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Engineers from Athens-based Danaos Shipping together with ExxonMobil, re-portedly extended the overhaul interval required for a piston in a DOOSAN-MAN B&W 12-cylinder K98MC-C en- gine from 16,000 hours to 42,575 hours.A recent overhaul revealed that cylinder number 11 was in remarkably good con- dition, with a negligible liner wear rate. The achievement took place aboard the containership MV CSCL Europe, whichis chartered to China Shipping ContainerLines. Representatives from Danaos Shipping and ExxonMobil systematicallymonitored the condition of the enginethroughout the overhauling process. The results were all the more significant be- cause the containership has been slow steaming since 2009, averaging 15.6 knots with engine loads as low as 30 to 40 percent, and also operating with a re-duced cylinder oil feed rate. Since it was built in 2004, MV CSCL Europe has been lubricated with Mobil-gard 570, a cylinder oil formulated by ExxonMobil to reduce piston wear anddeposits, and to extend overhaul intervals in two-stroke diesel engines. The ship is equipped with MAN Diesel & Turbo?s Alpha Adaptive Cylinder Oil Control (ACC), a system that controls the dosage of cylinder oil according to the amount of sulfur entering the cylinder with the fuel. Danaos Shipping also uses ExxonMobil?s Cylinder Condition Monitoring (CCM)program to detect changes in cylinder condition so that vessel engineers can safely reduce Mobilgard 570 feed rates without increasing wear. Ship engineers gradually extended the overhaul period on successive pistons in the 12-cylinder engine. Overhauling started at 16,000 hours and continued atextended intervals based on the good condition of the pistons, rings and liners.In cylinder number 11, the overhaul was done at 42,575 hours. Fuel sulfur level averaged approximately 2.62 percent throughout the period. Just before cylin- der number 11 was overhauled, all mon- itoring parameters were within normalrange, based on the results of scavenge air port inspections. A graph of liner wear rate over time shows that the rate in fact fell from a high of 0.02mm/1,000 hoursto a rate at time of overhaul that was neg- ligible. The overhaul revealed that even at 42,575 hours, cylinder number 11 was in remarkably good condition, suggest-ing that the interval could have been ex- tended much further. Liner wear rate, piston ring wear and the ring groove clearance were all well below the thresh- olds identified by MAN Diesel & Turbo. No evidence of scuffing was found. Danaos Shipping used the Alpha ACC to reduce the amount of Mobilgard 570 cylinder oil from a factor of 0.34 g/k/Wh x S% to the current minimum factor of 0.2 g/k/Wh x S%, which equates to 0.6g/KWhr (the minimum setting recom-mended by MAN B&W) at normal loads.According to ExxonMobil, the benefits of using Mobilgard 570 often become even more pronounced at feed rates below 0.6 g/KWhr. ?We operate a high- quality fleet of 56 container ships with areputation for reliability and cost-effi- ciency,? said Danaos Shipping?s Techni- cal Manager Dimitrios Vastarouchas. ?We have seen that Mobilgard 570 can help significantly extend piston overhaul intervals and for us the benefits of this technical achievement are financial and environmental.? wwwexxonmobilmarinelubes.comMarch 2012 www.marinelink.com 81TECHNICALDanaos Extends Piston Overhaul from 16K to 42K Hours MV CSCL Europe?s 12-cylinder DOOSAN-MAN B&W K98MC-C engine is lubricated with Mobilgard 570, a cylinder oil for- mulated by ExxonMobil to reduce piston wear and deposits, and extend piston overhaul intervals in two-stroke marine diesel engines.Voith: First Voith Linear Jet Order Voith announced its first Voith Linear Jet order with Turbine Transfers UK for a 19m BMT Nigel Gee de- signed Wind Support Vessel. The Voith Linear Jet provides for this application a higher bollard pull without a requirement for increased installed power, allowing the vessel to work in higher sea states. Turbine Transfers - a wholly owned subsidiary of Holyhead Towing Company - operates a fleet of more than 20 fast catamarans that transport personnel and equipment to and from offshore wind turbines. Its long term customers include Siemens, RWE npower, Van Oord, Dong Energy, EnBW and Royal Boskalis Westminster. The Voith Linear Jet (VLJ), a new ship propulsor that, according to the manufactuere employs the simplicity and efficiency of a conventional propeller installation, yet delivers the possibility to design for 40 knot top speeds without the shake and rattle of an extreme power-dense propeller. Typical VLJ applications will be any ship with a mixed operating profile between low speed cruising and sprint speeds like Navy and Coastguard vessels and Yachts. Ferries operating at sustained speeds around 30 knots em- ploying high-speed or medium speed Diesel or LNG engines will also benefit of this new propulsion option. Assisting the Naval Architect with making performance predictions, Voith developed a powerful ?Numerical Towing Tank? in Computational Fluid Dynamics (CFD), optimized for the performance prediction of the Voith Linear Jet in any hull form. The VLJ Numerical Towing Tank is validated with several hull forms, with cavitation tunnel tests at tank test institutes and with VLJ self propelled hulls. www.voithturbo.com MR March 12 # 11 (81-88):MR Template 3/6/2012 12:24 PM Page 81