Fig:LNG carrier underway
(4) Filling of the cargo tanks may cause a significant loss of pressure in the hold or inter-barrier spaces, depending upon the cargo system design. This should be continuously monitored and pressure maintained by the addition of supplementary inert gas, dry air or dry nitrogen.
(5) Filling limit regulations should be observed. The maximum liquid level in each tank should be calculated before or during the early stages of loading.
(6) If large quantities of vapour are being generated (i.e. the cargo liquid is boiling rapidly) the bubbles created will increase the liquid volume. To measure tank contents accurately under such circumstances it is recommended that vapour removal should be reduced temporarily to allow the liquid level to stabilize.
(7) In all tanks, whether or not being loaded, the liquid level and pressure readings should be monitored throughout loading. A reading which does not change as expected may indicate a fault which should be investigated.
(8) When liquid flow is diverted from one tank to another the valves on the tank about to receive cargo should be fully opened before those on the tank being isolated are shut.
(9) On completion of loading all ship’s lines should be drained into the cargo tanks using the facilities provided. Liquid in hoses or loading arms should also be drained to the cargo tanks, if possible, or blown to shore and pressed past shore valves by vapour pressure. If possible the ship-shore connection should be purged before being disconnected. Ship-shore connections should not be broken until it has been ascertained that all liquid has been removed and the lines are depressurized. Adjacent isolating valves on ship and shore and any other relevant valves should then be closed before connections are broken.
(10) Bonding wires, if fitted, should not be disconnected until after the hoses have been disconnected.
(11) The relief valves of some ships have dual or multiple settings, either for operational purposes or to meet differences in national regulations. Changes to the relief valve setting should be carried out in accordance with the procedures specified and under supervision of the master. Changes should be recorded in the ship’s log and a sign posted at the relief valve and in the cargo control room, if provided, stating the set pressure.
Preparation for loading LNG
It is assumed that all preparatory tests and trials have been carried out on the ballast voyage prior
to arrival at the loading terminal.
All operations for the loading of cargo are controlled and monitored from the ship’s CCR. The
loading of LNG cargo and simultaneous de-ballasting are carried out in a sequence to satisfy the
- The cargo tanks are filled at a uniform rate.
- List and trim are controlled by the ballast tanks.
- The cargo tanks are to be topped off at the fill heights given by the loading tables.
- During topping off, the ship should if possible be kept on an even keel.
- During the loading, the ship may be trimmed according with terminal maximum
draught, in order to assist in emptying the ballast tanks.
- The structural loading and stability, as determined by the loading
computer/loadicator, must remain with safe limits.
An officer responsible for the operation (OOW) must be present in the CCR when cargo is being
transferred. A deck watch is required for routine checking and/or any emergency procedures that
must be carried out on deck during the operation.
During the loading operations, communications must be maintained between the ship’s CCR and
the terminal by telephone and radio. The ESD system must remain in contact with the terminal in
order to ensure signals for the automatic actuation of the Emergency Shutdown from or to the
At all times when the ship is in service with LNG and mainly during loading, the following are
Alongside of terminal as applicable
- The pressurization system of the insulation spaces must be in operation with its
automatic pressure controls.
- The secondary Level Indicating system should be maintained ready for operation.
- The temperature recording system and alarms for the cargo tank barriers and
double hull structure should be in continuous operation.
- The gas detection system and alarms must be in continuous operation.
- Normally when loading cargo, vapour is returned to the terminal by means of the
H.D. compressors or shore compressor. The pressure in the ship’s vapour header is
maintained by adjusting the compressor flow.
- The cargo tanks must be maintained in communication with the vapour header on
deck, with the vapour valve on each tank dome open.
- A suitable Vent Mast is maintained ready during the loading operation, for
- If the tanks have not been previously cooled down, LNG spraying is carried out.
- If required by the terminal, connect and bolt up the shore ground cable.
- Connect and test the shore communication cable.
- Test the telephone for normal communication with the terminal.
- Test the back-up communication arrangements with the terminal, usually handheld
- Ensure hull water curtain is in operation.
- Change over the blocking switch for the shut down signal from the terminal, from
the at sea position to the terminal position.
- Connect the terminal loading arms to the LNG cross-overs and one vapour
crossover. This operation is normally done by the terminal personnel.
- Check that the coupling bolts or QSDC are lubricated and correctly torqued.
- In the cargo control room (CCR), switch on the cargo tank level alarms and level
shutdowns which may have been blocked at sea.
- Switch the independent level alarms from blocked to normal on each tank.
- Switch the derived level alarms from blocked to normal on each tank.
- Verify that alarms for level shutdowns are unblocked.
- Record the arrival conditions for custody transfer documentation. Official
representatives of both buyer and seller are present when the printouts are run.
Gas carrier cargo containment procedure
Cargo conditioning, reliquefaction and boil-off control requirement for a liquefied gas carrier
Cargo Containment Systems in Liquefied Gas Carriers
cargo emergency shutdown requirement
damage stability guideline for liquefied gas carriers
Various Cargo handling equipments onboard
Cargo hoses connection guideline
Documents accompanying a liquid gas cargo
How LNG transferred from shore to ships cargo tanks ?
Cargo operation guideline onboard a liquefied gas carrier
Cargo piping Systems in Liquefied Gas Carriers
cargo planning requirement
cargo and pumproom safety precautions
cargo stripping guideline
Emergency response for cargo system leaks
Emergency response for cargo tank rupture
Risk of overfilling of cargo tank during loading onboard a liquefied gas carrier
Preparation for cargo transfer
cargo transfer between vessels- safety guideline
- Liquefied gas Cargo safe handling & responsibility on board
- Cargo emergency shutdown requirement for liquefied gas carrier
- Gas analyzing equipment
- Custody Transfer Measurement (CTM) System
- Details of various cargo handling equipment onboard
Tank construction materials for a modern gas tanker
- LNG vessel construction -Advantages of membrane technology
Advantages of Moss rosenberg cargo containment system
- Type of gas carriers - variation in the design, construction and operation
- Transporting liquefied natural gases by LNG ships
- Cargo conditioning, reliquefaction and boil-off control requirement for a liquefied gas carrier
- The sea transport of liquefied gases in bulk -Where do the products come from ?
Gas carrier cargo handling additional guidelines
More Info pages
Procedure for cargo planning in Liquefied Gas Carriers
Details of various cargo handling equipment onboard
Cargo piping layout for LNG carriers
Procedure for commissioning the cargo system
Preparation for Cargo Transfer
Procedure for discussion prior cargo transfer
Procedure for loading Liquefied Gas Cargoes
Procedure for Cargo Conditioning in Liquefied Gas Carriers
Cargo Transfer between Vessels (STS Operation)
Procedure for segregation of Liquefied Gas Cargoes
Procedure for Stripping Liquefied Gas Cargoes
Procedure for Changing Liquefied Gas Cargoes
Displacing with Vapour of the Next Cargo (Purging)
Procedure for Water washing after Ammonia Cargoes
- Procedures for various cargo handling equipment onboard
- Personal protective equipments for people working onboard gas carriers
- Volatile nature of liquefied gases
- How to achieve maximum drainage of liquid during discharge
- The hazards of liquefied gases - Cargo information and safety factors
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