Construcciones Navales del Norte (La Naval de Sestao) of Spain’s Basque country delivered the Simon Stevin to Jan de Nul in February. Driven by a diesel-electric propulsion system comprising a series of MAN Diesel 32/40 engines, the new addition to the Belgian group’s fleet is claimed to be the world’s largest fall-pipe and rock-dumping vessel with a capacity of 19,500 m3.
Construction of the ship lasted 26 months, with keel-laying taking place in April 2008 and launching in March 2009. The Simon Stevin recently departed for Australia for its first commercial projects.
The Simon Stevin is powered by five MAN Diesel nine-cylinder 32/40 main engines. Each delivers 4,500 kW at 720 rpm and is manufactured by STX Engine Co., Ltd., MAN Diesel’s Korean licensee. The five engines comprise a diesel-electric power plant that generates enough electricity to power a city of 130,000 people, according to the ship owner.
The Simon Stevin will mostly be deployed in offshore applications, such as the laying of oil and gas pipes at great depths; the vessel can level the seabed and dump rocks down to a depth of 2,000 m. According to Jan de Nul, the fall pipe can process rocks with a diameter up to 400 mm, a figure greater than any other fall-pipe vessel in service.
The fall pipe has an advanced, fully automatic unfolding system, featuring an ROV (Remotely Operated Vehicle) at its bottom that accurately corrects its position. The 298.5-ft vessel has a 33,500 tons loading capacity, some 25% greater than the previous record-holder, and is capable of dumping 2,000 tons of rock per hour. The Simon Stevin can accommodate more than 70 persons and has its own helipad.
The four-stroke engines run on HFO and are capable of continuous operation at loads down to 20%; running at even lower loads is possible for limited periods, thanks to the engine’s optimized design. The 32/40 can also accept overloads of 10% in conditions characterized by frequency variation.
As the Simon Stevin is subject to a dynamic load demand, high and sharp load variations can also occur. Accordingly, each engine is fitted with a so-called “jet assist” device that enables a quick response to such variations by injecting compressed air directly into the compressor wheels of the turbochargers.
MAN Diesel’s 32/40 type is characterized by an optimized, operational economy and minimal maintenance requirements. One of its stand-out characteristics is its low lube-oil consumption of approximately 0.5 – 0.8 g/kWh, a figure that was considered as a design parameter for the piston liners, covers and rings.
Another stand-out characteristic is the 32/40’s stepped piston. Here, the crown is forged with high-quality, stable steel (with shaker cooling), while the skirt is cast in spheroidal graphite cast iron. This kind of piston, together with a fire ring, prevents bore polishing of the cylinder liner and reduces lube-oil consumption. Furthermore, the chromium-ceramic composition of the first piston ring provides a resistance that contributes to long periods between maintenance.
As with all MAN Diesel engines, NOx emission levels for 32/40 engines fall below the upper limits specified by the IMO without negatively affecting fuel consumption or operation. The 32/40 type can also take advantage of SCR (selective catalytic reduction) technology to meet even more stringent NOx limits.