Protection of Fuel Tanks Safety ahead! - GL Group

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MARITIME SERVICES | ERS INTERVIEW “GL customers expect superior performance” Norbert Kray, Technical Support (BCS) nonstop: The 500 th ERS certifi cate was issued recently. The Emergency Response Service was established 13 years ago. What have you learned during these years? Henning Schier: Each emergency is different. There are no general rules. What really matters is that there are at least three people available for emergencies at any given time so we are able to address virtually any inquiry presented to us. We are optimized for stability and resilience. But inquiries often take an unexpected turn. To give an example, in December 2005 there was a fi re on board a container ship, and we had to fi nd out how various chemicals positioned in the vicinity of the fi re would react to water. By collaborating with the Hamburg fi re department, we Service of GL and the calculations they made when the ‘Kim Jacob’ had stranded gave us every reason to be satisfi ed.” The good reputation of GL’s Emergency Response Service is a fact known to many. The supplementary ERS class label is more in demand than ever before. “As of 1 January 2007, BACKGROUND: 100 YEARS OF “SOS” “S-O-S” – this distress call has saved the lives of countless seamen and passengers. One hundred years ago, on 3 October 1906, the “three dots – three dashes – three dots” signal began its career. At the fi rst International Radiotelegraphic Conference in Berlin, 139 representatives from 29 countries agreed to introduce the S-O-S Morse code distress call. Their goal was to establish an unmistakable code that could be used to alert radio stations around the world about ships in distress. Today, Morse code is no longer used in shipping. Modern ships are equipped with a satellite-based emergency radio system. The audio distress call used today is “Mayday”, derived from the French phrase “m’aidez”, meaning “help me”. Distress-at-sea calls are handled world-wide by Maritime Rescue Coordination Centres (MRCC), including the German Maritime Rescue Service (GMRS) in Bremen, which handled 1,700 emergency deployments in 2005 and closely cooperates with GL’s ERS team. 22 nonstop 4/2006 were able to provide specifi c recommendations to the ship`s crew. nonstop: How do you prepare for emergencies? Schier: Any ERS deployment requires that all necessary data about the ship have been incorporated in our mathematical model. We rehearse once or twice a month. These drills are initiated by ship-owners mostly without notice. This way, ship-owners can test emergency scenarios to see how well they cooperate with us. The drills force our team to be on guard constantly. As a consequence, we are always ready. Norbert Kray: And that includes readiness for a worst-case scenario, as well. For us, that would mean two GL-classed ships are involved in an accident at the same time. And we have the resources to deal with such a situation, as well. We wouldn’t have any problems operating two teams concurrently. nonstop: How do you cooperate with ship-owners, captains, tugboat and recovery teams? Kray: We maintain excellent relationships with national and international recovery companies. One of the most important factors for our work is the quality of Henning Schier, Emergency Response Service communication. We need an accurate, detailed description of the damages. Schier: Problems occur when we have diffi culties communicating. Sometimes a fax is illegible or there are misunderstandings because people get nervous. That is understandable during sea damage. The more important it is that we keep our calm and our eyes on the big picture. nonstop: The motto of Germanischer Lloyd is “24/7”… Kray: At ERS, we live up to that motto. Our team is available day and night, and in an emergency, everybody can be at headquarters within an hour. Quality and a strong commitment to our mission are top priorities for us. GL customers expect superior performance. We are well aware of our responsibility. MARPOL requires all oil tankers above 5,000 dwt to subscribe to an emergency response system,” Schier explains the high number of requests. “Many tankers have had to upgrade at short notice. We have profi tted from that.” Nearly 50 shipowners are currently subscribers of GL’s Emergency Response Service. 60 per cent of all ERS certificates issued to date have been for container ships, 24 per cent for tankers, and 16 per cent for other types of vessels such as bulk carriers, ferries or luxury yachts. “The ERS is available for marine ships, as well,” Norbert Kray emphasizes. “Furthermore, we are working on accelerating the data exchange between ships and emergency headquarters,” Schier adds. “The electronic process saves a full hour, helping to mitigate further risks.” Speeding up and improving its emergency service and delivering help even faster continue to be goals for Germanischer Lloyd. This necessitates exchanging information with customers continuously, not only in an emergency. “To that end, we are cooperating with the GL Academy to set up a training programme to teach customers how to handle emergencies, and to practise working with the ERS.” Courses are to begin in the autumn of 2007. ■ AG For further Information: Norbert Kray, Head of Department, Technical Support, Phone: +49 40 36149-203, E-Mail: norbert.kray@gl-group.com Henning Schier, ERS-Emergency Response Service, Phone: +49 40 36149-269, E-Mail: henning.schier@gl-group.com
Fluids in Motion What can earthquakes do to ship lift chambers? Germanischer Lloyd provides an answer Germanischer Lloyd investigated fluid motions caused by precalculated longitudinal (surge) and transverse (sway) motions of the lifting basin of the ship lift facility at China’s Three Georges Project. The investigation served to ensure the reliability and safety of this facility when earthquakes occur. Both harmonic and inharmonic motions of the lifting basin as well as the corresponding accelerations, obtained from finite element structural computations carried out by Krebs und Kiefer International, represented earthquake events in China’s Three Georges area. The precalculated motions of the ship lift chamber may lead to water spilling over the chamber’s sides and cause high structural loads acting on the chamber’s walls and bottom, especially if the period of the water’s motion inside the partially filled chamber is close to the water’s natural period. Analytical methods are unsuitable to analyze this highly nonlinear phenomenon, called sloshing. Therefore, it was necessary to employ an advanced numerical technique to obtain accurate predictions of these sloshinginduced fluid motions and loads. Elaborate Analysis The technique employed is based on simulating the twophase flow by solving the Reynolds averaged Navier-Stokes equations (RANSE), using the finite-volume code Comet. This kind of code, implementing an interface-capturing technique of the volume-of-fluid type, is the obvious choice to compute complex free-surface shapes with breaking waves, sprays, and air trapping, phenomena that should be considered to predict hydrodynamic pressures. The conservation equations for mass and momentum in their integral form serve as the starting point. The solution domain is subdivided into a finite number of control volumes that may be of arbitrary shape. The integrals are numerically approximated using the midpoint rule. The mass flux through the cell face is taken from the previous iteration, following a simple Picard iteration approach. The flow field inside the ship lift chamber was computed as a transient process. The fluid domain was idealized by a volume grid comprising about forty thousands cells for the two-dimensional discretizations and about one million cells for three-dimensional dicretizations. On the wall surfaces a no-slip condition was enforced on fluid velocities and on the turbulent kinetic energy. The time step size was chosen such that the Courant number is unity on aver- Photo: Corbis Lock. A ship waiting to be hoisted. Simulation. The ship hoist at the dam. Time Series. Normalized water level in the caisson. SHIPLIFTING | MARITIME SERVICES age. The impulse equations were discretized using 90 percent central differences and 10 percent upwind differences. The entire flow field was initialized by the hydrostatic pressure and zero velocity. At the ship lift chamber walls, no-slip conditions were enforced on fluid velocities and on the turbulent kinetic energy. Chamber motion was taken into account in two ways, namely, by moving the grid and by adding a variable body force due to chamber acceleration. Both methods gave nearly the same solution. For each time step up to ten outer iterations were needed. Various scenarios were investigated for different positions of the chamber in the lifting installation, whereby the chamber was subjected to harmonic as well as inharmonic motions. Results comprised time histories of water elevation inside the chamber, forces and moments acting on the chamber’s sides and bottom, and computer animations of the water motion inside the chamber. In general, the chamber’s sway motions were found to be more critical than the surge motions, resulting in higher wave elevations in the chamber and larger loads on the cross walls and the bottom. Furthermore, harmonic motions caused higher wave elevations to occur than inharmonic motions. Consequently, harmonic motions tended to give rise to the largest wave-induced loads. The inharmonic sway motions did not cause the maximum water elevation to exceed the height of the chamber’s longitudinal and side walls. ■ OEM For further information: Dr Ould El Moctar, Head of Department, Fluid Dynamics, Phone: +49 40 36149-1552, E-Mail: ould.el-moctar@gl-group.com nonstop 04/2006 23
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