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Dry powder extinguishing method for fire protection onboard chemical tankers

Many new chemical tankers use dry powder extinguishing system as the main fire fighting method in the cargo tank extinguishing area.

There are to be found centralized powder systems with possibilities of discharging several thousand kgs of powder. Release boxes and hose reels are strategically located on deck so that any point can be reached by two hoses, each being usually max 25 m length. On smaller vessels self-contained powder containers of 1000-3000 kgs are located in small deckhouses.

chemical tanker navigation at sea
As mentioned above the IMO-Code accepts dry powder as equivalent to foam. Dry powder has decided limitations, which are explained below.

The extinguishing effect of dry powder originates mainly from an inhibiting effect on the combustion. The smothering and cooling effects are small.

Dry powder has a particularly good extinguishing effect on larger volumes of burning gases and strongly vapourizing liquids, as compared with other means of fire fighting. But it has virtually no cooling effect on any steel, cargo liquid or other matter that has become heated from the fire. Once the flames have been thrashed out with dry powder there is a great risk for a fire back flash which can be more violent than the original fire. At a major fire therefore, the fire area should be cooled down with water fog as much as possible prior to application of powder.

Water cooling must be continued after the flames have been extinguished If a fire can be fought immediately after its outbreak and only little heating has occurred one should of course immediately start with dry powder, not awaiting water fog assistance.

Common types of dry powder have a tendency to break down a foam layer. Therefore the two methods should be avoided being used together. Some new powders are claimed not to have this deteriorating effect on foam. Always place two dry powder extinguishers at hand on deck aft of the cargo manifold, when loading /unloading.

Summarized below are recommended fire fighting methods for modern chemical tankers:

Total flooding method for seagoing chemical tankers

Water extinguishing method for fire protection

Foam extinguishing method for chemical tankers

Dry powder fire extinguishing method

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Following reference publications provide useful guidance and international regulations for carrying hazardous chemicals at sea.

Our detail pages contain somewhat larger lists of resources where you may find more useful information.

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