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