EP2218636B1 - Device for protecting ship seawater intakes from corrosion and fouling - Google Patents

Description

The invention relates to a ship with a device for protection against fouling and corrosion of seawater inlets in the hull with connected pipes through anodes as external current anodes.

It has been shown that protection against fouling and corrosion in water entrances and pipelines in shipbuilding are very important because blockages and corrosion damage require time-consuming and costly repairs.

Furthermore, fouling and corrosion increase the risk that seawater valves, pipelines and other important parts of the equipment may be impaired in their function, which may jeopardize the viability and safety of the vessel.

It has been shown that a suppression of fouling and corrosion is technically complicated. The seawater contains a large number of minerals, such as chlorides and sulfides, which can cause corrosive attack on many metallic materials and lead to corrosion damage. Other harmful chemicals, including fluorine, occur in different concentrations depending on location. If material surfaces such as inner walls of pipes constantly or predominantly come into contact with seawater, a large number of organisms living in seawater, plant and animal organisms cause them to settle on the material surfaces. It comes to a fouling process, which also anaerobically, i. without oxygen supply, can run off. On the other hand, sulfate-reducing bacteria and balanids, such as barnacles, play a major role since a reduction product produced is sulfide as the salt of hydrogen sulfide. This reacts directly with metals and creates so-called corrosion cells. Sulfide-containing corrosion cells react anodically with oxygen-containing areas and lead to the continuous decomposition process of the metal.

The natural sulphide content of seawater coupled with sulphate reducing organisms and bacteria is the reason for corrosion reactions of metallic surfaces in the form of electrochemical corrosion.

It is known to counteract these shipbuilding typical problems by different fouling and corrosion protection concepts. These include plastic-like or ceramic coatings, injection of biocidal compounds, classical sacrificial anodes, and extraneous anodes to protect vulnerable metallic materials from attack and destruction by chemical or electrochemical reactions.

In both overwater and underwater shipbuilding, the use of external current anodes has proved to be a favorable preventive measure for the protection of piping systems.

To eliminate the biosphere, it has been shown that copper ions dissolved in seawater have a cell-killing effect on organisms and thus can no longer deposit in pipelines. As a result, cross-sectional constrictions up to blockage of the pipes are prevented. The eliminated microorganisms increasingly collect in the arranged seawater filter and can be routinely disposed of from here. The copper anodes thus ensure anti-fouling within the piping system.

Furthermore, it has been shown that dissolved aluminum (aluminum ions) serve to protect against corrosion. The aluminum ion integrates into the typical passive layer of the CuNi10Fe pipes used for seawater-bearing pipelines and additionally stabilizes them. The pipe inner wall is permanently sealed.

The formation of a passive layer is a corrosion protection and reason why CuNi10Fe is used on special ships. A trained passive layer has ceramic-like properties in its strength. However, complex marine hydrodynamics issues can partially remove the protective effect and promote corrosion.

Based on these findings, external current anodes are installed in a remote installation position from the seawater inlet into the pipe sections. The defect here is that there is a critical pipe section with an unprotected area between the seawater inlet and the corrosion protection unit.

These deficiencies occur especially in submarines and ships without central seawater harvesting. In this case, safety-relevant on-board barriers are mounted directly after seawater entry on an inner side of the ship / hull.

Sacrificial anode applications are after DE 25 20 948 A1 also with shaft seals of propellers against corrosion, or after US-A-3066090 known.

The object of the invention is to provide a simple arrangement in the region of the seawater inlet for the protection of the connected pipelines, which withstand submarines also an expected diving pressure and ensure a simple anode exchange.

The solution of this object is achieved according to the invention in that the anode is formed in a ring shape and fixable at the seawater inlet and formed the ring shape of Halbringen different materials for releasing ions and the half rings as an anode ring by plastic against each other and against a receiving area at seawater inlet through a sheath partially are insulated, wherein an inner region of the anode ring facing the seawater is formed as a passage area without insulation.

In this way, with the materials of the anode, taking into account the mass required for sufficient release of ions, a simple arrangement is created which can be used as a compact unit in a seawater inlet and is exchangeable. Furthermore, only small contact surfaces between the anodes are to be isolated.

A good material selection of the anodes is that the materials of the half rings are formed by copper and aluminum.

The choice of sacrificial material for corrosion protection depends on many chemical and electrochemical constraints, e.g. used material pairings in the construction of the ship, used pipe material (Cu, CuNi10Fe, galvanized steel, etc.), seawater composition. Aluminum is widely used, and iron can also be used as corrosion protection within this arrangement.

A robust water-impermeable enclosure is provided by the fact that the plastic is formed to the insulating covering by polyurethane.

In order to enable a uniform power supply, it is proposed that the electrical connections of the half rings are arranged on guide plates, such as copper, on the outer circumference of the anode ring.

Furthermore, it is provided for the isolation of the anodes and avoiding tensions by volume change, that the anode ring through holes for fixing via screws, wherein the through holes accommodate insulating bushings.

To hold the anode ring by screwing it is provided that the outer region of the seawater inlet to the anode ring is covered by a coarse dirt grid with an outer ring member and the ring member is placed on the isolated anode ring for mounting.

Furthermore, it is proposed that the ring element is formed by a zinc ring, which is conductively connected to the hull.

Fig.1

eine Fremdstromanode als Anodenring aus Halbringen, wobei eine Hälfte eine gemeinsame isolierende Umhüllung aufweist;

Fig. 2

einen Seewassereintritt mit einer Druckkörperdurchführung und eingesetzte Anordnung, der durch ein aufgesetztes Ringelement eines Grobschmutzgitters gehalten ist;

Fig. 3

einen isolierten Anodenring mit freier Innenmantelfläche und

Fig. 4

eine Schnittdarstellung einer Druckkörperdurchführung mit aufgesetztem Anodenring gemäß Fig. 2

In the drawing, an embodiment of the invention is shown schematically. Show it:

Fig.1

an external current anode as an anode ring of half-rings, one half having a common insulating sheath;

Fig. 2

a seawater inlet with a Druckkörperdurchführung and used arrangement, which is held by an attached ring element of a Grobschmutzgitters;

Fig. 3

an insulated anode ring with free inner circumferential surface and

Fig. 4

a sectional view of a pressure body bushing with attached anode ring according to Fig. 2

The illustrated anode ring 1 is formed of individual half-rings 2, 3 as a copper anode and aluminum anode. Other materials are also possible in adaptation to the boundary conditions. The two half rings 2, 3 are insulated from each other by a plastic and partially wrapped together, so that a molded ring is formed. The formed envelope 4 and insulation made of polyurethane as plastic releases the half rings 2, 3 as anodes in the inner jacket region 5 for the passage of the seawater.

In order to form electrical connections of the half rings 2, 3 and formation of an external current anode, baffles 6 made of copper are applied in the outer jacket region of the anode ring 1 on each half ring 2, 3, which cables are connected to cables 7 led to the outside. These baffles 6 are also included in the enclosure 4 made of plastic.

Such a trained anode ring 1 is used in this training at the seawater inlet 8 via mounting screws 9 in a receptacle 10 a pressure body bushing 11 of a submarine. For attachment, the anode ring 1 has through holes 12, into which corresponding insulating sleeves 13 are inserted.

In this embodiment, the seawater inlet 8 is covered above the inserted anode ring 1 by a ring element 14 with a coarse dirt grid 15 and is connected together with the pressure body bushing 11 via the fastening screws 9.

The connected cables 7 are guided in a known manner via Kabelquetschverschraubungen or the like through the pressure body bushing 11 via a threaded bushing 16 for supply to the boat interior.

Claims (7)

1. Ship having a device for fouling protection and corrosion protection of seawater inlets in the hull with connected piping by means of anodes as impressed-current anodes, the anode (1) being designed flange-like in a ring shape and fixed to the seawater inlet (8) and the ring shape being formed from half rings (2, 3) of different materials for releasing ions, characterised in that the half rings (2, 3) as an anode ring are partially insulated by plastic with respect to one another and with respect to a receiving area at the seawater inlet (8) by a casing (4), an inner area (5), facing the seawater, of the anode ring (1) being designed as a passage area without insulation.
2. Ship according to Claim 1, characterised in that the materials of the half rings (2, 3) are formed by copper and aluminium.
3. Ship according to Claim 1 or 2, characterised in that the plastic for the insulating casing (4) is formed by polyurethane.
4. Ship according to one of Claims 1 to 3, characterised in that the electrical connections (7) of the half rings (2, 3) are arranged via conducting plates (6), such as ones made of copper, at the outer circumference of the anode ring (1).
5. Ship according to one of Claims 1 to 4, characterised in that the anode ring (1) has through-bores (12) for
   fixing it by means of screws (9), the through-bores (12) receiving insulating bushes (13).
6. Ship according to one of Claims 1 to 5, characterised in that the outer area of the seawater inlet (8) with the anode ring (1) is covered by a coarse dirt grating (15) having an outer ring element (14) and the ring element (14) can be placed onto the insulated anode ring (1) in order to retain the latter.
7. Ship according to Claim 6, characterised in that the ring element (1) is formed by a zinc ring which is conductively connected to the hull.

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