1. The main parameters relevant for the determination of the tank volumes and the location of the transverse and longitudinal bulkheads are shown in Fig. 4. LA and LF are the horizontal distance from the aft perpendicular to the aft cargo tank compartment and the horizontal distance from the fore perpendicular to the frontmost cargo tank compartment. LT, BT and DT are the cargo tank compartment length, width and depth and Vi the volume of tank i. The double hull width is denoted w and the double bottom height has notation h. The volume Vi of a given
tank is determined CH5424802 as: equation(6) Vi=CiBTLTDTVi=CiBTLTDTwhere Ci is a volumetric coefficient, accounting for the actual shape of the tank in comparison with a rectangular prism. Values for this factor are given in Table 1, taken as averages of an analysis by Smailys and Česnauskis (2006). The tank length, width and depth LT, BT and DT are determined as: equation(7) LT=(L-LA-LF)n equation(8) BT=(B-2w)m selleck equation(9) DT=D-hDT=D-hwhere n is the number of tanks in the longitudinal direction and m the number of tanks
in the transversal direction. It is thus assumed that all tanks have the same width BT and length LT. Values for LA and LF are given in Table 1, taken as average values reported by Smailys and Česnauskis (2006). The double bottom height h and double hull width w are determined based on the relevant rules for classification of ships ( Det Norske Veritas, 2007). The above information can be used to determine the set of positions of the longitudinal and transversal bulkheads, respectively noted LBH and TBH, as follows: equation(10) TBH=LA+kLT,k=0…n equation(11) LBH=w+kBT,k=0…m As the procedure to determine
tank arrangement is based on a series of simplifying assumptions, the methodology presented in Section 4.2.1 is validated by comparing the total calculated cargo tank volume with the DWT as available from the data of the 219 tankers, see Fig. 3. Fig. 5 shows a SPTLC1 comparison between the DWT as available in the tanker database (DWTD) with the DWT as calculated from the cargo tank volume (DWTC), assuming an oil density of 0.9 tonne/m3. It is seen that the calculation procedure generally overestimates the cargo tonnage. The histogram shows that the cargo tonnage is overestimated by ca. 15% on average, ranging from an underestimate of ca. 20% to a maximum overestimate of ca. 35%. Overall, the procedure thus leads to a conservative estimate for the possible oil outflow. While important for the evaluation of the oil outflow, it is not possible to validate the methodology in terms of bulkhead locations as the detailed tanker layouts are not available. A limited study by Smailys and Česnauskis (2006) indicates reasonable agreement for this aspect as well. The oil outflow in a given damage scenario for a particular tanker size and tank configuration is illustrated in Fig. 6.