LNG is stored as a cryogenic liquid at about -163 deg C at near-atmospheric pressure. The bunker tank arrangements on ships are:

1. Type C (pressure vessel) tanks: cylindrical or spherical pressure vessels (e.g. IMO Type C) that can withstand the pressure of the LNG vapour; they are the most common for LNG-fuelled ships because they are simple, robust, and do not require a secondary barrier. They are insulated and can be of the "membrane" or "self-supporting" type; Type C tanks are self-supporting pressure vessels.
2. Type A (prismatic) tanks: prismatic tanks with a full secondary barrier, used on LNG carriers; they operate at low pressure and rely on the secondary barrier for safety.
3. Type B tanks: spherical (Moss) or prismatic (IHI) tanks with a partial secondary barrier, used on LNG carriers.
4. Membrane tanks: a thin membrane liner with a secondary barrier, used on large LNG carriers.

For bunkering/consumption on a ship (LNG-fuelled vessel), the most common is the Type C pressure vessel (cylindrical or bilobe) because it is simple, safe, and can be installed in the hull; the tank is insulated to keep the LNG cold and to control the boil-off gas (BOG).

1. The tank is a pressure vessel designed to contain the LNG at its operating pressure and temperature, with a relief valve to prevent over-pressure.
2. Insulation: the tank is insulated to minimise heat ingress and boil-off; the insulation must be maintained to prevent excessive BOG and pressure rise.
3. Secondary barrier (for membrane/Type A/B): a secondary containment to prevent leakage of LNG in the event of primary barrier failure.
4. Pressure/vacuum relief: the tank has pressure relief valves and vacuum relief to prevent over-pressure or collapse.
5. Level and temperature monitoring: the tank has level gauges, temperature sensors and pressure sensors to monitor the LNG.
6. Gas detection: gas detectors in the tank space and vent system to detect any leakage of methane.
7. Venting: a vent system (vent mast) to safely vent the BOG and any excess pressure.
8. The tank space is inerted/ventilated and the tank is protected from over-filling (high-level alarms and shut-off).

1. Bunkering of LNG must be carried out in accordance with the ship's bunkering procedure and the IGF Code (International Code of Safety for Ships using Gases or other Low-flashpoint Fuels).
2. The bunkering operation is supervised by a responsible officer; a bunkering plan and a risk assessment are prepared; the ship and the bunker supplier agree on the transfer rate, pressure and temperature.
3. The ship must be properly moored, the bunkering area is marked, and no smoking/naked lights; gas detection is active.
4. The transfer is done through a dedicated bunkering manifold with emergency shut-off valves (ESD), a vapour return line, and a dry-break/quick-release coupling.
5. The tank is filled to the correct level (not over-filled), the temperature and pressure are monitored, and the BOG is handled (returned to the supplier or vented).
6. After bunkering, the lines are purged and disconnected safely, and the quantity is recorded in the bunker delivery note.
7. Personnel are trained in LNG bunkering and emergency procedures.