US3589040A

US3589040A - Mechanism for anticipating the concentration of sand in a dredging suspension

Info

Publication number: US3589040A
Application number: US729229A
Authority: US
Inventors: Jan De Koning; Romke Van Der Veen
Original assignee: Ingenieursbureau voor Systemen en Octrooien Spanstaal BV
Current assignee: Ingenieursbureau voor Systemen en Octrooien Spanstaal BV
Priority date: 1967-05-24
Filing date: 1968-05-15
Publication date: 1971-06-29
Anticipated expiration: 1988-06-29
Also published as: GB1174706A; FR1565971A; DE1759588B2; NL145919B; DE1759588C3; DE1759588A1; BE715482A; NL6707167A

Abstract

In underwater dredging, the ambient pressure in the soil or sand being dredged adjacent the tip of the dredging pipe which is buried in the sand is used to control the dredging machinery so that the output of dredged material is increased. A pressure sensitive device is used to anticipate variations in concentration of the sand in the suspension of sand in water being dredged.

Description

ite ties atent Inventors Jan De Honing Amsterdam; Romhe Van der Veen, Jutplmas, both of, Netherlands Appl. No. 729,229

Filed May 15,1968

Patented June 29, 1971 Assignee N. V. ingenieurshureau voor Systemen en Octrouien Spnnstanl Rotterdam, Netherlands May 24, 1967 Netherlands Priority MECHANISM FOR ANTICIPATING THE CONCENTRATKON 0F SAND IN A DREDGING SUSPENSION 2 Claims, 4 Drawing Figs.

Int. C1 E02f 3/88 Field of Search 37/58, 59,

DIG. 19; 73/299301; 302/35, 42

m1 sesame [56] References Cited UNITED STATES PATENTS 934,031 9/1909 Askew 37/58 2,661,550 12/1953 Graham 1. 37/58 1,255,034 1/1918 Mason,.... 73/301 2,328,954 9/1943 Conley 1 1 4 1 1 73/301 2,645,128 7/1953 Walker et a1. 73/300 X 2,931,225 4/1960 Pleuger 73130] X 3,224,121 12/1965 Denning 37/58 FOREIGN PATENTS 999,635 7/1965 Great Britain 302/42 6,501,404 8/1966 Netherlands 37/58 6,501,405 8/1966 Netherlands 37/58 Primary Examiner-William B. Penn Assistant Examiner-C1ifiord D. Crowder Attorney-Snyder and Butrum ABSTRACT: In underwater dredging, the ambient pressure in the soil or sand being dredged adjacent the tip of the dredging pipe which is buried in the sand is used to control the dredging machinery so that the output of dredged material is increased. A pressure sensitive device is used to anticipate variations in concentration of the sand in the suspension of sand in water being dredged.

PATENTEU JUN29 |97i INVENTOR 3 JAN 0E KaNinc RONKE VAN DER VEEN ATTORNIc'YS MECHANISM FOR ANTICIPATING TIIE CONCENTRATION OF SAND IN A DREDGING SUSPENSION The invention relates to a suction dredger installation, comprising a suction pipe connected to a pump. A known suction dredger installation of the kind specified is used in many cases for sucking up dredger spoil, the end of the suction pipe being inserted in the soil. The suction process is then influenced by the particular varying circumstances present adjacent the end of the suction pipe. The output which can be obtained with the prior art suction dredger installation depends considerably on the technical skill and experience of the dredging supervisor in groping in the dark.

The invention provides an improved suction dredger installation which is characterized by at least one pressure-sensitive element which senses the pressure, in the soil adjacent the end of the suction pipe.

A larger output can be obtained with the improved suction dredger installation according to the invention if the pressure in the soil adjacent the end of the suction pipe is known. This is an important indication which is not available with the prior art suction'dredger installation. Hitherto, for regulating the suction process, a quantity to be regulated e.g., the conveyed concentration of dredger spoil in the suspension sucked up, has been regulated by measuring this quantity, or a quantity dependent thereon, in the suction pipe and correcting this quantity in dependence on the difference between the measurcd and required values, whereas the suction dredger installation accordingto the invention enables the future value of the quantity to be regulated to be predicted by taking into account the pressure in the soil adjacent the end of the suction pipe, thus also enabling this particular quantity to be regulated in anticipation, in dependence on the pressure in the soil.

in a further development of the suction dredger installation according to the invention at least one regulating member for regulating the suction process is acted upon by the sensed value emanating from the first-mentioned pressure-sensitive element.

Preferably, the pressure-sensing element forms part of a depth-measuring system for measuring the depth at which the end of the suction pipe is situated below the surface of the soil.

if it is known at what depth the end of the suction pipe is situated in the dredger spoil the suction pipe can be duly displaced, or duly inserted more deeply into the soil, to prevent clay and other impurities floating on the sand from being sucked up instead of sand. When the top layer of the soil is being sucked up there is a considerable risk that the suction mouth may be clogged by large objects which are otten to be found on the surface of the soil. Stagnation caused by clogging of this kind can be substantially obviated by using the suction dredger installation according to the invention.

Preferably, the suction dredger installation according to the invention is so constructed that the depth-measuring system comprises a pressure-difference pickup, one side of which is acted upon by the first-mentioned pressure-sensing element disposed adjacent the end of the suction pipe, the other side being acted upon by a second pressure-sensitive element which senses the water pressure above the soil.

These and other features of the invention will be clearly gathered from the following description of a number of cmbcdimsnts of a suction dredger installation according to the invention, with reference to the diagrammatic drawings. wherein: 3

FlG. i is s drawing illustrating a suction dredger installation according to thc invention during the sucking up of sand and FIG. 2, 3 and 4 each show the lower end of the suction pipe of variant embodiments of the suction dredger installation according to the invention.

The suction dredger installation according to the invention shown in FIG. 1 comprises a ship 10, a pump ii, a pressure line 12 connected to the pressure side of the pump ii, and s suction pipe 13 which has a suction mouth 20 and is connected to the suction side of the pump 11. in the embodiment illustrated, the pump 11 is disposed at. the level of the water 14, and the suction pipe 13 can pivot around the center line of the pump 11.

P10. 1 shows (counting upwards) a layer of sand 15, a layer of clay 16, and water 18. The free end of the suction pipe 13 is inserted into the soil, to a great depth, for instance 20 m. The soil shown enclosed by a chaindot line 19 and surrounding the end of the suction pipe 13 is brought into suspension by underdigging. Outside the line 19, the :soil is in its normal undisturbed condition.

if during the sucking up of sand, the quantity of sand brought into suspension which is still above the suction mouth 20 is known, this quantity can be taken into account during the sucking up of sand and the displacement of the suction pipe 13.

To this end, the suction dredger installation shown in FIG. 1 has a measuring system mainly consisting of a pressure pickup 21 at the end of the suction pipe 13 and an indicator 22. The pressure pickup 21 measures, by means of a pressure-sensitive element forming part of the pressure pickup 21 and not shown in detail, the local prevailing pressure produced by a column of sand H a column of clay li and a column of water H,.

The indicator 22 consists of a pointer 23 which is attached to the suction pipe 13 and has a graduated scale 24 from which the angle a can be read off, which the suction pipe 13 encloses with the horizontal plane.

The depth H of the pressure pickup 21 below the surface 14 of the water is equal to k sin a, where k :is the length of the suction pipe from the surface 14 of the water to the pressure pickup 21. The height H of the column of sand can now be calculated by the equation:

Where:

P is the pressure measured by the pressure pickup 2i,

l! is the water column 8,, is the specific weight of the clay H, is the column of clay and S, is the specific weight of the sand.

From the two above equations there follows:

The column of clay l-i,, and the specific weight 5,, are measured by carrying out drillings. The specific weight 8,, of the drifting sand is a value known for a particular kind of sand, for instance, l.8 kgJdm".

The column of sand H can be measured considerably more simply and accurately by means of a known pressure-difference pickup 25 which is used in the suction pipe 45 illustrated in FIG. 2; in the pressure-difference pickup 25 one pressure chamber 28 is acted upon by the local pressure in the soil the other pressure chamber 26 being connected via a line 27 to the water 18 above the soil. in this case the relative pressure pickup 25 measures a pressure The pressure chamber 28 is separated from the soil by a diaphragm 17. Thus the measuring diaphragm 47 is protected from damage. The diaphragm 17 forms a first pressure-sensing element which is directly acted upon by the pressure in the soil and transmits this pressure via the liquid in the chamber 28 to the measuring diaphragm 47, while the inlet aperture 46 of the line 2.7 forms the second pressure-sensing element, from which the sensed pressure is transmitted via the liquid in the line 27 and in the chamber 26 to the measuring diaphragm 47.

The suction pipe 323 shown in F116. 3 has a measuring system formed by a pressure water line 29 which is connected to a pressure source and branches into two narrow branches 3t 31 which have respectively a first outflow aperture 32 in the soil adjacent the suction mouth 34, thus forming a first pressuresensing element, and an outflow aperture 33 which discharges above the soil into the water 18, thus forming a second pressure-sensitive element, Adjacent the

outflow apertures

32, 33 the branches 3th, 311 are connected to either side of the pres sure-difference pickup 3'7 via measuring lines 35 and 36 respectively. The pressuredifference pickup 37 thus measures the difference in pressure between the

apertures

32 and 33. The column of sand H above the outflow aperture 3?. can be derived therefrom.

, The suction pipe 325 shown in FIG. 3 comprises a pipe 39 which is connected to the pump ill, and a telescopic pipe 40 which can be moved axially in the pipe 39 by a hydraulic ram 41. Disposed around the pipe 39 and the telescopic pipe 30, is an external jacket 42 which is attached to the pipe 39 and whose upper side is open and in communication with the water 13. The suction mouth 3% in which a heavy suspension of a large quantity of sand with a little water enters, is disposed at the lower end of the outer jacket 42. In proportion as the telescopic pipe 30 is drawn further upwards, a larger quantity of water comes into the telescopic pipe 4 via the outer jacket 42 along the lower edge 43 of the telescopic pipe db, and is also sucked up. On the other hand, the sand rises higher in the outer jacket M3 in proportion as the jacket 42 is inserted more deeply into the soil. The concentration of sand in 'the suckedup suspension can now be regulated by adjusting the distance of the edge 43 above the suction mouth 34 in depen' dence on the depth thereof in the soil, or in other words in dependence on the pressure measured by the relative pressure pickup 37.

The measuring system is very useful for regulating the concentration of dredge: spoil in the suckedup suspension.

The aperture 32, and the pressure pickups 2H and 25 are preferably not disposed in exactly the same place as the suction mouth, but at a small distance m thereabove, where the flows around the suction mouth have little effect on the pressure measured, if any. when determining the depth of the suction mouth, the depth of the pressure pickup is then added with m sin a.

The pressure pickup 21 and the

relative pressure pickups

25 and 37 are, for instance, of the known electric type and are each connected via electric wires to an indicating system (not shown) disposed on the control panel on board of the ship.

The members of the suction pipe 138 shown in FIG. 4 corresponding with members of the suction pipe 38, have like reference numbers that are MW higher however.

The suction pipe 138 has a measuring system formed by a pressure water line 129 which is connected to a water source and has an outflow aperture 132 in the soil adjacent the suction mouth 13 1, the outflow aperture 132 forming a pressuresensitive element connected via a measuring line 135 to a pressure pickup 137 whose diaphragm 144 picks up the pressure sensed in the soil. The electric output signal from the pressure pickup 137 is fed via a line 148 to a measuring member 149 which operates a hydraulic regulating valve 150. This regulating valve 150 controls a hydraulic ram 141 for adjusting the height of telescopic pipe 140.

The output signal from the pressure pickup 137 can also be controlled by other regulating members (not shown) for regulating the suction process, for instance, the governor (not shown) of the pump motor. Moreover, as well as being adjusted in dependence on the pressure in the soil sensed by the pressure-sensitive element, the height of the telescopic pipe M0 in relation to the suction mouth 134 can be adjusted in dependence on other measured values (not indicated in detail).

What we claim is:

)1. A suction dredger assembly of the type including a fluid pump having a suction inlet and a pressure outlet, and

dredging conduit means havingone end connected to said suction inlet and having an opposite end inserted below the bottom of a body of water into a region of material desired to be dredged so as to deliver a suspension of said material in water at said outlet of the pump, the improvement of which comprises,

pressure sensing means supported on said opposite end of the conduit means for producing an output signal proportional to the pressure in said material outside said opposite end of the conduit means whereby the depth at which said opposite end of the conduit means is situated in said material may be determined; and

control means for controlling said dredger assembly to maximize the output of said material delivered by said pump in accordance with the pressure sensed by said pressure sensing means.

2. The assembly as defined in claim 1, wherein said conduit means comprises an outer pipe defining, at its lower extremity, said opposite end of the conduit means, and having its upper extremity above the level of said bottom and within said body of water, an inner pipe connected at its upper end to said suction inlet and having a lower end portion presenting a lower extremity disposed within the confines of said outer pipe;

said control means being connected to said lower end portion of said inner pipe for varying the spacing between the lower extremity of said inner pipe with respect to the lower extremity of said outer pipe.

Claims

1. A suction dredger assembly of the type including a fluid pump having a suction inlet and a pressure outlet, and dredging conduit means having one end connected to said suction inlet and having an opposite end inserted below the bottom of a body of water into a region of material desired to be dredged so as to deliver a suspension of said material in water at said outlet of the pump, the improvement of which comprises, pressure sensing means supported on said opposite end of the conduit means for producing an output signal proportional to the pressure in said material outside said opposite end of the conduit means whereby the depth at which said opposite end of the conduit means is situated in said material may be determined; and control means for controlling said dredger assembly to maximize the output of said material delivered by said pump in accordance with the pressure sensed by said pressure sensing means.

2. The assembly as defined in claim 1, wherein said conduit means comprises an outer pipe defining, at its lower extremity, said opposite end of the conduit means, and having its upper extremity above the level of said bottom and within said body of water, an inner pipe connected at its upper end to said suction inlet and having a lower end portion presenting a lower extremity disposed within the confines of said outer pipe; said control means being connected to said lower end portion of said inner pipe for varying the spacing between the lower extremity of said inner pipe with respect to the lower extremity of said outer pipe.