NL1025078C2 - Bin cooler. - Google Patents

Abstract

The disclosure relates to a well cooler ( 3 ) for cooling a cooling medium of a driving unit on a ship ( 1 ), such as a marine motor, by means of outboard water ( 8 ), which well cooler ( 3 ) can be placed in a well space ( 2 ) present in the ( 1 ), which lies at least partially below the outboard water level and which in open communication with the outboard water ( 8 ), the well cooler ( 3 ) comprising at least one cooling element ( 4 ) for the cooling medium, which extends into the well space ( 2 ) and which is surrounded by outboard water ( 8 ) during operation, and the ship ( 1 ) furthermore being provided with a cathodic corrosion protection system ( 10 ). The object of the disclosure is to provide a well cooler ( 3 ) of the above kind which on the one hand exhibits and retains an effective cooling efficiency, and which on the other hand is not affected by stray current corrosion, which reduces the life span of the well cooler. According to the disclosure, the well cooler ( 3 ) is provided with means ( 14 ) that prevents the cooling element ( 4 ) from being affected by stray current corrosion.

Description

Short indication: bin cooler.

DESCRIPTION

The invention relates to a bin cooler for cooling a cooling medium from a propulsion unit on a ship, such as a ship's engine, with the aid of outboard water, which bin cooler can be accommodated in a vessel present in the ship and located at least partially below the outboard water level and with the hopper space in open communication, the hopper cooler comprising at least one cooling element extending into the hopper space and during operation surrounded by outboard water for the cooling medium and wherein the ship is furthermore provided with a cathodic corrosion protection system.

Bin coolers of the above-mentioned type have already been known for a long time and are used in particular for cooling ship engines, such as propulsion, generator, pump and auxiliary engines, which are often present on a ship. The functionality of such bin coolers can be seen in the effective utilization of the outboard water as a continuously supplied coolant for the cooling medium (engine water) of the various drive units.

The outboard water enters the hopper through an opening and flushes the cooling element of the hopper. The warm cooling medium is transported through the cooling element from the drive unit, which medium is cooled by means of heat transfer through the outboard water. The cooled cooling medium is led back to the drive unit, while the outboard water can leave the storage space through another opening. As a result of the warming of colder outboard water by the warm cooling water, an upward outboard water flow occurs in the hopper space. Thus, the entrance and exit opening (s) for the outboard water in the hopper space 30 are often arranged at different heights in the ship's wall of the hopper space.

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A well-known phenomenon in ships is their sensitivity to the growth of algae and other aquatic animals, such as cockles and mussels, on the parts of the ship that are in contact with the outboard water. In order to limit the fouling on the ship's hull as much as possible, the ship's hull is provided with an antifouling coating on most ships.

If this anti-fouling coating is damaged, local corrosion will occur on the ship's hull at the site of the damage. A cathodic corrosion protection system is used to prevent local corrosion damage to the ship's hull.

Also the cooling element 1s placed in the outboard water is in principle sensitive to algae growth, which after a while adversely affects the cooling efficiency of the bin cooler. The use of the copper alloy CuNilOFe (Copper Nickel 90/10) as a material for the bundle of the bin cooler greatly reduces biological growth. This is due to the natural properties of this specific material. For this, however, it is required to mount the bin cooler completely insulated from the ship's skin. However, this makes the bin cooler susceptible to attack by stray currents in general, whether or not caused by the cathodic corrosion protection system present.

The most important cause for the increased risk of attack is the fact that a bin cooler has a relatively enormously large heat-exchanging surface, and that surface consists of a blank or cq. uncoated metal surface in a conductive medium.

It is an object of the invention to provide a bin cooler of the above-mentioned preamble, which has an effective cooling efficiency, is in the long term not or hardly susceptible to biological fouling and is not influenced by life-limiting attack as a result of stray current corrosion.

According to the invention, the bin cooler is provided with 10250/8 4

The invention also relates to an electrical corrosion protection system for use on a ship provided with the means as described in this patent application.

The invention furthermore relates to a ship provided with an electrical corrosion protection system provided with the means as described in this patent application.

The invention will now be explained in more detail by way of example with reference to a drawing, which drawing successively shows: Figure 1 shows diagrammatically a section of a ship provided with a bin cooler according to the prior art;

Figure 2 shows a bin cooler according to the state of the art in more detail;

Figure 3 shows schematically the effects caused by a cathodic corrosion protection system in a bin cooler according to the prior art;

Figure 4 shows a first embodiment of a bin cooler according to the invention;

Figure 5 shows a second embodiment of a bin cooler 20 according to the invention;

Figure 6 shows a test setup for testing the effects of a cathodic corrosion protection system in a bin cooler according to the prior art and according to the invention;

Figure 7 shows a table with measurement results obtained with the test arrangement from Figure 6.

For a better understanding of the invention, the corresponding parts are designated in the following description with the same reference numeral.

Figure 1 shows a ship provided with a known bin cooler according to the state of the art. The ship 1 has in its ship hull 1a a closed hopper space 2, which space is in open communication with the outboard water 8 via one or 1025078 more entrance openings 7a and exit openings 7b, respectively.

A hopper cooler 3 can be received in the hopper space 2 via an opening 3a, which opening can be closed with a pipe plate 6. A known embodiment of a bin cooler according to the prior art is shown in Figure 2. The known bin cooler 3 is provided with a cooling element 4, which is built up from a large number of vertically arranged bundle pipes 5. The bundle pipes 5 are fixed with their one end 5a as well as with their other end 5b in the pipe plate 6. The pipe plate 6 is thereby provided with a supply 7a and a drain 7b for a cooling medium (cooling water) for a ship drive unit.

In this application, propulsion units include propulsion, generator, pump and auxiliary engines that can be used on a ship.

Because such drive units are usually operated at full power on a ship, the cooling of these drive units is of great importance. To this end, the cooling medium (cooling water) with a high operating temperature is fed into the bundle pipes 5 via the supply 7a and one end 5a. The cooling medium is pumped through the bundle pipes 5 in the direction of the other ends 5b and the drain 7b, after which it is led back to the drive unit.

During operation, the vertically arranged bundle pipes 5 are flushed by the outboard water 8 present in the hopper space 2. Due to the generally present temperature difference between the warmer cooling medium in the bundle of pipe 5 and the temperature of the outboard water, heat transfer to the outboard water is created, which is heated thereby. The rinsing of the bundle pipes 5 by outboard water flowing along cools the warmer cooling medium flowing through the bundle pipes 5, which leaves the hopper cooler 3 via the outlet 7b in the direction of the drive unit with a lower operating temperature.

The heated outboard water rises thereby, 1025078 6, which results in a convection current of outboard water prevailing in the hopper space 2, which is directed from below upwards. Due to the created vertical convection flow of the outboard water 8 in the hopper space 2, the entrance openings 2a and the exit openings 2b are arranged at different heights in the ship's wall 1a, the exit openings 2b being located higher and more near the outboard water level. Thus, during operation in the hopper space 2, an upward flow of entering outboard water 8a (with a low temperature) and an outgoing flow of outboard water 8b (with a higher temperature) is created.

On the other hand, the flow of the outboard water 8 through the hopper space 2 is forced while the ship is sailing.

In order to give the bin cooler 3 built up from a large number of bundle pipes 5, the bin cooler 3 is furthermore provided with horizontally extending support plates 9, which connect the bundle of tubes 5 to each other. Although a stable construction of the bin cooler 3 is hereby obtained, the horizontally extending supporting plates 9 function as an obstacle to the billow-borne water flow created by heat convection and directed upwards. A generally known phenomenon in ships is their sensitivity to the growth of algae and other aquatic animals, such as cockles and mussels, on the parts of the ship that are in contact with the outboard water. In order to limit the fouling on the ship's hull as much as possible, the ship's hull is provided with an antifouling coating on most ships.

If this anti-fouling coating is damaged, corrosion will occur at the site of the damage to the ship's hull. In contrast to (general corrosion), in which a material is evenly spread over its entire surface by corrosion, whereby damage to the antifouling coating is concentrated on the ship's hull in a specific location (local corrosion).

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In order to prevent local corrosion damage to the hull, use is made of a passive, possibly in combination with an active corrosion protection system.

A passive corrosion protection system consists of a calculated number of anodes (eg zinc, aluminum) which are attached in metallic contact with the ship's skin.

An active cathodic corrosion protection system has an external current source between a cathode and anode, which creates an external potential field around the ship. This external potential field also prevails in the outboard water, so that a (weak) electric current will flow through the outboard water under the influence of ion transport. This current enters the ship through the local damage to the anti-fouling coating. Because the ship's hull is electrically connected to the active cathodic corrosion protection system, local corrosion damage is prevented at the specific damaged locations where the induced current enters the ship's hull.

The cooling element 4 of a known bin cooler 3 according to the state of the art is included in the hopper space 2 and is continuously flushed with outboard water and is therefore very sensitive to the growth of algae, coke, mussels or other marine animals. Although any local attack of the cooling element 4 by growth does not necessarily adversely affect the cooling efficiency of the bin cooler 3, the cooling capacity of the bin cooler 3, however, strongly decreases if the cooling element built up from many bundle pipes 5 is completely damaged and in particular if all kinds of growth have nestled among the many bundle pipes 5.

In the latter situation, the flow of the outboard water through the bundle of bundle pipes is seriously blocked, if not counteracted, so that the cooling capacity of the cooling element 4 is virtually completely eliminated. It is therefore known to provide the cooling element 4 on the outboard water side with a shielding and insulating coating, in combination with a system consisting of an electrically activated copper rods.

These rods slowly dissolve and create a toxic environment for biological organisms around the 5 coated bundle pipes. The shielding and insulating coating, however, strongly affects the heat transfer from the warmer cooling medium to the colder outboard water, thereby adversely affecting efficiency. In addition, the shielding and insulating coating lowers the surface temperature of the bundle pipes, making them more susceptible to possible biological growth.

A better protection against the attack of the cooling element 4 (the bundle pipes 5) by algae growth etc. can be achieved by manufacturing the cooling element 4 from a material which naturally has a resistance to biological growth (such as

CuNilOFe), and isolates it completely electrically from the rest of the ship.

Although this electrically insulated arrangement of the bin cooler 3 relative to the rest of the ship including the cathodic corrosion protection system, algae attack etc.

greatly reduces, the cooling element 4 and more particularly the many bundle pipes 5 is confronted with another form of corrosion, namely stray current corrosion.

Roaming current corrosion is a form of local corrosion of a part of a ship, which is caused by the conducting transfer at the interface between the material and its environment as a result of an external current or voltage source or an externally generated potential field, for example the external potential field potential field generated by a cathodic corrosion protection system.

The phenomenon "stray current corrosion" will now be explained in more detail with reference to Figure 3.

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Figure 3 shows a container filled with outboard water 8, which figuratively speaking must represent the sea. The positive electrode 11 (anode) and the negative electrode 12 (cathode) are connected with respective connections 11a-12a to a cathodic corrosion protection system 10. This system 10 creates an external external water 8 between the electrodes 11 and 12 potential field 13. The arrows in Figure 3 indicate the field line orientation of the electric potential field 13.

Reference numeral 4 schematically represents the cooling element 4 of a bin cooler 3, which cooling element 4 is completely electrically insulated from the ship and the cathodic corrosion protection system in a bin space 2 and is completely surrounded by the outboard water 8. A part of the charge current between the electrodes 11 and 12, which usually takes place via the outboard water (seawater) by ion transport, will now take place via the metal of the electrically insulated cooling element 4. The introduction of the ion current between the positive electrode 11 and the metal of the cooling element 4 at the location indicated by A in Figure 3 leads to the following reduction reactions (1) and (2): 02 + on the metal surface 2 H2 O + 4 th '** 4 OH' (1) 2 H2 O + 2nd th '* H2 (gas) + 2 OH' (2)

These reduction reactions (1) and (2) can occur on the metal surface, because the potential in the outboard water surface on the metal surface is (much) higher than the potential of the metal. The charge current in the metal of the cooling element 4 electrically insulated from the vessel 25 takes place by means of electron conduction.

Subsequently, the ion flow near B from the metal 4 enters the outboard water 8 in the direction of the negative electrode 12. This ion outflow is accompanied by oxidation reactions, which can take place because the potential of the outboard water 8 directly on the metal surface at the location indicated by B in Figure 3 (much) lower is 1025078 than the potential of the metal material. The oxidation reaction which mainly takes place at the metal surface at location B is the oxidation of the metal according to the reaction equation (3): M * rr + ne '(3) On the basis of this reaction comparison (3), metal ions go from the metal surface in solution in the hump water 8. This metal dissolving reaction (3) dissolves the metal surface as it were: the metal surface is affected by corrosion. The charge current in the direction of the electrode 12 in the hump bored water 8 again takes place through ion transport.

Due to the presence of an external potential field such as that set by a cathodic corrosion protection system (Impressed Current Cathodic Protection: ICCP), metal parts isolated electrically from the cathodic corrosion protection system and placed in this potential field will enter a metal field. very fast attack by stray current corrosion.

According to the invention, the ship and more particularly the known bin cooler is provided with means which counteract this attack by stray current corrosion.

A first embodiment is shown in Figure 4, wherein the means which counteract the attack of the cooling element 4 by stray current corrosion are represented with the reference numeral 14. According to the invention, the means 14 are accommodated in the hopper space 2 and are surrounded by at least partially the cooling element 4. In order not to adversely affect the cooling capacity of the cooling element 4, the means 14 are at least partially permeable to the hump water 8. In particular, the means 14 are made of an electrically conductive material and more particularly made from a metal mesh, which surrounds the cooling element 4.

This mesh 14 acts as an electrical shield, 1025O7ft 11, which prevents the ion current from penetrating into the metal of the cooling element 4 as a result of the generated external potential field between the positive electrode 11 and the negative electrode 12 of the cathodic corrosion protection system 10. .

By applying an electrical shielding in the form of a metal mesh around the cooling element 4 of the hopper cooler 3, the potential differences which prevail over the cooling element 4 arranged in the external potential field are greatly reduced. Thus, no stray current can start to flow through the metal of the cooling element 4, which stray current therefore cannot exit and causes no stray current corrosion.

Figure 5 shows another embodiment in which the metal mesh 14 completely surrounding the electrically insulated cooling element 4 is further electrically connected by means of an electrical connection 14a to the ship's cathodic corrosion protection system 10.

In an analogous manner to Figure 4, the potential differences across the metal surface of the cooling element 4 are greatly reduced by arranging a metal mesh 14 around the cooling element 4. Thus, no stray current can be induced in the metal of the cooling element 4, which therefore cannot exit from the metal in the direction of the negative electrode 12 near point B either. Corrosion caused by stray currents can thus be effectively prevented.

The electrical coupling of the metal mesh 14 with the cathodic corrosion protection system 10 ensures that the stray currents entering the mesh 14 (see the arrows in Figure 5) are effectively diverted by this electrical coupling with the negative electrode 12 (cathode).

In another embodiment, the means which prevent attack of the cooling element 4 by stray current corrosion according to the invention may consist of a cylindrical or I 2 50 7 -7. 12 tubular closed enclosure that can be placed around the cooling element 4 and is closed at both ends by a metal mesh.

Figure 6 schematically shows this other embodiment according to the invention, wherein furthermore the effects of the various measures on the external potential field and therefore the occurrence of possible stray current corrosion can be measured very effectively.

The hopper space 2 is herein schematically formed by a cylindrical conduit part 1a, which must represent the ship's wall 1a. The two end-to-end open ends of the cylindrical pipe part 1a form the entrance opening 7a and 7a respectively. the outlet opening 7b for the outboard water 8. The two entrance and exit openings 7a-7b are closed by means of a metal mesh 14a-14b. Due to this construction, the cylindrical pipe part 1a can be completely flowed through with outboard water 8.

With the aid of the positive electrode 11 (anode) and the negative electrode 12 (cathode), an external potential field is applied by the cathodic corrosion protection system 10. With the aid of the contact electrodes 15a-15b, the potential field applied between the two electrodes 11-12 can be measured with a voltage meter V2.

Two metal elements are placed in the pipe part 1a, which are electrically insulated from the rest of the arrangement. Both metal parts 4a-4b are connected to each other by means of a flow meter Ax. Furthermore, in the conduit part 1a, which functions as hopper space 2, contact electrodes 16a-16b are arranged, which electrodes are connected to each other by means of a voltmeter Vx.

The two metal meshes 14a-14b are electrically connected to each other by means of a connection 18 and can in addition be electrically connected or isolated from the cathodic corrosion protection system 10-11-12 by means of a switch 17.

With this measuring arrangement a number of measurements have been made for different situations 1025078 13. In these measurements, an electric potential field is realized between the positive electrode (anode) 11 and the negative electrode (cathode) 12, with the aid of the contact electrodes 15a-15b and the voltmeter V2 representing the potential difference across the hopper space 2 (the lead part 1a). ) can be measured. During the test measurements, the electric potential field was increased from 0 to 1000 mV in 100 mV steps.

With each imposed external potential field, the potential difference prevailing in the hopper space 2 and over the two metal parts 4a-4b will be measured (in miivolt) under different conditions with the aid of the contact electrodes 16a-16b and the voltage meter Vj. With the flow meter A}, the stray current running between the two metal parts and 4a-4b can be measured, which in fact forms an indication of the possibly occurring stray current corrosion.

In the first measurement, the bell ends 7a-7b of the cylindrical tube part 1a are fully open, so that there is an open connection between the space 2 and the rest of the outboard water 8. Due to this open measurement situation, the external potential field will be everywhere and both outside (V2) as in (Vj the tube part la indicate the same measured potential difference. This is indicated in Figure 7 by the bar graph, which in the legend is indicated by "without shielding".

In the second and third measurement, as a stray current shielding use is made of a coarse mesh 14a-14b. With an open switch 17, that is, the situation in which the shielding means 14a-14b are not connected to the cathodic corrosion protection system 10 (indicated by "disconnected"), the lead part 1a between the contact electrodes 16a-16b becomes higher. potential differences measured, then when the switch 17 is closed and the shielding means 14a-14b are electrically coupled to the cathodic corrosion protection system 10.

In a fourth and fifth measurement, the screening means 1025078 14 are designed as a finer mesh than the mesh used in the second and third measurement. Both in the uncoupled situation (open switch 17) and in the coupled situation (closed switch 17) similar measurement results are obtained, i.e. lower potential differences in the lead part between the electrodes 16a-16b (the metal elements 4a-4b) at a closed switch 17 than with an open switch 17.

With a closed switch 17 the input ion currents are discharged directly to the earth.

It will be clear that with the measures as explained above and as described in the appended claims, an effective system can be realized, wherein the cooling element 4, which is usually electrically insulated from a ship, can be effectively protected against attack by stray current. corrosion. As a result, both the lifespan of the bin cooler 3 and the cooling efficiency are extended because, in addition to stray flow corrosion, attack by the growth of algae, cockles, mussels, etc. is also prevented.

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Claims (10)

15 1. Tank cooler for cooling a cooling medium from a propulsion unit on a ship, such as a ship's engine, with the aid of hump water, which tank cooler can be accommodated in a vessel present in the ship and at least partially located below the outboard water level and in open connection with the outboard water standing hopper space, wherein the hopper cooler comprises at least one cooling element extending into the hopper space and during operation surrounded by outboard water, and wherein the ship can further be provided with a cathodic corrosion protection system, characterized in that the hopper cooler is provided with means which prevent damage to the cooling element by stray current corrosion. Bin hopper according to claim 1, characterized in that the means are accommodated in the bin space. A bin cooler according to claim 1 or 2, characterized in that the means at least partially surround the cooling element. Bin hopper according to one or more of the preceding claims, characterized in that the means are at least partially permeable to the outboard water. Bin hopper according to one or more of the preceding claims, characterized in that the means are made of an electrically conductive material. Bin hopper according to one or more of the preceding claims, characterized in that the means are composed of a metal mesh. The bin cooler according to one or more of claims 1-6, characterized in that the means are electrically insulated from the cathodic corrosion protection system. The bin cooler according to one or more of claims 1-6, characterized in that the means are electrically connected to the cathodic 1025079 16 corrosion protection system. A cathodic corrosion protection system for use on a ship provided with the means as defined in one or more of the preceding claims. A ship provided with a cathodic corrosion protection system provided with the means as defined in one or more of the preceding claims. 10 1025078