Schiehallion floater given 20-year external protection

A section of the Shiehallion FPSO in Belfast undergoing protective coating treatment by Jotun.

Coating and cathodic protection systems from Jotun Paints will protect the world's largest newbuild FPSO. The vessel, built by Harland and Wolff in Belfast for BP's Schiehallion Field, will process 142,000b/d of oil with a storage capacity of 950,000bbl. It will be 246 meters long, 45m broad and with a draught of 27m, able to operate in 375-425m of water.

Protective systems to prevent corrosion and fouling were chosen following a 20-year life cycle cost assessment by BP and its Schiehallion venture partners.

For corrosion protection of the hull, Jotun is supplying Jotamastic 87, a well-proven treatment with good resistance to water, solvents and many chemicals. It has a low solvent content and no isocyanate, thereby offering improved health and environmental impact over most organic coatings, according to Jotun. (It also complies with current Norsok standards).

Substantial dry-film thicknesses of Jotamastic 87 can be applied to reduce application time. Further savings in Schiehallion's construction time have been achieved by the predominant use of Wintergrade versions of the product during the harsh weather conditions prevailing in Northern Ireland. Over large areas of the vessel, this coating is also combined with Hardtop HP polyurethane topcoat, said to offer excellent color retention.

Below the waterline, the required protection against fouling is provided by three coats of Jotun's Seamate HB 99. This self-polishing antifouling is specially formulated for vessels that are stationary for long periods, or operate at very low speeds, in waters heavily populated with fouling organisms. A tie coat of Safeguard coal tar epoxy provides the sealer between the anti-corrosive coating and the antifouling.

From the deep-load waterline to the main deck level, the FPSO's topsides also received a coating of Baltoflake, a glass-flake reinforced polyester coating offering years of resistance to extreme abrasion. Baltoflake is applied as well to areas subject to heavy wear, overcoated with an anti-skid treatment.

Internal surfaces of the crude storage tanks are treated with Penguard HB, a high-build coating based on epoxy resin with a high molecular weight. For the ballast tank coatings, Jotun supplied Balloxy HB Light, which is not only light in color for ease of application and inspection in dark restricted areas. Users can visualize easily when the two components of the treatment are thoroughly mixed and also when a minimum effective thickness has been applied. Balloxy HB Light is also free from tar and isocyanates.

Finally, to protect the hull a new concept cathodic protection system (ICCP) was chosen which can cope with a high level of coating damage. It can also be easily refitted, even under water. Jotun's package included zinc sacrificial anodes in the ballast tanks, and a Cuproban automated system for controlling fouling and corrosion in the vessel's seawater systems. With this technique, incoming seawater is treated using copper anodes, resulting in the formation of a very small, harmless quantity of floc. This is carried through the system to prevent fouling.

Laser-based seabed mapping under review for pipeline routes

In mid year the Norwegian navy was carrying out tests of Spotmap, Seatex's laser-based seabed mapping and visualization system. The Trondheim-based company will receive the navy's assessment of the system later in the year.

Spotmap is also of interest in offshore oil activities - its development was partly funded by Statoil and Amoco, which are interested in using it in the planning of pipeline corridors and for the assessment of seabed objects.

The system makes use of the laser radar concept, using the reflections of short pulses of light to obtain information on the range and intensity of terrain and objects and forming images of them.

There is a large area of overlap between the requirements of the offshore and military sectors, according to Vidar Bjoerkedal, head of Seatex's system department, and a reference from one sector is often relevant to the other. And a reference such as the GSA listing - official approval for supplying US government bodies - which Seatex has gained is relevant to all potential customers.

One of the basic building blocks of Seatex's high-end products is the motion reference unit (MRU) for motion sensing. The MRU, of which more than 100 were sold last year, forms part of a real-time motion compensation system incorporated in Spotmap.

Recent MRU deliveries include Statoil's Hugin autonomous underwater vehicle, on which it is used for attitude measurement purposes. The MRU also forms part of the positioning system installed on the ROV used by Statoil for the Troll landfall tunnel inspection.

Another product of mutual interest to the offshore and military sectors is the Seatex HMS 100, which uses a combination of the MRU and meteorological sensors to provide real-time measurement of wind speed and direction, air temperature and barometric pressure. It is one of several Seatex products used by PGS on its Ramform seismic boats.

Seatex is now discussing with the Norwegian navy and coastguard the integration of this system with other environmental sensors to further optimize the monitoring of helicopter operations at sea.

The Trondheim-based company, now part of the Navia group, has also enjoyed commercial success with the Seatex DARPS - differential absolute and relative positioning system. A DGPS-based system like many Seatex products, DARPS is used for monitoring the position of shuttle tankers during offshore loading operations relative to the buoy or FPSO.

Some 45 DARPS systems have been delivered, among others to the whole of Statoil's shuttle tanker fleet. It has also been selected by Sealaunch, the sea-based rocket launch system.