Hold cleaning at sea is a common practice when time constraints or port regulations make it impractical to clean cargo holds while docked. However, cleaning holds at sea comes with additional challenges, especially concerning environmental regulations, safety, and equipment usage. Here’s an overview of how it typically works:
1. Regulatory Compliance
– MARPOL (International Convention for the Prevention of Pollution from Ships) strictly regulates the discharge of any residues or washing waters from cargo holds into the ocean. Discharging cleaning wastewater containing harmful chemicals or residues is prohibited in most areas, especially near coastlines and sensitive ecological zones.
– Vessels must ensure they are in open ocean waters and comply with MARPOL Annex V guidelines when discharging hold washings, and even then, it must be free of hazardous substances.
2. Preparation for Cleaning
– Cleaning at sea typically starts with a thorough inspection of the holds to assess the condition and the extent of residue from the previous cargo.
– Safety procedures must be in place to protect the crew from hazards like slippery surfaces, falling debris, or exposure to cleaning chemicals.
3. Dry Cleaning
– Similar to cleaning in port, dry cleaning is the first step. This involves manually sweeping or vacuuming up large debris and dust, especially after dry cargoes like grains, coal, or ores.
– Special vacuum systems or pneumatic tools may be used to gather residues without creating dust clouds that could blow into the environment.
4. High-Pressure Washing
– The crew uses high-pressure water jets to wash down the interior of the cargo holds. Depending on the cargo, detergents or chemicals may be mixed with the water to break down oils, dust, or other residues.
– While using cleaning chemicals, care is taken to collect all wastewater for proper disposal, especially if it contains hazardous substances.
5. Water Collection & Disposal
– Bilge systems are used to collect the dirty water and prevent it from being discharged directly into the ocean. The collected wash water is then stored in slop tanks onboard.
– Once the ship reaches a port with adequate facilities, the wastewater is pumped off the ship and treated at a designated reception facility.
– Some ships may use onboard filtration systems to treat the water before disposal at sea (if compliant with MARPOL standards).
6. Safety Considerations
– Hold cleaning at sea is more dangerous due to ship movements, weather conditions, and limited access to external help in case of emergencies.
– Crew members need to be equipped with safety gear such as harnesses, anti-slip boots, and masks, especially in rough sea conditions or when using chemicals.
7. Environmental Considerations
– Discharging residues into the sea is subject to stringent environmental regulations, especially in Special Areas where discharges are completely prohibited, such as the Mediterranean Sea, Baltic Sea, and others. Failure to comply can result in significant fines and legal consequences.
– Some cargo residues, like coal or fertilizers, are considered harmful, and extra care must be taken to ensure these do not enter the marine environment.
8. Final Inspection and Drying
– Once the holds are cleaned, drying is done using fans or ventilation to ensure no moisture remains. This is important to avoid contamination or damage to the next cargo.
– A final inspection is conducted to verify cleanliness, especially when the ship is transitioning to carrying sensitive cargo like grains or foodstuffs.
Would you like to explore a particular aspect of hold cleaning at sea or compare it to port-based cleaning?