Gas Freeing – Definition and Pronunciation

[ɡæs ˈfriːɪŋ]

What is Gas Freeing?

Gas freeing is the removal of toxic, flammable and inert gas from a tank or enclosed space, followed by the introduction of fresh air. It includes two distinct operations, i. e. inerting and aeration.

Examples of Gas Freeing

On membrane ships, ensure that tank pressures are always higher than insulation space pressures by at least 10 mbar, but not exceeding 180 mbar above atmospheric pressure. It is beneficial during gas freeing to keep the tank pressure low to maximise the “piston effect”.

From Gas Freeing of Cargo Tanks on Liquefied Natural Gas Carriers“Procedures and Principles of Gas Freeing LNG Cargo Tanks”.

Large ships are equipped with high-flow, centrifugal blowers to deal with cargo vapour and also to speed up the gas freeing/inerting operation.

From Other Characteristics Specific to Liquefied Gas Tankers“Main technical characteristics of LNG LPG tankers”.

There may be several reasons for single tank gas freeing. For example, it may be necessary for in-tank repairs to be carried out with the ship in service. The primary difficulty of single tank gas freeing is ensuring the total isolation from other tanks.

From Non-Standard and Emergency Operations on Liquefied Natural Gas Carriers“LNG Emergency Situations and Handling Non-Standard”.