Inerting & cooling down LNG carriers

Inerting

In order to guarantee the highest level of safety, oxygen must be evacuated from the tanks of LNG carriers before every LNG loading operation.

This inerting service is available at Zeebrugge and Dunkirk : the oxygen in LNG carriers is evacuated and replaced by nitrogen (N2). The nitrogen must be purchased beforehand and supplied by truck.

The inerting service is not mandatory. As an alternative, the tanks of any LNG carrier to be loaded with LNG can be placed under a natural gas atmosphere, with the following specifications:

• maximum 1 ppm H2O vapour
• maximum 100 ppm CO2
• maximum 100 ppm O2

Cooldown

The tanks of LNG carriers have to be cooled very slowly so that they reach a good temperature for loading. Cooldown can take +/- 12 hours.

The cooldown service is not mandatory. However, the tanks of the LNG carriers must be cold enough to permit loading:

-110°C : MOSS LNG carriers
-130°C : Membrane LNG carriers

Vapour return

The cooldown of LNG carrier tanks produces vapour, which must be evacuated and reinjected into the natural gas grid.