NL2006957C2

NL2006957C2 - Pump structure and method for conducting pumping operation.

Info

Publication number: NL2006957C2
Application number: NL2006957A
Authority: NL
Inventors: Eirik Holmefjord; Hallvard Rosvold
Original assignee: Frank Mohn Fusa As
Priority date: 2010-06-18
Filing date: 2011-06-17
Publication date: 2013-11-20
Also published as: NO20100879A1; NO335507B1; NL2006957A; GB201110151D0; GB2481316B; GB2481316A

Description

PUMP STRUCTURE AND METHOD FOR CONDUCTING PUMPING OPERATION.

The present invention relates to a pump structure for conducting a pumping operation of fluids of liquid and gas, said device comprising a pump having a pump inlet arranged to be 5 submerged in a liquid and comprising an impeller structure operated by a drive means for pumping the fluid into an upward rising discharge line, as appearing in the preamble of claim 1.

Further, the invention also relates to a method for pumping of fluids, by using a device comprising a pump having a pump inlet arranged to be submerged in a liquid and comprising 10 an impeller structure operated by a drive means for pumping the fluid into an upward rising discharge line as appearing in the preamble of claim 10.

The inventive pump structure is intended to be used in handling fluids, and in particular a liquid or gas, or a mixture thereof, and more specified fluids like water and air or mixture thereof.

15

In particular the invention relates to a pump structure and a method for conducting a pumping process of water and air, or a mixture thereof, in a water ballasting system of a vessel.

Generally, the pump structure of the invention is designed for pumping of any liquids and 20 gases, or mixtures thereof. In the following disclosure, the invention is disclosed with reference to water and gas.

The invention also includes a method for pumping of fluids, by using a device comprising a pump having a pump inlet arranged to be submerged in a liquid and comprising an impeller 25 structure operated by a drive means for pumping the fluid into an upward rising discharge line.

It is an object of the invention to develop an impeller pump structure including a vertical shaft, and which is self priming. A self priming impeller pump means that the pump, at start up mode, does not need any additional built-in equipment for supplying liquid to the inlet suction area of 30 the impeller for suction of liquid up into the discharge pipe.

The pump inlet area normally contains a trapped air pocket, on which air the pump does not work. The primary object of the invention is to provide for a structure where the inlet area to the impeller is placed in a liquid seal structure in a pump casing. Further it is an object of the 35 invention to primarily apply this liquid volume in the start up mode, in order to suck up the air that normally is trapped in the inlet pipe to the pump, i.e. to replace the air with water from the ballast tank.

2

Traditionally ballast pumps have been located in an aft cofferdam, between the engine room and a cargo section, for example. Ballast tanks are normally filled with water by gravity flow into the tank from the outside sea.

5 Later on, submerged ballast pumps have come into use, thus eliminating any need for separate pump rooms of the hull, and also providing that larger volume will become available for cargo. These pumps also include built in priming systems.

Such submerged impeller pumps include vertical axis for pumping/handling ballasting water in ballast tanks.

10

Regarding the state of art, reference is made to the following patent documents: JP-4187895, W0-2008/009048 and DE-35 02 999.

A schematic example of submerged impeller pumps are illustrated in the enclosed drawing 15 figure 1. The figure shows the bottom hull (shell) section 100 of a vessel, and one pump unit 102 being situated on each side of the hull, lowered from the deck level of the vessel. The pump housing itself is shown by numeral 10 in figure 3. The pump 10 is further mounted inside a casing 110, said casing defining a lower bottom space 112 wherein the impeller is supplied with water to be pumped out of the ballast tank. The pump 10 sucks water through a pipe 11, 20 into said space 112 and discharges the water further through discharge pipe 18. The inlet to pipe 11 includes a suction bell mouth 14 that is positioned as low as possible in the ballast tank bottom 100 as shown (figure 2). In order to ensure optimum water flow forward to the bell mouth 14, and avoid loss of suction, the stiffeners 17 and webs 19 include holes 21 of optimal design and sizes, as shown in figure 2.

25

The casing 110 and pump 10 is normally positioned at a lowest possible tank level also. The horizontal rotating impeller sucks water through pipe 10 and pumps it through the discharge pipe 18 and into the free water volume outside the vessel. As shown the discharge outlet 18 is at a lower height level in the pump casing 110, compared with the inlet pipe 11.

30

As the ballast tank empties, the water level 16 falls below the inlet level 14 of the pipe 11, a gradually an amount of air will enter the pump suction line via the vortex forming at the suction bell mouth 14. Air will accumulate in the pump casing 110 and the pump looses its suction power and is turned off.

35

This situation is shown in figure 4. The ballast tanks are normally filled with water as a cargo is discharged from the cargo holds. To begin with, the water flows into the ballast tanks by gravity. The air pocket is however still inside the casing 110, and prevents the pump from operating. The air pocket volume must be removed and replaced by water in the lower bottom 40 space 112 before the pump is able to operate and handle ballast water again. An auxiliary 3 ejector pump system 20 is therefore connected to the top side of the pump housing 10. When the ballast water is to be removed again, the ejector system is started to pump the air upwards and out of the system to suck water into the pipe 11 and further into the pump and its lower bottom space 112, and then the pump 10 may be restarted for handling the ballast water.

5

In order to operate the pump must be "filled" with water, either by using the air-ejector system, as disclosed above, or by allowing water to flow into the impeller pump to allow the air to escape from the pump housing.

10 It is an aim of the invention to provide for a self priming pump system, i.e. a system which, in its start mode, is not dependent of any auxiliary ejector pump system 20 to start the pump again.

The pump structure of the present invention is characterised by the pump structure being arranged in a casing structure defining a liquid seal casing arrangement for establishing a given 15 minimum liquid volume in which the inlet to the pump impeller is submerged. The preferred embodiments of the device appear in the dependent claims 2-12.

The present invention

According to the invention, a device of a pump structure is defined, said pump structure is for 20 conducting a pumping operation of fluids of liquid and gas, said device comprising a pump having a pump inlet arranged to be submerged in a liquid and comprising an impeller structure operated by a drive means for pumping the fluid into an upward rising discharge line, wherein the pump structure is arranged in a casing structure defining a liquid seal casing arrangement for establishing a given minimum liquid volume in which the inlet to the pump impeller is 25 submerged.

The pump structure is characterised in that an auxiliary pump element defined by a mixing cone having a part-conical outline is connected to the shaft, said cone on rotation is arranged to pull water up internally axially in the cone, and in a radial direction into a level above the 30 lower portion of the impeller, where the water is caught by the impeller blades, the lower edge level of the cone extends a distance D below the similar lower edge level of the impeller, and the discharge line defines an enlarged volume section for providing a gas/liquid separation of the pumped gas and liquid mixture, in that the gas is arranged to rise further 35 upwards into the discharge line, while the water corresponding to said minimum liquid volume flows back into the water seal.

The preferred embodiments of the pump device appear in the dependent claims 2-9.

4

According to a further aspect the invention also relates to a method for pumping of fluids, by using a device comprising a pump having a pump inlet arranged to be submerged in a liquid and comprising an impeller structure operated by a drive means for pumping the fluid into an upward rising discharge line, and the method is characterised in that to enable the pump to 5 pump a gaseous fluids, a sufficient volume of liquid is used as a pumping medium to draw gas through the inlet pipe into in pump casing, further through the pump and into an discharge line.

According to a preferred embodiment, there is described a use of a two-piece pumping system, comprising 10 a horisontally rotating impeller, and an auxiliary pump element of cone, the lower entrance edge of which, being arranged at a distance D below the similar entrance edge of the impeller, and as the water level falls below the level, gas is sucked into the impeller and mixed with water supplied to the impeller by the rotating cone element, and the mixture of gas bubbles and water is pushed upwards into a 15 transition space that exits upwards and into a discharge pipe, in that the transition space reinforcing a separating of air bubbles out of the of rising water and air mixture, said air being discharged further up into the discharge line, while water flows back to impeller and bottom of the water seal casing.

20 According to a further preferred embodiment a ballast tank system is operated, where in the initial water evacuation stage, air entrapped in the inlet pipe is, by means of said minimum water volume in said water seal trap acting as the pump medium, pumped through of the pump casing, impeller and discharged through the discharge pipe, and in the further stage where the pump operates pumping the ballast water only, through the pump device.

25

The drawing figures.

The invention shall be disclosed in more detail with reference to the enclosed drawings, in which: 30 Figures 1 to 2 show the bottom (keel) structure of a vessel and its previous known submerged ballast pump system.

Figure 3 shows the previous known pump structures in a normal water ballast pumping mode.

35 Figure 4 shows the situation where the ballasting tank is empty and air is drawn into the pump casing.

Figure 5 shows the new pump structure according to the present invention.

40 Figure 6 shows an enlarged section of the inventive pump structure of the invention.

5

Figure 7 shows an enlarged section of the lower section of the pump

The pump structures and application thereof are previously disclosed referring to drawing 5 figures 1-4.

In the following disclosure, the inventive pump structure will be disclosed with reference to figures 5, 6 and 7.

10 Inside the pump casing 110 a standard impeller pump unit 1 for submerged operation is mounted. The drive motor 34, for example a high pressure hydraulic drive motor, is arranged centrally inside the pump unit 1. As the drive motor is not part of this invention it is not disclosed any further here.

15 At the bottom inlet section 7/9 to the pump, an impeller 4 includes a plurality of impeller blades connected to a drive shaft 30. The inlet level to the impeller is indicated by the dashed line 14' on figure 7. A special wear ring is designed for turning the liquid 180 degrees back into the impeller, said liquid otherwise would flow back into the bottom of liquid seal 110. As shown by reference numeral 8 on figures 6 and 7, the stationary wear ring 8 exhibits a U-shaped cross 20 section. The periphery edge of the impeller disc extends downwardly into recess of said U-shape. The effect of this structure is that the water reflux back to water seal bottom is delayed, and the water volume amount adjacent to the impeller to be pumped, is higher. Thus an increased the air pumping efficiency is observed.

25 Further an auxiliary pump element defined by a mixing cone 7 having a part-conical outline is connected to the shaft 30. The mixing cone is designed with a plurality of flow openings. On rotation around the shaft axis as shown by reference numeral 35 on figure 7, water is pulled up internally axially in the cone and flows in radial direction into a level above the lower portion of the impeller, and the water is then caught by the impeller blades.

30

As can be seen also from figure 7, the lower edge level of the cone 7, according to the invention, extends downwardly a distance D to a level 14" below the similar lower edge level 14' of the impeller 8. The impeller blades push water upwards and into the circular space 31 between the drive motor cover and the pump unit 10, in which space a number of guide vanes 35 are positioned also.

The upper section of the casing 110 defines an enlarged transition space 32 that exits upwards and into the discharge pipe 6. The transition space 32 is to reinforce a separating of air bubbles out of the rising water and air mixture.

40 6

The upper section level of this space 32, shown at reference numeral 13, is denoted an air disposal 13 where the separation of air from water is completed. The air from the pocket in the casing bottom is transferred further upwards through the pipe 6, while the water portion flows back into the space 32 and eventually down into the casing bottom.

5

As disclosed above, the discharge pipe 6 defining the water exit from the casing 110 is now placed in the upper section of the casing 11, and thus a water seal or water trap is established in the lower part of the pump casing 110.

10 A minimum volume of water will always fills the casing water seal, and so functions as the pump drive medium so that the pump, by rotating the impeller, is able to displace any air pocket in the casing or in the inlet pipe 11 which transfers water from the ballast water level 15. When the impeller is at stagnant/standstill this minimum water volume 36 fills up the casing up to a water level shown at 14. See figures 5-7.

15

This volume acts as the pump medium at a start up mode of pump operation, to replace air with water.

As mentioned above the lowest edge of the mixing cone 7 reaches lower than the impeller, 20 Indicated by the dashed lines 14' and 14" respectively. This feature contributes to boost the admixing of air bubbles from the air pocket and into the water. As the water level falls below level 14', air starts being sucked into the impeller area, and is mixed with water as said raising bubbles.

25 At this stage the mixture of water in a manner is saturated with air bubbles, resulting in an upward flow, and in the upper part, the air and water separates as disclosed before. Thus the pump acts as an air pump also, but it is not intended for long-time use in this aspect, only for the upstart mode of the pump to discharge water from the ballast tank.

30

Vertical self priming pump - functional description.

As disclosed above and with reference to figure 5, the pump is designed with a vertical shaft which is different from other self priming pumps with a horizontal shaft.

35 As the pump is self priming it may be installed at a level above the reservoir 15 of ballast water.

The principle of operation is as follows:

The lower part of the casing 110 has a spherical bottom (but not limited thereto), leaving an amount of liquid left after use 14.

40 7

When starting the pump, liquid is drawn through the impeller 4 and into the area of the guide vanes 3. The liquid level will thereby be lowered to the lowest part of the impeller. When the liquid level sinks to the underside of the main impeller edge, air is pulled into the impeller underneath the edge, while the cone 7 still pumps water upwards into the impeller. This creates 5 a mixture of water and air or air bubbles/droplets, said air bubbles droplet contributing to lifting the water upwards into the enlarged transition space 32 as shown in figure 5.

At this stage the mixing cone 7, which reaches lower than the impeller, will draw a mixture of liquid and air gas and eject it into the impeller and further up into the air separation area 12. 10 Here the air will rise further up into the air disposal area 13. In this process the liquid will fall back through the impeller and wear-ring 8 on re-circulation. The special cross sectioned wear ring is provided and designed by the invention for turning the liquid 180 degrees back into the impeller to increase the water retaining effect of the impeller structure. Therefore, there is no need for refilling of liquid into the casing.

15

As more air evacuates through the discharge pipe the pressure in the inlet area of the impeller will fall continuously and subsequently the liquid level in the suction pipe will rise until it is completely filled and the impeller operates with liquid only. Then all air has left the structure which is now completely filled with water.

20

When the pump is turned off, the suction pipe will drain liquid back to the reservoir and liquid from the discharge pipe will drain back to the housing 2 leaving a volume of water 36 (indicated by level 14) inside the pump casing. Thus the water inlet to impeller structure is always submerged in water.

25

Claims

A device of a pump structure for performing a pumping operation of fluids of liquid and gas, the device comprising: a pump having pump inlet adapted to be immersed in a liquid and comprising a propellant structure operated by means of drive means for pumping the fluid to an upwardly extending discharge line (6), the pump structure being arranged in a housing structure which defines a liquid-tight housing device (110) for setting a given minimum liquid volume (36) in which the inlet of the pumping means (1) is submerged, characterized in that an auxiliary pump element, defined by a mixing cone (7) having a partially conical shape, is connected to the shaft (30), the cone (7) being arranged to When rotation occurs, pull water axially upward towards the interior of the cone, and in a radial direction n at a level above the lower part of the impeller, where the water is caught by the blades of the impeller, the level (7 ') of the lower edge of the cone (7) extending a distance D below the similar level (14' ) from the lower edge of the impeller (4), and the ejector conduit defines an enlarged volume section (32) for providing a gas / liquid separation of the pumped mixture of gas and liquid by providing the gas further ascends to the discharge line (6), while the water corresponding to the minimum liquid volume flows back to the water seal. 25

Device according to claim 1, characterized in that a fluid inlet is arranged in the upper section of the housing device (110).

Device according to claim 1, characterized in that the section of the increased volume ejection line (32) is an integrated part of the housing device (110).

Device according to claim 1, characterized in that the liquid discharge line defines from the inlet of the propeller up to the increased volume an annular coating that envelops the propeller-drive means (34).

5. Device as claimed in claim 1, characterized in that the fluid inlet is a pipe (11) which is in fluid communication with a fluid source chamber.

Device according to claim 1, characterized in that the upstream end of the pipe (11) is directed downwards, towards the upper part of the liquid source chamber, and the lower end of which defines the minimum liquid level 10 and gas can drag in the pipe .

7. Device as claimed in claim 1, characterized in that the liquid source chamber is a ballast tank which, when filled with water, is gradually emptied by the operation of the pumping device, until a gas of air enters the pipe and is mixed with water and rises to a separation chamber (32), where water and air are separated, and air is ejected upwards to the ejection line as water flows back to the propellant structure and the bottom of the water-sealed housing (110).

Device as claimed in claim 1, characterized in that the pumping device is arranged at a level above and outside the ballast tank.

9. Device as claimed in claim 1, characterized in that the stationary part of the pump comprises a wear ring (8) of U-shaped cross section, that the peripheral edge of the rotating impeller disc is arranged downwardly in the recess of the U-shape to form a labyrinth-shaped seal.

10. Method for pumping fluids, using a device comprising: a pump which has a pump inlet adapted to be immersed in a liquid and comprises a propellant structure which is operated by means of driving means for transferring to a upwardly-extending discharge conduit pumping the fluid, characterized in that, in order to allow the pump to pump gaseous fluids, a sufficient fluid volume is used as pumping medium for gas through the inlet pipe in the pump housing, further through the pump and to a discharge line

A method according to claim 10, characterized in that a two-part pump system is used, comprising a horizontally rotating impeller, and an auxiliary pump cone element (7), the lower entry edge (7 ') of which is arranged at a distance D below the similar inlet edge (8A) of the impeller (8), and when the water level becomes lower than the level (8A), gas is sucked into the impeller and mixed with water supplied to the impeller by means of the rotating cone element, and the mixture of gas bubbles and water is pushed up to a transition space (32) which opens upwards and to an ejector pipe (6), and that the transition space (32) which reinforces a separation of air bubbles from the rising mixture of water and air wherein the air is ejected further upward into the discharge conduit while water flows back to the propeller and the bottom of the water-sealed housing. A method according to any of claims 10-11, characterized in that a ballast tank system is operated in which, in the initial step of water removal, air trapped in the inlet pipe (11), in that the minimum water volume in the water-sealed trap functions as pumping medium, is pumped through the pump housing and the impeller and is ejected via the ejector pipe (6), and, in the further step in which the pump functions solely to pump the ballast water, through the pumping device.