Question

The fire protection provided for the propulsion motor and generator of a diesel electric drive vessel is usually one of the following methods:

(a) Fixed foam extinguisher. (5)

(b) Fixed CO2 system. (5)

(c) Steam smothering system. (5)

(d) Dry Chemical Powder. (5)

Briefly state in a comparative analysis, how each one of these methods has some disadvantages when used with propulsion system as stated above.

Answer 1

Part (a)

Part (b)

Has a limited quantity of extinguishing agent.
Single-use system; requires refilling at next port.
Relatively slow to inert a high engine room volume.
No cooling effect.
Ineffective if seating has been destroyed by explosion or other accidents.
Poses grave risk to life in case of accidental release or if persons are lying injured in the protected space.
Re-entry into the space is not possible for a considerable time without a breathing apparatus.

Part (c)

Though steam in its gaseous state is an effective extinguishing medium, it can rapidly condense into visible water particles, reducing its smothering capability.
Offers very limited cooling effect.
Its high temperature makes controlling a smouldering fire prolonged and difficult.
Can cause damage to electrical machinery.

Part (d)

Can damage delicate machinery by affecting electrical relays and choking narrow spaces.
Not suitable for smouldering or deep-seated fires.
Provides little cooling effect.
There is a danger of reignition.
Toxic fumes may be produced under certain conditions, especially in engine rooms.
The powder can cause discomfort to personnel not equipped with breathing apparatus.
The powder is subject to windage and may be less effective in open or ventilated spaces.

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