Tank Inerting: This process is generally carried out after the vessel dry-docking in shipyard before they proceed to the next loading terminal for loading of cargo. Normally, a surveyor would be engaged to issue a certificate of the tank gas content to certify fit for loading at the terminal.
Tank Blanketing: Generally, this process is done onto cargo tanks that are loaded, as in the case hot work that is needed to be done on deck. The nitrogen gas serves as a layer of blanket over the cargo inside the tank so that hot work can be carried out safely on the deck. This reduces the risk of tank explosion or other unexpected accidents.
Change of Cargo: Occasionally, when the vessel is required to load a different cargo after its previous one, the requirement of the gas content in the cargo tank will be more stringent. Thus, it is necessary to purge the cargo tank to the new specified requirement of gas content as needed by the next loading terminal. For this case, a surveyor would also be engaged to certify the tank readiness with a certificate.