Liquefied Gas Carrier

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Problem with helicopter operations on gas carriers & other deck precautions

Gas carriers are recommended not to undertake routine helicopter operations unless a purpose-built helicopter platform is provided. Whenever helicopter services are used the safety measures recommended in the ICS “Guide to Helicopter / Ship Operations” should be taken into account.

Types of operating areas

Ships operating areas fall into two distinct types:
Design limitations

The potential hazards associated with helicopter operations involving LNG vessels must be clearly recognised by all concerned. Before any helicopter operations are allowed to take place permission must be obtained from the Managing Office.

The major problem with helicopter operations on gas carriers is the lack of clear space available for an operating area, coupled with the high risk of damage to the deck installations and the difficulty in controlling any resulting fire. As most gas carriers are unable to provide a suitable clear space in the cargo area or on the forecastle for helicopter operations, the only suitable and safe place where operations may be carried out is on the poop deck.

This area has advantages for helicopter operations due to its remoteness from the cargo tank area, but it has some disadvantages.
  1. The lack of clear deck space because of mooring equipment

  2. The requirement to protect the accommodation against the potential hazards of a helicopter accident.
  3. Problems such as excessive pitch, roll and heave
  4. Turbulent air flow above the accommodation block and funnel which may make control of the helicopter difficult.

The ideal solution is for the gas carrier to have a purpose built platform, specially designed to alleviate the problems (a) and (b) above. It may also be helpful, if the ship is manoeuvered so that the wind is within 35 degrees of the beam, preferably on the port side, although final instructions and requests regarding this will be given by the helicopter pilot prior to final approach. On receipt of this advice, the Master must consider the request having due regard to his obligations for safe navigation and collision avoidance. If the Master is unable to comply fully with these obligations for safe navigation and collision avoidance, then this fact must be communicated to the helicopter pilot and operations delayed until the Master is able to comply with these obligations.

It is recommended that routine helicopter operations should not take place unless a platform is provided. Winching operations at a designated winching area away from the poop deck, may however be permitted on occasions, and a full Risk Assessment must be carried out before the permission is given for the operation to proceed.

Vapour emission control

The venting of cargo vapours to atmosphere under normal operating conditions should not occur, unless there has been some malfunction or mal-operation of the cargo system. The only possible sources of vapour on deck should therefore be minor, such as leakage from valve glands, pipeline joints or improperly seated pressure relief valves.

In order to eliminate any possibility of a major escape of vapour during helicopter operations due to the lifting of safety valves, cargo tank pressures should be reduced prior to the arrival of the helicopter. However due to the design function and safety procedures inherent in the gas burning system, there is no requirement for these operations to be suspended during helicopter operations. All tank lids and other openings must be closed securely to restrict the effects of any accident.

General deck precautions for Gas carriers at sea

To avoid an over reliance on computerised alarms systems, it is important that daily rounds of the cargo deck and compressor house are carried out. Areas which should be particularly sighted on these rounds are;
  1. bellows pieces, as deformation of the bellows is an indication of excess pressure in the line,
  2. readings on local temperature and pressure gauges on vapour and liquid lines, to ensure that the readings given are as expected at that stage of the voyage,
  3. Areas of un-insulated pipework for any unexpected ice build up, particularly on the vapour lines,
  4. Any movement of the liquid and vapour lines through the sliding feet, noting direction and amount of movement,
  5. Any signs of leakages from valves, vents and flanges,
  6. Overall condition of the cargo system

Any anomalies or unexpected observations are to be investigated, and where necessary corrective action taken. The managing office should be informed of any observed problems. An entry should be made in the deck log Book when deck rounds have been completed, along with the results of the inspection. Any deficiencies or unexpected conditions must be recorded, along with an entry when corrective action has been taken.

Lashing of Movable Articles

Articles that are likely to generate sparks, such as iron, aluminum or other light metal articles, shall be secured or stored in preparation for rolling of the vessel.

The Scupper Plug

The scuppers should be effectively plugged and condition of scupper plugs should be satisfactory. Scuppers on gas carriers will only be required to be plugged when bunkering or if carrying a MARPOL Annex 1 cargo.

Indicating Regulation Signals

While the vessel carrying dangerous cargo shall exhibit a ‘B’ flag in the daytime and a red light in the night time where they can best be seen. And even outside the port, exhibit the signals stipulated in the Marine Traffic Safety Law both while being navigating and while being moored in waters where the Marine Traffic Safety Law is applicable (Japan).

Related Information:

More safety precautions and instructions for liquefied gas carrier :

Mooring requirements for gas carrier

Means of access to ship

Standards for use of Mobile-phone

Precautions against abnormal weather

Dispersal of vented cargo vapours

Openings in deckhouses

Engine room precautions

Cargo machinery room precautions

Ship’s readiness to move

Related Information:

  1. Cargo Information - physical and chemical properties necessary for the safe containment of the cargo

  2. LNG spill risk during marine transportation and hazards associated

  3. How to tackle fire on board LNG ship

  4. Displacing with Vapour of the Next Cargo (Purging)

  5. Fire fighting plan for LNG cargo

Drying of Cargo Tanks and preparation for loading LNG cargo

Inerting of Cargo Tanks prior loading LNG cargo

Initial Cool Down of cargo tanks

Gas cargo containment systems - primary barrier (the cargo tank),secondary barrier, thermal insulation and more

Preparatory operations of drydocking for LNG carriers

Procedure for transporting remote gas

Development and potential of todays emerging gas technologies

Transporting economically viable compressed gas liquids from remote fields

The risk of laden voyage - a brief guide to liquefied gas carriers

Connection and disconnection of cargo hoses and hard arms

The risk of ballast voyage - a brief guide to liquefied gas carriers

The risk of laden voyage - a brief guide to liquefied gas carriers

Liquefied gases - Health hazards

Safety equipment

Liquefied gas cargo reactivity

Liquefied gas cargo corrosion

Liquefied gas cargo vapour characteristics

Liquefied gas cargo - low temperature effects

Liquefied gas carrier -monitoring cargo pressure

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