge
output is of the order of 22 to 24 % at water jet velocity in the range of 14
to15 m/s with nozzle angle in the range of 30° to 45° with horizontal plane
and standoff distance in the range of 40 to 50 mm.
10. A water jet dredging device substantially as herein described with reference to the examples and drawings accompanying this specification.

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Patent Number

268809

Indian Patent Application Number

1762/DEL/2006

PG Journal Number

39/2015

Publication Date

25-Sep-2015

Grant Date

17-Sep-2015

Date of Filing

02-Aug-2006

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

ANUSANDHAN BHAWAN, RAFI MARG, NEW DELHI-110001, INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	PREM RANJAN SAMADDAR	CENTRAL MECHANICAL ENGINEERING RESEARCH INSTITUTE, M.G. AENUE, DURGAPUR-713209
2	LALGOPAL DAS	CENTRAL MECHANICAL ENGINEERING RESEARCH INSTITUTE, M.G. AENUE, DURGAPUR-713209
3	ARUN BAIJU VELUKUTTY GOMATHY	CENTRAL MECHANICAL ENGINEERING RESEARCH INSTITUTE, M.G. AENUE, DURGAPUR-713209
4	PRASANTA KUMAR SEN	CENTRAL MECHANICAL ENGINEERING RESEARCH INSTITUTE, M.G. AENUE, DURGAPUR-713209
5	MAW NANDI SARKAR	CENTRAL MECHANICAL ENGINEERING RESEARCH INSTITUTE, M.G. AENUE, DURGAPUR-713209

PCT International Classification Number

E02F3/88; E02F3/92

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA