Exam Question
Q5
With reference to LNG bunkering procedure on board vessels fuelled with LNG fuel. Please explain the following processes:
(16)
(a) Gassing-up.
(b) Cooling-down.
(c) Vapour Management.
(d) Emergency release coupling procedure.
Class 1 (Chief Engineer)
Engineering Management
📅 Mar 2026
Reference Answer
### (a) Gassing-up
Gassing-up is the process of replacing the inert atmosphere (typically Nitrogen) or air within the LNG fuel tank with warm natural gas vapor before introducing cryogenic liquid LNG. This is a critical safety step to prepare the tank for receiving fuel.
**Purpose:**
* **Prevent Freezing of Inert Gas:** If Nitrogen is used for inerting, introducing LNG at -162°C would cause the Nitrogen to freeze (freezing point -210°C), potentially blocking lines, valves, and instrumentation.
Gassing-up is the process of replacing the inert atmosphere (typically Nitrogen) or air within the LNG fuel tank with warm natural gas vapor before introducing cryogenic liquid LNG. This is a critical safety step to prepare the tank for receiving fuel.
**Purpose:**
* **Prevent Freezing of Inert Gas:** If Nitrogen is used for inerting, introducing LNG at -162°C would cause the Nitrogen to freeze (freezing point -210°C), potentially blocking lines, valves, and instrumentation.
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