Cool-Down

Gradual cooling of LNG/LPG cargo tanks with cargo vapour before loading to prevent thermal shock to membrane / pressure vessel walls.

In practice

Performed under the cargo officer's supervision before every loading. The cargo control room logs tank-wall temperatures every hour; abrupt temperature drops on membrane LNG carriers risk cracking and trigger ESD-2.

Regulatory detail & full definition

On membrane LNG carriers cool-down typically takes 8-12 hours, achieved by spraying cargo through ring-mains and bleeding vapour to the GCU. Aim is to bring the tank wall to a few degrees above cargo temperature before bulk loading at full rate. Skipping or rushing cool-down risks cracking the membrane and triggering ESD-2.

Authoritative source: IGC Code ↗

LNG carrier
Boil-Off Gas

Source: IGC Code Ch. 4 (cargo containment); SIGTTO LNG Operations Manual

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Cool-Down

In practice

Related

Cool-Down

In practice

Related