Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
BALLAST WATER EXCHANGE
Document Type and Number:
WIPO Patent Application WO/2003/018394
Kind Code:
A1
Abstract:
Plant (1) for continuous ballast water exchange on a vessel, without transfer of nonindigenous biological organisms with the ballast water, which plant is comprising at least one pump (8) to pump up seawater and direct it through pipes to at least one heating device (9) for heating, and therefrom further through pipes, via an optional booster pump (1), to a distribution manifold (2, 3, 7) and therefrom further to one or more completely water filled ballast water tanks (4), from which water can be passed out in the same flow rate as water was passed in, to a collecting line (7, 2), from which water passed out from the ballast water tanks can be directed over board. The plant is distinguished in that it is comprising valves (10, 11, 12) and lines (2, 3, 7) arranged such that water that is directed into the ballast water tanks, based on difference in density between water directed in and water already present in the tanks, can be passed into and distributed without substantial shifting in a layer at the top (16) or at the bottom (17) of the ballast water tanks, while a corresponding flow rate of water is passed out from the bottom or from the top of the ballast water tanks, respectively. Method for continuous ballast water exchange by use of the plant according to the invention.

Inventors:
HILDEN TOR ERIK (NO)
Application Number:
PCT/NO2002/000294
Publication Date:
March 06, 2003
Filing Date:
August 23, 2002
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
NAVION ASA (NO)
HILDEN TOR ERIK (NO)
International Classes:
B63B57/00; B63J2/12; C02F1/02; C02F1/32; (IPC1-7): B63B13/00; B63B43/06
Domestic Patent References:
WO1998023539A11998-06-04
WO2001036339A12001-05-25
Foreign References:
US5816181A1998-10-06
JP2001000974A2001-01-09
Attorney, Agent or Firm:
Tandbergs, Patentkontor AS. (Oslo, NO)
Download PDF:
Claims:
Claims
1. Plant (1) for continuous ballast water exchange on a vessel, without transfer of nonindigenous biological organisms with the ballast water, which plant is comprising at least one pump (8) to pump up seawater and conduct it through pipes to at least one heating device (9) for heating, and further through pipes, via an optional booster pump (1), to a distribution manifold (2,3, 7) and further to one or more completely filled ballast water tanks (4), from which water can be passed out at the same flow rate as it was passed in, to a collecting line (7,2), from which water passed out from the ballast water tanks can be passed over board, characterized in that the plant is comprising a valve (10) downstream the at least one heating device, with which valve the heated water or a part thereof can be directed through the optional booster pump to a further valve (12) that can be adjusted to either direct the water to the manifold (2) or the manifold (3,7), such that water that is directed into the ballast water tanks, based on difference in density between water that is passed into and water already present in the tanks, can be passed into and distributed without substantial shifting in a layer at the top (16) or at the bottom (17) of the ballast water tanks, while a corresponding flow rate of water is passed out from the bottom or from the top of the ballast water tanks, respectively.
2. Plant according to claim 1, characterized in that the heating device is a heat exchanger connected to transfer heat from the machinery of the vessel.
3. Plant according to claim 1 or 2, characterized in that the at least one pump (8) is the seawater pump (s) of the vessel, pumping up seawater that is heated in heat exchange against fluid flows in the cooling system of the machinery and is directed into the top or bottom of the ballast water tanks such that heavier water is directed into the bottom while lighter water is directed into the top of the ballast water tanks.
4. Plant according to claim 1, charactrized in that for directing water into or taking water out from the top of the ballast water tanks, in the top of each tank a horizontal pipe or a nozzle device is arranged in form of a horizontally placed sealing plate or sealing disk in the end of a vertically oriented pipe, arranged in the center in the upper part of the tanks, with many small horizontally directed holes in the pipe or along the circumference of the sealing plate or sealing disk.
5. Plant according to claim 1, characterized in that in order to direct water into or take water out from the bottom of the ballast water tanks, it is in the bottom of each tank arranged a part of a conventional ballast water system, preferably in form of a pipe that is centered into the tank and is directed straight downwards just above the tank bottom.
6. Plant according to claim 1, characterized in that instrumentation is arranged for measuring density, either by measuring directly or indirectly by measuring salinity, temperature or conductivity, in heated water (13) that is to be directed to the ballast water tanks, in water into the ballast water tanks (14), and in the discharge line (15) from the ballast water tanks.
7. Method for continuous ballast water exchange on a vessel, without transfer of nonindigenous biological organisms with the ballast water, by use of the plant according to claim 1, by pumping up seawater with at least one pump, to direct the water through pipes to at least one heating device where the water is heated, and to direct the heated water further through pipes, through an optional booster pump, to a distribution manifold and therefrom further to one or more completely water filled ballast water tanks, from which the water is passed out in the same flow rate as water was passed in, to a collecting line from which water passed out from the ballast water tanks is directed over board, characterized by adjusting a valve arranged downstream of the heating device and the optional booster pump in order to direct heated water either to a distribution manifold connected to the bottom intake of the ballast water tanks or to a distribution manifold connected to the top intake of the ballast water tanks, such that water that is lighter than water already present in the tanks is passed into and distributed without substantial shifting in a layer on top of the ballast water tanks, while a corresponding flow rate of water is passed out from the bottom of the ballast water tanks, or opposite if water passed into the tanks is heavier than water already present in the tanks, whereby water is passed into and distributed without substantial shifting in a layer at the bottom of the ballast water tanks, while a corresponding flow rate of water is passed out from the top of the ballast water tanks.
8. Method according to claim 7, characterized in that heated water is passed into and distributed without substantial shifting in a layer at the top of the ballast water tanks, while a corresponding flow rate of water is passed out from the bottom of the ballast water tanks, at approximately similar salinity between water passed into and water already present in the tanks, or heated water is passed into and distributed without substantial shifting in a layer at the bottom of the ballast water tanks, while a corresponding flow rate of water is passed out from the top of the ballast water tanks, if the water that is passed in has higher salinity than the water already present in the tanks.
9. Method according to claims 7 or 8, characterized in that the water is heated 10 to 40 °C in the heating device.
10. Method according to claims 7,8 or 9, characterized in that the water by requirement is treated in a UVtreatment unit or another treatment unit to further reduce the content of biological organisms.
Description:
BALLAST WATER EXCHANGE The present invention regards ballast water exchange on vessels, and more particular continuous ballast water exchange, in particular while the vessel is in operation, without transfer of nonindigenous biological organisms with the ballast water.

Ballast water is used in ships to maintain stability and safety. In connection with ballast water exchange several nonindigenous species have been introduced to new waters. Some known examples are inter alia introduction of the zebra mussel (Dreissena polymorpha) to the North American great lakes, the toxic dinoflagellate Gymnodinium catenatum to Tasmania, Australia in 1972, and introduction of the American comb jelly Mnemiopsis leidyi to the Black Sea.

Exchange of ballast water takes place according to two methods, namely by so called re-ballasting or by continuous ballast water exchange.

Reballasting takes place by emptying the tanks and then refilling them.

Reballasting can be undertaken without additional investments in the vessel, but may result in large problems with respect to bending moments, shear tensions, tensions in the hull and the stability of the vessel. Reballasting results in 90-100% effective ballast water exchange, so that risk for transfer of nonindigenous biological organisms via the remaining ballast water may exist.

By continuous ballast water exchange seawater is pumped up with ballast water pumps to the ballast water tanks, from where overflow is back to the sea. The tanks are full at all times, whereby the above mentioned problems with respect to mechanical tensions and stability are avoided. However, there is a risk for over-pressurizing the tanks. The effectiveness of the ballast water exchange depends primarily of the number of tank volumes being replaced.

With effectiveness with respect to ballast water exchange it is traditionally meant to which extent the ballast water per se has been replaced. 100 % effective ballast water exchange means that all the water has been replaced. However, the content of organisms in water may vary largely from place to place and between different times, and 100 % ballast water exchange is not necessarily sufficient. It exists both very mobile and very robust organisms that will require very rigid ballast water exchange if unwanted transfer to new waters is to be avoided.

With the above mentioned methods varying effectiveness are achieved depending on the mechanical detail design of tanks, pipe arrangements, pumps, the movements of the vessel and the state of the sea. Several factors have influence, and it appears most appropriate to consider what is acceptable ballast water exchange for each occasion, for example for each travel route. The purpose is to avoid unwanted transfer of biological organisms, a requirement that should be fulfilled.

Increased awareness regarding environmental problems has resulted in work by the UN agency IMO (International Maritime Organisation) in order to introduce regulations that are meant to avoid further spreading of organisms. In the near future it is probable that each vessel that can be suspected to bring unwanted organisms has to set forth an acceptable plan how the above mentioned problems are to be avoided.

In connection with the ballast water exchange it is known to treat the water with techniques or equipment such as heating, filtering, UV-radiation, ultra sound, electrical charges, salinity increase, chemicals, hydro cyclones and other techniques, in order to expel or kill biological organisms. A thorough review of all known techniques and all known problems are found in the article"Ballast water management and treatment options", Trans IMarE, Vol 113, part 3, p. 79-99, G. Rigby and A. Taylor, made available to the public in March 2001.

According to the above mentioned article it is known that heating of water that is to be directed to ballast water tanks, either under way to the ballast water tanks or in a closed loop from a ballast water tank and back (as described in patent publication US 5816181), results in a significant reduction of the content of organisms in the ballast water. Heating to 35-40 °C in half an hour will in most cases be sufficient to eliminate unwanted biological organisms.

In connection with a closed loop where the water is heated in a heat exchanger it is known that the ballast water can be pumped from the bottom of the ballast water tanks and be returned to the top of the ballast water tanks. It is set forth that a thermal layering results in less dilution of the treated water in the ballast tank. The effectiveness of the heating and the extent of the non-mixing have not been further demonstrated yet and appear as somewhat doubtful in the above mentioned article (see page 87, left column, second last and third last paragraph).

Regarding continuous ballast water exchange it is known to pump heated water into the bottom of the tanks. Regarding continuous ballast water exchange it is set forth as preferable to achieve a good mixing in the ballast water tanks, and the effectiveness is considered better at sea under sea impact than in harbor. Good mixing of the tank contents is set forth as essential to achieve sufficient heating in the whole tank. (See the above mentioned article, page 87, left column, third paragraph; page 84, last section, left column to first paragraph, right column; and page 98, right column, last paragraph).

Regarding continuous ballast water exchange it is not found other advice or specific guidance than directing heated water into the bottom of the ballast water tanks and to achieve good mixing of the full tank contents, and nothing specific is indicated beyond the heating and the importance of good mixing of the tank contents.

The objective of the present invention is to provide an improved version of continuous ballast water exchange in a vessel, without unwanted transfer of biological organisms with ballast water being replaced, at a competitive cost.

The objective of the present invention is met with a plant for continuous ballast water exchange, according to claim 1, and with a method for continuous ballast water exchange, according to claim 7.

Figure 1 illustrates a plant according to the present invention for continuous ballast water exchange.

Reference is made to Figure 1, which illustrates a plant 1 for continuous ballast water exchange on a vessel, without transfer of biological organisms to new waters, which plant is comprising, in addition to the vessel's already installed cooling water pumps 8 and central coolers 9, a valve arrangement that directs cooling water further through pipes, via an optional booster pump 1, to a distribution manifold 2,3, 7 and further to one or more completely water filled ballast water tanks 4, wherefrom water can be passed out at the same flow rate as it was passed in, to a collecting line 7,2, from which water passed out from the ballast water tanks can be passed over board, via a vacuum breaker 8 placed at higher elevation that said tanks. The plant is distinguished in that it comprises valves 10,11, 12 and pipes 2,3, 7 arranged such that water that is directed into the ballast water tanks, based on difference in density between water that is passed into and water already present in the tanks, can be passed in and distributed without substantial shifting in a layer at the top 16 or at the bottom 17 of the ballast water tanks, while a corresponding flow rate of water is passed out from the bottom or from the top of the ballast water tanks, respectively.

On figure 1 is illustrated a t-piece or a three way valve 10 that is put into the seawater cooling system for the machinery, between the heat exchangers 9 and the discharge over board. Thereby is provided connection to the ballast water tanks, via an optional booster pump 1 that is put in if it is required for the circulation. Also illustrated is an optional UV-treatment unit that functions by W-radiation of the water, which according to choice or requirement may be put into the plant. Optionally another organism killing device may be used. A pipe system 2 is mounted on deck, and in the bottom is used preferably a part 7 of an existing ballast water system for distribution of the water, and said units have shiftable function according to how heated water is directed to and from the ballast water tanks, with the valves 10 and 12. The valve 12 is arranged such that the water can be directed into the top 16 or the bottom 17 of he tanks, dependent on the difference in density between ballast water in a tank and new water passed in. In occasions where new water is directed into the top of the tanks, displaced water is directed out via the bottom line 7 and therefrom further up to deck level, and via a vacuum breaker 6 over board.

The vacuum breaker 6 hinders siphon effect in the discharge line from the ballast water tanks. The plant also comprises further features, such as devices for tank venting 5, and a check valve 18 on the pressure side of the booster pump 1.

By only introducing heated water into the ballast water tanks only water without or with strongly reduced content of biological organisms is introduced.

It is preferable if water is heated with excess heat from the machinery of the vessel. It is assumed that for most vessels it will be sufficient only to use heat from the machinery of the vessel, but additional heating for example from boilers may be relevant, in particular if the plant does not contain a W-treatment unit or another unit with similar effect. In the introductory mentioned article there is a thorough review of different conditions regarding heating and removal of specific biological organisms, and different devices for heating and additional treatment, also with indications on economical aspects.

The plant according to the invention results in the contents of organisms in the ballast water being limited or strongly reduced by heating, and that the ballast water is replaced more effectively by making use of the density differences of the water.

With the plant according to the invention the ballast water is preferably seawater that is pumped up with the vessel seawater pumps, heated in heat exchange against fluid flows in the cooling system of the machinery and directed into the top or bottom of ballast water tanks such that heavier water is passed into the bottom while lighter water is passed into the top of the ballast water tanks.

Supply of water to the top of ballast water tanks takes place via a pipe and a nozzle device or a pipe that is not resulting in turbulence or shifting in the tanks. With shifting it is here meant any mixing of newly introduced water and original water in a ballast water tank. It is preferable that water is directed into or taken out from the top of the ballast water tanks through a horizontal pipe or a nozzle device in form of a horizontal placed sealing plate or sealing disk at the end of a vertically placed pipe, arranged in the center at the top of the tanks, with many small horizontally directed holes in the pipe or along the circumference of the sealing plate or sealing disk. It is essential with in substance horizontal inflow spread out as much as possible, whereby it is achieved a very careful mixing of introduced water. An alternative embodiment can be in form of a nozzle or a pipe bent 90° such that the liquid is only introduced in horizontal direction and not in vertical downward direction. A pipe with U-form in the end is also useable, optionally a horizontal pipe in the upper part of the tank, which pipe extends over the full tank length and is provided with many horizontally directed holes for good distribution.

By taking out liquid from the bottom of the tanks it is made use of a pipe or a nozzle at the end of a pipe that is directed downwards just above the tank bottom, preferably in form of a part of an existing ballast water system.

When liquid is passed into the bottom of a tank, liquid is taken out from the top of the same tank. This is taking place through the same nozzles or pipes as mentioned above, whereby the above mentioned fluid flows are opposed.

The plant according to the present invention for continuous ballast water exchange is operated as follows: 1. By introducing water having lower density than the water already present in the tanks, the new water is passed into the top of the tanks while the original water is taken out from the bottom of the tanks.

2. By introducing water having larger density than the original water in the tanks, the new water is introduced into the bottom of the tanks, while the original water is taken out from the top of the tanks.

By operation of the plant according to the above it is achieved a sharp layering of the completely water filled tanks because of the density difference between water introduced and the original water contents of the tanks. The layer of introduced water will to a very small extent be mixed with the original water, and the introduced water will by piston effect displace the original water until the full tank volume has been replaced, as indicated at an early phase on the drawing with reference numerals 16 and 17. By introduction into the top of the tanks the layer of introduced water will displace the original water from the top, and opposite by introduction into the bottom of the tanks. It is important that the tanks be completely filled to achieve minimum shifting of water.

The essential principle is that water of lower density than the original water of a tank is introduced into the top of said tank, while water having higher density is introduced into the bottom of said tank. It has been found that increased contents of salt have a larger influence than the increased temperature on the change of density of the water. Therefore seawater will in general be introduced into the bottom of the tanks and lay there as a sharp layer at the bottom of the tanks if the water already present in the tanks has lower content of salt.

In the plant according to the invention instrumentation is preferably provided for measurement of density, either for direct sensing or indirect by sensing salinity, temperature or conductivity, in heated water 13 that is to be introduced to the ballast water tanks, in water in the ballast water tanks 14, and in the discharge line 15 from the ballast water tanks, thereby full control of the operation of the plant may be achieved, for example by taking measurements and verifying which water is heavier or lighter, and complete filling of a tank can be registered. The above instrumentation may in principle be of any known type that may provide the requested measurement results.

It is by taking in relatively salt water with higher density than the original density that said new water will be directed into the bottom the tanks. Else water will be directed into the top of the tanks. Under conditions without significant difference is salinity for water taken in, it can as a minimum be sufficient to arrange a thermometer into the discharge line from the tank, whereby by use of the resulting temperature increase it may be registered when a tank volume is filled up and the next tank may be connected for ballast water exchange.

All water directed into the tanks are beforehand heated by the at least one heating device, whereby biological organisms completely or partly are eliminated. Most preferable it is the vessel's seawater pumps that from the seawater chests are pumping up seawater for cooling into the heat exchangers of the motors, against the closed cooling system of the motors, and further to the ballast water tanks, instead of directly over board.

The seawater is conveniently heated 10-40 °C before introduction into the ballast water tanks, for example to 35-40 °C, but as apparent from the introductory described article, what is sufficient heating, and optional additional treatment, must be considered for each occasion.

For a typical vessel will 100 % ballast water exchange, with respect to volume, take place in about 36 hours.

The present invention also provides a method for continuous ballast water exchange on a vessel, without transfer of biological organisms to new waters, by using the plant according to the invention. The method comprises to pump up seawater with at least one pump, directing the water through pipes to at least one heating device where water is heated, and to directed the heated water further through pipes, optionally through a booster pump, to a distribution manifold and therefrom further to one or more completely filled ballast water tanks, from which water is passed out in the same flow rate as water was passed in, to a collecting pipe, from which the water passed out from the ballast water tanks is directed over board, via a vacuum breaker placed at a higher elevation than said tanks. The method is distinguished in using valves, pipes and instrumentation such that water that are directed into the ballast water tanks, if said water is lighter than water already present in the tanks, is directed into and distributed without substantial shifting in a layer on top of the ballast water tanks, while corresponding flow rate of water is passed out from the bottom of the ballast water tanks, or opposite if the water directed into the tanks is heavier than water already present in the tanks, whereby water is directed into and distributed without substantial shifting in a layer at the bottom of the ballast water tanks, while corresponding flow rate of water is passed out from the top of the ballast water tanks.

More specific the method comprises that heated water is directed into and is distributed without substantial shifting in a layer at the top of the ballast water tanks, while corresponding flow rate of water is passed out from the bottom of the ballast water tanks, at approximately the same salinity between water passed in and water already present in the tanks, or heated water is passed in and distributed without substantial shifting in a layer at the bottom of the ballast water tanks, while corresponding flow rate is passed out from the top of the ballast water tanks, if water passed in has higher salinity than water already present in the tanks.

The water is preferably heated 10 to 40 °C in the heating device, and if required preferably treated in a UV-treatment unit or another treatment unit to reduce the content of biological organisms. Further heating is an alternative to a UV-treatment unit.

Examples The basic principle of the invention has been demonstrated by simple tests.

A tank was used in form of a vertical standing section of a transparent plastic pipe. Water that was directed into the pipe was heated 10 °C compared to the original water in the tank. By introduction in the top of the tank a nozzle having small holes around the circumference of a plate was used. By introduction into the bottom a vertical pipe directed straight downwards just above the tank bottom was used. The introduced water was colored yellow to observe the layering or the mixing. A corresponding flow rate of water to what was directed into the tank was taken out in the opposite end. In Table 1 the results are summarized.

Table 1: Introduction of yellow colored, heated water in a tank Test Tank content In Temp. diff. °C Nozzle Layering No. 1 Freshwater Freshwater 10 Top, small Good holes in a plate 2 Freshwater Freshwater 10 Bottom Bad 3 Freshwater Seawater 10 Bottom Very good 4 Freshwater Seawater 10 Top, small Bad holes in a plate The layering by pumping seawater (salt water) into the bottom of the tank, by test No. 3, was far better (5 liter yellow seawater, 16 cm thick layer) than the layering by pumping heated freshwater into the top of the tank, test No. 1 (4,5 liter yellow fresh water, 30 cm thick layer). Better layering means less mixing with the original water in the tank. Increased salinity or salt content has clearly a larger effect on the density change of the water than heating.