Regulation 12A – Oil fuel
tank protection
1 This regulation shall apply to all
ships with an aggregate oil fuel capacity of 600 m3 and
above which are delivered on or after 1 August 2010, as defined in
regulation 1.28.9 of this Annex.
2 The application of this regulation
in determining the location of tanks used to carry oil fuel does not
govern over the provisions of regulation 19 of this Annex.
3 For the purpose of this regulation,
the following definitions shall apply:
-
.1 "Oil fuel" means any oil used as fuel oil in
connection with the propulsion and auxiliary machinery of the ship
in which such oil is carried.
-
.2 "Load line draught (dS)" is the
vertical distance, in metres, from the moulded baseline at mid-length
to the waterline corresponding to the summer freeboard draught to
be assigned to the ship.
-
.3 "Light ship draught" is the moulded draught
amidships corresponding to the lightweight.
-
.4 "Partial load line draught (dP)"
is the light ship draught plus 60% of the difference between the light
ship draught and the load line draught dS. The partial
load line draught (dP) shall be measured in metres.
-
.5 "Waterline (dB)" is the vertical
distance, in metres, from the moulded baseline at mid-length to the
waterline corresponding to 30% of the depth DS.
-
.6 "Breadth (BS)" is the greatest moulded
breadth of the ship, in metres, at or below the deepest load line
draught (dS).
-
.7 "Breadth (BB)" is the greatest moulded
breadth of the ship, in metres, at or below the waterline (dB).
-
.8 "Depth (DS)" is the moulded depth,
in metres, measured at mid-length to the upper deck at side. For the
purpose of the application, “upper deck” means the highest
deck to which the watertight transverse bulkheads except aft peak
bulkheads extend.
-
.9 "Length (L)" means 96% of the total length
on a waterline at 85% of the least moulded depth measured from the
top of the keel, or the length from the foreside of the stem to the
axis of the rudder stock on that waterline, if that be greater. In
ships designed with a rake of keel the waterline on which this length
is measured shall be parallel to the designed waterline. The length
(L) shall be measured in metres.
-
.10 "Breadth (B)" means the maximum breadth of
the ship, in metres, measured amidships to the moulded line of the
frame in a ship with a metal shell and to the outer surface of the
hull in a ship with a shell of any other material.
-
.11 "Oil fuel tank" means a tank in which oil
fuel is carried, but excludes those tanks which would not contain
oil fuel in normal operation, such as overflow tanks.
-
.12 "Small oil fuel tank" is an oil fuel tank
with a maximum individual capacity not greater than 30 m3.
-
.13 "C" is the ship’s total volume of oil
fuel, including that of the small oil fuel tanks, in m3,
at 98% tank filling.
-
.14 "Oil fuel capacity" means the volume of a
tank in m3, at 98% filling.
4 The provisions of this regulation
shall apply to all oil fuel tanks except small oil fuel tanks, as
defined in 3.12, provided that the aggregate capacity of such excluded
tanks is not greater than 600 m3.
5 Individual oil fuel tanks shall not
have a capacity of over 2,500 m3.
6 For ships, other than self-elevating
drilling units, having an aggregate oil fuel capacity of 600 m3 and
above, oil fuel tanks shall be located above the moulded line of the
bottom shell plating nowhere less than the distance h as specified
below:
h |
= |
2.0 m, whichever
is the lesser. |
The minimum value of h = 0.76 m
In the
turn of the bilge area and at locations without a clearly defined
turn of the bilge, the oil fuel tank boundary line shall run parallel
to the line of the midship flat bottom as shown in Figure 1.
Figure 1 Oil fuel tank boundary lines for the purpose of paragraph 6
7 For ships having an aggregate oil
fuel capacity of 600 m3 or more but less than 5,000 m3,
oil fuel tanks shall be located inboard of the moulded line of the
side shell plating, nowhere less than the distance w which, as shown
in Figure 2, is measured
at any cross-section at right angles to the side shell, as specified
below:
The minimum value of w = 1.0 m, however for individual
tanks with an oil fuel capacity of less than 500 m3 the
minimum value is 0.76 m.
8 For ships having an aggregate oil
fuel capacity of 5,000 m3 and over, oil fuel tanks shall
be located inboard of the moulded line of the side shell plating,
nowhere less than the distance w which, as shown in Figure 2, is measured
at any cross-section at right angles to the side shell, as specified
below:
w |
= |
2.0 m, whichever
is the lesser. |
The minimum value of w = 1.0 m
Figure 2 Oil fuel tank boundary lines for the purpose of paragraphs 7 and
8
9 Lines of oil fuel piping located at a distance
from the ship’s bottom of less than h, as defined
in paragraph 6, or from the ship’s side less than w,
as defined in paragraphs 7 and 8 shall be fitted with valves or similar
closing devices within or immediately adjacent to the oil fuel tank.
These valves shall be capable of being brought into operation from
a readily accessible enclosed space the location of which is accessible
from the navigation bridge or propulsion machinery control position
without traversing exposed freeboard or superstructure decks. The
valves shall close in case of remote control system failure (fail
in a closed position) and shall be kept closed at sea at any time
when the tank contains oil fuel except that they may be opened during
oil fuel transfer operations.
10 Suction wells in oil fuel tanks may protrude
into the double bottom below the boundary line defined by the distance
h provided that such wells are as small as practicable and the distance
between the well bottom and the bottom shell plating is not less than
0.5 h.
11 Alternatively to paragraphs 6 and either 7
or 8, ships shall comply with 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:
OM <
0.0157–1.14E–6·C
|
600 m3 ≤ C <
5,000 m3
|
OM < 0.010
|
C ≥ 5,000 m3
|
- Where
OM
|
= |
mean
oil outflow parameter; |
C |
= |
total oil fuel
volume. |
-
.2 The following general assumption
shall apply when calculating the mean oil outflow parameter:
-
.1 the ship shall be assumed loaded to the partial
load line draught dP without trim or heel;
-
.2 all oil fuel tanks shall be assumed loaded
to 98% of their volumetric capacity;
-
.3 the nominal density of the oil fuel (ρn)
shall generally be taken as 1,000 kg/m3. If the density
of the oil fuel is specifically restricted to a lesser value, the
lesser value may be applied; and
-
.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 shall be
used when combining the oil outflow parameters:
-
.1 The mean oil outflow shall be calculated independently
for side damage and for bottom damage and then combined into a non-dimensional
oil outflow parameter OM, as follows:
- where:
OMS
|
= |
mean
outflow for side damage, in m3
|
OMB
|
= |
mean
outflow for bottom damage, in m3
|
C |
= |
total oil fuel
volume. |
-
.2 For bottom damage, independent calculations
for mean outflow shall be done for 0 m and 2.5 m tide conditions,
and then combined as follows:
OMB
|
= |
0.7
OMB(0) + 0.3 OMB(2.5)
|
- where:
OMB(0)
|
= |
mean
outflow for 0 m tide condition, and |
OMB(2.5)
|
= |
mean
outflow for minus 2.5 m tide condition, in m3.
|
-
.4 The mean outflow for side damage
OMS shall be calculated as follows:
- where:
i |
= |
represents each
oil fuel tank under consideration; |
n |
= |
total number of
oil fuel tanks; |
PS(i)
|
= |
the
probability of penetrating oil fuel tank i from side damage, calculated
in accordance with paragraph 11.6 of this regulation; |
OS(i)
|
= |
the
outflow, in m3, from side damage to oil fuel tank i, which
is assumed equal to the total volume in oil fuel tank i at 98% filling.
|
-
.5 The mean outflow for bottom damage
shall be calculated for each tidal condition as follows:
-
.6 The probability PS of
breaching a compartment from side damage shall be calculated as follows:
-
.1
PS
|
= |
|
- where
PSL
|
= |
(1
– PSf – PSa) = probability the damage
will extend into the longitudinal zone bounded by Xa and
Xf;
|
PSV
|
= |
(1
– PSu – PSl) = probability the damage
will extend into the vertical zone bounded by Zl and Zu;
|
PST
|
= |
(1
– PSy) = probability the damage will extend transversely
beyond the boundary defined by y;
|
-
.2 PSa, PSf, PSu and
PSl shall be determined by linear interpolation from the
table of probabilities for side damage provided in 11.6.3, and PSy shall
be calculated from the formulas provided in 11.6.3, where:
PSa
|
= |
the
probability the damage will lie entirely aft of location Xa/L;
|
PSf
|
= |
the
probability the damage will lie entirely forward of location Xf/L;
|
PSl
|
= |
probability
the damage will lie entirely below the tank; |
PSu
|
= |
probability
the damage will lie entirely above the tank; and |
PSy
|
= |
probability
the damage will lie entirely outboard the tank. |
Compartment boundaries Xa, Xf,
Zl, Zu and y shall be developed as follows:
Xa
|
= |
the
longitudinal distance from aft terminal of L to the aft most point
on the compartment being considered, in m; |
Xf
|
= |
the
longitudinal distance from aft terminal of L to the foremost point
on the compartment being considered, in m; |
Zl
|
= |
the
vertical distance from the moulded baseline to the lowest point on
the compartment being considered, in m. Where Zl is greater
than DS, Zl shall be taken as DS;
|
Zu
|
= |
the
vertical distance from the moulded baseline to the highest point on
the compartment being considered, in m. Where Zu is greater
than DS, Zu shall be taken as DS;
and,
|
y |
= |
the minimum horizontal
distance measured at right angles to the centreline between the compartment
under consideration and the side shell, in mfootnote.
|
In way of the turn of the bilge, y need not to be
considered below a distance h above baseline, where h is lesser of
B/10, 3 m or the top of the tank.
-
.3 Table of Probabilities for side damage
Xa/L
|
PSa
|
|
Xf/L
|
PSf
|
|
Z1/Ds
|
PSl
|
|
Zu/DS
|
PSu
|
0,00
|
0,000
|
|
0,00
|
0,967
|
|
0,00
|
0,000
|
|
0,00
|
0,968
|
0,05
|
0,023
|
|
0,05
|
0,917
|
|
0,05
|
0,000
|
|
0,05
|
0,952
|
0,10
|
0,068
|
|
0,10
|
0,867
|
|
0,10
|
0,001
|
|
0,10
|
0,931
|
0,15
|
0,117
|
|
0,15
|
0,817
|
|
0,15
|
0,003
|
|
0,15
|
0,905
|
0,20
|
0,167
|
|
0,20
|
0,767
|
|
0,20
|
0,007
|
|
0,20
|
0,873
|
0,25
|
0,217
|
|
0,25
|
0,717
|
|
0,25
|
0,013
|
|
0,25
|
0,836
|
0,30
|
0,267
|
|
0,30
|
0,667
|
|
0,30
|
0,021
|
|
0,30
|
0,789
|
0,35
|
0,317
|
|
0,35
|
0,617
|
|
0,35
|
0,034
|
|
0,35
|
0,733
|
0,40
|
0,367
|
|
0,40
|
0,567
|
|
0,40
|
0,055
|
|
0,40
|
0,670
|
0,45
|
0,417
|
|
0,45
|
0,517
|
|
0,45
|
0,085
|
|
0,45
|
0,599
|
0,50
|
0,467
|
|
0,50
|
0,467
|
|
0,50
|
0,123
|
|
0,50
|
0,525
|
0,55
|
0,517
|
|
0,55
|
0,417
|
|
0,55
|
0,172
|
|
0,55
|
0,452
|
0,60
|
0,567
|
|
0,60
|
0,367
|
|
0,60
|
0,226
|
|
0,60
|
0,383
|
0,65
|
0,617
|
|
0,65
|
0,317
|
|
0,65
|
0,285
|
|
0,65
|
0,317
|
0,70
|
0,667
|
|
0,70
|
0,267
|
|
0,70
|
0,347
|
|
0,70
|
0,255
|
0,75
|
0,717
|
|
0,75
|
0,217
|
|
0,75
|
0,413
|
|
0,75
|
0,197
|
0,80
|
0,767
|
|
0,80
|
0,167
|
|
0,80
|
0,482
|
|
0,80
|
0,143
|
0,85
|
0,817
|
|
0,85
|
0,117
|
|
0,85
|
0,553
|
|
0,85
|
0,092
|
0,90
|
0,867
|
|
0,90
|
0,068
|
|
0,90
|
0,626
|
|
0,90
|
0,046
|
0,95
|
0,917
|
|
0,95
|
0,023
|
|
0,95
|
0,700
|
|
0,95
|
0,013
|
1,00
|
0,967
|
|
1,00
|
0,000
|
|
1,00
|
0,775
|
|
1,00
|
0,000
|
PSy shall
be calculated as follows:
PSy
|
= |
(24.96 – 199.6 y/BS)
(y/BS) |
|
for y/BS ≤
0.05
|
PSy
|
= |
0.749 + {5 – 44.4 (y/BS –
0.05)} {(y/BS) – 0.05} |
|
for 0.05 <
y/BS < 0.1
|
PSy
|
= |
0.888 + 0.56 ( y/BS -0.1) |
|
for y/BS ≥
0.1
|
PSy is not to be taken greater
than 1.
-
.7 The probability PB of
breaching a compartment from bottom damage shall be calculated as
follows:
-
.1
- where:
PBL
|
= |
(1
– PBf – PBa) = probability the damage
will extend into the longitudinal zone bounded by Xa and
Xf;
|
PBT
|
= |
(1
– PBp – PBs) = probability the damage
will extend into transverse zone bounded by Yp and Ys;
and
|
PBV
|
= |
(1
– PBz) = probability the damage will extend vertically
above the boundary defined by z;
|
-
.2 PBa, PBf, PBp and
PBs shall be determined by linear interpolation from the
table of probabilities for bottom damage provided in 11.7.3, and PBz shall be calculated from the formulas provided in 11.7.3, where:
PBa
|
= |
the
probability the damage will lie entirely aft of location Xa/L;
|
PBf
|
= |
the
probability the damage will lie entirely forward of location Xf/L;
|
PBp
|
= |
probability
the damage will lie entirely to port of the tank; |
PBs
|
= |
probability
the damage will lie entirely to starboard the tank; and |
PBz
|
= |
probability
the damage will lie entirely below the tank. |
Compartment boundaries Xa, Xf,
Yp, Ys and z shall be developed as follows:
Xa and Xf as defined in 11.6.2;
Yp
|
= |
the
transverse distance from the port-most point on the compartment located
at or below the waterline dB, to a vertical plane located
BB/2 to starboard of the ship’s centreline;
|
Ys
|
= |
the
transverse distance from the starboard-most point on the compartment
located at or below the waterline dB, to a vertical plane
located BB/2 to starboard of the ship’s centreline;
and
|
z |
= |
the minimum
value of z over the length of the compartment, where, at any given
longitudinal location, z is the vertical distance from the lower point
of the bottom shell at that longitudinal location to the lower point
of the compartment at that longitudinal location. |
-
.3 Table of probabilities for bottom damage
Xa/L
|
PBa
|
|
Xf/L
|
PBf
|
|
Yp/BB
|
PBp
|
|
Ys/BB
|
PBs
|
0,00
|
0,000
|
|
0,00
|
0,969
|
|
0,00
|
0,844
|
|
0,00
|
0,000
|
0,05
|
0,002
|
|
0,05
|
0,953
|
|
0,05
|
0,794
|
|
0,05
|
0,009
|
0,10
|
0,008
|
|
0,10
|
0,936
|
|
0,10
|
0,744
|
|
0,10
|
0,032
|
0,15
|
0,017
|
|
0,15
|
0,916
|
|
0,15
|
0,694
|
|
0,15
|
0,063
|
0,20
|
0,029
|
|
0,20
|
0,894
|
|
0,20
|
0,644
|
|
0,20
|
0,097
|
0,25
|
0,042
|
|
0,25
|
0,870
|
|
0,25
|
0,594
|
|
0,25
|
0,133
|
0,30
|
0,058
|
|
0,30
|
0,842
|
|
0,30
|
0,544
|
|
0,30
|
0,171
|
0,35
|
0,076
|
|
0,35
|
0,810
|
|
0,35
|
0,494
|
|
0,35
|
0,211
|
0,40
|
0,096
|
|
0,40
|
0,775
|
|
0,40
|
0,444
|
|
0,40
|
0,253
|
0,45
|
0,119
|
|
0,45
|
0,734
|
|
0,45
|
0,394
|
|
0,45
|
0,297
|
0,50
|
0,143
|
|
0,50
|
0,687
|
|
0,50
|
0,344
|
|
0,50
|
0,344
|
0,55
|
0,171
|
|
0,55
|
0,630
|
|
0,55
|
0,297
|
|
0,55
|
0,394
|
0,60
|
0,203
|
|
0,60
|
0,563
|
|
0,60
|
0,253
|
|
0,60
|
0,444
|
0,65
|
0,242
|
|
0,65
|
0,489
|
|
0,65
|
0,211
|
|
0,65
|
0,494
|
0,70
|
0,289
|
|
0,70
|
0,413
|
|
0,70
|
0,171
|
|
0,70
|
0,544
|
0,75
|
0,344
|
|
0,75
|
0,333
|
|
0,75
|
0,133
|
|
0,75
|
0,594
|
0,80
|
0,409
|
|
0,80
|
0,252
|
|
0,80
|
0,097
|
|
0,80
|
0,644
|
0,85
|
0,482
|
|
0,85
|
0,170
|
|
0,85
|
0,063
|
|
0,85
|
0,694
|
0,90
|
0,565
|
|
0,90
|
0,089
|
|
0,90
|
0,032
|
|
0,90
|
0,744
|
0,95
|
0,658
|
|
0,95
|
0,026
|
|
0,95
|
0,009
|
|
0,95
|
0,794
|
1,00
|
0,761
|
|
1,00
|
0,000
|
|
1,00
|
0,000
|
|
1,00
|
0,844
|
PBz shall
be calculated as follows:
PBz
|
= |
(14.5 – 67 z/DS)
(z/DS) |
|
for z/DS
≤ 0.1
|
PBz
|
= |
0.78 + 1.1 {(z/DS – 0.1)} |
|
for z/DS
> 0.1
|
PBz is not to be taken greater than 1.
|
-
.8 For the purpose of maintenance and inspection,
any oil fuel tanks that do not border the outer shell plating shall
be located no closer to the bottom shell plating than the minimum
value of h in paragraph 6 and no closer to the side shell
plating than the applicable minimum value of w in paragraph
7 or 8.
Figure 3 Dimensions for calculation of the minimum oil outflow for the purpose of
subparagraph 11.5.3.3
12 In approving the design and construction of
ships to be built in accordance with this regulation, Administrations
shall have due regard to the general safety aspects, including the
need for maintenance and inspection of wing and double bottom tanks
or spaces.
|