Class 2 (2nd Engineer) MEKG 📅 Sep 2025

Exam Question

(a) State the advantages of using steam turbine propulsion power for vessels carrying LNG cargo.

(b) With regard to the use of L.N.G. cargo as boiler fuel explain:

(i) The safety precautions relating to the gas pipeline supplying the boiler and burning the gas in the boiler,

(ii) The means of getting rid of "excess gases" during loading or discharge.

Reference Answer

### Part (a): Advantages of Using Steam Turbine Propulsion for LNG Carriers
Steam turbine propulsion, while a mature technology, offers distinct and compelling advantages for vessels carrying Liquefied Natural Gas (LNG) cargo. These advantages are primarily centered around the inherent properties of the cargo and the operational profile of the vessel.
1. **Inherent Utilization of Boil-Off Gas (BOG)**: This is the principal advantage. LNG is transported at its atmospheric boiling point (-163°C). Despite high-quality tank insulation, unavoidable heat ingress causes a portion of the cargo to continuously vaporize, creating Boil-Off Gas (BOG). A steam plant is exceptionally well-suited to utilize this BOG as a primary fuel source.
* **Direct and Simple Consumption**: Marine boilers can be readily fitted with dual-fuel burners that burn BOG with minimal processing, directly managing the cargo tank pressure.

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