MARPOL Consolidated Edition 2017

Chapter 4 - Requirements for the cargo area of oil tankers
Regulation 23
7 The mean outflow for bottom damage shall be calculated for each tidal condition as fol lows:
n
.1 O MB(Ol = L PsuPsuiCDB(il (m 3 )
where:
represents each cargo tank under consideration;
n = the total number of cargo tanks;
P 8
u> = the probability of penetrating cargo tank i from bottom damage, calculated in
accordance with paragraph 9.1 of this regulation;
0 8
u 1
= the outflow from cargo tank i, in m 3 , calculated in accordance with paragraph 7.3 of
this regulation; and
C 08 u>= factor to account for oil capture as defined in paragraph 7.4 of this regulation
/l
.2 OMB<2.si = L PsuPs(i)CDB!il (m 3 )
w here:
i, n, P 8 lil and Cosui = as defined in subparagraph .1 above;
0 8 m = the outflow from cargo tank,~ in m 3 , after tidal change .
. 3 The oil outflow OB(il for each cargo oil tank sha ll be calculated based on pressure-balance principles,
in accordance w ith the fol lowing assumptions:
.3.1 The ship shall be assumed stranded with zero trim and heel, with the stranded draught prior
to tidal change equal to the load line draught d 5 .
. 3.2 The cargo level after damage shall be calculated as follows:
(ds + t - Z1)(p) - 1,000p
/ C S g
1c =
SEE INTERPRETATION 50
Pn
w here:
he = the height of the cargo oil above Z 1 , in metres;
tc = the tidal change, in metres. Reductions in tide shall be expressed as negati\e
values;
Z 1
= the height of the lowest point in the cargo tank above baseline, in metres;
p 5
= density of seawater, to be taken as 1,025 kg/ m 3 ;
p = if an inert gas system is fitted, the norma l overpressure, in kilopascals, to be taken
as not less than 5 kPa; if an inert gas system is not fitted, the overpressure may be
taken as 0;
g = the acceleration of gravity, to be taken as 9.81 m/ s 2 ; and
p,, = nominal density of cargo oil, ca lculated in accordance with paragraph 4.4 of this
regulation .
. 3.3 For cargo tanks bounded by the bottom shell, unless proven otherwise, oil outflow 0 8 ui shall
be taken not less than 1% of the total volume of cargo oil loaded in cargo tank i, to account
for initial exchange losses and dynamic effects due to current and waves .
. 4 In the case of bottom damage, a portion from the outflow from a cargo tank may be captured by
non-oil compartments. This effect is approximated by application of the factor CoB(i) for each tank,
which shall be taken as follows:
Cosu>= 0.6 for cargo tanks bounded from below by non-oil compartments;
Cosul= 1.0 for cargo tanks bounded by the bottom shel l.
MARPOL CONSOLIDATED EDITIO N 2017 83