KUP 35 Have knowledge of safe handling, stowage and securing of cargoes, including dangerous, hazardous and harmful cargoes, and their effect on the safety of life and of the ship

Safe cargo handling, stowage, and securing are fundamental to maritime operations. These practices not only ensure the integrity of the cargo but also directly impact the safety of the ship, its crew, and the marine environment. This lesson will cover the principles and practices of cargo management, with a particular emphasis on dangerous, hazardous, and harmful cargoes.

General Principles of Cargo Handling and Stowage

Load Distribution

Proper load distribution is crucial for maintaining the ship’s stability, structural integrity, and seaworthiness.

Key Considerations:

• Even distribution of weight across the ship’s length to avoid excessive hogging or sagging.
• Vertical distribution to maintain an adequate metacentric height (GM) for stability.
• Consideration of the ship’s stress limits, including shear forces and bending moments.

Example: A 200-meter container ship is loading 5,000 TEU (Twenty-foot Equivalent Units). The cargo planner must ensure that the containers are distributed so that the ship’s draft remains within permissible limits, typically with a stern trim of no more than 1.5 meters. Heavier containers are placed lower in the stack and towards the center of the ship to lower the center of gravity and reduce stress on the hull.

Cargo Segregation

Segregation of incompatible cargoes is essential to prevent dangerous interactions.

Principles:

• Separation of reactive substances to prevent chemical interactions.
• Isolation of odor-sensitive cargoes from strong-smelling goods.
• Segregation based on physical properties (e.g., keeping dry cargoes away from moisture-sensitive goods).

Example: On a multipurpose vessel carrying both chemicals and foodstuffs, a shipment of hydrochloric acid must be stowed in a separate hold from food-grade vegetable oil to prevent any risk of contamination. Additionally, the acid containers are placed on special acid-resistant pallets and surrounded by neutralizing agents as a precautionary measure.

Handling and Stowage of Dangerous Goods

The International Maritime Dangerous Goods (IMDG) Code provides comprehensive guidelines for the safe transport of dangerous goods by sea.

Classification of Dangerous Goods

The IMDG Code classifies dangerous goods into nine classes:

1. Explosives
2. Gases
3. Flammable Liquids
4. Flammable Solids
5. Oxidizing Substances and Organic Peroxides
6. Toxic and Infectious Substances
7. Radioactive Material
8. Corrosive Substances
9. Miscellaneous Dangerous Substances and Articles

Practical Application: A chemical tanker is loading a cargo of benzene, a Class 3 flammable liquid. The crew must ensure that:

• The ship’s tanks are properly inerted to reduce oxygen levels below 8%.
• All electrical equipment in the vicinity is intrinsically safe.
• Appropriate personal protective equipment (PPE) is worn during cargo operations.
• Firefighting equipment specific to flammable liquids is readily available.

Stowage Requirements

Stowage of dangerous goods must comply with specific requirements based on their properties and potential hazards.

Key Considerations:

• On-deck vs. under-deck stowage
• Proximity to accommodation areas
• Segregation from incompatible substances
• Access for emergency response

Example: A container ship is carrying a mix of dangerous goods, including:

• 10 containers of Class 1.4S explosives (fireworks)
• 5 containers of Class 5.1 oxidizing substances (hydrogen peroxide)
• 15 containers of Class 8 corrosive substances (sulfuric acid)

The stowage plan must ensure that:

• The explosives are stowed away from the ship’s living quarters.
• The oxidizing substances are separated from any combustible materials.
• The corrosive substances are placed in areas with proper drainage and spillage containment.
• All dangerous goods containers are accessible for firefighting and emergency response.

Securing of Cargo

Proper securing prevents cargo shift, which can compromise ship stability and safety.

Lashing Systems

Various lashing systems are used depending on the cargo type:

• Container lashing systems (twist locks, lashing rods, turnbuckles)
• Web lashings for break-bulk cargo
• Chain lashings for heavy machinery
• Dunnage and blocking for general cargo

Calculation Example: A 40-foot container weighing 30 tons is stowed on the deck of a vessel. The ship is expected to encounter Beaufort force 8 winds and corresponding sea states. Using the Advanced Calculation Method from the CSS Code (Cargo Securing Systems Code):

1. Calculate the external forces acting on the container due to ship motions.
2. Determine the required strength of lashings to counteract these forces.
3. Select appropriate lashing equipment (e.g., 4 lashing rods with a minimum breaking load of 180 kN each).

Cargo Securing Manual

Every ship must have a Cargo Securing Manual approved by the flag state administration. This manual provides:

• Detailed information on the ship’s cargo securing equipment
• Guidance on the proper use of securing devices
• Calculations for determining the required strength of securing arrangements

Special Considerations for Bulk Cargoes

Bulk cargoes present unique challenges, particularly regarding stability and liquefaction risks.

Grain Cargoes

The International Grain Code provides specific requirements for the transport of grain in bulk.

Key Points:

• Proper trimming to minimize free surface effect
• Use of shifting boards or saucers to prevent cargo shift
• Calculation of volumetric heeling moment

Example: A bulk carrier is loading 50,000 tons of wheat. The grain is loaded in stages, with each hold filled to capacity and properly trimmed to eliminate any void spaces. Shifting boards are installed in partially filled holds to prevent cargo movement. Before sailing, stability calculations are performed to ensure compliance with the Grain Code’s stability criteria.

Liquefaction-Prone Cargoes

Some bulk cargoes, such as certain mineral concentrates, can liquefy if their moisture content exceeds the Transportable Moisture Limit (TML).

Safety Measures:

• Moisture content testing before loading
• Ongoing monitoring during the voyage
• Proper ventilation to prevent cargo sweating

Case Study: A bulk carrier loaded with 55,000 tons of nickel ore encounters heavy weather. Despite pre-loading moisture tests showing the cargo was below its TML, the prolonged exposure to humid conditions causes the cargo to liquefy. The ship develops a severe list due to cargo shift. This scenario emphasizes the importance of:

• Rigorous pre-loading testing
• Careful voyage planning to avoid areas of high humidity or severe weather
• Continuous monitoring of cargo condition throughout the voyage

Environmental Considerations

Cargo operations must also consider environmental protection.

Key Aspects:

• Prevention of cargo spillage into the marine environment
• Proper disposal of cargo residues and wash water
• Use of vapor recovery systems for volatile organic compounds (VOCs)

Example: A tanker loading crude oil implements the following measures:

• Closed loading system to prevent VOC emissions
• Proper setting of P/V valves to control tank pressures
• Use of oil-water separators for handling ballast water
• Implementation of a Shipboard Oil Pollution Emergency Plan (SOPEP)

Conclusion

Safe handling, stowage, and securing of cargoes are complex tasks that require a thorough understanding of various factors, including cargo properties, ship characteristics, and environmental conditions. For dangerous, hazardous, and harmful cargoes, these considerations become even more critical, with potential consequences ranging from minor incidents to catastrophic accidents.

Mastery of these principles and practices is essential for maritime professionals to ensure the safety of the ship, its crew, and the marine environment. It requires not only theoretical knowledge but also practical experience and continuous updating of skills to keep pace with evolving regulations and best practices.

By adhering to these principles and continuously improving cargo management techniques, maritime professionals can significantly enhance the safety and efficiency of shipping operations, contributing to the overall reliability and sustainability of global maritime trade.