Every ship of 400 gross tonnage (GT) and above must be provided with tanks of adequate capacity to receive oil residues (sludge) extracted during the normal operation of the ship.

• Adequate Capacity: The tank capacity must be sufficient to hold sludge generated from the purification of fuel and lubricating oils, as well as separated sludge from oil filtering equipment, based on the ship's operational profile and voyage duration.
• Piping Constraints: To prevent accidental discharges, there must be no direct connection between the sludge tank discharge piping and the bilge system, oily bilge water holding tanks, or overboard discharge lines (other than the standard discharge connection to reception facilities).
• Cleaning & Design: The tanks must be designed and constructed to facilitate cleaning and the smooth discharge of residues.
• Disposal: Residues must be disposed of via the standard discharge connection to shore reception facilities, an approved onboard incinerator, or other auxiliary means approved by the administration.

This regulation is designed to mitigate the risk of oil pollution from fuel tanks in the event of a collision or grounding. It applies to ships delivered on or after August 1, 2010, with an aggregate oil fuel capacity of 600 m³ and above.

• Protective Location (Double Hulling): Oil fuel tanks must be located at a minimum protective distance from the ship's bottom and side shell plating.
• Clearance Dimensions: The required minimum distance from the side shell (width 'w') and bottom shell (height 'h') is mathematically derived based on the ship's dimensions and total fuel capacity.
• Maximum Capacity: The maximum allowable capacity of any individual oil fuel tank is restricted to 2,500 m³ to limit the volume of a potential spill.
• Suction Wells: Suction wells in oil fuel tanks may protrude into the double bottom provided they are as small as practicable. The distance from the bottom of the well to the bottom shell plating must not be less than 0.5 times the required height 'h'.

The requirements for handling machinery space bilges and utilizing the Oily Water Separator (OWS) depend strictly on the ship's gross tonnage.

• Ships of 400 GT to less than 10,000 GT: Must be fitted with approved oil filtering equipment capable of ensuring that any oily mixture discharged into the sea has an oil content not exceeding 15 parts per million (ppm).
• Ships of 10,000 GT and above: Must be equipped with the 15 ppm oil filtering equipment, a 15 ppm alarm, and an automatic stopping device. This device ensures that any overboard discharge is automatically halted if the effluent's oil content exceeds the 15 ppm limit.
• Testing Standards: Modern equipment must be type-approved in accordance with IMO Resolution MEPC.107(49), which dictates rigorous testing specifications, including the equipment's proven ability to handle heavy fuel oils and stable emulsified oils.