Iranian Classification Society Rules

Section 5 Subdivision and Stability

501. General

502.

The ships that are subject to this chapter are to be accordance with the requirements of relevant international conventions in addition to the requirements of this section.

Documentation

1. Documentation for approval

- preliminary damage stability calculations

- final damage stability calculations

(not required in case of approved limit curves, or if approved lightweight data are not less fa- vourable than estimated lightweight data).

2. Documentation for information

- internal watertight integrity plan.

3. Other plans and documents deemed necessary by the Society

503.

504.

Intact stability

Under all loading conditions to be encountered in service and which are in agreement with the purpose of the ship, the intact stability shall be sufficient for satisfying damage stability requirements.

The requirements of intact stability are to be in accordance with Ch 2, 104. 1 (1)

Arc class ships

For the purpose of damage stability calculations, the following extent of ice damage shall be as- sumed

(a) longitudinal extent 0.045 of upper ice waterline length if centered forward of the point of max- imum beam on the waterline, and 0.015 of upper ice waterline length otherwise

(b) depth 760 mm measured normal to the shell over the full extent of the damage and

(4) location of ice damage from the keel to the level of 1.2 and

(5) the vertical extent of damage may be assumed from the keel to the level of

2. 1.2

When performing damage stability calculations, the number of floodable compartments shall be de-

3. termined proceeding from the location of the assumed ice damage in Table 3.39.

Arc class ships are subject to SOLAS regulation II-1/Part B-1 ~ Part B-4 shall be such that the factor , as defined in SOLAS regulation II-1/7.2, equals 1 for all loading conditions in case

4. of ice damage specified in Par 1, in positions as defined in Par 2.

Arc class ships not subject to Par 3 above shall be in accordance with the damage stability re-

Table 3.39 Location of ice damage

Item No.

Arc class

Location of ice damage mentioned in 504. 1

Arc4 ~ Arc6

Anywhere in the ice damage area

Ice strengthened salvage ships with Arc2 ~ Arc6 class

Ice strengthened ships with Arc2 and Arc3 class not mentioned in item 2

Between watertight bulkheads, platforms, decks and plating 1. With

the hull length it is permitted not to comply with the requirements for damage trim and stability where engine room located aft is flooded in case of ice damage.

Ice strengthened ships with Arc1 class not mentioned in item 2

Between watertight bulkheads, platforms, decks and plating1. With

the hull length it is permitted not to comply with the requirements for damage trim and stability where engine room located aft is flooded in case of ice damage.

Note 1 : Where the distance between two consecutive watertight structures is less than the extent of damage,

relative adjacent compartments shall be considered a single floodable compartment when checking damage stability.

505. Icebreakers

1. For the purpose of damage stability calculations, the extent of ice damage shall be determined in accordance with 504. 1.

2. Damage as defined Par 1 shall be assumed at any position along the side shell in the ice damage area.

3. Icebreakers that are subject to SOLAS regulation II-1/Part B-1 ~ Part B-4 shall be such that the factor , as defined in SOLAS regulation II-1/7.2, equals 1 for all loading conditions in case of ice damage specified in Par 1, in positions as defined in Par 2.

4. In case of the Icebreakers with freeboard length 50m and upwards that are not subject to Par 3 ,

shall be fined in

in accordance with the damage stability requirement of Par 6 considering damage as de-

Par 5 and the number of floodable compartment shall be one. However, Icebreaker3 or

Icebreaker4 which perform icebreaking operations periodically shall be in accordance with the re-

quirements in Par

6 at damage extent and its position as defined in Par 1 and 2 and the damage

extent defined in Par 5 is not considered Par 5.

5. Extent of damage

The following extent of side damage shall be assumed when making damage stability calculations.

(1) longitudinal extent : or 14.5m(whichever is less)

(2) transverse extent measured inboard of ship side at right angles to the centerline at the level of the deepest subdivision load line : 1/5 of the ship breadth B or 11.5m(whichever is less)

(3) vertical extent : from the base line upwards without limit

6. Requirements for damage stability

(1) In the final stage of flooding, the initial metacentric height of a ship in the upright condition determined, shall not be less than 0.05m. For non-passenger ships, a positive metacentric height

below 0.05m may be permitted for the Society approval.

(2) For unsymmetric flooding the angle of

upright condition in the final stage of flooding on the

heel shall not exceed 20˚ before equalization measures

and cross-flooding fitting being used, 12˚ after equalization measures and cross-flooding fittings

being used.

(3) The static stability curve of a damaged ships shall have a sufficient positive lever arm section.

In the final stage of flooding and after the equalization of the ship, a length of positive lever arm curve, flooding angle considered, shall be ensured not less than 20˚.

(4) The angle of submersion of the opening which are not equipped with watertight or weathertight covers through which water may spread to intact compartments may be taken as flooding angle.

(5) The maximum lever arm shall be at least 0.1m within this length, i.e. within the heel angel equal to the static one plus 20˚. The positive lever arm section within the said extant shall not

be less than 0.0175m·rad.

(6) In the intermediate stages of flooding, the maximum lever arm of the static stability curve shall be at least 0.05m, and the length of its positive section shall not be less than 7˚.

(7) The damage waterline shall be at least 0.3m or (whichever is less) below the opening in the bulkheads, decks and sides through which progressive flooding could take place. Such opening include the outlets of air and vent pipes and those which are closed by means of weathertight doors and covers. These do not necessarily include :

(a) non-opening side and deck scuttles

(b) manholes having covers with closely space bolts

(d) remotely controlled sliding doors, watertight doors with indication systems and access hatch normally closed at sea

506.

Requirements to watertight integrity

1. As far as practicable, tunnels, ducts or pipes which may cause progressive flooding in case of damage, are to be avoided in the damage penetration zone.

2. The scantlings of tunnels, ducts, pipes, doors, staircases, bulkheads and decks, forming watertight boundaries, are to be adequate to withstand pressure heights corresponding to the deepest equili- brium waterline in damaged condition.

3. Excluding cases that comply with Par 4, no Arc class ships and Icebreakers should carry any pol- lutant directly against the outer shell. Any pollutant should be separated from the outer shell of the ship by double skin construction of at least 760 mm in width.

4. All Arc class ships and Icebreakers should have double bottoms over the breadth and the length between forepeak and after peak bulkheads. Double bottom height should be in accordance with the rules of the Classification Societies in force. Double bottoms should not be used for the carriage of pollutants except where a double skin construction complying with Par 3 is provided, or where

working liquids, are carried in way of main machinery spaces in tanks not exceeding 20 m3 in- dividual volume.

5. All Arc class ships and Icebreakers with icebreaking bow forms and short forepeaks may dispense with double bottoms up to the forepeak bulkhead in the area of the inclined stem, provided that

the watertight compartments between the forepeak bulkhead and tween the stem and the keel are not used to carry pollutants.

the bulkhead at the junction be-

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