Tankerman · Inert Gas — Topping Up Pressure
Between cargo operations, cargo tanks on an IG-fitted tanker are kept at a slight positive inert-gas pressure to:
- ACool the cargo
- BPrevent air ingress (which would raise oxygen toward the flammable range) and detect any loss of integrity✓ Correct
- CIncrease the oxygen content deliberately
- DAllow free venting to atmosphere
Explanation
A positive IG pressure (topped up by the IG plant or topping-up generator) keeps air from leaking in and raising the oxygen content of the inerted tanks. A falling pressure that cannot be held indicates a leak. Inerted tanks are kept below 8% oxygen and slightly above atmospheric pressure.
Authority: SOLAS II-2; ISGOTT
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