- Laws of Fiji

[MAT 42,820] Oil fuel tank protection164

164

(1) 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 = B/20 m or,

h = 2.0 m, whichever is the lesser.

The minimum value of h = 0.76 m.

(2) 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 4.

Figure 4 — Oil fuel tank boundary lines for oil tankers with oil fuel capacity of 600 m³ or more but less than 5,000 m³

(3) 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 5, is measured at any cross-section at right angles to the side shell, as specified below—

w = 0.4 + 2.4 C/20,000 m

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.

(4) For ships having an aggregate oil fuel capacity of 5,000 m³ or more, 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 5, is measured at any cross-section at right angles to the side shell, as specified below—

w = 0.5 + C/20,000 m or

w = 2.0 m, whichever is the lesser.

The minimum value of w = 1.0 m

Figure 5 — Oil fuel tank boundary lines for the purposes of subregulations (3) and (4)

(5) Lines of oil fuel piping located at a distance from the ship’s bottom of less than h, as defined in subregulations (1), or from the ship’s side less than w, as defined in subregulations (3) and (4) 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.

(6) 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.

(7) Alternatively to subregulations (1) and either (3) or (4), ships shall comply with the accidental oil fuel outflow performance standard specified below—

(a)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 = mean oil outflow parameter;
C = total oil fuel volume.
(b)the following general assumption shall apply when calculating the mean oil outflow parameter—
- (i)the ship shall be assumed loaded to the partial load line draught dP without trim or heel;
- (ii)all oil fuel tanks shall be assumed loaded to 98% of their volumetric capacity;
- (iii)the nominal density of the oil fuel (Pn) 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
- (iv)for the purpose of these outflow calculations, the permeability of each oil fuel tank shall be taken as 0.99, unless proven otherwise;
(c)the following assumptions shall be used when combining the oil outflow parameters—
- (i)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—
  OM = (0.4 OMS + 0.6 OMB) / C
  where—
  OMS = mean outflow for side damage, in m³
  OMB = mean outflow for bottom damage, in m³
  C = total oil fuel volume.
- (ii)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 0m tide condition, and
  OMB(2.5) = mean outflow for minus 2.5 m tide condition, in m³.
(d)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 subregulation (7)(f);
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.
(e)the mean outflow for bottom damage shall be calculated for each tidal condition as follows—
- (i)where—
  i = represents each oil fuel tank under consideration;
  n = total number of oil fuel tanks;
  PB(i) = the probability of penetrating oil fuel tank i from bottom damage, calculated in accordance with subregulation (7)(g)
  OB(i) = the outflow from oil fuel tank i, in m³, calculated in accordance with subregulation (7)(e)(iii); and
  CDB(i) = factor to account for oil capture as defined in subregulations (7)(e)(iii).
- (ii)where—
  i, n, PB(i) and CDB(i) = as defined in this subregulation; and
  OB(i) = the outflow from oil fuel tank i, in m³, after tidal change.
- (iii)The oil outflow OB(i) for each oil fuel tank shall be calculated based on pressure balance principles, in accordance with the following assumptions—
  - (aa)The ship shall be assumed stranded with zero trim and heel, with the stranded draught prior to tidal change equal to the partial load line draught dP.
  - (bb)The oil fuel level after damage shall be calculated as follows—
    hF= {(dp + tC- Zl)(pS)}/pn
    where—
    hF = the height of the oil fuel surface above Zl, in m;
    tC = the tidal change, in m. Reductions in tide shall be expressed as negative values;
    Zl = the height of the lowest point in the oil fuel tank above the baseline, in m;
    pS = density of seawater, to be taken as 1,025 kg/m³; and,
    pn = nominal density of the oil fuel, as defined in subregulations (7)(b)(iii).
  - (cc)The oil outflow OB(i) for any tank bounding the bottom shell plating shall be taken to be not less than the sum of the following formula, but no more than the tank capacity—
    OB(i) = Hw A
    where—
    Hw = 1.0 m, when YB = 0
    Hw = BB/50 but not greater than 0.4 m, when YB is greater than BB/5 or 11.5 m, whichever is less and Hw is to be measured upwards from the midship flat bottom line. In the turn of the bilge area and at locations without a clearly defined turn of the bilge, Hw is to be measured from a line parallel to the midship flat bottom, as shown for distance “h” in Figure 6.
    For YB values outboard BB/5 or 11.5 m, whichever is less, Hw is to be calculated by linear interpolation.
    YB = the minimum value of YB over the length of the oil fuel tank, where at any given location, YB is the transverse distance between the side shell at waterline dB and the tank at or below waterline dB.
    A = the maximum horizontal projected area of the oil fuel tank up to the level of Hw from the bottom of the tank.
    Figure 6 — Dimensions for calculation of the minimum oil outflow for the purpose of subregulations (7)(e)(iii)(cc)
  - (dd)In the case of bottom damage, a portion from the outflow from an oil fuel tank may be captured by non-oil compartments. This effect is approximated by application of the factor CDB(i) for each tank, which shall be taken as follows—
    CDB(i) = 0.6 for oil fuel tanks bounded from below by non-oil compartments;
    CDB(i) = 1 otherwise

(f)The probability PS of breaching a compartment from side damage shall be calculated as follows—

(i) PS = PSL. PSV. PST
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;
(ii)PSa, PSf, PSu and PSl shall be determined by linear interpolation from the table of probabilities for side damage provided in subregulation (7)(f)(iii), and PSy shall be calculated from the formulas provided in that subregulation,
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 m.¹
In way of the turn of the bilge, y need not to be considered below distance h above baseline, where h is lesser of B/10, 3 m or the top of the tank.

(iii)Table of probabilities for side damage


X_a/L	P_sa	X_f/L	P_sf	Z_I/D_S	P_SI	Z_U/D_S	P_SU
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.

(g)The probability PB of breaching a compartment from bottom damage shall be calculated as follows:

(i)
- PB = PBL. PBT. PBV 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;
(ii)PBa, PBf, PBp and PBS shall be determined by linear interpolation from the table of probabilities for bottom damage provided in subregulation (7)(g)(iii), and PBz shall be calculated from the formulas provided in that subregulation, 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 subregulation (7)(f)(ii);
- 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.

(iii)Table of probabilities for bottom damage


X_a/L	P_Ba	X_f/L	P_Bf	Y_pB_B	P_Bp	Y_s/B_B	P_Bs
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	0.764	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=(14.5−67z/DS)(z/DS)forz/DS≤0.1
PBz=0.78+1.1í(z/DS-0.1)ï¿½forz/DS>0.1
PBz is not to be taken greater than 1.

(h)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 0.76 m and no closer to the side shell plating than the applicable value of w in subregulation (3) or (4).

(8) Individual oil fuel tanks shall not have a capacity of over 2,500m³.

(9) Before approving the design and construction of ships to be built in accordance with this regulation, the Chief Executive Officer shall be satisfied that the design—

(a)has due regard to the need for maintenance and inspection of wing and double bottom tanks or spaces; and
(b)is such to ensure that the ship is seaworthy in all respects.

1For symmetrical tank arrangements, damages are considered for one side of the ship only, in which case all “y” dimensions are to be measured from that side. For asymmetrical arrangements reference is made to the explanatory notes on matters related to the accidental oil outflow performance, adopted by the Organisation by resolution MEPC.122(52).

CDB(i)	=	0.6 for oil fuel tanks bounded from below by non-oil compartments;
CDB(i)	=	1 otherwise