MARPOL Consolidated Edition 2017
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MARPOL Consolidated Edition 2017

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06.09.2022 Views

Appendix 2Interim recommendation for a unified interpretationof regulations 18.12 to 18.15"Protective location of segregated ballast spaces"1 Regulation 18.15 of Annex I of MARPOL relating to the measurement of the 2 m minimum width of wing tanks andthe measurement of the minimum vertical depth of double bottom tanks of 2 m or ! in respect of tanks at the endsof the ship where no identifiable bilge area exists should be interpreted as given hereunder. No difficulty exists in themeasurement of the tanks in the parallel middle body of the ship where the bilge area is clearly identified. The regulationdoes not explain how the measurements should be taken.2 The minimum width of wing tanks should be measured at a height of j above the base line providing a reasonablelevel above which the 2 m width of collision protection should apply, under the assumption that in all cases ~ is abovethe upper turn of bilge amidships (see figure 1). The minimum height of double bottom tanks should be measured at avertical plane measured 0/ 5 inboard from the intersection of the shell with a horizontal line 0 / 5 above the base line (seefigure 2).3 The PAc value for a wing tank which does not have a minimum width of 2 m throughout its length would be zero; nocredit should be given for that part of the tank in which the minimum width is in excess of 2 m. No credit should be givenin the assessment of PAs to any double bottom tank, part of which does not meet the minimum depth requirementsanywhere within its length. If, however, the projected dimensions of the bottom of the cargo tank above the doublebottom fall entirely within the area of the double bottom tank or space which meets the minimum height requirement andprovided the side bulkheads bounding the cargo tank above are vertical or have a slope of not more than 45° from thevertical, credit may be given to the part of the double bottom tank defined by the projection of the cargo tank bottom.For similar cases where the wing tanks above the double bottom are segregated ballast tanks or void spaces, suchcredit may also be given. This would not, however, preclude in the above cases credit being given to a PAs value in thefirst case and to a PAc value in the second case where the respective vertical or horizontal protection complies with theminimum distances prescribed in regulation 18.15.4 Projected dimensions should be used as shown in examples of figures 3 to 8. Figures 7 and 8 representmeasurement of the height for the calculation of PAc for double bottom tanks with sloping tank top. Figures 9 and 10represent the cases where credit is given in calculation of PAs to part or the whole of a double bottom tank.Figure 1 - Measurement of minimum width of wing ballast tank at ends of shipSection viewCentretankWingtankww must be at least 2 m along the entire length of the tank for the tank to be used in the calculation of PAc156 MARPOL CONSOLIDATED EDITION 2017

Unified Interpretations - Appendix 2Figure 2 - Measurement of minimum height of double bottom tank at ends of shipSection viewDouble bottomD5h must be at least 2 m or ~. whichever is less, along the entire length of the tank for the tank to be used in thecalculation of PAsFigure 3 - Calculation of PA 0and PA 8for double bottom tank amidshipsSection view1----....L..---'-----l- i- - a-_..1-iIf hdb is at least 2 m or ~. whichever is less, along entire tank length,PA 0= h db x double bottom tank length x 2PAs = B x double bottom tank lengthIf hdb is less than 2 m or~. whichever is less,PAc = hdb x double bottom tank length x 2PAS = 0MARPOL CONSOLI DATED EDITION 201 7 157

Unified Interpretations - Appendix 2

Figure 2 - Measurement of minimum height of double bottom tank at ends of ship

Section view

Double bottom

D

5

h must be at least 2 m or ~. whichever is less, along the entire length of the tank for the tank to be used in the

calculation of PAs

Figure 3 - Calculation of PA 0

and PA 8

for double bottom tank amidships

Section view

1----....L..---'-----l- i

- - a-_..1-i

If hdb is at least 2 m or ~. whichever is less, along entire tank length,

PA 0

= h db x double bottom tank length x 2

PAs = B x double bottom tank length

If hdb is less than 2 m or~. whichever is less,

PAc = hdb x double bottom tank length x 2

PAS = 0

MARPOL CONSOLI DATED EDITION 201 7 157

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