ORによる鉄鉱石専用船の積荷役シーケンスの決定法

抄録

Of late we observe that alien ore exporting ports have been rapidly improved in response to the jumboizing of ore carriers and bulk carriers. However, there are difficulties in preparing the practical loading procedure due to the fact that the loading rate of ore tends to exceed the ship's ballast pump capacity, and due to the port administrator's severe requirements for more than 100, 000dwt carriers that, for example, (1) berthing trim be less than 8ft., trim while loading be maintained less than 15ft., (2) loader/hatch-top clearance and ship's bottom/sea bed clearance be no less than 3ft., respectively, (3) ballasting and shifting be avoided, and de-ballasting alone be done, etc. A few of OR techniques have been applied to prepare loading procedure and computer programs were coded in FORTRAN. First method is that keeping same the lot size of cargo to be loaded at one time, ballast quantity retained in each tank to satisfy the constraints stated above was calculated for every possible loading stage. Then loading sequence which gives the least loading time was chosen by using dymamic programming. As a second method, a heuristic approach is applied to find an early-optimal loading sequence in trial-and-error manner with the lot size of cargo maximized at each stage, consequently, the number of shifts of ore loader minimized, satisfying the constraints above. The comparison made between DP and heuristic approach shows that the latter method seems more powerful when the memorial space of a computer is limited. The computer programs constructed will help deck officers prepare a loading procedure for bulk carriers berthing with arbitrary draft condition and sailing with also arbitrary loaded condition by a shipboard digital computer.