Large Crude Oil Carrier Research Articles

Investigation of Stern Plain Bearings for Contra-Rotating Propeller System. (4th Report. Design of Stern Bearings for Large Ships and Application to a Very Large Crude Oil Carrier).

A hydrostatic bearing with pressurized oil supplied through an inner shaft was applied as a stern bearing of a 258 000 DWT tanker equipped with a contra-rotating propeller system. This paper presents the design method of this stern bearing and measurement results of oil film thickness, inner shaft center locus, inclination angle of inner shaft and temperature of the stern bearing during sea trial. It is confirmed that the stern bearing operates under full film lubrication in various operation mode, including high-speed straight run, high-speed turn, blackout and emergency sailing, and that estimated results of bearing performance, taking account of propeller forces, are in good agreement with measured ones.

Unstable Brittle Crack-Arrest Toughness of Newly Developed Steel Plate with Surface Layers having Ultra Fine Grain Microstructure (2)

A new type steel plate with ultra fine grain surface layers (SUF plate) has been developed to improve crack arrestability. In order to prevent the catastrophic damage of hull, which might cause ocean pollution and casualties, caused by serious accidents such as collisions and/or grounding of VLCCs (Very Large Crude oil Carriers), application of SUF plates with ultra-high crack arrestability has been investigated using both computer simulation for a collision of VLCCs and large scale fracture testings for crack arrestability in emergency cases.The computer simulation results suggest that a collision generates significant plastic strain in surroundings of a struck part. For example, the plastic strain reached a 5-10% level before an inner-hull of the VLCC was ruptured at sheer strake plates near the struck part.Therefore, the effect of plastic strain (10% level) on crack arrestability in steel plates (the SUF plate and a conventional TMCP plate) was examined by standard ESSO test, ultra-wide plate duplex ESSO test, and sheer strake model fracture test. The test results suggest the followings : 1) Plastic strain deteriorates crack arrestability.2) Sufficient crack arrestability at 0 deg. C cannot be expected in the conventional TMCP steel plate with 10% plastic strain induced.3) The SUF plate with 10% plastic strain induced possesses high crack arrestability against emergency cases for ships.Therefore it is expected that application of SUF plates can prevent serious accidents in which a large amount of oil flows out through hull structural plates damaged by brittle fracture.

Design of Longitudinal Beam Layout on a Curved Shell Based on the Production-Oriented Design Concept

A VLCC (very large crude oil carrier) has approximately 1000 curved longitudinal beams, many of which have three-dimensional complicated curvatures. Due to the shortage of highly skilled workers and the need to keep costs down, production and structural designers have worked to reduce the number of such beams. In order to meet the requirements of production, the authors' company has attempted several design approaches for the longitudinal beam layout to reduce the number of beams that have complicated curvature. Recently, through the application of a computer-aided design system, which has been improved for shipbuilding based on the Calma's system, a new design method for the longitudinal beam layout has been successfully developed. A significant number of beams with a twisted configuration have been eliminated and replaced with beams of simpler, two-dimensional shapes. This paper shows the transition of these design approaches, and the application of the new design to building a VLCC.

Marine structural integrity programs

This paper summarizes results from a two-year project sponsored by the Ship Structure Committee to develop a procedure for definition of advanced Marine Structural Integrity Programs (MSIP) for commercial ships that would include more efficient inspection, more economical and safer operation, and more effective maintenance. This procedure was to be based on the recent developments in Airframe Structural Integrity Programs (ASIP) for commercial and military aircraft. The MSIP procedure suggests a sequence of technical and organizational developments to better ensure the integrity and durability of ship structures during their useful lifetimes. Particular emphasis is given to large crude-oil carriers (tankers). Notwithstanding this focus, it is felt that the MSIP procedure is applicable to most commercial ships with few modifications.