Marine structures platforms

Protection with impressed current, with galvanic anodes, and a combination of both processes is used for marine structures and offshore pipelines. Their properties, as well as their advantages and disadvantages, are given in Table 16-1. The protective measures must be optimized for every structure. In the impressed current protection of offshore platforms, for example, the difficulties of maintenance and repair will be of major importance, whereas in harbor installations these problems can be... 

In the corrosion protection of marine structures, it is often found that the corrosion rate decreases strongly with increasing depth of water, and protection at these depths can be ignored. Investigations in the Pacific Ocean are often the source of these assumptions [7], However, they do not apply in the North Sea and other sea areas with oil and gas platforms. Figure 16-1 is an example of measurements in the North Sea. It can be seen that flow velocity and with it, oxygen access, is responsible for the level of protection current density. Increased flow velocity raises the transport of oxygen to the uncoated steel surface and therefore determines the... 

Sacrificial anodes Small land based schemes and for avoidance of interaction problems. Marine structures, e.g. offshore platforms High soil/water resistivities and small driving e.m.f. may require a large number of anodes Reasonably uniform Cannot be applied in high-resistivity environments... 

Cathodic protection has many applications, e.g. in refineries, power stations, gas, water, and oil utilities on marine structures, e.g. jetties, piers, locks, offshore platforms, pipelines, ships hulls, etc. and on land structures, e.g. buried pipeline, storage tanks, cables, etc. For each use, the cathodic protection system requires careful design, either impressed current, sacrificial anodes, or a combination of both may be chosen. There may also be other protection systems, e.g. paint, the nature of which will affect the design parameters and must be taken into consideration. 

The sea and the salty atmosphere are saline media that are highly aggressive to metals. Marine structures such as ships, bridges, and drilling rigs and platforms usually show signs of severe corrosion xmless they have been properly protected. Cars kept near oceans show signs of corrosion. 

Cathodic protection is used widely for the protection of submerged steel in waterfront structures. It also can provide considerable benefit in the intertidal zone and can even reduce the usually high corrosion rate experienced at the boundary between the intertidal zone and the splash and spray zone. Cathodic protection also is used to prevent corrosion of the soil side of steel in marine structures such as sheet steel bulkheads. Cathodic protection also is effective in the control of the corrosion of reinforcing steel in concrete in all exposure zones in waterfiont structures. Particularly for impressed current systems, it is important to select materials for the cathodic protection system components such as rectifiers and junction boxes with consideration of the environment to which they will be exposed. When considering cathodic protection, periodic inspection and maintenance is required for proper system operation. The costs for inspection and maintenance must be considered in the overall cost of cathodic protection. While there are no specific standards for cathodic protection of piers and docks, information in NACE RP0176 (Corrosion Control of Fixed Offshore Platforms Associated with Petroleum Production) and NACE RP-0187 (Design Considerations for Corrosion Control of Reinforcing Steel in Concrete) contain information that is applicable to marine piers and docks. 

Marine Structures (0951-8339). This journal aims to provide a medium for presentation and discussion of the latest developments in research, design, fabrication, and in-service experience relating to marine structures, i.e., all structures of steel, concrete, light alloy or composite construction having an interface with the sea, including ships, fixed and mobile offshore platforms, snhmarine and submersibles, pipelines, subsea systans for shallow and deep ocean operations, and coastal structures such as piers. 

Baarholm, G.S., Flaver, S. and 0kland, O.D. Combining contours of significant wave height and peak period with platform response distributions for predicting design response. Marine Structures (23) 147-163, 2010. 

Since the 1950s, the 90-10 alloy has become accepted for condenser service as well as for seawater pipe work in merchant and naval service. In naval vessels, the 90-10 copper-nickel is preferred for surface ships, whereas the 70-30 alloy is used for submarines because its greater strength makes it more acceptable for the higher pressures encountered. These alloys are also used for power station condensers and offshore seawater pipe work on oil and gas platforms. Large quantities are selected for the desalination industry, and they are additionally used for cladding and sheathing of marine structures and hulls. ... 

Submerged marine structures. Cathodic protection of submerged marine structures such as steel jackets of offshore oil and gas platforms and pipelines is widely provided by sacrificial anode systems. A... 

Nordal H, Cornell CA, Karamchandani A (1987) A structural system reliability care study of an eight-leg steel Jacket offshore production platform. In Proceedings of The Marine Structural Reliability Symposium, SNAME, Arlington, VA, October 1987. 

Properly designed process equipment, taking Into account all the marine vessel motions, Is essential to ensure process quality specifications are met and onstream time 1s maximized. The motions of tankers and semisubmerslbles are most severe and consequently the design of the process equipment for these applications has received the most attention. However, the technology can be utilized to Improve the performance of process equipment on structures such as guyed towers and tension leg platforms which only move 1n one plane and generally with lower amplitudes. 

According to Article I of [3] the aim of the convention is to prevent the pollution of the sea by dumping of waste and other matter that are liable to create hazards to hmnan health, to harm hving resources and marine life, to damage amenities or to interfere with other legitimate uses of the sea . Dumping is in Article III defined as (i) any deliberate disposal at sea of wastes or other matter from vessels, aircraft, platform or other man-made structures at sea and (ii) any deliberate disposal at sea of vessels, aircraft, platforms or man-made structures at sea . Article IV states that the dumping of wastes or other material listed in Aimex I is prohibited , and Annex I includes Radioactive wastes or other radioactive matter . From these Articles it seems obvious that the Convention applies to nuclear submarines. 

External corrosion problems in oil and gas production are similar to those in pipelines, but the economic impact on the total cost of production is limited as the lines are shorter and smaller in diameter. Atmospheric corrosion of structures and vessels is a problem for offshore fields and those operating in marine environments. The improved quality of the protective coatings for offshore environments resulted in reduced frequency of repainting platforms and tanks. 

Even when the water is shallow, it is not safe to send divers down because the structure may collapse while the diver is in the water. Moreover, if the wellhead has not been properly secured, a gas blowout could occur at any time—once more posing a great risk to divers in the vicinity. This means that ROVs (remotely operated vehicles) have to be used. (One estimate is that 85% of the remediation work is done by divers, the rest by ROVs.) Explosives are rarely used because of the potential impact on turtles and other marine creatures. Chemicals, including diesel fuel, that were on board the facility at the time of the platform collapse pose an environmental hazard and can be a safety hazard for divers in the area. 

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