Fishing – trapping – and vermin destroying – Vermin destroying
Patent
1987-07-15
1989-09-26
Crosby, Gene P.
Fishing, trapping, and vermin destroying
Vermin destroying
43 171, 114222, A01M 122
Patent
active
048690163
DESCRIPTION:
BRIEF SUMMARY
This invention relates to marine biofouling reduction.
There are a number of on-shore and off-shore installations, that utilise sea water either as a substance to be processed e.g. in desalination plants and in the production of sea water magnesia, or in cooling systems in, e.g. power stations or the like. In such usages, large volumes of sea water are drawn through the system. One effect of the intake of large volumes of sea water is an inevitable fouling of the system, in one or both of two forms. Thus, there is marine biofouling caused by the attachment of macroorganisms and microorganisms to the walls of the pipework of the system. If left unattended the build-up of such biofouling organisms can obstruct or even block the system, and to close down the system and clean the affected pipework is expensive and time-consuming. In addition to this there is so-called corrosion fouling where the surface of the material of the pipework or the like itself reacts with substances in the sea water producing either a deposit on or the direct degradation of the surface. Both types of fouling are closely interrelated as microbial biofouling almost invariably leads to corrosion fouling, a phenomenon generally known as microbially induced corrosion.
Similar considerations apply to sea water systems on board ships and to ships hulls and off-shore structures such as oil-rigs in permanent contact with sea water.
Fouling as is mentioned above constitutes a major economic problem it being currently estimated that the cost to the world's petrochemical industry alone exceeds l.4 billion, caused by such items as energy losses due to increased frictional resistance to the passage of water, increased heat transfer resistance, the provision of excess surface areas in heat transfer equipment to compensate for losses, premature replacement due to fouling, loss of power and production due to down time, and the provision for and rectification of safety hazards caused by corrosion failure in such items as heat exchange and associated equipment.
In an attempt to reduce the degree of marine biofouling, it is known to provide a copper electrode at the sea water intake of an installation or e.g., the intake of a cooling system of a ship, or on the surface of a structure sited in sea water, to which a DC current is applied. This causes the release of copper ions into the sea water to poison the marine biofouling organisms. However, micro-biofouling organisms are able to produce an outer skin to provide a degree of immunity to poisoning, and there is the progressive loss of electrode material.
It is the object of the present invention to provide a more effective method of reducing marine biofouling and associated corrosion fouling of sea water systems and on the hulls of ships and exteriors of oil rigs or other offshore installations.
According to a first aspect of the present invention, a method of preventing marine biofouling of structures in contact with sea water comprises generating across the structure an alternating current of a strength and frequency sufficient to shock marine biofouling organisms and sufficient to upset the normal behaviour patterns of the marine biofouling organisms entrained in the sea water passing around or through the structure. The structure may be a body such as a ships hull or the legs of an oil rig, or may be the ducting of a sea water system.
Preferably, the generation of the alternating current is achieved by strategically positioning on the structure appropriate electrodes, e.g., at the inlet to a sea water system, or spaced along the surface of a structure.
The generated electric fields produce a current density dependent on the electrode type, form and value of the impressed current, and by the resistance dictated by the salinity of the sea water and the distance between electrodes, and is adjusted so as to disrupt the settling behaviour, but not sufficiently high to cause the death of organisms. At this general level, there is believed to be a sufficient disruption of the action potentials at the nerv
REFERENCES:
patent: 1021734 (1912-03-01), Delius
patent: 2818672 (1958-01-01), Kreutzer
patent: 3180047 (1965-04-01), Kreutzer
patent: 3241512 (1966-03-01), Green
patent: 3524276 (1970-08-01), Thomas
patent: 3625852 (1971-12-01), Anderson
Diprose Michael F.
Knox-Holmes Brent
Williams Edward E.
Crosby Gene P.
Giangiorgi R. A.
The University of Sheffield
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