MARPOL Consolidated Edition 2017

Chapter 3 - Requirements for machinery spaces of all ships
Regulation 12A
11 Alternatively to paragraphs 6 and either 7 or 8, ships sha ll comply w ith the accidental oil fuel outflow
performance standard specified below:
.1 The level of protection against oil fuel pollution in the event of collision or grounding shall be
assessed on the basis of the mean oil outflow parameter as follows:
where:
OM ~ 0.0157 - 1.14£ - 6C for 600 m 3 ~ C < 5,000 m 3
OM~ 0.010
OM = mean oil outflow parameter;
C = total oil fuel volume .
for C :2: 5,000 m 3
. 2 The following general assumption shall apply when calcu lating the mean oil outflow parameter:
.2.1 the ship shall be assumed loaded to the partial load line draught (d p) without trim or heel;
.2.2 all oil fuel tanks sha ll be assumed loaded to 98% of their volumetric capacity;
.2.3 the nominal density of the oil fuel (pn) shal l generally be taken as 1,000 kg/ m 3 . If the density
of the oil fuel is specifically restricted to a lesser value, the lesser value may be applied; and
.2.4 for the purpose of these outflow calculations, the permeability of each oil fuel tank shall be
taken as 0.99, unless proven otherwise .
. 3 The following assumptions shal I be used w hen combining the oil outflow parameters:
.3.1 The mean oil outflow shall be calcu lated independently for side damage and for bottom
damage and then combined into a non-dimensional oil outflow parameter OM, as follows:
0.40MS + 0.60MB
OM=
where:
C
OMs = mean outflow for side damage, in m 3
OMs = mean outflow for bottom damage, in m 3
C = total oil fuel volume .
. 3.2 For bottom damage, independent calculations for mean outflow shall be done for O m and
minus 2.5 m tide conditions, and then combined as fol lows:
0MB
0.70MB(O) + Q.30M8(2.5)
w here:
OMB(Ol = mean outflow for O m tide condition, and
0Ms( 2 .si = mean outflow for minus 2.5 m tide condition, in m 3 .
.4
The mean outflow for side damage O Ms shall be ca lculated as follows:
n
where:
OMs = L PsuPsui (m 3 )
n
Ps(i)
Os 111
i
= each oil fuel tank under consideration;
= total number of oil fuel tanks;
= the probability of penetrating oil fuel tank ifrom side damage, calculated in accordance
with paragraph 11.6 of this regulation;
= the outflow, in m 3 , from side damage to oil fuel tank i, which is assumed equal to the
total volume in oil fuel tank i at 98% filling.
MARPOL CONSOLIDATED EDITION 2017 59