We are all familiar with the IBC Code requirement 16.1.3:
“Tanks carrying liquids at ambient temperatures shall be so loaded as to avoid the tank becoming liquid-full during the voyage, having due regard to the highest temperature which the cargo may reach.”
However, there are many times when a chemical tanker has been diverted such that the vessel now finds the voyage route passes through temperatures at which the load calculation were not foreseen. The Panama Canal for example.
Or, when a cargo is loaded directly from the cracker and received on-board at unexpectedly high temperatures. Sodium Hydroxide for example, and were cooling is now most certainly required.
Main Deck Cooling:
Old fire hoses pricked with multiple holes then spread on the main deck and connected to the fire main had proved to reduce the main deck heat and therefore the vapour space temperature by 15 degrees C, or more.
Cargo Tank Cooling:
Cargo tank heating coils, or a deck-mounted heater may be disconnected from the heat source and the connected to a fresh water supply or to the fire main with the exhaust spilling onto the main deck.
This method has been found to be able to reduce a cargo’s temperature by 10-15 degrees over a very short period and is highly effective.