1 General

1.1 Application

1.1.1

The requirements of this section cover the strengthening requirements for localised sloshing loads that may occur in tanks carrying liquid. Sloshing loads due to the free movement of liquid in tanks are given in Ch 4, Sec 6, [6].

1.2 General requirements

1.2.1 Filling heights of cargo and ballast tanks

The scantlings of all cargo and ballast tanks are to comply with the sloshing requirements given in this section for the following cases:

Unrestricted filling height for ballast tanks,
Unrestricted filling height for cargo tanks with cargo density equal to ρ_L, as defined in Ch 4, Sec 6,
All filling levels up to h_part for cargo tanks with cargo density equal to ρ_part taken as:

where:

h_part : Maximum permissible filling height, in m, associated with a partial filling of the considered cargo tank with a high liquid density equal to ρ_part.

h_tk : Maximum tank height, in m.

ρ_L : Cargo density as defined in Ch 4, Sec 6.

f_cd : Factor defined in Ch 4, Sec 6.

ρ_part : Maximum permissible high liquid density as defined in Ch 4, Sec 6.

1.2.2 Cargo holds of bulk carrier intended for the carriage of ballast water

Cargo holds of bulk carrier intended for the carriage of ballast water are assumed either full or empty in seagoing condition and are not required to be assessed for sloshing pressures.

1.2.3 Structural details

Local scantling increases due to sloshing loads are to be made with due consideration given to details and avoidance of hard spots, notches and other harmful stress concentrations.

1.3 Application of sloshing pressure

1.3.1 General

The structural members of the following tanks are to be assessed for the design sloshing pressures P_slh-lng and P_slh-t in accordance with [1.3.4] and [1.3.5].

Cargo and slop tanks of oil tankers.
Fore peak and aft peak ballast tanks.
Other tanks which allow free movement of liquid, e.g. ballast tanks, fuel oil bunkering tanks and fresh water tanks, etc.

Where the effective sloshing length, ℓ_slh is less than 0.03 L, calculations involving P_slh-lng are not required and where the effective sloshing breadth b_slh is less than 0.32 B, calculations involving P_slh-t are not required.

1.3.2 Minimum sloshing pressure

The minimum sloshing pressure, P_slh-min, as defined in Ch 4, Sec 6, [6.2] is to apply to tanks in which the effective sloshing length, ℓ_slh or breadth b_slh, is less than defined in [1.3.1].

1.3.3 Structural members to be assessed

The following structural members are to be assessed:

Plates and stiffeners forming boundaries of tanks.
Plates and stiffeners on wash bulkheads.
Web plates and web stiffeners of primary supporting members located in tanks.
Tripping brackets supporting primary supporting members in tanks.

1.3.4 Application of design sloshing pressure due to longitudinal liquid motion

The design sloshing pressure due to longitudinal liquid motion, P_slh-lng, as defined in Ch 4, Sec 6, [6.3.3] is to be applied to the following members as shown in Figure 1.

Transverse tight bulkheads.
Transverse wash bulkheads.
Stringers on transverse tight and wash bulkheads.
Plating and stiffeners on the longitudinal bulkheads, deck and inner hull within a distance from the transverse bulkhead taken as:
- 0.25 ℓ_slh,
- The distance between the transverse bulkhead and the first web frame if located inside the tank at the considered level,
whichever is less.

In addition, the first web frame next to a transverse tight or wash bulkhead if the web frame is located within 0.25 ℓ_slh from the bulkhead, as shown in Figure 1, is to be assessed for the web frame reflected sloshing pressure, P_slh-wf, as defined in Ch 4, Sec 6, [6.3.4].

The minimum sloshing pressure, P_slh-min, as defined in Ch 4, Sec 6, [6.2] is to be applied to all other members.

Figure 1 : Application of sloshing loads due to longitudinal liquid motion

1.3.5 Application of design sloshing pressure due to transverse liquid motion

The design sloshing pressure due to transverse liquid motion, P_slh-t, as defined in Ch 4, Sec 6, [6.4.3], is to be applied to the following members as shown in Figure 2.

Longitudinal tight bulkhead.
Longitudinal wash bulkhead.
Horizontal stringers on longitudinal tight and wash bulkheads.
Plating and stiffeners on the transverse tight bulkheads including stringers and deck within a distance from the longitudinal bulkhead taken as:
- 0.25 b_slh,
- The distance between the longitudinal bulkhead and the first girder if located inside the tank at the considered level,
whichever is less.

In addition, the first girder next to the longitudinal tight or wash bulkhead if the girder is located within 0.25 b_slh from the longitudinal bulkhead, as shown in Figure 2, is to be assessed for the reflected sloshing pressure, P_slh-grd as defined in Ch 4, Sec 6, [6.4.4].

The minimum sloshing pressure, P_slh-min, as defined in Ch 4, Sec 6, [6.2], is to be applied to all other members.

Figure 2 : Application of sloshing loads due to transverse liquid motion

1.3.6 Combination of transverse and longitudinal fluid motion

The sloshing pressures due to transverse and longitudinal fluid motion are assumed to act independently. Structural members are therefore to be evaluated based on the greatest sloshing pressure due to longitudinal and transverse fluid motion.

1.3.7 Additional sloshing impact assessment

For tanks with effective sloshing breadth, b_slh, greater than 0.56 B or effective sloshing length, ℓ_slh, greater than 0.13 L, an additional sloshing impact assessment is to be carried out in accordance with the individual Society’s procedures.