Cofferdams act as barriers, preventing leakage between tanks containing different liquids (e.g., fuel oil, diesel oil, lubricating oil, freshwater, and ballast water). This prevents contamination. They also facilitate tank inspection. Regular sounding of cofferdams is necessary for detecting leaks. Additionally, cofferdams contribute to the vessel's reserve buoyancy and can provide access to the main engine's holding-down bolts.

(i) Dry Cargo Ships: Cofferdams on dry cargo ships are typically located between fuel and lubricating oil tanks, between fuel oil, fresh water and ballast tanks, and around the main engine's lubricating oil drain tank.

(ii) Oil Tankers: Oil tankers have cofferdams in locations similar to dry cargo ships (between fuel tanks and other liquid tanks) but also importantly between cargo spaces and the machinery space (or pump room). Again, a cofferdam is usually present around the main engine's lubricating oil drain tank.

(i) Information About Void Space Hazards:

Void spaces are classified as enclosed spaces with potential risks due to:

• Limited openings for entry and exit.
• Poor natural ventilation, which may cause a buildup of hazardous gases.
• Lack of continuous worker occupancy, making them prone to:
  • Toxic or flammable gases (e.g., hydrocarbons, H₂S).
  • Oxygen deficiency.
  • Cargo vapours that may pose health and safety risks.
• According to SOLAS Chapter 3, Regulation 19, entry into such spaces requires regular enclosed space entry drills and rescue training every two months.

(ii) Precautions Before and During Entry

Before Entry:

• An enclosed space entry permit must be filled and signed by a responsible officer.
• Use portable instruments to measure:
  • Oxygen concentration (should be above 20%).
  • Hydrocarbons (should be below 1% of the lower explosive limit (LEL)).
  • Toxic gases (should be nil).
  1. Ensure the space is properly ventilated before entry and continuously during work.
  2. Provide adequate lighting inside the space.
  3. Conduct and document a risk assessment.
  4. Prepare rescue equipment, including breathing apparatus (BA sets) and a first aid kit, at the entrance.
  5. Establish clear communication protocols and intervals for contact.
  6. Assign a responsible person at the entrance and inform the duty officer.

  During Entry:

  • Carry a portable atmosphere testing instrument and check the space’s atmosphere at regular intervals.
  • Ensure continuous ventilation throughout the duration of the work or inspection.
  • Maintain regular communication with the supervising personnel.
  • Observe for any abnormalities, such as dizziness or unusual smells, and exit immediately if conditions become unsafe.