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Offshore Wind Journal

Offshore Wind Journal

New-generation heavy lifter will work across markets

Mon 19 Jun 2017

New-generation heavy lifter will work across markets
Bokalift 1 combines a 3,000 tonne crane, large deck and DP2 dynamic positioning capability

As highlighted recently in Riviera Maritime Media’s publications OSJ and OWJ, a number of companies have ordered vessels targeting the growing market for ships capable of decommissioning offshore platforms and installing jacket foundations for offshore wind turbines

 

Heavy-lift vessel contractors have faced a challenging market in recent years as the low oil price environment combined with a shift towards subsea installation and deepwater activity has seen fixed platform installations decline globally. The number of fixed assets installed in 2017 is expected to be around 45% less than 2014 levels. This has resulted in a difficult outlook for heavy-lift vessels in the market for topside and jacket installation, leading contractors to seek out opportunities in less traditional markets.

As noted in the April 2017 issue of OSJ, two bright spots for heavy-lift companies are offshore wind and decommissioning – the former being increasingly attractive as the volume of installed turbines per year grows rapidly and the projects become larger and further from shore.

Whilst the market for turbine installation is predominantly covered by purpose-built turbine installation vessels, installation of foundations and substations is accessible to conventional heavy-lift vessels. A key requirement for this market is sufficient deck space, with the ability to carry at least four monopiles typically preferred. Although turbine size, and hence the size of the supporting foundation, are increasing with water depth, it is unlikely that heavy-lift vessels will need lifting capacity of more than 3,000 tonnes. Crane capacity in the range of 1,500–3,000 tonnes is suitable for most offshore wind installations. Much larger, single-lift decommissioning units, such as Allseas’ Pioneering Spirit, operate in a different segment of the market.

Among the forthcoming newbuilds targeting the decommissioning and offshore wind markets are Orion, DEME’s new vessel, which was described in the April issue of OSJ, and Bokalift 1, based on an existing semi-submersible heavy-lift ship that the Dutch company is converting into a 3,000 tonne crane ship.

Boskalis’s new vessel will combine the 3,000 tonne lifting capacity revolving crane with a deck area of 165 m x 43 m and a DP2 dynamic positioning capability. Like Orion, it will be used to install jackets and monopiles for offshore wind turbines and to remove obsolete oil and gas platforms and transport. Boskalis says it could also be used to transport and install certain types of newbuild oil and gas production platforms. Having DP2 will mean that the vessel will not rely on the installation of an anchor spread. The vessel will have accommodation for 149 people and a helicopter deck for offshore transfers. Delivery is expected at the beginning of 2018. A sister vessel is also scheduled for conversion into another 3,000 tonne capacity crane vessel.

Bokalift 1 will be capable of lifting 3,000 tonnes at a radius of 28 m and 1,200 tonnes at 50 m. The load a heavy-lift crane can lift is important, but so too is the height to which it can lift a load. Using its main block, the crane on the vessel, which is being built by Huisman, will be capable of lifting a load to 90 m above deck at a radius of 30 m and 99 m at a 35 m radius.

The 216 m long vessel has a breadth of 43 m, moulded draught of 13 m and operating draught of approximately 8.5 m. The deck will be strengthened to 25 tonnes/m2. The machinery takes the form of four 3,840 kW Wärtsilä engines and two 4,800 kW Bergen engines with a 1,110 kW auxiliary engine from Wärtsilä. Bokalift 1 will have a ballast capacity of 2 x 1,500 m3/hr and an anti-heeling system with a capacity of 8 x 2,000 m3/hr. The vessel will have a transit speed of 14 knots.

In decommissioning mode, the vessel will position itself using its dynamic positioning system and cut the legs of a jacket between the topside and the jacket. It would then lift the topside onto its deck. The vessel will also have the ability to deploy an internal cutting tool, which will cut the legs of the jacket below seabed level, after which it will lift the jacket onto its deck and depart for a disposal yard where it would offload the topsides/jack using its own crane.

In foundation installation mode for the offshore wind market, the vessel would load itself with jack or other types of foundation using its crane and, having arrived at the location of the windfarm, would lift the foundations and stab them into place on pre-installed pin piles using the crane whilst in DP mode.  

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