Following are the hazards associated with carriage of solid bulk cargo:
- Improper weight distribution resulting in structural damage
- Excessive concentration on deck or inner bottom
- Improper distribution of weights between holds
- Improper stability or reduction in stability
- Excessive stability (stiff ship) resulting in violent rolling and possible cargo shift and structural damage.
- Reduction of stability as a result of :
- A transverse shift of the cargo surface as in the case of “DRY” cargoes and cargoes which do not become fluid when wet.
- A transverse shift of “WET” cargoes which become fluid and give rise to free surface effect.
- Spontaneous heating may occur in some cargoes eg. Fine copper ore, metal turnings and borings are subject to spontaneous heating.
- Chemical reaction. Some categories of bulk cargo may be liable to chemical reaction, eg coal cargo emits toxic or explosive gas and have the effect of causing corrosion to steel structure.
You may also know :
Bulk cargo must be properly distributed throughout the ship in order that the structure will never be over stressed.
- Where above information is not available , the following precautions should be observed :
- A general cargo vessel is normally constructed to carry cargoes of about 50 – 6Oft3/ton (1.39 to 1.67m3/tonne) when loaded to full bale and deadweight capacity. In such cases, the ship master should be provided with comprehensive loading information so that the ship may not be over stressed.
- When loading a high density bulk cargo with a S.F. of about 2Oft3/ton (0.56m3/tonne) or lower, the loaded condition are different from normal and particular attention should be paid to the distribution of weights to avoid excessive stresses.
- An excessively stiff ship may roll very violently, resulting in damage to the ship. However, a vessel with a relatively large GM is better able to resist the tendency to list, if a shift of cargo should occur.
- A stability booklet provided giving relevant information pertaining to loading, precautions and any necessary data should be provided to the Master. Prior to sailing, the Master should calculate the stability for the anticipated worst conditions during the voyage as well as that on departure and ensure they are satisfactory.
- The general fore and aft distribution of weight should not differ appreciably from that found satisfactory for general cargo.
- The maximum number of tonnes of cargo loaded in any space should not exceed : 9 x L x B x D (tonnes)
- If cargo is untrimmed, the height of the cargo pile above the floor (in Metres) should not exceed :
1.1 x D x Stowage Factor (m)
where L=L of hold(m), B=Av breadth of hold(m), D=Summer Load Draft(m), stowage factor in m3/tonne.
- If the cargo is trimmed entirely level, the maximum load in the lower hold may be increased by 20% subject to compliance with (a) in the preceding page.
- In holds with a shaft tunnel, lower holds may be loaded to 10% in excess of the trimmed or untrimmed values subject to compliance with (a). A shaft tunnel has an extra stiffening effect.