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Handling ballast & maintaining safe stability - Self-unloading bulk carriers guideline

The Chief Officer is responsible to the Master for the safe loading or ballasting of the vessel so that stability, stress and trim are acceptable throughout the voyage, and that the vessel remains manageable in a seaway without excessive shear forces, bending moments, pounding or vibration. This is particularly important when carrying 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.

All ships are supplied with stability data, and loading and unloading instructions to comply with statutory requirements. These instructions are to be carefully studied and followed. In order to ensure adequate monitoring of the vessel’s stress and stability condition, calculations must be made and recorded, using the vessel’s loading computer, on an hourly basis during cargo and ballast operations. Intact stability criteria for any dry cargo ship has shown in digram below


If any loss of stability becomes evident during loading or discharging, all cargo, ballast and bunker operations must be stopped and a plan prepared to restore positive stability. If the vessel is at a terminal this plan must be agreed with the terminal representative, and with respect to grain loading plant, the hoses are to be disconnected.

The Chief Officer must ensure that the loading or discharging sequence is such that the vessel’s stability is never compromised and that permitted stress limits are never exceeded. The Master must check and approve all calculations for bending, stress and stability moments of the vessel.

The most critical times are during loading and discharging, during which the bending and stress limits must be carefully monitored. Care must also be exercised, to ensure that the shore installation personnel are adhering to the predetermined loading, or discharging programme.

Caution must also be exercised when loading and discharging, in a way 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.

Stress monitoring system

Some vessels may be fitted with strain/stress gauges, which will automatically alarm at pre-set levels. Whilst this equipment provides valuable information it is essential that an accurate cargo/ballast plan is calculated and that stresses will remain within acceptable limits. The vessel must not be loaded/discharged purely on the strain/stress gauges. If during cargo/ballast operations the stress alarm sounds, all operations must stop until the situation is appraised.

Ballasting and deballasting operations

Ballasting and deballasting operations must be carried out under the supervision of the Duty Officer, and are to proceed as per the ballast programme predetermined by the Chief Officer. When there is no ballast console provided in the Cargo Control Room, the Duty Engineer is to control the ballasting operation from the Engine Room. When a ballast console is provided by the Cargo Control Room, the Duty Engineer is to assist in setting the ballast lines, and assisting generally as requested by the Duty Officer. If any problem is encountered which upsets the (de) ballast programme, the Master and Chief Engineer must be informed.

When compiling the ballast programme, the Chief Officer is to take the following into account:
The Duty Officer is to closely monitor the operation, and keep in close communication with the Duty Engineer, ensuring that all is going according to the predetermined programme. Any abnormalities are to be reported immediately to the Chief Officer. Soundings are to be taken on commencement of pumping a tank, in or out, to ensure that the correct valves have been opened and the correct tank is being pumped. Soundings are also to be taken at regular intervals throughout the operation, to ensure that all is proceeding at the correct rate, and that ample warning is obtained before the need to cease operation or change tanks.

All ballast tank vent/air pipes must be opened and verified before any ballasting / deballasting operations.

Filling of double bottom tanks, hopper-side tanks, or wing tanks, is when possible to by gravitating, to avoid overflow and stress. When topping up a sounding must be taken and the pump stopped, before the water level reaches a maximum.

It must be noted that overflow of ballast may cause wetting damage to the cargo, the shore installation, electrical cables etc. Care must also be taken when discharging into barges as overflowing water can flood them.

When dumping from topside tanks using overboard dump-valves, care must be taken not to dump onto shore installations, barges etc with resultant damage and claims. Also, these types of dump valves must be closed after dumping, in order that water does not re-enter the tanks as the loading proceeds. Defective ballast tank valves must be immediately dealt with and repaired.

All remote operating valves must be operating from the remote position, and the markings of full ‘open’ and full ‘shut’ established. The reliance on remote controls of valves must be verified, as a valve could remain partially open, even if the indicator is in the fully shut position.

Fig: Intact stability criteria for dry cargo ships

Related information:

  1. Bulk carriers damage stability rules and guidelines

  2. Checklist for confirming stabilty and hull stress prior loading

Our detail pages illustrated many safety aspects of Bulk carrier

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Operation of sea going bulk carriers involved numerous hazards . Careful planning and exercising due caution for all critical shipboard matters are important . This site is a quick reference to international shipping community with guidance and information on the loading and discharging of modern bulk carriers so as to remain within the limitations as specified by the classification society.
It is vital to reduce the likelihood of over-stressing the ship's structure and also complying with all essential safety measures for a safe passage at sea. Our detail pages contain various bulk carrier related topics that might be useful for people working on board and those who working ashore in the terminal. For any remarks please Contact us

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