MAN Diesel & Turbo has signed a contract with Sembcorp Marine in Singapore to supply a dual fuel propulsion system – including exhaust gas after-treatment – for Heerema Offshore Services’ new semi-submersible crane vessel (NSCV).
The scope of the contract provides for 12 × MAN 8L51/60DF four-stroke engines + 12 × MAN SCR (selective catalytic reduction) systems. MAN Diesel & Turbo states that the total power output of the engines is some 96 megawatts (MW) and believes it – with the exception of power barges – to be one of the largest engine installations the world has ever seen aboard a single ship. It is certainly the first vessel of this size to feature dual fuel technology and, on completion, will be the largest vessel of its kind globally. The engines are due to be delivered in the first quarter of 2017 with the vessel delivery due to be delivered in the fourth quarter of 2018.
The package ensures full fuel-flexibility and more than meets NOx Tier III emission limits at all times – whether within Tier III zones or not – both during operation on liquefied natural gas (LNG), as well as during operation on MGO with the help of the SCR system. MAN Diesel & Turbo states that the engines will maintain their high efficiency – also during SCR operation – through integrated and customised control strategies.
“The entire project has special requirements in all aspects – it is absolutely a customised solution and a notable feather in our cap to have been selected as propulsion-system supplier for this unique vessel,” said Lex Nijsen, head of four-stroke marine at MAN Diesel & Turbo. “This is not just the largest, dual-fuel propulsion system ever featured on a single vessel, it also ensures Tier-III compliance in all operational scenarios, whether in gas or MGO modes, and whether within or without NOx Tier III-controlled areas.”
The company said a key determinant in the selection of the 51/60DF engine was its ability to fulfil the particularly high load-ramp requirements demanded by the NSCV’s huge 10,000 tonne cranes in both diesel and gas modes while maintaining its efficiency. Another key characteristic of the four-stroke unit is its ability to operate at 100 per cent MCR and above, in gas mode, and to switch smoothly and seamlessly from gas to liquid-fuel operation (and vice versa) at full load without any fluctuation in output or speed. These are all essential features to satisfy the NSCV’s DP3 (dynamic positioning) stationkeeping requirement. With the aim of becoming the most environmentally friendly crane vessel ever built, operation will be on ultra-low sulphur fuel, a fuel type that the 51/60DF readily handles.
With a length of 220 and breadth of 102m, the NSCV will be the world’s largest crane vessel. Despite these impressive dimensions, optimally locating the engines and SCR systems aboard proved a challenge, one which MAN Diesel & Turbo and the flexibility of the SCR system helps resolve. The vessel features four engine rooms, each with 3 × MAN 8L51/60DF engines. The integration of SCR and engine-control system enables the SCR to be operated at a relatively low exhaust-gas temperature, which is the basis for a high engine efficiency, and enables the SCR to be positioned further away from engines. In this way, no compromises have to be made with the vessel layout and the SCR systems will be positioned under the ship’s funnel in a vertical arrangement, some 80m away from the engines.
The dual cranes on the vessel will provide the heavy lifting capacity to install and remove offshore facilities and be utilised for the installation of subsea structures, foundations, moorings and floating structures in deep water. Each crane will be capable of lifting 10,000 tonnes in revolving mode, making them the largest offshore cranes in the world.