Why is Cargo Tank Atmosphere Evaluation Done on Tanker Ships?

Ship safety is of utmost importance, and one aspect that cannot be overlooked is the evaluation of cargo tank atmospheres. On tanker ships, cargo tank atmospheres can be hazardous for three primary reasons. These include exposure to toxic cargo gases, lack of oxygen due to cargo properties, and the risk of explosive atmospheres. This article explores the significance of evaluating cargo tank atmospheres and the methods used to ensure safety on board.

Exposure to Toxic Cargo Gases

Certain cargo gases can be highly toxic, posing a significant threat to personnel entering tanks or working near vents. These gases can interfere with the respiratory system, leading to serious health issues. Even brief exposure can result in severe damage to the respiratory tract and lead to other secondary health complications.

Lack of Oxygen

Certain cargo properties and residues can lead to a lack of oxygen in the tank atmosphere. This poses a serious suffocation risk for individuals entering the tanks or performing operations near them. The risk is heightened when hatches are closed, and ventilation systems malfunction or fail to work effectively.

Explosive Atmospheres

Cargo tank atmospheres can also contain a dangerous mixture of air and cargo vapours that fall within the explosive range. This risk is particularly high during operations such as tank cleaning and gauging, where sparks from electrostatic discharges can ignite these gases, leading to catastrophic explosions. For instance, a tanker explosion in a ship's cargo hold can cause extensive damage, as seen in a ship that experienced an explosion, resulting in the removal of an entire side of the vessel. The ship had to be stabilized and had a new section fabricated and fitted.

Evaluation Methods and Critical Safety Measures

To mitigate these risks, various portable gas instruments are used to assess cargo tank atmospheres before any entry is permitted or critical operations can be initiated. These instruments continuously monitor the presence of toxic gases, levels of oxygen, and the potential for explosive atmospheres.

Portable Gas Instruments

Portable gas detection equipment is essential for ensuring that the atmosphere in cargo tanks is safe. These devices can detect hazardous gases, including carbon monoxide, hydrogen sulfide, and other toxic substances. Additionally, they can measure the levels of oxygen and the combustible content of the air. By monitoring these parameters, the crew can prevent accidents and ensure compliance with safety regulations.

Regular Maintenance and Calibration

The effectiveness of these instruments relies heavily on regular maintenance and calibration. Manufacturers and regulatory bodies have set strict standards for the calibration of these devices, and it is crucial to adhere to these to maintain accuracy.

Training and Awareness

Crew members must undergo regular training to recognize the signs of a hazardous atmosphere and understand the procedures for safe entry into cargo tanks. Training programs should be comprehensive and diverse, covering different scenarios and emergency responses.

Emergency Response Plans

A well-defined emergency response plan is vital in the event of an unexpected situation. This plan should outline the steps to be taken to evacuate personnel, isolate the affected area, and mitigate the risk of further damage. Regular drills and updates to the plan ensure that all crew members are prepared for any emergencies.

Conclusion

Conducting thorough cargo tank atmosphere evaluation is crucial for maintaining the safety of tanker ships and their crew. By addressing the risks of toxic gases, lack of oxygen, and explosive atmospheres, we can prevent catastrophic incidents. The use of portable gas instruments, regular maintenance, and comprehensive training programs are key to ensuring a safe and secure maritime environment.

Additional Resources

For more information on cargo tank atmosphere evaluation and ship safety, visit the following resources:
Occupational Safety and Health Administration (OSHA) HazChem International Association of Fire Safety Science (IAFSS) International Maritime Organization (IMO)