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How to minimise Bulk carrier structural damages during cargo operation

When a vessel requires repairs to damaged equipment or to the hull it is necessary for the work to be carried out to the satisfaction of the classification society surveyors. In order that the ship maintains its class, approval of the repairs undertaken must be obtained from the surveyors either at the time of the repair or at the earliest opportunity

Terminal operators should be aware of the damage that their cargo handling equipment can inflict on the ship's structure. It is important that the protective coatings in cargo holds and water ballast tanks are maintained.

The cargo holds and deck areas should be inspected by the ship's deck officers upon completion of cargo discharge to identify any signs of physical damage, corrosion or coating damage to the ship's structure. Where hull damage is identified, which may affect the integrity of the hull structure and the seaworthiness of the ship, it should be reported accordingly to the classification society.

The internal hold structure and protective coatings in the cargo hold and the adjacent double bottom are vulnerable to damage when the cargo is discharged using grabs. The weight of empty grabs can be 35 tonnes. Other types of equipment employed to free and clear cargo, including hydraulic hammers fitted to extending arms of tractors and bulldozers can inflict further damage to the ship's structure, especially in way of the side shell and the associated frames and end brackets. Chipping (sharp indentations) and the local buckling or detachment of side frames at their lower connection could lead to cracking of the side shell plating which would allow the ingress of water in to the cargo space.

The protective coatings which may be required to be applied in the cargo hold are also subject to deterioration caused by the corrosive nature of the cargo, high temperature cargoes, cargo settlement during the voyage and the abrasive action of the cargo. Where no protective coatings have been applied or the applied protective coatings have broken down, the rate of corrosion in that area will greatly increase, especially when carrying corrosive cargoes, such as coal.

Corrosion will weaken the ship's structure and may, eventually, seriously affect the ship's structural integrity. The severity of the corrosion attained by a structural member may not be easily detected without close- up inspection or until the corrosion causes serious structural problems such as the collapse or detachment of hold frames resulting in cracks propagating in the side shell.

Impact damage to the inner bottom plating or the hopper sloping plating will result in the breakdown of coatings in the adjacent water ballast tanks, thereby intensifying the rate of structural deterioration.

Solas 74 as amended Chapter XII: Additional safety measures for bulk carriers Regulation 5: (This regulation applies to bulk carriers constructed on or after 1 July 1999)

Bulk carriers of 150 m in length and upwards of single side skin construction, designed to carry solid bulk cargoes having a density of 1,000 kg/m3 and above, shall have sufficient strength to withstand flooding of any one cargo hold in all loading and ballast conditions, taking also into account dynamic effects resulting from the presence of water in the hold, and taking into account the recommendations adopted by the Organization.

Regulation 6: Structural and other requirements for bulk carriers

(This regulation applies to bulk carriers constructed before 1 July 1999)

1) Bulk carriers of 150 m in length and upwards of single side skin construction, carrying solid bulk cargoes having a density of 1,780 kg/m3 and above, shall comply with the requirements of this regulation in accordance with the implementation schedule specified in regulation 3.

2) The transverse watertight bulkhead between the two foremost cargo holds and the double bottom of the foremost cargo hold shall have sufficient strength to withstand flooding of the foremost cargo hold, taking also into account dynamic effects resulting from the presence of water in the hold, in compliance with the bulk carrier bulkhead and double bottom strength standards. For the purpose of this regulation, the bulk carrier bulkhead and double bottom strength standards shall be treated as mandatory.

3) In considering the need for, and the extent of, strengthening of the transverse watertight bulkhead or double bottom to meet the requirements of paragraph 2, the following restrictions may be taken into account:

.1 restrictions on the distribution of the total cargo weight between the cargo holds; and
.2 restrictions on the maximum deadweight.

4) For bulk carriers using either of, or both, the restrictions given in paragraphs 3.1 and 3.2 above for the purpose of fulfilling the requirements of paragraph 2, these restrictions shall be complied with whenever solid bulk cargoes having a density of 1,780 kg/m3 and above are carried.

Related Info:
  1. Procedure for cargo damage survey at discharging port

  2. Requirement for ballast exchange ar sea

  3. Risk of partially filled ballast tanks

  4. Deterioration of ships hull and consequences of hull damage /forward flooding

  5. Bulk carrier hull damage - causes and preventive measures

  6. How to avoid damage during cargo operation

  7. How to arrange repair of damage during cargo loading/unloading

  8. Bulk carrier water ingress problem

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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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