SHIP OPERATIONAL AND SAFETY ASPECTS OF BALLAST WATER EXCHANGE AT SEA

A dry bulk carrier, a tanker, and a containership-taken as typical of ships trading to U.S. ports-are analyzed for possible hazards caused b y emptying and refilling ballast tanks at sea. Using hydrostatic data furnished by the shipowners, hull bending moments and stabilities are investigated to find the tank-emptying operations that produce the gre atest changes in those parameters. As should be expected, bending mome nt changes do not exceed allowable stillwater values. Changes in GM ar e insignificant. The worst hydrostatic cases serve as a guide to condi tions that should be analyzed in rough water. The University of Michig an SHIPMO program shows that in waves of 10-ft significant height wave -induced bending moments and shears are far below the design values pu blished by the American Bureau of Shipping. On the other hand, in wave s of 20-ft significant height, the maximum wave heights that occur occ asionally can cause moments or shears that exceed design values. For t he 20-ft case, both linear and nonlinear versions of SHIPMO are used.