DETERMINACION Y CUANTIFICACION DE COLIFORMES FECALES

5.4.1 When partial filling of tanks or holds is contem- plated for sea-going conditions, the risk of significant loads due to sloshing induced by any of the ship motions is to be considered. An initial assessment is to be made to determine whether or not a higher level of sloshing investigation is required, using the following procedure which corresponds to the Level 1 Investigation outlined in the SDA Procedure for

Sloshing loads and scantling assessment, on tanks partially

filled with liquids.

5.4.2 In general, significant dynamic magnifications of the sloshing pressures are considered unlikely for the follow- ing cases:

(a) For internally stiffened tanks:

(i) where two (or more) deck girders (in the case of rolling) or deck transverses (in the case of pitching) are located not more than 25 per cent of the tank breadth or length respectively from the adjacent tank boundary, and the fill level is greater than the tank depth minus the height of the deck girders or transverses;

(ii) where the deck girders or transverses, at any location, are less than 10 per cent of the tank depth, and the fill level is greater than the tank depth minus the height of the deck girders or transverses;

(iii) where the fill level is less than the height of any bottom girders or transverses.

(b) For smooth tanks: where the fill level is less than 10 per cent or more than 97 per cent of the tank depth.

5.4.3 Significant dynamic magnification of the fluid motions, and hence the sloshing pressure, can occur if either of the following conditions exist:

(a) The natural rolling period, T_nr, of the fluid and the ship’s natural rolling period, S_nr, are within five seconds of each other.

(b) The natural pitching period, T_np, of the fluid is greater than a value of three seconds below the ship natural pitching period, S_np.

RULES ANDREGULATIONS FOR THECLASSIFICATION OFSHIPS, July 2000

Part 3, Chapter 3

LLOYD’SREGISTER OFSHIPPING

Structural Design

These values define the limits of the critical fill range for each tank.

5.4.4 The critical fill range, F_crit, is to be determined using the following formula:

F_crit =

( )[( )

( )

]

ln = natural logarithm to base e

h = for fill level at S_nr– 5 seconds

upper bound roll critical fill level

or hÿ = for fill level at S_nr+ 5 seconds lower bound roll critical fill level

or hÿ = for fill level at S_np– 3 seconds upper bound pitch critical fill level

or hÿ = for fill level at S_npseconds

The lower bound pitch critical fill level is 0,1 per cent fill. The value of F_critis limited to the range 0 to 100 per cent, see

also 5.4.6.

5.4.5 The natural periods of the ship for a given motion type are to be determined for the service loading conditions agreed between the Shipbuilder and LR. From this aspect the storm-ballast and the segregated ballast conditions and the condition with all tanks partially filled could be the most critical.

5.4.6 When a ship is to be approved for Unrestricted Filling Levels – Unspecified Loading Conditions, many arbitrary ship loading conditions are possible. In order to cover the complete range of loading conditions, the fully loaded and ballast conditions are to be considered. These two conditions give an upper and lower limit for the possible range of natural periods of the ship as shown in Fig. 3.5.3. Both the roll and pitch motion modes are to be examined.

Because of the unrestricted filling level requirement, the critical sloshing ranges extend from [S_nrBallast – 5] to [S_nrLoaded+ 5] seconds in roll and from [S_npBallast– 3] to [S_npLoaded] in pitch. Also, because of unrestricted filling levels, the ship natural period range extends from [S_nBallast] to [S_nLoaded] for both pitch and roll.

For sloshing in the roll motion mode shown in Fig. 3.5.3(a), the critical fill range extends from F₁to F₄. All fill levels between F₁and F₄are to be investigated:

• For fill levels between F₁and F₂, S_nrBallastis to be used. • For fill levels between F₃and F₄, S_nrLoadedis to be used. • For fill levels between F₂and F₃, S_nris to be equal to T_nr. Similarly, for sloshing in the pitch motion mode shown in Fig. 3.5.3(b), the critical fill range extends from F₁to F₄. All fill levels between F₁and F₄are to be investigated:

• For fill levels between F₁and F₂, S_npBallastis to be used. 4p L_s [(S_np)2_g] 4p L_s [(S_np– 3)2_g] 4p L_s [(S_nr+ 5)2_g] 4p L_s [(S_nr– 5)2_g] n n + 1 (1 + h) (1 – h) L_s 2p 100 H_t

• For fill levels between F₂and F₃, S_npis to be equal to

T_np.

• For fill levels between F₃and F₄, S_nploaded is to be used.

5.4.7 When a ship is to be approved for Restricted Filling Levels – Unspecified Loading Conditions, many arbitrary ship loading conditions are possible within the restrictions imposed. In order to cover the complete range of loading conditions, the fully loaded and ballast condition are to be considered. These two conditions give an upper and lower limit for the possible range of ship natural period. It is recognized that there might be ship natural period bands which will not be applicable as a result of the limitations on the fill levels. However, it is recommended that the Unrestricted Filling Levels – Unspecified Loading Conditions procedure outlined in 5.4.6 be applied.

Part 3, Chapter 3

(a) Roll motions 5 seconds 5 seconds Range of operating ship natural periods Fill (%) 100 F1 F2 F3 0 Snp ballast Snp loaded Period (s) (b) Pitch motions 3 seconds Range of operating ship natural periods 3945/01 F4 = 0,1

Structural Design

5.4.8 When a ship is to be approved for Unrestricted Filling Levels – Specified Loading Conditions, each specified loading condition is to be examined for the complete fill ranges to determine the critical sloshing fill range for each tank in both roll and pitch motion modes.

5.4.9 When a ship is to be approved for Restricted Filling Levels – Specified Loading Conditions, each specified loading condition is to be examined for the restricted fill ranges to determine the critical sloshing fill range for each tank in both roll and pitch motion modes.

5.4.10 Where the assessment indicates that all the intended fill levels are outside the critical fill ranges and, therefore, significant sloshing will not occur, no further evaluation is required with regard to sloshing pressure. In such cases, the scantlings of the tank boundaries are to be determined in accordance with the relevant Rule require- ments.

5.4.11 Where the separation of periods defined in 5.4.3 is not met other levels of assessment will be required as given in the SDA Procedure for Sloshing loads and scantling

assessment, on tanks partially filled with liquids.

5.4.12 The structural capability of the tank boundaries to withstand the dynamic sloshing pressures is to be examined. The magnitude of the predicted loads, together with the scantling calculations may be required to be submitted.

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Section 6

Minimum bow heights and extent