LNG Type B Bunker Tanks

GTT MKIII Membrane Tank

NO 96

NO 96

GTT CS1 Containment system

LNG Bunker vessel Both Types

LNG Bunker / Cargo handling Loading preparations

Drying

Purging

Gassing-up

Cool down

Loading

Loaded passage

Unloading

Ballast passage

Berthing preparations

Warming-up of tanks

Purging

Aeration of tanks (Degazation)

Cargo Tank Cleaning / Test & Securing

Pressure testing Inter Barrier and insulation space

Inspection of Tanks

• Debris

• Correct installation of equipment

• Water / Moisture

• Test of Equipment

• Tank Furniture

Testing

Legal AspectThe majority of LNG shippers and receivers have a legitimateconcern over foreign bodies getting into tanks and pipelines.

The main concern is the risk of valve blockage if (say) an oldwelding rod becomes lodged in a valve seat. Such occurrences arenot unknown with a ship discharging first cargoes after newbuilding or recently having come from dry-dock. Accordingly, anddespite discharge time diseconomies, it is common practice to fitfilters at the ship’s liquid manifold connections to stop any suchmaterial from entering the shore system. The ship normallysupplies filters fitting neatly into the manifold piping.Source: UK P&I Club

Post refit / Dry-dock checks

• Examine the operations required after Refit

• Examine what is done

• Investigate why some processes are performed in certain ways

Inerting of Insulation Spaces - Membrane Tanks

• To prevent a flammable atmosphere in the event of

leakage of LNG from Primary Barrier (membrane leak)

• Permit detection of a leak through a barrier

• Maintain a dry atmosphere in insulation spaces

• Prevent corrosion in insulation spaces

• Deter migration of leaked LNG from primary to

secondary spaces

NO96 - Vacuum pumps evacuate air, Vacuum is broken

with N2 vaporised on board from shore supplied liquid

MkIII - Smaller volume is swept with N2 generated on

board to remove air

Drying of Hold Spaces (Moss Tanks)Hold Space:-

• To reduce corrosion in the hold spaces.

• Reduce formation of ice at cold spots or Ice formation.

• DRY AIR is used so that CO2 in Inert Gas will not

create solid dry ice.

• Should flammability become a concern, Inert Gas can

quickly be introduced

Insulation and Annular Space

(Between tank and insulation)

• Insulation with the annular space is part of the leak

protection system (leak before failure)

• N2 in the annular space quickly transports leaking

vapour to gas detector

• Any leaking liquid is directed to the drip tray under the

tank