Damen to supply propeller nozzles for 4 ocean going tugs
Damen Marine Components will supply a total eight 5,050 millimetre propeller nozzles for four ultra long distance towing and anchor handling vessel newbuildings.
They are the largest nozzles that DMC will have manufactured with its spinning machine technique to date. The order was granted by Caterpillar Propulsion of Gothenburg.
Caterpillar is to provide the complete main propulsion units and has commissioned Damen Marine Components, a member of the Damen Shipyards Group, to design, engineer and produce the nozzle and head box sets.
The four sister vessels are under construction in Japan for ALP Maritimes Services, a recently acquired Teekay Offshore Partners subsidiary. The 300+ tonne bollard pull, 24,400 BHP ocean towing and anchor handling vessels will have two propulsion units each in a CPP stern-drive and rudder configuration.
The vessels are primarily designed for towing of large structures over long distances. An oceangoing tug typically tow oil rigs, or FPSOs, from the building yards to the installation site at the oil field.
“We’ll manufacture the nozzles with the spinning machine in our plant in Jiang Yin, China”, DMC director Steef Staal says about the novel manufacturing technique which includes one single weld only. The nozzles – of DMC’s Optima design – have a 5,050 millimetre inside diameter to accommodate a 5,000 mm CP propeller. They will outsize any nozzle manufactured with DMC’s first spinning machine in the plant in Gdansk, Poland. The nozzles’ 0.5 L/D indicates a length of 2,500 mm, half their diameter. Steel S355J2+N will be used.
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“In co-operation with the vessels’ designers, and under Caterpillar Propulsion auspices, we’ve also engineered the streamlined head box bodies, which are part of the complete nozzle construction”, Staal adds.
“But significantly, we’ve also conducted the FEM calculations to assess the nozzles’ right frequency profile in order to prevent amplification of frequencies from snowballing with engine and propeller. The nozzles are designed with a relatively narrow head box and strut connection, but stiff enough to secure the frequency profile.
This requires a high power computer system, which is available in the Damen organization. This is one edge over other nozzle builders”, DMC’s director emphasizes. “We do not just blindly copy the propeller manufacturers’ specs. This is why the prominent OEM’s are our main clients.”
About 85 per cent of Damen Marine Components’ business production is third party (non-Damen) business.