Every bulk carrier has a loading and operation manual providing information about the ship's cargo and ballast loading patterns, salient structural features and strength and any restrictions or limitations on operations.
The safe operation of bulk carriers is dependant on not exceeding allowable stresses in the cycle of loading, discharging, ballasting and de-ballasting. Modern vessels now employ computer loading programmes to establish disposition of cargo, ballast fuel oil, fresh water and stores. Such software can be beneficial in producing the ships stability data, together with anticipated stress factors throughout the ships length
Your priority must always be to ensure that the proposed cargo can be safely loaded, always ensuring that your vessel has adequate stability for all stages of the intended voyage. This is particularly important for grain cargoes in the event of multiple port discharging, to ensure that grain moments are within acceptable limits when proceeding between ports with partially filled cargo compartments.
The distribution of the cargo must always be such that the vessel's stress or bending limits are never exceeded as defined by the builder's manual. Again you must ensure that this is the case for all stages of your intended voyage. The most critical times are during loading and discharging operations when it must be ensured that the shore installation personnel are adhering to the predetermined loading or discharging programme to ensure that stress and bending limits are not exceeded.
Caution must also be exercised when loading or discharging in such a manner which requires any compartment to remain empty for any stage of the voyage, such as multiple port loading/discharging or carriage of heavy cargoes which require one or more of the vessel's holds to be empty. If there is any doubt that the vessel may be over stressed during loading or discharging, operations must be ceased immediately. Operations must not be recommenced until such time as the situation has been re-checked, and you are satisfied that operations can continue without danger to the vessel.
It is the Chief Officer's responsibility to carry out the necessary calculations to ascertain the vessel's stability and stress/bending moments. It is the responsibility of the Master to check and approve or amend these as he sees fit.
Risk of exceeding loading limits
All ships engaged on international voyages are assigned with load line marks in accordance with the provisions of the International Load Line Convention 1966. The appropriate lines marked on the ship's side shall not be submerged at any time during the seagoing voyage. It is a statutory requirement that the ship is not to be loaded beyond the limits specified in its loadline certificate.
To allow for the difference between the dock water density and the sea water density, the ship may be loaded beyond the appropriate mark by the dock water allowance. The dock water allowance is only applicable in a port environment. It is a statutory requirement that the ship is not to be loaded beyond the limits specified in the Load Line Certificate.
The practice of inducing a hogging deflection of the hull girder by end hold(s) trimming to maximise the cargo carrying capacity of the ship to the appropriate marks is to be avoided as this may result in the over-loading of the end holds beyond the allowable limit and an increase in both the local and global stresses.
Risk of Heavy cargoes & Monitoring the Ship's Loading limits
Shearing forces & bending moments limitations in bulk carriers
Limitations of overloading of cargo holds - How to avoid damage from high density cargo
Structural standards & strengthening of bulk carriers
Our detail pages illustrated many safety aspects of Bulk carrier
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