EQUIPMENT/ENGINEERING: Remote inspection vehicle checks FPSO hull plates

For floating production, storage, and offloading (FPSO) vessels, maximizing production means avoiding drydocking and keeping key systems fully available.

For floating production, storage, and offloading (FPSO) vessels, maximizing production means avoiding drydocking and keeping key systems fully available. Hull integrity, particularly in bottom plating and cargo ballast tanks, is crucial. Bottom plating is susceptible to coating breakdowns and internal pitting, which will lead to leakage, pollution, loss of production and costly dry-docking - unless the problem is addressed. - Snoopy is an underwater, line-operated vehicle, launched or operated from the ship or FPSO.

Conventional inspection methods involve examinations from within and outside the tank. Attendant costs and risks associated with tank cleaning are high. Use of diver and remotely operated vehicle surveys increase these costs and also introduce the risk of collision from diving support vessels. Furthermore, tanks are unavailable for inspection.

In response, EM&I, based in Wilmslow, UK, has introduced Snoopy, a new technique which allows the bottom plate, its external coatings, and corrosion protection system (CPS) to be examined without requiring the tanks to be emptied and cleaned.

Snoopy is an underwater, line-operated vehicle, launched or operated from the ship or FPSO. A line is deployed around the hull to guide and tow Snoopy around hull obstructions, such as the bilge keels. Once in position, the unit's buoyancy is adjusted to bring it into close contact with the hull. Snoopy then tracks along the hull, continuously monitoring the condition of the plating thickness, coatings, and CPS.

Easy-to-read reports are produced on site using 3D color graphics and showing bottom plate condition, presence of corrosion pits, condition of coatings and CPSs, and time-to-failure of production. The system does not require a support vessel. Snoopy has been proven in a field offshore China and is currently being considered for a number of FPSOs in the European and Pacific sectors.

Since its introduction last summer, it has gained approval from the American Bureau of Shipping. Approvals are also being sought from other main classification societies. EM&I claims the system typically costs $15,000 per tank to deploy and can complete inspection work in days. Conventional tank cleaning and waste disposal can cost $75,000 or more before introducing the costs of ROVs and divers.

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