In recent years, Boskalis has successfully built a position in the offshore oil and gas and offshore wind industries, and a vessel it is currently converting will add to its capability in both sectors
As highlighted previously in OSJ and in our sister journal OWJ, a number of companies have ordered vessels targeting the growing market for ships capable of decommissioning offshore oil and gas platforms and installing extra-large monopiles and jacket foundations for offshore wind turbines.
Self-propelled jack-ups have tended to undertake a lot of foundation and turbine installation work to date, but for the installation of foundations for new-generation, larger turbines, large monohulls rather than jack-ups seem to be becoming more popular, if recent orders are anything to go by.
Back in 2012, A2SEA, the well known owner-operator of foundation and turbine installation vessels, was developing a new installation vessel with Teekay Corporation. A2SEA got as far as sending out specifications to shipyards to obtain pricing for the project, which was based on the conversion of an oil tanker rather than a jack-up vessel.
Ultimately, A2SEA didn’t press ahead with the plan, but two well known owners have now done so. One is DEME Group, which has ordered construction of a large monohull installation and decommissioning vessel, Orion, which is profiled elsewhere by OSJ. A second example is Bokalift 1, which, strictly speaking, is not a newbuild at all, being a conversion of one of Boskalis’s F-class semi-submersible heavy lifters, Finesse.
However, such is the nature of its change of role that it qualifies for OSJ’s Annual Review issue – in which we look at many of the new vessels currently on order or that have been delivered in the last 12 months.
The ‘new’ vessel for Boskalis will combine the 3,000-tonne lifting capacity revolving crane with a deck area of 165 m x 43 m and a dynamic positioning class 2 (DP2) 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. It will have accommodation for 149 people and a helicopter deck for offshore transfers. Delivery is expected at the beginning of 2018. The conversion work is being undertaken in Singapore at Keppel Shipyard. 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 DP 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/jacket 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.