As per IMSBC Code the Cargoes are divided into three groups:-
Group A Cargo: Which may liquefy if shipped at a moisture content exceeding their TML.
Group B Cargo: which possess a chemical hazard which could give rise to dangerous situation on a ship
Group C Cargo: which neither liquefy nor poses chemical hazard. Cargoes in this group may still be considered hazardous.
Classification of Solid Bulk Cargoes:-
Group B cargoes are classified in two ways within the code, Sec.9
i) Dangerous goods in solid form in bulk (under the IMDG Code)
ii) Materials Hazardous only in Bulk (MHB)
i) Dangerous goods in solid form in bulk are further classified as under:
Class 4.1: Flammable Solids
Class 4.2: Substances liable to spontaneous combustion.
Class 4.3: Substances which in contact with water emit flammable gases.
Class 5.1: Oxidizing Substances.
Class 6.1: Toxic Substances
Class 7: Radioactive Materials
Class 8: Corrosive Substances
Class 9: Miscellaneous Dangerous Substances & Articles
Substances / Cargoes classified as “dangerous goods in solid form in bulk”, will also have a UN Number in BCSN as specified under individual schedules for the cargo under the IMSBC Code.
ii) Materials Hazardous only in Bulk (MHB):
MHB are materials which possess chemical hazard when transported in bulk that do not meet the criteria for inclusion in the IMDG classes above. They present significant risk when carried in bulk and require special precaution. They are described as follows:
- Combustible solids materials which are readily combustible or easily ignitable.
- Self heating solids: Materials that Self – Heat
- Solids that evolve flammable gasses when wet.
- Solids that evolve toxic gases when wet.
- Toxic solids materials that are acutely toxic to humans if inhaled or brought into contact with skin.
- Corrosive solids: Materials that are corrosive to skin eyes metals respiratory sensitive.
Purpose and Objectives of IMSBC Code:-
- Problems involved in the carriage of bulk cargoes were recognized and an IMSBC code under the (IMO) was drawn.
- Prime hazards of solid bulk cargoes are those relating to
- Structural damage due to improper cargo distribution.
- Loss of reduction of stability during a voyage and
- Chemical reactions of cargoes.
- Primary aim of the code is
- To facilitate the safe stowage and shipment of solid bulk cargoes.
- By providing
- Information on the danger associated with the shipment of certain types of solid bulk cargoes and
- Instructions on the procedures to be adopted when the shipment of solid bulk cargoes is planned.
Precautions given in the IMSBC Code pertaining to shifting of Bulk Cargoes:
A ship’s motion may cause a cargo to shift sufficiently to cap size the vessel. Cargo shift can be divided into two types namely sliding failure or liquefaction consequences.
Precautions to prevent sliding failure:-
- Non-Cohesive Cargo with an Angle of Repose less than or equal to 30O. Have properties of that of a grain cargo & therefore should be carried according to the provisions of grain code, determining stability effect of free cargo surface.
- Non- Cohesive Cargo having Angle of Repose from 30O to 35O inclusive should be trimmed as per following contents. Unevenness of surface measure between highest & lowest leads should not exceed B/10 or Δ H = 15m.
- Cargo should be loaded with care & ensured that it is trimmed to an angle significantly less that AOR.
- Cargoes with low AOR are more likely susceptible to dry surface movement. To overcome this problem the code states that such cargo should be trimmed as reasonable level and spaces in which they are loaded should be filled as fully as is practicable with overstowing adjoining structure.
- Special securing arrangements should be made for stowing dry cargoes that flow freely by means of securing arrangements such as shifting boards or bins, etc.
Liquefaction of Cargo:-
- A cargo shift caused by liquefaction may occur when the moisture content of the cargo exceeds the TML.
- Some cargoes are susceptible to moisture migration and may develop a dangerous wet base even if the average moisture content is less than the TML. Although the cargo surface may appear dry undetected liquefaction may take place resulting in cargo shift.
Precautions for preventing Cargo shift due to Liquefaction:-
- Concentrates or other cargoes which may liquefy shall only be accepted for loading when the actual Moisture Content of cargo is less than TML not with standing the provision, such cargo may be accepted for shipment if approved on specially constructed or fitted cargo ship.
- Cargoes which contain liquid, other than packaged canned goods, shall not be stowed in the same cargo space above adjacent to these cargo spaces.
- Adequate measures shall be taken to prevent liquid entering the cargo spaces in which these solid bulk cargoes are stowed during the voyage.
- Masters shall be cautioned about possible danger of using water to coal these cargoes while at sea.
- The design and positioning of special arrangements if fitted to restrain cargo shift shall be such as to adequately restrain immense forces generated by flow movement of high density cargo but also reduce the level of potentially unsafe heeling moments developing cargo shift.
Factors to be considered by you as Chief Officer in preparing a loading / unloading plan as prescribed in Appendix 2 of IMSBC Code:
- Due consideration shall be paid to bilge wells and strainer plates for which spread preparation is necessary to facilitate drainage & to present entry of cargoes into the bilge system.
- Bilge lines, sounding pipes and other service lines within the cargo spaces shall be in good order.
- Because of the velocity at which some high-density solid BC are loaded special care may be necessary to protect cargo spaces from damage.
- As far as practicable ventilation system shall be shut down or screened and air conditioning system placed on re-circulation during loading and discharge.