Offshore Platform & FPSO
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Offshore Platform & FPSO
Addtime：2016-05-19 17:59:54 Print
Offshore platforms are structures that require anti-corrosion protection due to their installation in marine environments. The most efficient method of protection against corrosion for offshore platforms is through the use of cathodic protection systems with sacrificial anodes.
Maximum corrosion occurs on a structure at a small distance below the water surface and gradually decreases with depth. Corrosion in the mud part areas is usually much less severe than below the water surface. Both the submerged steel surfaces and the steel in the mud part areas can be cathodically protected.
However, corrosion in the tidal zone or the “splash” zone, which is located above the low water level, may be severe and cannot be fully protected by cathodic protection. In these areas, protection shall be provided by the use of heavy-duty coatings and adequate corrosion allowance by design.
The submerged sections of offshore drilling and production platforms are normally uncoated and rely completely on cathodic protection.
For offshore structures, sacrificial anodes are the standard type of cathodic protection systems. It is preferable to use aluminum-zinc-indium alloy or zinc anodes for cathodic protection, due to their high dependability, immediate availability, and no subsequent maintenance requirements during their design operational life. Anodes are welded onto the structure prior to the installation of the platform. The welding connection serves as both a mechanical and electrical connection.
For offshore structures, the aluminum-indium alloy is mainly used because this combination of materials provides the highest long-term output per unit weight. The design of sacrificial anodes on uncoated structures should take into account the high current required to polarize the steel, and occasional high currents required to repolarize it after heavy storms.
Platforms and Floating Production, Storage and Offloading units (FPSOs) are considered to be special cases as far as cathodic protection is concerned, because their cathodic protection systems are required to have the same operational life expectancy as the intended application (for example 30 years).
Tanks of such structures (platforms, FPSOs) differ in their type of service from tanks on normal trading vessels. The platform and FPSO tanks are used for processing crude oil and may contain large amounts of production water, stationary ballast, or mixtures of (sour) hydrocarbons and water. Also the temperatures of these tanks are typically elevated, and may require a different approach to providing cathodic protection.
For offshore platforms & FPSOs the intervals between dry-docking are much longer than those for ships, thus it is essential for the design life of the sacrificial anode systems to be adequate to cover the full operational period.
In the previous：Offshore PipelineMaximum corrosion occurs on a structure at a small distance below the water surface and gradually decreases with depth. Corrosion in the mud part areas is usually much less severe than below the water surface. Both the submerged steel surfaces and the steel in the mud part areas can be cathodically protected.
However, corrosion in the tidal zone or the “splash” zone, which is located above the low water level, may be severe and cannot be fully protected by cathodic protection. In these areas, protection shall be provided by the use of heavy-duty coatings and adequate corrosion allowance by design.
The submerged sections of offshore drilling and production platforms are normally uncoated and rely completely on cathodic protection.
For offshore structures, sacrificial anodes are the standard type of cathodic protection systems. It is preferable to use aluminum-zinc-indium alloy or zinc anodes for cathodic protection, due to their high dependability, immediate availability, and no subsequent maintenance requirements during their design operational life. Anodes are welded onto the structure prior to the installation of the platform. The welding connection serves as both a mechanical and electrical connection.
For offshore structures, the aluminum-indium alloy is mainly used because this combination of materials provides the highest long-term output per unit weight. The design of sacrificial anodes on uncoated structures should take into account the high current required to polarize the steel, and occasional high currents required to repolarize it after heavy storms.
Platforms and Floating Production, Storage and Offloading units (FPSOs) are considered to be special cases as far as cathodic protection is concerned, because their cathodic protection systems are required to have the same operational life expectancy as the intended application (for example 30 years).
Tanks of such structures (platforms, FPSOs) differ in their type of service from tanks on normal trading vessels. The platform and FPSO tanks are used for processing crude oil and may contain large amounts of production water, stationary ballast, or mixtures of (sour) hydrocarbons and water. Also the temperatures of these tanks are typically elevated, and may require a different approach to providing cathodic protection.
For offshore platforms & FPSOs the intervals between dry-docking are much longer than those for ships, thus it is essential for the design life of the sacrificial anode systems to be adequate to cover the full operational period.
The next article：Deep Water CP
