New technology is ensuring the propellers for the world's largest container ships have an exact fit between the design and manufacturing geometry
While the 7.5 m-diameter propeller that welcomed delegates to this year’s SMM conference in Hamburg was certainly impressive, an even larger unit – in fact, the world’s largest so far - was awaiting transfer at the city’s docks.
The Mecklenburger Metallguss GmbH (MMG)-designed and produced unit weighs in at 110 tonnes and measures 10.5 m in diameter. It had come by road from MMG’s production facility in Waren an der Müritz in Mecklenburg-Western Pomerania, for loading onto container ship Hyundai Supreme at the port of Waltershof, with the assistance of Hamburger Hafen und Logistik’s HHL IV floating crane. Hyundai Supreme set sail for South Korea on 16 September and was under way at the time of writing.
Upon arrival at the port of Busan, the propeller will be transferred to Daewoo Shipbuilding & Marine Engineering, where it will be mounted on the first of 11 vessels being built by Daewoo and Samsung in a 5:6 split contract for Mediterranean Shipping Company (MSC).
"While these techniques have been used at smaller scales for some time, the complexity of the processes increases exponentially with component size"
MMG is designing and producing propellers for all 11 of the single-screw vessels, with six 10.4 m-diameter, 117 tonne, six-bladed units going to the Samsung vessels and five 10.5 m-diameter, 110-tonne, five-bladed units going to the Daewoo vessels. MSC’s new vessels will have a capacity of 23,000 TEU, making them the largest containerships in the world.
Other significant jobs MMG currently has on its books include nine 10.1 m-diameter, 94-tonne five-bladed units for CMA CGM’s 22,000 TEU vessels, under construction at Hudong-Zhonghua Shipbuilding and Shanghai Waigaoqiao Shipbuilding in China, and five propellers for HMM’s 23,000 TEU vessels to be built by Samsung.
MMG will utilise its Virtual Contact Test (VCT) technology to ensure certain units are fitted correctly. This optical measurement system was invented by MMG and involves the prop shaft being measured by an MMG team, with the propeller then manufactured to fit exactly, based on these measurements. VCT removes the need for male and female gauges and extra scrapping allowance entailed when using the traditional blue-bedding method. VCT is possible because all MMG propellers undergo 3D scanning, both during and at the end of production, giving the company detailed knowledge of the surface contours of the entire propeller. This exceeds the ISO standards that specify particular points of particular sections of the unit are tested. The exact picture of the propeller that this process creates ensures a true fit between the design geometry and the manufacturing geometry.
While not utilised on the propellers being manufactured for MSC’s vessels, MMG is running various research projects in the areas of 3D printing, additive manufacturing and automation of production. While these techniques have been used at smaller scales for some time now, the complexity of the processes increases exponentially with component size. MMG’s sales and project engineer Arne Falkenhorst noted the company is optimistic that it will be able to successfully upscale these techniques.