All technology topics
Cargo & BOG
Boil-off Gas Management
How vessels control tank pressure using boil-off gas as fuel, gas combustion units or reliquefaction.
Educational data
Schematic placeholder
Layer 01
Cargo tank vapour space
Layer 02
BOG compressor
Layer 03
Main engines / boilers (fuel)
Layer 04
Reliquefaction plant (return to tank)
Layer 05
Gas combustion unit (surplus disposal)
What it is
- Boil-off gas is the vapour generated when heat enters the cargo, and managing it is primarily about controlling tank pressure.
- Vessels combine several strategies rather than relying on a single device.
Where it is used
- All LNG carriers and floating units; the chosen strategy follows the propulsion concept and trade.
Key design characteristics
- BOG compressors routing vapour to consumers.
- Gas combustion units for safe disposal when vapour exceeds demand.
- Reliquefaction plant on designs where cargo retention is prioritised.
Benefits
- Using vapour as fuel converts an unavoidable process into useful propulsion energy.
- Multiple strategies give operational flexibility across voyage phases.
Operational considerations
- Boil-off figures are indicative and depend on insulation, filling level, sea state and voyage length.
- Reliquefaction adds machinery, energy demand and maintenance scope.
Related vessel segments
Related glossary terms
Technical information
- Status
- Educational overview — editorial review required
- Seeded educational summary awaiting editorial and technical review.
- Last reviewed
- 15 September 2026
- Source status
- Sources pending editorial review.
Technical parameters are indicative and may vary by vessel design, generation, shipyard, operator and intended service.