Hazards on Board Bulk Carriers

The marine industry is an essential link in international trade, with ocean-going vessels representing the most efficient and often the only method of transporting large volumes of basic commodities and finished products.

Bulk carriers play a major role in the global economy. Dry bulk cargoes cover a wide range of products. Some of the most commonly handled dry bulk materials are coal, cement, grain, sulphur, fertilizers, iron ore and sugar. These products are generally not packaged separately but transported in large quantities in the hold of a ship.

Many dry bulk cargoes are also classified as ‘dangerous goods’ requiring special attention during loading, transportation and discharging. The carriage of solid bulk cargoes possess potential hazards and thus require efficient and safe stowage and shipment.

Some of the most common hazards of bulk cargoes onboard ships are mentioned below:

1.  Cargo shift: Cargo shift has always remained one of the greatest dangers on bulk carriers. This problem is greater for ships carrying grain cargoes. Grain settles by about 2% of its volume. Because of this settling, small void spaces exist on the top of the grain surface. These void spaces permit the grain to shift. The free-flowing characteristics of grain reduce the stability of any ship carrying it. Trimming is undertaken to reduce the danger of cargo shifting. Rolling can also cause shifting of cargo from one side to the other and reduce her positive stability resulting in the vessel capsizing.

2. Cargo falling from height: Cargoes like iron ore, quartz and steel scraps are high-density cargo. There is a possibility of cargo falling from height during cargo operations. Cargo may either fall from the conveyor belt of the ship loader or from the discharging grab onto the deck of the ship. People working on the deck can get injured badly if hit by the sizeable lumps of the bulk cargo. It can be as bad as death. Cargo operation should always be monitored by responsible officers and care should be taken that no unwanted personnel are present on the working area of the deck. Persons who are involved in the cargo operation should wear protective clothing including hard hats, safety shoes and highly visible vests.

3.Dust from working cargo: Dust is one of the most common hazards in bulk carriers. Many bulk cargoes are dusty by nature. Dust particles are small enough to be inhaled and if inhaled can have disastrous effects on health. Anyone working on the deck can be exposed to high levels of dust. Dust can cause sneezing and irritation of the eyes. Where possible it is always best to avoid exposure to cargo dust however if exposure cannot be avoided protective face masks should be worn. Those involved in cargo operation and need to be present on deck when a dusty cargo is being loaded or discharged and anyone sweeping cargo with a brush or with air should wear a suitable respirator. Filters should be renewed when soiled. Deck machinery should be properly protected as it can be adversely affected by dust.

4. Cargo Liquefaction: Liquefaction is a phenomenon in which solid bulk cargoes are abruptly transformed from a solid dry state to an almost fluid state. Many common bulk cargoes such as iron ore fines, nickel ore and various mineral concentrates are examples of materials that may liquefy. Liquefaction occurs as a result of compaction of the cargo which results from engine vibrations, ship’s motion and rolling and wave impact that further causes cargo agitation.

5. Structural damage: Heavy cargoes place high loads on the structure and structural failure is therefore probable. High-density cargoes occupy a small area for a large weight that is they have a low stowage factor. It is therefore important that the tank top has sufficient strength to carry heavy cargoes like iron ore, nickel ore, bauxite etc. The load density of the tank top should never be exceeded. Tank top strength is provided in the ship’s stability booklet. Exceeding the maximum permissible cargo load in any of the holds of a ship will lead to overstressing of the local structure. Overloading will induce greater stresses in the double bottom, transverse bulkheads, hatch coamings, hatch covers, mainframes and associated brackets of individual cargo holds. Poor distribution of and/or inadequate trimming of certain cargoes can result in excessive bending and sheer forces.

6. Fire: Bulk cargoes are deemed to present a lot of fire hazards. Many bulk cargoes have a tendency to heat due to the oxidation process taking place during the voyage. Common cargoes like coal, sulphur, cotton, fishmeal are liable to spontaneous heating. Coal also emits methane which is a flammable gas. When mixed with air it can form an explosive mixture. Dust created by certain cargoes may constitute an explosion hazard. Sulphur dust can readily ignite causing an explosion. Friction between cotton bales can cause spontaneous combustion and produce heat. Fire precautions should be strictly observed on bulk carriers.

Qinhai Shipyard has many years of experience that good design, quality control, safety awareness and teamwork are the key elements to successfully complete a shipbuilding job. With the development of technology and changing needs, the shipbuilding industry is advancing and we need to keep learning and innovating to keep up with the times.

In a word，The ship as a carrier is obliged to care for the cargo in an expert manner to ensure it is discharged in the same state in which it was loaded. The IMSBC code should be consulted for the safe stowage and shipment of solid bulk cargoes. Suitable precautions and good seamanship should be adopted to minimise and overcome the hazards of bulk cargoes.