An unusual set of operational challenges has led to an innovative, front-loaded propulsion arrangement on a heavy cargo deck carrier under construction at Jiangsu Zhenjiang Shipyard
A new heavy cargo deck carrier will feature a clever front-loaded propulsion arrangement to improve its ability to transport very heavy but fragile turbine components, which must be rolled rather than lifted onto the deck. Designed by Hamburg-based engineering company HeavyLift@Sea, the carrier will initially operate in the North Sea and Baltic for offshore wind specialist United Wind Logistics (UWL) before being made available for offshore installation projects worldwide, potentially through UWL sister companies United Heavy Lift and United Engineering Solutions.
The deck carrier boasts diesel engines at the bow and thruster drives in an aft propulsion room
HeavyLift@Sea managing director Hendrik Gröne explained that this operational requirement, demanding a wide cargo deck, had to be balanced against other constraints. "The deck width had to be reconciled with a ship that was small enough for the approach to a particularly small Danish port and to meet the requirements of the Kiel Canal," he said.
"Putting main engines at the fore would usually require a very long propeller shaft, disrupting the layout across the length of the ship and increasing the risk of alignment issues"
The ship design squeezes 3,600 m2 of deck space, with a loading capacity of 10,000 tonnes at maximum draught, onto a vessel that is 148.5 m long and just 28 m wide. This was achieved in part by making the superstructures, including the 21-person accommodation block, as compact as possible.
"In the first few years, the deck carrier will transport wind power components in the North and Baltic Seas, and we have optimised it for this purpose," said Mr Gröne. "At the same time, however, we also designed the ship to meet the shipping company's need for flexible worldwide deployment and maximum utilisation of such a special vessel."
The requirement for deck space also proved challenging for the propulsion installation, especially for the positioning of the exhaust funnel and selective catalytic reduction (SCR) units. Project manager Frank Schernikau explained that deck space was optimised by putting the funnels near the superstructure close to the bow of the vessel. But putting main engines at the fore would usually require a very long propeller shaft, disrupting the layout across the length of the ship and increasing the risk of alignment issues.
The solution was to opt for a diesel-electric configuration, with engines installed near the ship’s bow and a propulsion room with electric motors driving fixed-pitch propellers via conventional shafting in the aft. Although the diesel-electric configuration is not as efficient as directly driven propulsion, due to conversion losses, it regains some of the lost efficiency by allowing engines to be run at a consistent, optimal load, which also reduces engine wear.
The shipyard has ordered two MAN 9L 21/31 and two MAN 6L16/24 gensets for the DP2 vessel. The engines will meet IMO’s Tier III NOx emission regulations thanks to their SCR systems, which will ensure compliance should the proposed North Sea and Baltic Sea NOx Emission Control Areas enter force in 2021 as planned.
MAN Energy Solutions head of four-stroke marine Lex Nijsen said: “This new order confirms our solid foothold within the segment for small-bore, medium-speed engines powering specialised vessels. I welcome this new reference and feel that it highlights the diversity of our product portfolio.”
Steel was cut in November and delivery is expected at the end of 2019. UWL is employing Peter Döhle Schiffahrts for building supervision and technical management. MAN Energy Solutions’ licensee CMP will build the engines in China
Meanwhile, HeavyLift@Sea has been awarded the basic design contract for the shipowner’s next vessel, a special ship for offshore wind operations.