First ever Voith powered jack-up vessels

About 131m in length, with a width of 39m, an input power of 11.4 MW, 5,300 tonnes maximum load, an operating platform covering some 3,200 m² and an installation crane capable of lifting loads weighing up to 800 tons up to a height of 24m, the two identical jack-up vessels will be built by the Dubai shipyard Lamprell Energy and are scheduled for delivery in May and September 2012. Their future task is transporting and installing offshore wind energy plants, especially in the North Sea.

High performance, manoeuvrability and reliability are the key requirements for the propulsion system, which Voith says led Fred Olsen to decided on Voith Schneider Propellers since the three VSPs will ensure propulsion and accurate positioning while also providing a service speed of 12 knots when in transit.

A typical design characteristic of these vessels are the four columns or ‘jack-up legs’, which can be lowered to the bottom of the sea, lift the vessel and turn it into a stable operating platform. For this process, the vessels have to hold their position with extreme precision which is where the advantages of the VSP in direct combination with the dynamic positioning system come into special effect. It takes 3s for the drives to reverse, thus preventing the ship from making leeway, which is normally inevitable due to the swell of the sea. The moment when the vessel is lifted from the water is critical and, during this transitional phase of lifting, the VSP is claimed to deliver significantly better thrust than other propulsion concepts.

The VSPs also allow a simple hull shape enabling these vessels to be built with an hydrodynamically efficient design which has a positive impact on consumption figures and emissions. Voith carried out a relevant model test during which these advantages were demonstrated. Another feature of the jack-up vessel is the intelligent Voith Roll Stabilisation (VRS). If weather conditions are difficult, a frequent occurrence in stormy offshore wind parks, the VSP reduces the rolling motions of the vessel.