Boskalis is converting and upgrading one of its F-class semi-submersible heavy transport vessels into a transport and installation crane vessel. It will be equipped with a 3,000 tons capacity revolving crane, dynamic positioning (DP2) and additional accommodation for up to 150 people. Potential markets include renewable energy, decommissioning and salvage projects.

Boosting lifting capacity to 3,000 tons

Boskalis has decided to invest in converting the heavy transport vessel (HTV) Finesse into a heavy lift vessel (HLV), named Bokalift 1. Current developments within the renewable energy, decommissioning and oil and gas market require specific lifting and installation capabilities - in both capacity and flexibility - not yet available within the Boskalis fleet.

Peter Berdowski, CEO Boskalis:
This investment is part of our strategy to strengthen our position on the renewable energy, decommissioning and salvage market.

Due to a steep increase in activity in the renewables market Boskalis sees opportunities in the installation of offshore wind farms, decommissioning of obsolete oil and gas platforms, and salvage operations. Given the slowdown in the oil and gas market, it is an obvious choice to convert an existing semi-submersible heavy lift vessel (SSHTV) into a crane vessel. The distinct characteristics of an SSHTV combined with a high capacity crane will make this vessel unique in today's market.

Unique capabilities

  • Available deck space: no other crane vessel has an empty deck of 165m x 43m - combined with the mid-ship starboard side positioned, 3,000 tons revolving crane this creates unique opportunities
  • The existing diesel-electric power system provides a transit speed between 11 and 12 knots  - combined with the massive deck space, it ensures a reduction in pick-up runs and significantly more time on site. Adding a DP-2 positioning system is crucial for these types of works. The recently built m/v Finesse already has redundant modern diesel-electric layout. This made it less complex to reconfigure compared to a shaft drive. 
  • Accommodation will be enlarged to host a maximum of 150 persons crew and workers. The addition of a helicopter deck will allow for crew changes while working offshore.

Vessel specifications

The vessel is 216m long and 43m wide and allows for a free deck space of 165m by 43m. Despite tripling accommodation size – from 50 to 150 – there still is a sizeable clear working area of around 6,500 m2. The 3,000 tons Huisman crane is located centrally amidships, securing the crane reach covers the entire deck. Main advantage is that heavy lift crane vessel Bokalift 1 can double the usual load of two to three jackets or monopiles in one run. Together with a transit speed of between 11 and 12 knots, operators will see significantly more time in the offshore field and less on pick-up runs.

Technical challenge

In general, it is challenging to convert a vessel designed for a specific purpose (SSHTV) into a vessel with a different operational concept (heavy lift crane vessel). The challenge lies in using the specific strengths of the SSHTV and have these work to your benefit, and to have focus on the specific areas where the vessel needs improvements. These modifications should be smart and efficient.

These changes demand a fair amount of room. A number of the original semi-submersible ballasting tanks are giving way to the requirements of a hefty pair of 7.5MW Rolls-Royce engines, giving a total installed power of around 25MW, and to four large 3.5MW Rolls-Royce thrusters. As the Bokalift 1 will have a fair amount of load to carry, remaining ballasting tanks will be modified to suit the new, faster trim requirements.

Key players

The relatively long lead time of about 18 months for the conversion is mostly down to the DP-2 system and the crane. Fitting the Rolls-Royce engines to power it and the Kongsberg control system takes time. Huisman, operating worldwide and based in Schiedam, The Netherlands has extensive experience in the design and manufacturing of heavy construction equipment. They will deliver the revolving crane, which will have 3,000 tons capacity at up to 28 m radius, and 800 tons at up to 78 m radius.

Class approval

Class approval is vital. Bokalift 1 will be classed by Bureau Veritas, a process started by Boskalis in 2016. Feasibility studies for reinforcement showed that SSHTV F-Class vessels are very strong. Stability checks were also carried out, given the crane hook height will be 75 to 80 m above deck.

The Bokalift 1 is scheduled to be deployed by the end of 2017- right on time for installation projects in 2018. The conversion is executed by Keppel, Singapore. Dry-docking commenced in March 2017.

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