Fig :Grab discharging of a typical bulk carrier
When heavy cargo is poured into a cargo space at one end of the cargo hold, the lateral cargo pressure acting on the transverse bulkhead, as a result of the cargo piling up at one end of the cargo space , will increase the loads carried by the transverse bulkhead structure and the magnitude of transverse compressive stresses in the cross deck.
When the same loading pattern is also adopted for the adjacent cargo hold , the lateral cargo pressure acting on the transverse bulkhead will be largely cancelled out. However, in this situation, a large proportion of the vertical forces on the double bottom is transferred to the bulkhead between the two loaded holds which could lead to shear buckling of the transverse bulkhead structure, compression buckling of the cross deck and increased SWBM in way of the transverse bulkhead. Cargo should always be stowed symmetrically in the longitudinal direction, and trimmed, as far as practical.
Stowing cargo asymmetrically about the ship's centre line in a cargo space induces torsional loads into the structure which causes twisting of the hull girder. When the hull girder is subjected to torsion, warping of the hull section occurs which gives rise to shearing and bending of the cross deck structure. Water ballast should always be carried symmetrically in port and starboard tanks with equal levels of filling. The final fill level of all water ballast tanks and holds must satisfy the requirements specified in the ship's approved loading manual to avoid damage to the internal structure due to sloshing effects.
For the Ballast Water Management Plan to be effective the Master and chief officer must ensure that it is:
- available to guide crew in safe operation of the BWM system realistic, practical, and easy to use
- understood by everybody engaged in ballast water management, both on board and ashore
- evaluated, reviewed, and updated as necessary
- consistent with the operational ballasting requirements of the ship written in the working language of the ship
- approved by a recognised Classification Society.
The ballasting and deballasting of port and starboard ballast tanks should be carried out simultaneously so that the amount of water ballast in each corresponding pair of port and starboard ballast tanks remains the same through out ballasting or deballasting operations . Asymmetrical distribution of water ballast induces torsional loads, causing twisting of the hull girder.
Torsional loading of the hull girder is considered to be an important contributory factor to recurring cracking at the hatch corners and to problems associated with hatch cover alignment and fittings. In extreme cases, this can lead to extensive buckling of the cross deck structure between the hatch openings.
Exceeding the permissible limits specified in the ship's approved loading manual will lead to over-stressing of the ship's structure and may result in catastrophic failure of the hull structure.
Ballast exchange procedure at sea
Practical method for the control of transportation of harmful marine organisms
Safety precautions during ballast operation
Regulation of pumping system of bulk carriers
Risk of partially filled ballast tanks
Handling water ingress problems in bulk carrier, investigation and countermeasures
- MARPOL 73/78
- IMO Resolution A.774 (18) Guidelines for Preventing the Introduction of Unwanted Aquatic Organisms and Pathogens from Ships Ballast Water and Sediment Discharged
- Ships Procedure and Arrangements manual (Approved by Class)
- Guide to Port Entry
- US NPDES Vessel General Permit Compliance Manual
- Bulk carrier types - Ore carriers, OBO ships, forest product carrier , self unloader and more
- Risk of partially filled ballast tanks
- Bulk carrier design limitations - Over stressing on ships structure & countermeasures
- Causes of structural damage and countermeasures
- Deterioration of ships hull and consequences of hull damage /forward flooding
- Bulk carrier hull damage - causes and preventive measures
- Ventilation requirement for bulk cargo loaded
- How to avoid damage during cargo operation
- How to arrange repair of damage during cargo loading/unloading
- Limitations of overloading of cargo holds & countermeasures
- Preparation for ships carrying bulk cargo & standard loading condition
- Various categories of garbage and management onboard
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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