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Cargo area fire onboard LPG carrier - How to tackle ?

Cargo vapours in flammable concentrations are likely to be present in areas such as cargo tanks, cargo machinery spaces and at times on deck. It is essential that all possible sources of ignition are eliminated from these areas .The fire may affect the cargo and increase the boil off and subsequent cargo tank pressure. Cool area by actuating water spray system. Use reliquefaction plant.



The source of fuel should be cut off and the initial attack should be with dry powder. If necessary use fixed fire fighting system - Foam, CO2, Halon ensuring area has been evacuated. Consider:
Vent Mast Fire

Ignition can be caused by a lightning strike or other source of ignition when venting. Consider:
Fire on ship or vicinity

It is the duty of any person on board who discovers an outbreak of fire to raise the alarm immediately. Thereafter they should attempt to control the fire using the nearest available appropriate means until an organised party takes over.

In port, shore assistance must be called immediately, if possible all cargo hoses should be isolated and disconnected. Bring main engines to readiness. At sea the ship should be manoeuvred so as to minimise the risk of fire spreading. Consider stopping mechanical ventilation in affected area.

Various extinguishing agents

Water : Water must never be applied onto a burning liquefied gas pool since it will provide a heat source for more rapid vaporisation of the liquid and thereby increase the rate of burning. Nevertheless, water remains a prime contributor to liquefied gas fire fighting. Being freely available in most circumstances, water is an excellent cooling agent for surfaces exposed to radiation or direct fire impingement. It may be used in spray form as a radiation screen or to deflect an unignited vapour cloud away from ignition sources. In some circumstances, water can be used to extinguish a jet or column of burning gas. Fixed water deluge systems are fitted for covering ship structures deck tanks and piping.

Water spray from fixed monitors or from hand held hose nozzles can provide radiation protection for personnel in their approach to shut off valves or to leaking jet or vent fires in order more effectively to deliver an attack by dry chemicals to extinguish the flame.


Dry chemical powder

Dry chemical powders such as sodium bicarbonate, potassium bicarbonate and urea potassium bicarbonate can be very rapidly effective in extinguishing small LNG or LPG fires. Gas carriers are required by IMO Codes to be fitted with fixed dry powder systems capable of delivering adequate powder to any part of the cargo area by means of fixed monitors and/or hand held hoses. Jetty manifold areas are also usually provided with substantial portable or fixed dry powder systems.

Dry chemical powders are effective in dealing with ignited spills on deck or in manifold drip trays or in extinguishing flames torching from a pipeline flange or fracture and have been used successfully in extinguishing fires at relief valve mast head outlets. Dry chemicals attack the flame by the absorption of free radicals in the combustion process but have a negligible cooling effect. Re-ignition from adjacent hot surfaces, therefore, must be guarded against by cooling any obvious hot areas with water before extinguishing the flame with dry powder.


Inert gas

Inert gas from combustion generators or nitrogen gas provided from insulated liquid nitrogen containers is commonly used on gas carriers and in terminals for permanent inerting of interbarrier spaces or for protective inerting cargo related spaces, such as ships' hold spaces or enclosed plant spaces on shore, which are normally air filled but in which flammable gas may be detected. Because of the comparatively low rate at which such gas can be delivered, it is not normally used for the rapid inerting of an enclosed space in which a fire has already begun. For this, high pressure bottled CO2 gas or halon is injected through multiple nozzles, the mechanical ventilation system to the space having been first shut off.

While CO2 injection systems are rapidly effective in enclosed space fire extinguishing, they have two disadvantages. Their fire extinguishing action is achieved by displacing oxygen in the space to a level which will not support combustion and it is therefore essential that all personnel completely evacuate the space before the injection beings. Secondly, the necessarily rapid injection of CO2 produces electrostatic charging which can be an ignition hazard if CO2 is injected inadvertently or as a precautionary measure into a flammable atmosphere.




CO2 or nitrogen injected into safety relief valve vent outlet risers may be used as an alternative to the external use of a dry powder screen as an effective means of extinguishing vapour fires at the vent outlet, particularly once the initial full pressure gas flow has subsided.


Foam

In general foam installations are not provided on gas carriers for liquefied gas fire fighting. However when the vessel has the capability of carrying cargoes also covered by the IBC code then the flag administration may require a foam installation.



Below is more guideline on Fire hazards, sources of ignition and necessary precautions

Fire hazards and precautions - Atmosphere Control For Gas Carrier

Fire hazards and precautions - Sources of Ignition in Liquefied Gas Carrier

Matters that require attention to onboard work

Fire hazards and precautions against statistic electricity in liquefied gas carrier





Related Information:

  1. Guideline to tackle fire on board LNG ship


  2. Fire fighting plan for liquefied gas carrier


  3. Design characteristics of liquefied gas carriers


  4. Liquefied gas carrier -applicable regulations


  5. Vapour Characteristics of liquefied gases


  6. Low temperature effects of Liquefied gases


  7. Reactivity of liquefied gas cargo and safety guideline


  1. Various type LPG tanker - Design characteristics and usability


  2. LPG tanker cargo work equipments & product line system


  3. Carriage of LPG cargo at sea & safety guideline


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  5. Preparations for LPG cargo discharging, pumping & stripping guideline


  6. Preparations for loading compatible cargo onboard LPG tanker


  7. Preparation for changing different grade cargo or drydocking -LPG tanker guideline


  8. Cargo tank inerting prior to gassing up - LPG tanker procedure


  9. LPG cargo tank purging & safety guideline


  10. LPG cargo tank cooling safety procedure


  11. LPG cargo loading special guideline


  12. Tackling fire onboard LNG & LPG ships


  13. Detail guideline for Ballast operation at sea by LPG carrier


  14. Handling cargo related documents for LPG carrier


  15. Cargo sampling procedure for liquefied gas cargo


  16. Cargo measurement and calculation guideline for LPG carriers


  17. Handling Propylene oxide, Ethylene oxide mixtures


  18. Special characteristics of Vinyl Chloride Monomer & Butadiene




Liquefied gases - Health hazards

How LNG is transported ? Is it safe ?

Liquefied gases - How to remove all cargo liquid from tanks

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

Liquefied gas carrier -monitoring cargo pressure






External links :

  1. International maritime organization




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