5.11 Gas-freeing
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Statutory Documents - IMO Publications and Documents - Specifications and Manuals - Inert Gas Systems - 5 Application to Cargo Tank Operation - 5.11 Gas-freeing

5.11 Gas-freeing

  5.11.1 Gas-freeing of cargo tanks should only be carried out when tank entry is necessary (e.g. for essential repairs). It should not be started until it is established that a flammable atmosphere in the tank will not be created as a result. Hydrocarbon gases should be purged from the tank (see 5.10).

  5.11.2 Gas-freeing may be effected by pneumatically, hydraulically or steam-driven portable blowers, or by fixed equipment. In either case it is necessary to isolate the appropriate tanks to avoid contamination from the inert gas main.

  5.11.3 Gas-freeing should continue until the entire tank has an oxygen content of 21% by volume and a reading of less than 1% of lower flammable limit is obtained on a combustible gas indicator. Care must be taken to prevent the leakage of air into inerted tanks, or of inert gas into tanks which are being gas-freed.

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