Polycrest provides more details on Polycastle

Polycrest AS in Norway has provided OSJ with more details about the DP3 monohull multipurpose accommodation vessel that it has under construction at the Barreras yard in Vigo, northwest Spain for delivery in the fourth quarter of 2010.

The concept draws on 25 years of offshore accommodation experience at Polycrest, and offers accommodation for 400 in single and double cabins – all with integrated sanitary facilities. The ship is also equipped with an anti-roll system that should reduce roll by approximately 60 per cent, which thus greatly improves operability and enhances comfort.

Polycastle has a large open storage deck of 1,150m2 and a shelter deck of 700m2, in addition to 200m2 of well-equipped shops for pipe work, welding, mechanical tasks and electrical/instrument repair and servicing. The vessel also benefits from a 150 tonne active heave compensated knuckleboom crane, which is able to work at depths down to 2,000m.

A telescopic gangway with a maximum extension of 42m is also installed. In keeping with the vessel’s multipurpose role, large areas for installation of ROV systems and diving spreads are available, both on the main and shelter decks.

The ship has been designed by LMG Marin AS in Norway in co-operation with Polycrest, and has been tank tested in Potsdam, with excellent results (100 per cent for the Bay of Campeche in the Gulf of Mexico, and 98.3 per cent operability for the Campos field, Brazil).

The 125m long hull is arranged with the accommodation forward and the cargo/working/shelter deck aft. The operational concept is to hold station adjacent to an FPSO, offshore rig or fixed installation by use of a fully redundant dynamic positioning system. Access for embarkation of offshore personnel to an FPSO will be via the above-mentioned gangway, which, when not in use, is stowed forward on the bridge deck.

Apart from the large deck area, Polycastle will also benefit from a weathertight hatch down to the work/storage deck below (900m2), with sufficient height available to move containers. The sheltered under-deck workshops will enable those on board to carry out repairs to electrical components, or carry out welding and other work. There are container lay down and securing points on the deck, and deck outlets for electrical power, water and work air.

A helideck for S92 and S61 or equivalent helicopters will be another important feature, complemented by a flight lounge in the accommodation, with efficient and easy access to the flight deck by means of a lift. Refuelling systems for the aircraft will also be installed.

The accommodation is well insulated from the main machinery, providing very low noise and vibration levels, and takes the form of 190 double cabins and 10 single cabins. The vessel has been designed in such a way that a large proportion of the cabins will have outside windows. The accommodation is also equipped with an air conditioning and ventilation system with a high level of redundancy. Apart from the features mentioned above, Polycastle will also have a fire-fighting system to FiFi Class II, DP3 and the ability to conduct ROV operations.

The vessel is intended for work in deepwater off West Africa, Brazil, the Gulf of Mexico or in Asia, and will be built to DNV’s highest comfort class C (1) V (1), which has rigorous requirements for noise and vibration. This feature will, says Polycrest, make Polycastle unique, as no other offshore accommodation vessel – existing or under construction – has this standard, which is currently found only on new cruise vessels. The normal offshore standard is C (3) V (3).

Polycrest says it believes that a monohull accommodation and service vessel is considerably less expensive to build and operate than a semi-submersible or jack-up rig, and a monohull has considerably lower costs when transiting from one site to another, and can move much faster. Tank tests show a service speed of 15 knots, whereas a semi-submersible usually only moves at approximately 6 knots.

The vessel also has DNV’s highest environmental classification, with environmentally friendly diesel-electric propulsion with low levels of emissions of NOx and CO₂, along with a ballast water treatment system. Polycastle will also have SPS class (as on passenger vessels), which means much reduced heeling in the case of hull damage. Fuel oil tanks have been located in such a way that they are not close to the sides of the shell, thus reducing the likelihood of environmental pollution in the event of a hull breach, and the vessel has separate enginerooms, which provide 100 per cent redundancy.