Recent Trends in Ship Technology (2005.04.01-2006.12.31)
The launching of The Japan Society of Naval Architects and Ocean Engineers in April 2005 by consolidating three previous organizations of naval architects (The Society of Naval Architects of Japan, The Kansai Society of Naval Architects, Japan, and The West-Japan Society of Naval Architects) paved the way to more efficient R&D activities in Japanese shipbuilding technology. As shipbuilding demand is increasing worldwide, R&D themes in shipping and shipbuilding now predominantly concern "conservation of the global environment" instead of previously favored cost saving pursuits. Many ships and offshore structures built today reflect design ideas focused on "conservation of the global environment." Also, the basic technology for the Mega-Float has been applied to conceptual designs of many recent offshore structures. This report will take up specific examples indicating the latest trends in Japan's new shipping and shipbuilding technology in this direction.
New Ships Developed and Built
Techno Super Liner (TSL)
The Techno Super Liner (TSL) was planned as an ultra-high speed cargoship embodying the foremost in Japanese shipbuilding industry, developed as a novel type vessel faster and more seaworthy than conventional vessels and capable of carrying more cargo than aircraft or trucks over a distance of 500 sea miles or greater. The TSL research project was launched in 1989, and completed with the construction of two model ships for sea trial, HISHO and HAYATE, and their trials at sea. The first TSL for commercial service was completed in the fall of 2005. This vessel is an air-cushion vehicle measuring 140 meters in overall length, 29.80 meters in breadth and 10.50 meters in depth, a catamaran built of aluminum alloy. The TSL - which was outfit with two 25,000 kW gas-turbine engines and two water jet propulsion systems as well as four 4,000 kW diesel engines for floatation - ran at a maximum speed of 42.8 knots in a sea trial, which was higher than the originally planned speed. Weighing in at some 14,000 G/T, the passenger-cargo ships can accommodate 740 passengers and a maximum of 210 tons of cargoes (40 12-foot containers). She has a cruising range of some 2,500 kilometers.
Techno Super Liner under sea trial (fall of 2005)
Courtesy of Mitsui Shipbuilding & Engineering Co., Ltd.
Super Eco-Ship MIYAJIMA MARU
MIYAJIMA MARU, co-owned by the Japan Railway Construction, Transport and Technology Agency and West Japan Railway Company, has been plying as a railway ferry between Hiroshima Prefecture's Miyajimaguchi Station in Hatsukaichi and Miyajima Station in Itsukushima since May 2006 as the first Super Eco-Ship of the agency. The 250-GT MIYAJIMA MARU is an electro-driven catamaran, measuring 35 meters in overall length and 12 meters in breadth, and powered by two prime movers including a 400-kW motor and a 360° turning twin-propeller-type POD propulsion system.
The POD propulsion system and catamaran hulls of MIYAJIMA MARU
(from the Japan Railway Construction, Transport and Technology Agency's website)
Deep-sea Drilling Vessel CHIKYU
The CHIKYU is the world's first riser-type drilling vessel intended to engage in scientific research to elucidate changes in the global environment, to search for living organisms inside the Earth's crust and to research the mechanism of earthquakes using the plate techniques theory by inquiring into the internal structure of the globe. Its operating water depth is 4,000 meters (2,500 meters in the first phase) with a drill pipe 12,000 meters long (10,000 meters in the first phase). Built jointly by Mitsubishi Heavy Industries and Mitsui Engineering & Shipbuilding, the vessel successfully test-drilled off the coast of the Shimokita Peninsula after its delivery to the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) on July 25. After its trial operation, CHIKYU will be commissioned to the Integrated Ocean Drilling Program (IODP), where it is expected to play a significant role. Measuring 192 meters in overall length, 38 meters in overall breadth, 16.2 meters in depth and drawing 9.2 meters, the 57,087-GT CHIKYU is a large research vessel accommodating a research staff of 150 persons. It is powered by a total of six azimuth thrusters (of 4,200 kW each), three each at the bow and the stern plus one side thruster (2,550 kW). The vessel is equipped with the first Japanese-built deep-sea drilling DPS to safely and accurately keep the ship's position in an offshore drilling assignment, which may take months by automatically and optimally controlling the angles and thrusts of these thrusters according to precise positional data available from GPS and other sources on a global scale. Its derrick height of over 120 meters above the sea surface, and suspension load of 1,250 tons are, respectively, the greatest in the world. Other notable features include the world's latest functions of its drilling system, which make it an offshore research base with state-of-the-art research facilities enabling on-board analysis of core samples picked up from the crust as readily as on shore. Presently, concerted government and private sector efforts are being made to support its mission to drill the Nankai Trough, and its success will once again convince the world of Japan's prowess in the shipbuilding industry. CHIKYU has been featured in many print articles both in Japan and abroad, including major mainstream newspapers, scientific periodicals and academic journals. The Japan Society of Naval Architects and Ocean Engineers also honored the vessel with the technical special award, a new prize category established in fiscal 2005.
CHIKYU at sea
A computer graphic image of CHIKYU Courtesy of JAMSTEC
Development of New Elemental Technologies
Development of Non-Ballast Water Ship (NOBS)
Development of a new ship type (non-ballast water ships, abbreviated to NOBS), which could safely navigate even without ballast when unloaded, was attempted under a three-year program beginning in fiscal 2003, as a fundamental solution to environmental problems arising from the transport of ballast water from one sea area to another. Studies were made on the optimal hull form for NOBS, a propulsion system compatible with a shallow draft and a system for estimating impacts on the hull bottom. A trial model was put to tank tests and other examinations to compare it with conventional hull forms. Furthermore, problems in practical use other than the hull form aspects were identified and economic evaluation was made by drawing a trial design which took into account structural requirements of the actual vessel and other factors; it was confirmed that the intended NOBS would be fully satisfactory in propulsion performance, hull motion performance, strength and other relevant respects. Future research is planned to pave the way for its actual application and extensive use of such vessels.
Development of NOBS (from the website of the Ministry of Land, Infrastructure and Transport (MLIT))
Development of NGH Carrier
Natural gas is an energy resource not only deposited extensively in areas other than in the Middle East but it is also clean, with less of an impact on the environment than fossil fuels. It is important because of both its availability and its environmental friendliness. In Japan, the demand for natural gas is expected to increase in the coming years as its Basic Energy Program (adopted in October 2003) under the Energy Policy Basic Law (enacted in June 2002) calls for “acceleration of shifting to natural gas.” Transport of natural gas in the natural gas hydrate (NGH: a solid substance in which natural gas molecules are surrounded by basket-shaped water molecules) form would cost much less than that in the liquefied natural gas (LNG) form in initial investments in plants and ships. Therefore, it would enable smaller gas fields, many of which are found in Oceana and Southeast Asian waters, to be economical, and accordingly it is a promising technology expected to make it possible to satisfy the expected greater natural gas needs in the future.
Regarding the marine transport of NGH, inquiries were made into the basic properties of NGH and other aspects as a basic research theme of the Japan Railway Construction, Transport and Technology Agency from fiscal 2001 through 2003. The pertinent technology was established at the laboratory level. A four-year study was commenced in fiscal 2005, focusing on the development of hold and cargo-handling systems for the carriage of NGH by sea and the optimization of transport systems. The study aims to complete an NGH transport chain, consisting of production, maritime transport, and re-gasification procedures. In fiscal 2007, a simulation test will be conducted with a large amount of NGH to understand its behavior as cargoes, while regulation discussion will begin from the fiscal year in question on the practical application of NGH carriers.
Outline of NGH Transport Chain (from the MLIT's website)
New Designing Techniques
Utilization of CFD in Propeller Designing
While the use of computer fluid dynamics (CFD) in hull form designing is becoming a general practice, it has come to be used also in the designing of propellers intended to reduce environmental loads. The Akishima Laboratories (MITSUI ZOSEN) Inc. has developed a design approach from prototype propellers, under which all specifications ― such as propeller efficiency, cavitation performance, blade strength and propeller exciting forces ― can be confirmed in a numerical simulation developed based upon the vortex lattice method and RANS (Reynold's Averaged Navier-Stokes). Using this approach together with final checks in cavitation tests, the laboratory has invented a system for designing higher-performance but smaller-exciting-forces of propellers.This system has been applied to the designing of the propeller for a 310,000 DWTclass VLCC, and its validity and reliability have been confirmed with data obtained on the actual vessel.
Development of SBD: CFD Based Hull Form Designing Technique
Whereas it is now a general practice to evaluate a hull form design by CFD, which uses numerical calculations instead of conducting tank tests, the National Maritime Research Institute has developed a simulation-based design technique with which the resistance of a high speed car ferry in smooth water is determined by CFD, and their overall evaluation is further carried out with increased resistances in the navigation of actual sea and other factors also taken into account.
Enhancement of the total operation efficiency with increased resistance due to waves is one of the most important criteria among ship operators, and this achievement is attracting notice as representing one of the directions in which Japan's technological superiority can be firmly maintained.
New Construction Methods
Use of FSW for Large High Speed Vessels
Friction stir welding (FSW) was applied to the superstructure of the ultra-high speed cargo/passenger vessel Techno Super Liner (TSL) as a new joining technique for aluminum plates to replace traditional arc welding. Previously, an aluminum manufacturer fabricated panels of 2.4 meters in maximum width for a superstructure with FSW but the recent attempt is for a maximum width of 7.8 meters. Compared with conventional arc welding of aluminum alloys, FSW has advantages in the construction process including (1) less thermal hysteresis due to the absence of melting, less deformation due to joining and freedom from welding defects such as blow holes; (2) the absence of fumes and sputters keeping the product appearance beautiful, and preventing adverse effects on the environment and workers' bodies during the process, and (3) the automated mechanical joining method assuring higher quality of joints. With the FSW process, a rotating tool (hard round rod) is inserted between the butts of the materials to be joined, and moved along the joining line while giving frictional heat. It is a revolutionary aluminum alloy joining technique to replace arc welding. The principle of FSW and how it is accomplished are illustrated below.
Principle of FSW
How sheets are joined
Superstructure member for TSL Courtesy of Mitsui Shipbuilding & Engineering Co., Ltd.
Pitting occurs in many portions of the bottom plates of crude oil tanks in double-hull VLCCs in their first two or three years of service, and shop priming is known to be effective for their prevention and, accordingly, for enhancing the structural safety of huge tankers. In this experiment, the number of holes due to pitting, which surpassed 1,000 in the first two-and-a-half years when no primer was applied, was reduced to 50 by shop priming. Qualitative analysis of cut-out samples of bottom plates of crude oil tanks revealed that shop primer became a conjugated oxide of zinc and iron, and formed a fine and hard film, whose thickness increased from 15 microns to 50 microns during the first two-and-ahalf years of service. On the other hand, steelmakers tried to develop new anti-corrosive steel by making steel plates more resistant to corrosion on the basis of the elucidated mechanism of pitting; they have succeeded in developing steel plates for crude oil tank bottoms whose maximum pitted depth detected at regular inspection could be about 30% of the usual level and therefore need no initial priming. Shop priming of these plates could further reduce the pitting prevention rate to 35%.
Development of Strongest High Tensile Steel
Mitsubishi Heavy Industries and Nippon Steel jointly developed 47 kg-class high tensile shipbuilding steel plates, the strongest in the world, and the new product item has been selected for longitudinal strength members of 8,000 TEU-class large containerships for Mitsui O.S.K. Lines. Previously the strongest steel plates for use in hull structures of general merchant ships were the 40 kg-class introduced 15 years ago but the growing thickness of such plates along with the increase in usual vessel size tends to sacrifice their tenacity. The recently developed product is not only more tenacious besides being stronger and thinner but also is as readily weld-able as the 40 kg-class steel thanks to the development of the optimal welding method. As the use of 47 kg-class high tensile steel will contribute to increasing the safety of ships by virtue of its greater tenacity, and the ultimate savings in the volume of steel used will serve to reduce the upper hull weight and, accordingly, to increase the cargo capacity. Therefore, future optimal designs of huge vessels will presuppose the improved quality of new steel.