US3878946A

US3878946A - Apparatus for loading a hopper of a suction dredger with sand

Info

Publication number: US3878946A
Authority: US
Inventors: Koning Jan De
Original assignee: SPANSTAAL
Current assignee: Nv Ingenieursbureau Voor Systemen En Octrooien 'spanstaal'nl196811086815921; SPANSTAAL
Priority date: 1968-11-08
Filing date: 1971-06-15
Publication date: 1975-04-22
Anticipated expiration: 1992-04-22

Abstract

In loading a hopper of a floating suction dredger with sand a suspension of sand and water is pumped into the hopper. After the hopper is filled up to its maximum permissable carrying capacity in a first loading step additional suspension is pumped into the hopper in a second loading step during simultaneously draining off by lowering drain means in dependence on the weight of the load of the hopper for maintaining the suction dredger substantially loaded at its maximum permissable carrying capacity.

Description

United States Patent 1191 De Koning Apr. 22, 1975 [54] APPARATUS FOR LOADING A HOPPER F [56] References Cited A SUCTION DREDGER WITH SAND n- STATES PATENTS [75] Inventor: Jan De Koning, Amsterdam, 764.784 7/1904 Van Den Haspcl 214/15 B X Netherlands 934.593 9/1909 Carlesimo 37/59 l.l40.l3l /l9l5 ..2l0/83 [731 AS51811: lngemeursburea" 3.381.709 5/1968 Pregno 137/578 Systemen en OcIrooien Spanst 3.438.215 4/1969 Frijlink 137/578 x Rotterdam. Netherlands 22 i June 1971 Primary Brominer-Frank E. Werner Attorney, Agent. or Finn-John P. Snyder [21] Appl. No.: 153,226

Related US. Application Data [57] ABSTRACT [62] Division of Ser. No. 874.212. Nov. 5. 1969. Pat. No. in loading a hopper f a floating suction i h sand a suspension of sand and water is pumped into the hopper. After the hopper is filled up to its maxi- Fore'gn Apphcatlo Pnomy Dam mum permissable carrying capacity in a first loading Nov. 8. 1968 Netherlands 681592 step additional suspension is pumped into the hopper in a second loading step during simultaneously drainl l CI 214/15 7/59; 1 1 /2 ing off by loweringvdrain means in dependence on the 137/403 weight of the load of the hopper for maintaining the {51] Int. Cl. B63) /30 uction l -edger substantially loaded at its maximum [58] Field Of Search 2l4/l2, l3, l4, 15 R, 15 B; permissable carrying capacity.

13 Claims, 7 Drawing Figures Ill PATENTEUAPRZZIHYS SHEET 1 0f 3 miruwmzzms 3,878,946 sumeqfs 22p l 2 2 l2 22p APPARATUS FOR LOADING A HOPPER OF A SUCTION DREDGER WITH SAND This is a division of application Ser. No. 874,212, filed Nov. 5, 1969, now US. Pat. No. 3,630,400.

The invention relates to a method of loading a hopper of a floating suction dredger with sand.

Such a method is known.

In this known method a suspension of sand and water is pumped into the hopper in a first step. When the hopper is completely filled, the hopper contains only a little amount of sand. In a second step additional suspension is pumped into the hopper during simultaneously draining off until the amount of sand does not increase any more.

The settling of sand depends on the size of the grains and the flow velocity of the suspension. In a given hopper-cross-section the free flow area above the settled sand decreases as sand settles, resulting in an increase of the flow velocity of the suspension up to a value preventing further settlement'of sand. At this value of the flow velocity of the suspension pumped into the hopper this suspension is drained off with all its sand. The quotient of the sand volume and the hopper volume, which sand volume can be reached with a given grain size of the sand, a given capacity of the pump and a given hopper-cross-section is called the bulking factor.

As the specific gravity of wet sand is about 2, the hopper of the known suction dredger has a volume in m substantially equal to half its maximum permissable carrying capacity.

As such hopper cannot be filled completely with sand owing to said bulking factor it has been proposed already providing the hopper with an upstanding upper edge comprising draining off flaps, for loading the hopper with a little more sand owing to the increased free flow area above the settled sand. In a third loading step during which no suspension is pumped into the hopper, sand is allowed to settle. After that the water is drained off by suddenly lowering the draining off flaps. This third loading step may be reproduced.

The invention has the object to shorten the loading time. To this aim the invention provides a method of loading a hopper of a floating suction dredger with sand, wherein a suspension of sand and water is pumped into the hopper during a loading operation carried out in at least two steps:

a first step of pumping suspension into the hopper until the suction dredger is loaded substantially up to its maximum permissable carrying capacity,

and a subsequent second step of pumping additional suspension into the hopper during simultaneously draining off by lowering drain means in dependence on the weight of the load of the hopper for maintaining the suction dredger substantially loaded at its maximum permissable carrying capacity.

Further the invention provides a floating suction dredger comprising a hopper and a pump for pumping suspension of sand and water into said hopper, characterised by load measuring means controlling adjustable drain means.

The invention further has the object to load the floating suction dredger up to its maximum permissable carrying capacity with sand. To this aim the volume of the hopper is so great, that the suction dredger is loaded up to its maximum permissable carrying capacity when the hopper is substantially completely filled with sucked up suspension of sand and water.

If the sucked up suspension has a specific gravity of about 1.2 the hopper is filled only up to 20 percent with sand at the end of the first step, while than no suspension may be pumped into the hopper anymore for preventing that the maximum permissable carrying capac ity of the suction dredger will be exceeded. Therefore in the second step of the method according to the invention the drain means are put in operation as soon as the suction dredger is loaded up to its maximum permissable carrying capacity during simultaneously pumping of additional suspension into the hopper.

For safety the drain means preferably have a capacity exceeding the pump capacity.

Preferably the drain means comprise at least one drain siphon having a depth-adjustable inlet.

For safety the floating suction dredger according to the invention preferably comprises a safety device which is controlled by load measuring means and which becomes operative when the weight of the load of the hopper exceeds a predetermined value. This safety device may actuate an alarm device, may put the pump out of working and/or may in case of emergency put in operation unloading means for discharging sand from the hopper.

It is an additional advantage that owing to the floating suction dredger being loaded in a short time up to its maximum permissable carrying capacity the pump of the suction dredger is lowered to a great extent relatively to the water level immediately after starting the loading operation, resulting in increase of suction force of said pump of about 1 m water column.

The mentioned and other features according to the invention will be illucidated in the following description with reference to the accompanying drawing.

FIGS. Ia and 1b show graphs of the known method for loading a known suction dredger,

FIG. llc shows a cross section of said known suction dredger,

FIGS. 2a and 2b show graphs of the method according to the invention for loading a suction dredger,

FIG. 3 shows a longitudinal section of a preferred embodiment of a suction dredger according to the invention,

FIG. 4 shows a plan view of the suction dredger of FIG. 3 and FIG. 5 shows diagrammatically the control and safety devices of the suction dredger of FIGS. 3 and 4.

In FIGS. la and 2a interrupted lines show the suspension volume and uninter-rupted lines show the sand volume at any time during loading operation.

In FIGS. lb and 2b interrupted lines show the suspension weight and uninterrupted lines show the sand weight at any time during loading operation.

In comparing the method according to the invention with the known method, FIGS. 1 and 2 are based on equal maximum permissable carrying capacities of the suction dredgers and on equal suspension flows which can be pumped into the hopper, said suspension flows having equal rates of sand.

For conveying a volume V of wet sand (FIG. la) in the known method a suction dredger is applied having a maximum hopper volume V which can be reduced by lowerable draining off flaps 6 to a volume V In carrying out the known method, suspension is pumped into the hopper 2 of the suction dredger l of FIG. 16 during a first loading step 3 starting at the point of time and ending at the point of time A at which the hopper 2 is completely filled up to its upper edge 5. The hopper 2 has draining off flaps 6 being closed during the first loading step 3. In this first loading step 3 the volume V and also the weight W increase considerably. During the subsequent loading step 4 in the period AD suspension is continuously pumped into the hopper 2, liquid being drained off to an equal extent. The rate of sand of this drained off liquid increases gradually. The volume of sand settling per time unit is so little at the point of time D, that continuation of the second loading step 4 is not efficient anymore. For this reason the operation of pumping sand into the hopper 2 is stopped and during a third loading step 7 the sand of the suspension is allowed to settle. At the point of time E the draining off flaps 6 are lowered into the draining off position 6', for draining off the upper water. The hopper volume is then V,,. In a subsequent fourth loading step 8 the draining off flaps 6 are closed and the hopper 2 is filled with additional suspension in the period FG. In the period GH the sand of the suspension is allowed to settle, during which period no suspension is pumped into the hopper 2. At the point of time H the required sand volume V is obtained.

In FIGS. 3 and 4 a floating suction dredger for carrying out the method according to the invention is shown. This suction dredger consists of a trailing suction dredger having a hopper 12, a pump connected to a trailing suction pipe 9 at its suction side and to a supply pipe at its pressure side and having swingable draining off siphons 16,, and l6,- forming draining off means. Each draining off siphon comprises a fixed siphon pipe elbow 41 connected to a vertical pipe and through a flexible conduit 42 to a movable siphon pipe 43 pivotably mounted at the siphon pipe elbow 41. The movable siphon pipe 43 is operated by means of a hydraulic jack 17. In the bottom of the hopper l2 sand outlets 18 are provided with discharge valves 19.

The hopper 12 could be divided into two longitudinal parts. The suction dredger could comprise two hoppers 12 arranged behind each other.

The operation for loading this suction dredger I1 is as hereinafter described:

In a first loading step 13 suspension sucked up through the suction pipe 9 is pumped by the pump 10 through the supply pipe 15 into the hopper 12 until the suction dredger 11 is loaded up to its maximum permissable carrying capacity corresponding to the volume V in FIG. 2a. It will be appreciated that the dashed line curve in FIG. 2a depicts the instantaneous volume of material in the hopper l2, and consequently shows the instantaneous height of the material therein.

The hopper 12 now contains and water of which sand a volume V of sand has been settled at the point of time B. The draining off siphons 16 now are in raised position.

In the subsequent second loading step 14 additional suspension is pumped into the hopper l2, and the draining of siphons 16 are gradually lowered into the hopper 12 while being operated at sufficient capacity that more liquid is drained off through said draining off siphons 16 and the pipes 20 connected thereto than there is suspension being pumped in. The amount of liquid drained off is controlled so that whereas the liquid height in the hopper decreases, the suction dredger is maintained loaded at its maximum permissable carrying capacity W, as shown in FIG. 2b. The draining off siphons 16 are gradually lowered from positions corresponding to the height at V to the height at V,

FIG. 2b clearly shows, that the total required loading time DC of the loading steps 13 and 14 of the method according to the invention is considerably less than the total required loading time OH of the known method, whereas the sand volume V is about equal to the sand volume V of FIG. 1. The short loading time is a result of the second loading step 14, in which the suction dredger is continuously loaded up to its maximum permissable carrying capacity. The total weight W, is thus continuously maximum (see FIG. 2b), whereas the total weight W, in FIG. lb increases gradually during the second loading step 4, but is maintained under the maximum value of W The load is measured with

pressure pick ups

22,, 22 and 22 each arranged at the bottom of the suction dredger 11 and each comprising a pressure sensitive membrane 33, limiting a chamber 24 connected to the outboardwater 21. Each pressure pick up 22,,, 22 and 22 picks up the pressure corresponding with its depth in the outboardwater, which is a measure for the draught of the suction dredger 11 and the weight of the load. Nine

pressure pick ups

22,,, 22 and 22 are provided: at port board, in the longitudinal center plane and at starboard respectively as well as at the front, the rear and the mid part of the suction dredger.

Preferably in the second loading step 14 at each load situation the corresponding hopper volume is adjusted automatically, for maintaining the suction dredger loaded at its maximum permissable carrying capacity.

In FIG. 5 the automatic control means for carrying out the method according to the invention are shown diagrammatically.

The

pressure pick ups

22,,, 22 and 22 provide signals to receivers 25 25 and 25 respectively. From these signals the draughts of the corresponding ship parts are determined in calculating units 26,, 26 and 26,. The outputs of these calculating units are provided to the draught-, listand trim-calculating unit 27, providing signals to the draught indicator 28, trim indicator 29 and the safety device 30, the calculating unit 26, providing signals concerning the starboard draught to the comparing and calculating device 31 which in turn provides signals to the signal convertors 32,. These signal convertors 32 provide signals to the control valves 33,. for controlling the hydraulic jack 17 of the draining off siphon 16,. Calculating unit 31, provides signals concerning the central draught to both signal convertors 32, and 32,,, whereas calculating unit A, in the same way provides signals to signal convertor 32 and thus operates the jack 17,, of draining off siphon 16,,.

As the calculating device 31 signals like reference signals to both signal convertors 32 and 32,, the list of the suction dredger owing to unequally loading may be corrected.

In case of an overloading and/or an inadmissible list, which is insufficiently corrected by the above mentioned automatic control signals through calculating devices 31,, 31, and 31 the safety device 30 provides signals to-an alarm device 34 formed by a red light, an accoustic alarm device 35 and to an automatic safety unit 36 providing signals for lowering the draining off siphons 16 and 16 through signal convertors 32 and 32,, signals for putting the pump 10 out of work through signal convertor 37 and signals for opening the sand discharge valves 19 through signal convertor 38.

In order, however, to maintain the suction dredger 11 in operation when the automatic control means are out of order, the draining off siphons 16,, and 16,, the pump 10, and the discharge valves 19 may be controlled from an operating panel by hand through the hand operated members 40, 40,. and 39.

Owing to the application of a plurality of load sensitive elements, formed by a plurality of pressure pick ups 22 the lack of indication of the excess of the maximum permissable carrying capacity is prevented.

When sucking up a suspension having a low rate of sand, the hopper 12 which has a great volume, may be completely filled, although the suction dredger is not yet loaded up to its maximum permissable carrying capacity. In this case suspension is still pumped into the hopper, during a period in which the draining off si phons are kept in their positions corresponding to the height V and in which liquid mainly consisting of water is drained off over the upper edge 44 of the hopper 12. When the suction dredger is loaded up to its maximum permissable carrying capacity in this way, additional suspension is pumped into the hopper 12 in the second loading step 14, in which liquid is drained off by lowering the draining off siphons 16 which are adjusted in dependence on pressure pick ups 22 so that the suction dredger is maintained loaded at its maximum permissable weight carrying capacity.

At the end of the second loading step 14 the pump is put out of work and the sand in the suspension standing above settled sand is allowed to settle in a subsequent period, at the end of which the water standing above all settled sand is drained off by lowering the draining off siphons down to the surface of sand. In this way the suction dredger is even loaded less than its maximum permissable carrying capacity during the trip to the unloading place.

The suction dredger 11 preferably comprises a water pump 45 pumping up outboardwater 21 through inlet pipe 46 and being connected by conduits 47 to jetnozzles 48 mounted in the siphon pipes 41. These jetnozzles function like jet pumps for starting the siphon operation of the draining off siphons 16, when necessary.

It should be remarked, that at the point of time C the pump 10 is put out of work and that the trip to the unloading place can be started. In the subsequent period of time CD the sand found in the suspension above settled' sand settles. At the point of time D all liquid standing above settled sand is drained off, resulting in a suction dredger which is loaded less than its maximum permissable carrying capacity during the remaining time of this trip, resulting in a greater speed of the suction dredger.

If the level of the settled sand is lower than the water surface of outboardwater the liquid above the settled sand may be drained off owing to the jet-nozzles 48 operating like jet pumps. After draining off operation the draining off siphons are raised into their uppermost position.

What I claim is:

1. A floating suction dredger comprising, in combination:

a buoyant hull having a displacement sufficient to float a predetermined maximum load weight; hopper means carried by said hull and having a volumetric capacity substantially greater than that predetermined volume of settled dredger spoil required to impose said predetermined maximum load weight on said hull;

suction dredger means carried by said hull for discharging a liquid suspension of dredger spoil in I water into said hopper means whereby dredger spoil progressively settles in said hopper means correspondingly to increase the settled volume thereof in the hopper means toward said predetermined volume which imposes said predetermined maximum load weight on said hull;

, drain means for draining off liquid from said hopper means; and

control means controlling said drain means for main taining the volume of liquid above the settled dredger spoil at a value continuously to impose substantially said predetermined maximum load weight on said hull once such weight is reached and while said suction dredger means is operating whereby rapidly to achieve said predetermined volume of settled dredger spoil in said hopper means.

2. Floating suction dredger as claimed in claim 1, characterised in that the volume of the hopper means is so great, that the suction dredger is loaded up to its maximum permissable carrying capacity when the hopper means is substantially completely filled with sucked up suspension of sand and water.

3. Floating suction dredger as claimed in claim 1, characterised in that the drain means comprise at least one drain siphon having an adjustable inlet.

4. Floating suction dredger as claimed in claim 1, characterised by a safety device which is controlled by said control means and which actuates said drain means for lowering the drain level thereof when the weight of the load of the hopper means exceeds said predetermined maximum load weight.

5. Floating suction dredger, as claimed in claim 1, characterised by an alarm device which is actuated by said control means when the weight of the load of the hopper means exceeds said predetermined maximum load weight.

6. Floating suction dredger as claimed in claim 1, characterised by a safety device which is controlled by said control means to terminate operation of said suc tion dredger means when the weight of the load of the hopper means exceeds said predetermined maximum load weight.

7. Floating suction dredger as claimed in claim 1, characterised by unloading means controlled by said control means for discharging dredger spoil from the hopper means when the weight of the load of the hopper means exceeds said predetermined maximum load weight.

8. A floating suction dredger comprising, in combination:

a buoyant hull having a displacement sufficient to float a predetermined maximum load weight; hopper means carried by said hull and having a volumetric capacity substantially greater than that required to accommodate a predetermined volume of settled dredger spoil which loads said bull to said predetermined maximum load weight; suction dredger means carried by said hull for filling said hopper means with a liquid which is a suspension of dredger spoil in water at such a rate that the liquid height in said hopper means continuously is greater than the height of settled dredger spoil therein;

liquid drain off means for substantially said predetermined maximum load weight on said hull while said suction dredger means is operating; said liquid drain off means comprising siphon means operated at a discharge capacity rate greater than said rate at which the suction dredger means is operated and control means for controlling the withdrawal height of said siphon means. 9. A floating suction dredger as defined in claim 8 wherein said control means produces a signal related to the draught of said floating suction dredger.

10. A floating suction dredger as defined in claim 1 wherein said control means produces a signal related to the draught of said floating suction dredger.

11. A floating suction dredger comprising, in combination:

a buoyant hull having a displacement sufficient to float a predetermined maximum load weight;

suction dredger means carried by said hull and including a suction pump having an inlet and an outlet and a suction pipe connected to said inlet to project downwardly therefrom into suction contact with a body of dredger spoil below said hull;

a hopper carried by said hull, said suction dredger means also including a discharge pipe connected to said outlet of the pump to discharge a liquid suspension of dredger spoil in water into said hopper, said hopper having a volumetric capacity sufficient to accommodate a volume of said suspension which at least approaches said predetermined maximum load weight and is thereby of substantially greater volume than that required to accommodate a volume of settled dredger spoil which imposes a load on said hull exceeding said predetermined maximum load weight;

means for operating said suction dredger means quickly to fill said hopper with said suspension and for thereafter draining off liquid in said hopper at a sufficiently greater rate than the discharge rate of said suction dredger means as to maintain said predetermined maximum load weight on said hull and thereby maximize the operating depth of said inlet of the pump.

12. A floating suction dredger as defined in claim 11 wherein the means for operating includes siphon means having an inlet mouth for progressive and gradual lowering thereof downwardly from adjacent the top of said hopper.

13. A floating suction dredger as defined in claim 12 wherein said means for operating also includes means responsive to the draught of said hull for gradually lowering said inlet mouth of the siphon means.

UNITED STATE E ATENT @FFHJE E I TlFl Cl F Qtlltllfifill PATENT NO. 1 3,878,946

DATED April 22, 1975 mvmrorrrs) I d8 Koning It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown beiow:

Column 7, line 3 before "substantially" insert --reducing the liquid height in said hopper from a maximum value continuously to matntain-.

Signed and sealed this 15th day of July 1975.

(SEAL) Attest:

(3., MARSHALL DANN RUTH C. MASON Grmmissianer of Patents Attesting Officer and Trademarks

Claims

1. A floating suction dredger comprising, in combination: a buoyant hull having a displacement sufficient to float a predetermined maximum load weight; hopper means carried by said hull and having a volumetric capacity substantially greater than that predetermined volume of settled dredger spoil required to impose said predetermined maximum load weight on said hull; suction dredger means carried by said hull for discharging a liquid suspension of dredger spoil in water into said hopper means whereby dredger spoil progressively settles in said hopper means correspondingly to increase the settled volume thereof in the hopper means toward said predetermined volume which imposes said predetermined maximum load weight on said hull; drain means for draining off liquid from said hopper means; and control means controlling said drain means for maintaining the volume of liquid above the settled dredger spoil at a value continuously to impose substantially said predetermined maximum load weight on said hull once such weight is reached and while said suction dredger means is operating whereby rapidly to achieve said predetermined volume of settled dredger spoil in said hopper means.

6. Floating suction dredger as claimed in claim 1, characterised by a safety device which is controlled by said control means to terminate operation of said suction dredger means when the weight of the load of the hopper means exceeds said predetermined maximum load weight.

8. A floating suction dredger comprising, in combination: a buoyant hull having a displacement sufficient to float a predetermined maximum load weight; hopper means carried by said hull and having a volumetric capacity substantially greater than that required to accommodate a predetermined volume of settled dredger spoil which loads said hull to said predetermined maximum load weight; suction dredger means carried by said hull for filling said hopper means with a liquid which is a suspension of dredger spoil in water at such a rate that the liquid height in said hopper means continuously is greater than the height of settled dredger spoil therein; liquid drain off means for substantially said predetermined maximum load weight on said hull while said suction dredger means is operating; said liquid drain off means comprising siphon means operated at a discharge capacity rate greater than said rate at which the suction dredger means is operated and control means for controlling the withdrawal height of said siphon means.

9. A floating suction dredger as defined in claim 8 wherein said control means produces a signal related to the draught of said floating suction dredger.

11. A floating suction dredger comprising, in combination: a buoyant hull having a displacement sufficient to float a predetermined maximum load weight; suction dredger means carried by said hull and including a suction pump having an inlet and an outlet and a suction pipe connected to said inlet to project downwardly therefrom into suction contact with a body of dredger spoil below said hull; a hopper carried by said hull, said suction dredger means also including a discharge pipe connected to said outlet of the pump to discharge a liquid suspension of dredger spoil in water into said hopper, said hopper having a volumetric capacity sufficient to accommodate a volume of said suspension which at least approaches said predetermined maximum load weight and is thereby of substantially greater volume than that required to accommodate a volume of settled dredger spoil which imposes a load on said hull exceeding said predetermined maximum load weight; means for operating said suction dredger means quickly to fill said hopper with said suspension and for thereafter draining off liquid in said hopper at a sufficiently greater rate than the discharge rate of said suction dredger means as to maintain said predetermined maximum load weight on said hull and thereby maximize the operating depth of said inlet of the pump.