1 Pressure due to Liquids

1.1 Application

1.1.1 Pressures for the strength and fatigue assessments of intact conditions

The internal pressure due to liquid acting on any load point of a tank and ballast hold boundary, in kN/m², for the static (S) design load scenarios, given in Ch 4, Sec 7, is to be taken as:

P_in = P_ls but not less than 0.

The internal pressure due to liquid acting on any load point of a tank and ballast hold boundary, in kN/m², for the static plus dynamic (S+D) design load scenarios is to be derived for each dynamic load case and is to be taken as:

P_in = P_ls + P_ld but not less than 0.

where:

P_ls : Static pressure due to liquid in tanks and ballast holds, in kN/m², as defined in [1.2].

P_ld : Dynamic inertial pressure due to liquid in tanks and ballast holds, in kN/m², as defined in [1.3].

1.1.2 Pressures for the strength assessments of flooded conditions

The internal pressure in flooded condition, in kN/m², acting on any load point of the watertight boundary of a hold, tank or other space for the flooded static (S) design load scenarios, given in Ch 4, Sec 7, is to be taken as:

P_in = P_fs but not less than ρgd₀

The internal pressure in flooded condition, in kN/m², acting on any load point of the watertight boundary of a hold, tank or other space for the flooded static plus dynamic (S+D) design load scenarios, is to be derived for each dynamic load case and is to be taken as:

P_in = P_fs + P_fd but not less than ρgd₀

where:

P_fs : Static pressure of seawater in flooded condition in the compartment, in kN/m², as defined in [1.4].

P_fd : Dynamic inertial pressure of seawater in flooded condition in the compartment, in kN/m², as defined in [1.5].

For corrugations of vertically corrugated bulkheads of bulk carrier cargo holds, the flooded pressures and forces specified in [3] for bulk cargoes are to be applied.

1.2 Static liquid pressure

1.2.1 Normal operations at sea

1.2.2 Harbour/sheltered water operations

The static pressure, P_ls due to liquid in tanks and ballast holds for harbour/sheltered water operations, in kN/m², is to be taken as:

P_ls = ρ_L g (z_top – z + h_air) + P_drop for ballast tanks

P_ls = ρ_L g (z_top – z) + P_PV for cargo tanks filled with liquid cargo

P_ls = ρ_L g (z_top – z + 0.5 h_air) for ballast holds with h_air=0 and for other cases

1.2.3 Sequential ballast water exchange

The static pressure, P_ls due to liquid in ballast tanks associated with sequential ballast water exchange operations, in kN/m², is to be taken as:

P_ls = ρ_L g (z_top – z + 0.5 h_air)

1.2.4 Flow through ballast water exchange

The static pressure, P_ls due to liquid in ballast tanks associated with flow through ballast water exchange operations, in kN/m², is to be taken as:

P_ls = ρ_L g (z_top – z + h_air) + P_drop

1.2.5 Ballasting using ballast water treatment system

The static pressure, P_ls due to liquid in tanks and ballast holds associated with ballasting operations using a ballast water treatment system is to be taken as defined for sequential ballast exchange in [1.2.3]. The ship designer has to inform the Society if the ballast water treatment system implies additional pressure to be considered as P_drop, etc in addition to the pressure defined in [1.2.3].

1.2.6 Static liquid pressure for the fatigue assessment

The static pressure due to liquid in tanks and ballast holds, P_ls to be used for the fatigue assessment, in kN/m², is to be taken as:

P_ls = ρ_L g (z_top – z) for all tanks (cargo and water ballast tanks, ballast hold and other tanks).

1.3 Dynamic liquid pressure

1.3.1 The dynamic pressure, P_ld due to liquid in tanks and ballast holds, in kN/m² is to be taken as:

P_ld = f_β f_cd ρ_L [a_Z (z₀ – _z) + f_ull-l a_X (x₀ – x) + f_ull-t a_Y (y₀ – y)]

where:

ℓ_fs : Cargo tank length at the top of the tank or length of the ballast hold hatch coaming, in m.

b_top : Cargo tank breadth at the top of the tank or breadth of the ballast hold hatch coaming, in m, determined at mid length of the tank or ballast hold hatch coaming.

x₀ : X coordinate, in m, of the reference point.

y₀ : Y coordinate, in m, of the reference point.

z₀ : Z coordinate, in m, of the reference point.

The reference point is to be taken as the point with the highest value of V_j, calculated for all points that define the upper boundary of the tank or ballast hold as follows:

V_j = a_X (x_j – x_G) + a_Y (y_j – y_G) + (a_Z + g) (z_j – z_G)

where:

x_j : X coordinate, in m, of the point j on the upper boundary of the tank or ballast hold.

y_j : Y coordinate, in m, of the point j on the upper boundary of the tank or ballast hold.

z_j : Z coordinate, in m, of the point j on the upper boundary of the tank or ballast hold.

1.4 Static pressure in flooded conditions

1.4.1 Static pressure in flooded compartments

The static pressure, P_fs in kN/m², for watertight boundaries of flooded compartments is to be taken as:

P_fs = ρg (z_FD – z) but not less than 0.

where:

z_FD : Z coordinate, in m, of the freeboard deck at side in way of the transverse section considered or the deepest equilibrium waterline in the damaged condition whichever is the greater.

1.5 Dynamic pressure in flooded conditions

1.5.1 Dynamic pressure in flooded compartments

The dynamic pressure, P_fd, in kN/m², for watertight boundaries of flooded compartments is to be taken as:

P_fd = f_β ρ [a_Z (z_0FD – z) + f_ull-l a_X (x₀ – _x) + f_ull-t a_Y (y₀ – y)]

where: