Tank cleaning
- Carry clean ballast.
- Gas-free tanks for internal inspections, repairs, or before entering the dry dock.
- Remove sediments from tank top plating.
Tank cleaning is the process of removing hydrocarbon vapors, liquids, or residues from cargo tanks onboard a tanker. Tank cleaning may be required for one or more of the following reasons: To carry clean ballast. To gas-free tanks for internal inspections, repairs, or before entering the dry dock. To remove sediments from tank top plating. This may be required if the vessel is engaged in the repetitive carriage of fuel oil or similar sediment settling cargoes to meet specifications performing tank Inspection too.
Cargo Tank entry shall not be permitted unless the Oxygen Content is 21%, and the hydrocarbon vapor content is less than 1% of the Lower Flammable Level (LFL). Follow the company's "Procedure for Entry into Enclosed Spaces" with related permits. If the previous cargo contains Hydrogen Sulfide (H2S) or other toxic contaminants that could evolve poisonous gases (e.g., benzene, toluene, Mercaptans, etc.), the tank should be checked for such gases. Carrying out "Hot Work" inside Tanks within the 'Dangerous Area' need special caution as per "Procedures for Hot Work" and carry out preparation accordingly.
For the operations to be followed, (Tank cleaning, H.C. Gas Purging, Gas Freeing, and Re-Inerting), the Chief Officer shall carry out the following precautions. Detailed guidance on preparations and safety precautions are also described within relevant sections of ISGOTT. Have persons engaged in the operations observe the necessary precautions described in this section and the "Precautions during Gas-freeing Operations." Complete the necessary sections of "Tank Cleaning, Purging and Gas Freeing Checklist" to strictly confirm safety.
Tank cleaning procedures
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1)Tank preparation. The tank must be emptied and purged to remove any
flammable or toxic gases or vapours before cleaning commences.
2)Chemical product selection.
3)Application of chemical products.
4)Exposure time.
5)Clearing.
6)Inspection and evaluation.
7)Increased efficiency.
8)Time and energy saving.
