3.7 Operational measures for ships carrying timber deck cargoes
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Statutory Documents - IMO Publications and Documents - International Codes - 2008 IS Code – International Code on Intact Stability, 2008 - Part B – Recommendations for ships engaged in certain types of operations, certain types of ships and additional guidelines - Chapter 3 – Guidance in preparing stability information - 3.7 Operational measures for ships carrying timber deck cargoes

3.7 Operational measures for ships carrying timber deck cargoes

  3.7.1 The stability of the ship at all times, including during the process of loading and unloading timber deck cargo, should be positive and to a standard acceptable to the Administration. It should be calculated having regard to:

  • .1 the increased weight of the timber deck cargo due to:

    • .1.1 absorption of water in dried or seasoned timber, and

    • .1.2 ice accretion, if applicable (chapter 6 (Icing considerations));

  • .2 variations in consumables;

  • .3 the free surface effect of liquid in tanks; and

  • .4 weight of water trapped in broken spaces within the timber deck cargo and especially logs.

  3.7.2 The master should:

  • .1 cease all loading operations if a list develops for which there is no satisfactory explanation and it would be imprudent to continue loading;

  • .2 before proceeding to sea, ensure that:

    • .2.1 the ship is upright;

    • .2.2 the ship has an adequate metacentric height; and

    • .2.3 the ship meets the required stability criteria.

  3.7.3 The masters of ships having a length less than 100 m should also:

  • .1 exercise good judgement to ensure that a ship which carries stowed logs on deck has sufficient additional buoyancy so as to avoid overloading and loss of stability at sea;

  • .2 be aware that the calculated GM0 in the departure condition may decrease continuously owing to water absorption by the deck cargo of logs, consumption of fuel, water and stores and ensure that the ship has adequate GM0 throughout the voyage; and

  • .3 be aware that ballasting after departure may cause the ship's operating draught to exceed the timber load line. Ballasting and deballasting should be carried out in accordance with the guidance provided in the Code of Safe Practice for Ships Carrying Timber Deck Cargoes, 1991 (resolution A.715(17)).

  3.7.4 Ships carrying timber deck cargoes should operate, as far as possible, with a safe margin of stability and with a metacentric height which is consistent with safety requirements but such metacentric height should not be allowed to fall below the recommended minimum, as specified in part A, 3.3.2.

  3.7.5 However, excessive initial stability should be avoided as it will result in rapid and violent motion in heavy seas which will impose large sliding and racking forces on the cargo causing high stresses on the lashings. Operational experience indicates that metacentric height should preferably not exceed 3% of the breadth in order to prevent excessive accelerations in rolling provided that the relevant stability criteria given in part A, 3.3.2 are satisfied. This recommendation may not apply to all ships and the master should take into consideration the stability information obtained from the ship's stability booklet.

Parent topic: Chapter 3 – Guidance in preparing stability information
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